We Are Aliens – A Guide for Educators
Transcript of We Are Aliens – A Guide for Educators
EUGENE SCIENCE CENTER2300 Leo Harris Parkway, Eugene, OR 97401. [email protected], 541-682-7888
We Are Aliens – A Guide for Educators
Prepared by Haley Sharp, Eugene Science Center Planetarium Director, [email protected] About the Planetarium Show We Are Aliens invites your students to explore how our understanding of life on Earth guides the hunt for alien life elsewhere in the universe. We visit Mars, Europa and distant exoplanets to help answer the ultimate question... are we alone? Explore what life needs to thrive and how astronomers use clever techniques to find planets around distant stars in this immersive program that perfectly balances science, education, and entertainment. Next Generation Science Standards
We Are Aliens explores topics in each of the four disciplinary core ideas as outlined in the Next Generation Science Standards: physical sciences; life sciences; earth and space sciences; and engineering, technology, and applications of science. From a thorough investigation of the incredible diversity of lifeforms found on Earth, to imagining space missions that can hunt for alien life in our solar system and beyond, there are many ways to connect this planetarium program to your current science lessons. Some relevant standards are listed below: K-LS1-1 Use observations to describe patterns of what plants and animals need to survive.
1-ESS1-1 Use observations of the sun, moon, and stars to describe patterns that can be predicted.
2-LS4-1 Make observations of planets and animals to compare the diversity of life in different habitats.
2-ESS2-3 Obtain information to identify where water is found on Earth and that it can be solid or liquid.
3-LS4-3 Construct an argument with evidence that in a particular habitat some organisms can survive well, some survive less well, and some cannot survive at all.
3-LS3-2 Use evidence to support the explanation that traits can be influenced by the environment.
4-PS4-1 Develop a model of waves to describe patterns in terms of amplitude and wavelength.
5-PS3-1 Use models to describe that energy in animals’ food was once energy from the sun.
5-ESS2-1 Describe and graph the amounts and percentages of water and fresh water in various reservoirs to provide evidence about the distribution of water on Earth.
MS-PS2-4 Construct and present arguments using evidence to support the claim that gravitational interactions are attractive and depend on the masses of interacting objects.
MS-LS4-2 Apply scientific ideas to construct an explanation for the anatomical similarities and differences among modern organisms and between modern and fossil organisms to infer evolutionary relationships.
For more information on Oregon’s Science Standards, visit http://www.ode.state.or.us/search/page/?id=1577
EUGENE SCIENCE CENTER2300 Leo Harris Parkway, Eugene, OR 97401. [email protected], 541-682-7888
Before Your Visit • Begin by assessing what your students already know about the search for life beyond Earth.
Specifically, invite them to share what they have heard on their own. For example: o What does Earth have that makes it such a haven for life? o Where else in our solar system could we look for life? How are these places similar to
and/or different from the Earth. o Is the Sun the only star that has planets? Are planets common in the universe? o Poll your students to see how many of them believe in alien life.
Remind your students that some of these may be open-ended questions, like many great questions in science! While scientists are looking for signs of life beyond Earth, we haven’t found any yet. Activities For Before or After Your Visit • In any astronomy unit, one of the most challenging concepts to convey is just how big and
empty space truly is. This activity will allow your students to work together to create a scale model of the Earth, Earth’s moon, and Mars using balloons. Students will first make their models based on what they think is the correct scale before you show them the accurate model. Use this activity to explore as a group why it is so challenging to travel to Mars and beyond. Full activity description: https://marsed.asu.edu/sites/default/files/stem_resources/Earth_Moon_Mars_ Balloons _K-4_Lesson_8_2013.pdf
• In space exploration, robotic rovers are sent to destinations like Mars to test landing procedures and explore these locations before humans can safely travel there. But studying the Martian environment through the “eyes” of a robotic rover is no easy task. In this activity, students will bring an item from home in a paper bag. Then, these bags of items will be randomly distributed to students and they will have to use their senses to make inferences about the nature of the hidden item based on their indirect observations. Full activity description: http://www.nasa.gov/audience/foreducators/topnav/materials/listbytype/ Whats_Hidden_Inside_Activity.html
• This activity will demonstrate that when scientists look for life on Mars, or elsewhere in the universe, the signs of life are not always easy to determine. Begin by discussing with your students how they think life is defined and then conduct a simple experiment looking for signs of life in three different “soil” samples. Following the experiment, you may need to reassess how living things vs. non-living things are defined. Full activity description: www.lpi.usra.edu/education/explore/LifeOnMars/activities/searchingForLife/
• When scientists discover exoplanets – planets orbiting stars other than our sun – the first thing they will do is try to determine if that exoplanet is orbiting in its stars’ “habitable” zone where it is not too hot and not too cold, but just the right temperature for liquid water. This video is an example of a demonstration you can do in class with your students exploring what the habitable zone is using the innermost planets or our solar system as an example. Full activity description: https://nightsky.jpl.nasa.gov/download-view.cfm?Doc_ID=311
EUGENE SCIENCE CENTER2300 Leo Harris Parkway, Eugene, OR 97401. [email protected], 541-682-7888
Useful Websites • NASA’s exoplanet site: https://exoplanets.nasa.gov/
o New exoplanet discoveries are announced all the time. While this is exciting from a scientist’s perspective, as an educator it can be frustrating to have out-of-date information. NASA’s exoplanet archive is the go-to resource for the current number of confirmed exoplanets in our galaxy.
• NASA’s Mars exploration site: http://mars.nasa.gov/ o This is a great collection of all things Mars. Highlights include a history of Mars
missions, the latest press releases of new discoveries made about the red planet, and a wonderful collection of multimedia resources to share with your students.
• NASA’s Space Place: http://spaceplace.nasa.gov/ o NASA’s Space Place website is a wonderful resource for general space information.
This site includes kid-friendly educational games, hands-on activities, and lots of beautiful space images to help visualize the cosmos.
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WeAreAliens!–Classroomactivity1(Biology)
Istherelifeinthere?
Background:
AlllifeformsonEartharebasedonorganicbiochemistry.Thisactivityrequiresstudentsto
analyseanunknownsoilsample(justrecoveredfromaspacemissiontoanotherplanet!)and
lookforsignsofcarbohydrates,lipidsandproteinsaspossibleindicatorsforlife.Theresultsfrom
thepracticalinvestigationmirrorthoseoftheVikingmissionsthatfirstanalysedthesurfaceof
Marsinthe1970’s.
TheactivitycoversavarietyofcurriculumareasandcanbeusedacrossKS3,KS4,andKS5with
modificationanddifferentiation.
Curriculumareascovered:
• Cellbiology
• Foodtests–biochemicaltestsforprotein,fatandcarbohydrates(starchandreducingsugar)
• Practicalskills–handlinglaboratoryglasswareandreagents,makingobservations,preparing
slides,usingalightmicroscope
• HowScienceWorks–formulationofatheory,needforreliability,peerreview
Equipmentlist:
• ThreecontainerslabelledA,BandC(sizeoptional)
• Soilsamplesineachcontainer.Eachsampletovaryintermsofitscontent–examplebelow:
Theexactquantitiesofeachsubstanceinthecontainersarenotcrucial–thetestsaresensitive
enoughtopickupsmallamountsofeachorganicmolecule.Asaroughguide,about4parts
sandto1part‘extraingredients’isusuallysufficient.
• Testtubes
• Spatulas
• Waterbaths
• Pipettes
• Handlenses
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• Sildes&coverslips
• Microscopes
Reagents:
• Benedict’ssolution
• BiuretA&BiuretBsolutions
• Ethanol
• PotassiumIodidesolution
Method:
Visualinspection:
1. Askstudentstotakeasmallamountofeach‘soil’typeandplaceonseparatepiecesofpaper
2. Studentsobservewiththenakedeyeandrecordanyobviousdifferencesbetweeneachsoil
typeontheresultssheet
3. Asmallquantityofeachsoilsampleisthenplacedintoadimpletile.Addafewdropsof
warmwater(enoughtocoverthesoil)toeachsample.Observecarefullyoverthenextfive
minutesandrecordobservationsontheresultssheet
Lookingforcells(yeast):
Placeasmallamountofeachhydratedsoilsample(useapipette)onseparateslidesandobserve
atlow,mediumandhighpowermagnification.Recordyourobservationsontheresultssheet
Starchtest:
1. Takeasmallamountofeach‘soil’typeandplaceinseparatetesttubes
2. Addapprox5cm3ofwatertothetesttubeandshake
3. Allowtimeforthesoiltoformasedimentatthebottomofthetube
4. Addafewdropsofiodinesolutiontothetesttubeandobserveanycolour
change.Ablackcolourindicatesthepresenceofstarch
5. Recordresultsontheresultssheet
Reducingsugartest:
1. Takeasmallamountofeach‘soil’typeandplaceinseparatetesttubes
2. Addapprox5cm3ofwatertothetesttubeandshake
3. Allowtimeforthesoiltoformasedimentatthebottomofthetube
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4. Addapprox5cm3ofBenedict’ssolutiontothetesttubeandplaceinahotwater
bathforfiveminutes.Abrickredcolourindicatesthepresenceoflargequantities
ofreducingsugars.Yellow/Green/Orangecoloursindicatesmallerquantities.
5. Recordresultsontheresultssheet
Proteintest:
1. Takeasmallamountofeach‘soil’typeandplaceinseparatetesttubes
2. Addapprox5cm3ofwatertothetesttubeandshake
3. Allowtimeforthesoiltoformasedimentatthebottomofthetube
4. AddafewdropsofBiuretAsolutiontothetesttubeandthenaddafewdropsof
BiuretBsolution.Observeanycolourchange.Apurplecolourindicatesthe
presenceofprotein
Lipidtest:
1. Addapprox5cm3ofethanoltothetesttubeandshake
2. Allowtimeforthesoiltoformasedimentatthebottomofthetube
3. Addafewdropsofwatertothetesttube.Observeanycolourchange.Amilky
whitecolourindicatesthepresenceofalipid.
TherapideffervescenceseeninBistypicalofashortbutunsustainedchemicalreaction–
reminiscentofthelabelledreleaseexperimentperformedbytheVikingprobesonMars
(seebelow).ThecontinualreleaseofgasinCillustratesanimportantfeatureoflife–that
ofsustainability.
Discussion:
Afterstudentshavecompletedthepracticalandfilledintheirresultssheets,two
studentsshouldactasa‘peerreviewpanel’andcollateresultsfromdifferentgroupsand
displayontheboard.Discussionfollowsontheoverallresultsoftheclass,reasonsfor
anydisagreement,contamination,anomalies,etc.DiscussionleadsintotheVikingLander
missionsandtheparallelsbetweenthisinvestigationandthosecarriedoutonthe
surfaceofMars.ThemainlinkistheideaofsandsampleBgivingoffagreatdealofgas–
butitbeingentirelyduetochemical,andnotbiological,reactions.
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SoilA SoilB SoilC
Visual
inspection
Responseto
hydration
Testforstarch
Testforsugar
Testforprotein
Testforfat
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Backgroundinformation-Mars
Marsisbyfarthemoststudiedplanetinoursolarsystem.Ithasnotablesurfacesimilaritieswith
Earthincludingvolcanoes,mountains,valleys,desertsandpolaricecaps,althoughitis
approximatelyonlyhalfthesizeoftheEarth.Marscurrentlyhoststhreeactivespaceprobesin
orbit(MarsOdyssey(NASA),MarsExpress(ESA)andtheMarsReconnaissanceOrbiter(NASA)).Italsohastwoexplorationroversonthesurface(SpiritandOpportunity(NASA))plusahostofinertprobesfromthepast–includingtheBritishBeagle2probeandNASA’sPhoenixprobe,whichrecentlycompleteditsmissiontoresearchthehistoryofwaterontheplanet.
Thedatagatheredthusfarhasshownthat:
• Thesurfaceiscomposedoffineiron(III)oxide–givingMarsitsrustredcolouration
• Thereisevidenceofgeologicalactivityandplatetectonics(asevidencedbyVallesMarineris,
OlympusMonsandpaleomagnetismofminerals),butthisseemstohavestoppedalong
timeago.ThisispossiblyduetothefactthatMarsismuchsmallerthanEarthandsolost
heatmorerapidly,leadingtocoolingandsolidificationofthecore.
• Marsappearstohavelostitsmagneticfieldearlyoninitshistory,meaningthattheSolar
Windhasstrippedawaymuchofitsatmosphere.Whatatmosphereremainsisverythinand
iscomprisedmainlyofcarbondioxide(95%)withsmallerquantitiesofnitrogen(3%),argon
(1.6%)andtraceamountsofoxygen.
• Alackofozoneintheatmospheremeansthatthesurfaceisirradiatedwithlargequantities
ofUVradiation–meaningthatorganicmoleculesonthesurfacewouldbequicklybroken
down
• Thethinatmospheremeansthatairpressureisverylowrangingfrom0.03KPa(summitof
OlympusMons)to1.155KPa(depthsofHellasPlanitia).
• MethanehasbeenfoundintheMartianatmospherewithaconcentrationofabout30ppb
byvolume.Sincemethaneisanunstablegasthatisbrokendownbyultravioletradiation,
typicallylastingabout340yearsintheMartianatmosphere,itspresencewouldindicatea
currentorrecentsourceofthegasontheplanet.
• SignificantamountsofwatericehavebeenfoundatthepolesofMarsandhavealsobe
foundunderthesurfaceinotherlocations.NASAhasestimatedthatthereissufficientwater
iceatthepolesalonetofloodtheplanettoadepthof11metresifmelted.Surfacefeatures
ofMarsindicatethatinthepastwatermayhaveexistedinliquidform.
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VikingInvaders…
Itisnowmorethan30yearssincethefirstsearchforlifetookplaceon
anotherplanet–Mars.Inthemid1970’sNASA’stwoVikinglandersconductedbiologyexperimentslookingforbiosignatures.Theseexperimentsincluded:
GasChromatograph—MassSpectrometer
Designedtoseparate,identifyandquantifyalargenumberofdifferent
chemicals.Particularinterestwascenteredaroundtheidentifyingany
organicmoleculesthatcouldindicatelife.
GasExchange
Designedtolookforgasesgivenoffbyanincubatedsoilsample.
Metabolismbylivingorganismsshouldresultinchanging
concentrationsofseveralgasesincludingoxygen,carbondioxide,
methane,nitrogenandhydrogen
LabeledRelease
DesignedtotestasampleofMartiansoilinoculatedwithadropof
verydiluteaqueousnutrientsolution.Thenutrientsweretaggedwith
radioactive14Candtheairabovethesoilwasthenmonitoredforthe
evolutionofradioactive14CO2gas(possiblyindicatingrespiration).This
experimentwasthenrepeated,butthistimethesoilwasfirstheated
toaveryhightemperaturerenderingitcompletelysterile(actingasa
control).
PyrolyticRelease
Thisinvolvedprovidingasoilsamplewithlight,water,carbondioxide
andcarbonmonoxide.Thecarbonwaslabelledwith14C–theidea
beingthatthiswouldbeincorporatedintothebiomassofa
photosyntheticorganism.Afterremovingthegases,thesoilwasthen
bakedathightemperaturestovaporiseanybiomassinthesoil.If14Cwasdetected,itwould
providesomeevidenceforabiologicallifeform.
Theresultsinitiallycausedagreatdealofexcitementwhenasteady
streamofradioactivegases(includingcarbondioxide)werereleased
inthelabelledreleaseexperiment.However,thiswasnotsustained–
subsequentinjectionsofnutrientsdidnotresultinanyreaction.The
findingsfromtheotherinvestigationsfailedtofindanyevidencefor
organicmoleculesonthesurface,asidefromtracesthatweredueto
contaminationofthespacecraftfromEarth.Theexperimentscarried
outbyVikingthereforeremaininconclusive–itispossiblethat
Martiansoilhasbuiltupathinlayerofanoxidantchemicalwhich
reactsstronglywithnutrientstoproduceCO2.
Fig01(above)
Fig02(above)
Fig03(above)
Fig04(above)
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FromVikingtoExoMars
SinceViking,missionstoMarshavefocusedmainlyongeologicalor
atmosphericanalysis.However,thisisabouttochangewiththe
launchoftheESAExoMarsmission(currentlyscheduledfor2016).
Theaimofthemissionwillbetofurthercharacterisethebiological
environmentofMarsinpreparationforroboticmissionsandthen
humanexploration.Datathatisgatheredduringthemissionshould
provideuswithaclearerpictureofwhetherlifehaseverevolvedon
theplanet.
Themissionwillcarryarover(designedandtestedintheUK)whichis
intendedtoactasa‘fieldbiologist’onthesurfaceofMars.Unusually,
thisroverwillcarryadrillthatisdesignedtotakesamplesfromtwo
metresbelowthesurface–wherescientiststhinkthattheremaybe
waterandhencelife.
Theroverwillthendeliversoilandrocksamplestoaninstrument
(calledthe‘Urey’instrument)whichwillgrindthesamplesandexposethemtoafluorescent
dyethatattachestomoleculescontaininganamine(NH2)group.Thedyeiscalledflourescamine,andisahighlyspecificreagent.
Alaserinsidetheinstrumentwillilluminatethesample,causingamine-containingcompounds
labeledwithflourescaminetoappearinadetectoreveniftheyarepresentonlyinminute
amounts.ThedetectorisestimatedtobeonemilliontimesmoresensitivethanViking.Ifamino
acidsorDNAispresent,thereisthereforeaverygoodchancethattheywillbedetected.
AlllifeonEarthassembleschainsofaminoacidstomakeproteinsduringtheprocessof
translationatribosomesinacell.However,aminoacidscanbemadeeitherbyaliving
organismorbynon-biologicalmeans.ThismeansitispossiblethatMarshasaminoacidsand
otherchemicalprecursorsoflifebuthasneverhadlife.Todistinguishbetweenthatsituation
andevidenceforpastorpresentlifeonMars,theUreyinstrumentteamwillmakeuseofthe
knowledgethatmosttypesofaminoacidscanexistintwodifferentformscalled
stereoisomers.Oneformisreferredtoas"left-handed"andtheotheras"right-handed."Justas
therighthandonahumanmirrorstheleft,thesetwoformsofanaminoacidmirroreachother.
Aminoacidsfromanon-biologicalsourcecomeinaroughly50-50mixofright-handedandleft-
handedforms.LifeonEarth,fromthesimplestmicrobestothelargestplantsandanimals,
makesandusesonlyleft-handedaminoacids,withrareexceptions.Comparableuniformity--
eitherallleftorallright--isexpectedinanyextraterrestriallifeusingbuildingblocksthathave
mirror-imageversionsbecauseamixturewouldcomplicatebiochemistry.
AUreycomponentcalledthemicro-capillaryelectrophoresisunithasthecriticaljobofseparatingdifferenttypesoforganiccompoundsfromoneanotherforidentification,including
separationofmirror-imageaminoacidsfromeachother.ThedeviceforsendingtoMarswillbe
asmallversionincorporatingthisdetectiontechnology,whichisalreadyinuseforbiomedical
proceduressuchaslaw-enforcementDNAtestsandcheckingforhazardousmicrobes.
Sourceofinformation:NASAJetPropulsionLaborator
Fig05(below)
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RISKASSESSMENT Overallrisk(provided
safetyproceduresare
followed)=LOWSubstance Hazard Comment
Food
bBIOHAZARDUncookedsamplesoffoodmaybecontaminatedwithmicrobes.)
Somepeopleareallergictosomefoods,especiallypeanuts.
Benedict’ssolutionUsedtotestfor
reducingsugars.
LOWHAZARD Containsslightly-alkalinecoppersulfatesolution,butatconcentrations
whichpresentonlyaLOWHAZARD.Someriskofspittingifheatingtest
tubes.
EthanolUsedtotestforfats(lipids).
FHIGHLYFLAMMABLE
IfBunsenburnersarebeingusednearbyforotherfoodtests,thereisa
seriousfirerisk.
IodinesolutionUsedtotestforstarch.
LOWHAZARDWeareyeprotection,thoughthesolutioninwaterisdiluteandonly
presentsaLOWHAZARD.
BiurettestUsedtotestforproteins.
IIRRITANTUsesverydilutecoppersulfatesolution(LOWHAZARD)andsodium
hydroxidesolutionwhichisIRRITANT(notCORROSIVE)ifkeptdilute(below
0.5M).
Additionalcomments:
• Donottastefoodsinlaboratories;avoidusingproductscontainingpeanutsetcifthereisaknownallergy.Wear
eyeprotectionandusethesmallestpossibleamountsofchemicals.Heatwithawaterbath.Donotuseethanoliftherearenakedflamesnearby.
• Providedthatconcentrationsofreagentsarekeptasrecommendedaboveandthatawaterbathisusedforheating,therisk
forthesetestsislow.Themainhazardcomesfromethanolwhichishighlyflammable–nakedflamesshouldnotbeallowed
anywherenearethanolforthisreason.
• Eyeprotectionshouldbewornthroughoutallofthepracticalproceduresandlatexglovesarealsodesirabletopreventskin
irritationfromthereagentsused.
Incaseofaccident/incident:
••••••
IntheeyeSwallowedSpiltonskinorclothingClothingcatchesfireOtherethanolfiresSpiltonfloor,bench,etc
Floodtheeyewithgently-runningtapwaterfor10minutes.Seeadoctor.
Donomorethanwashoutthemouthwithwater.Donotinducevomiting.Sipsofwatermayhelpcool
thethroatandhelpkeeptheairwayopen.Seeadoctor.
Removecontaminatedclothing.Drenchtheskinwithplentyofwater.Ifalargeareaisaffectedor
blisteringoccurs,seeadoctor.
Smotherflamesonclothingorskinwithafireblanketorothermaterial.Coolanyburntskinwith
gently-runningtapwaterfor10minutes.Allowfiresinsinks,etctoburnout.
Firesatthetopoftesttubes,beakers,etcshouldbesmoth-eredwithadampclothorheat-proofmatif
thiscanbedonesafely.Forsmallamounts,useadampcloth.Rinsewell.Forlargeramounts,coverwith
mineralabs-orbent(eg,catlitter)andscoopintoabucket.Neutralisealkaliwithcitricacid.Rinsewith
water.
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ImageReferences:
Figure01-ASTROBIOLOGYMagazine(2012)AlienSafari;AlienvsPredator[WWW]Credit:
NASA/JPL/MalinSpaceSciencesSystemAvailablefrom:http://www.astrobio.net/debate/3062/alien-vs-predator[03/12/2012]
Figure02-THEENCYCLOPEDIAOFSCIENCE;ASTROBIOLOGY(dateunknown)VikingLabeledRelease(LR)experiment[WWW]http://www.daviddarling.info/encyclopedia/V/VikingLR.html
[03/12/2012]
Figure03-KIMBALL,J(May2012)Is(Was?)ThereLifeonMars?[WWW]
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Mars.html[03/12/2012]
Figure04-KIMBALL,J(May2012)Is(Was?)ThereLifeonMars?[WWW]
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Mars.html[03/12/2012]
Figure05-DLR;PRESSRELEASES(2009)PressReleases2009[WWW]Credit:ESA-AOES
Medialabhttp://www.dlr.de/en/desktopdefault.aspx/tabid-5105/8598_read-20530/gallery-
1/gallery_read-Image.1.11546/[03/12/2012]
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WeAreAliens!–Classroomactivity2(Biology)
MartianDeathRays...
Background:
CouldtherebelifeonMars?Perhapsso,althoughthehighintensityofUVlightmeansthatitisunlikelytobefoundonthesurface.Thefollowingexperimentwilldemonstratewhythisisthecase.
BacterialcellscontainDNAjustasplantandanimalcellsdo,andtheDNAincellsisdamagedbyUVradiation.OnEarthwehaveouratmosphere,particularlytheozonetoprotectourDNAfromharmfulUVradiation.Marshoweverhasnoozonelayerandsoitssurfaceisnotprotectedfromthisradiation.FollowthemethodbelowtoseetheeffectofUVlightoncellularlifeforms(bacteria).TheexperimentismainlyaimedatKS5,butcanbeadaptedtolowerkeystagesasrequired.
Curriculumareascovered:
• Microbiology• Cellbiology• Aseptictechnique• HowScienceWorks–collecting,analysing(viastatisticaltests)andinterpretingdata
Equipmentlist:
• UVcleaningdevice• 4nutrientagarplatespergroup• 4sterileswabspergroup• 1dirtyplace–computerkeyboardsareidealastheyaredifficulttoclean• Tape• Markerpen• Accesstoanincubator
Method:
1. Takeasterileswabofanareaonthekeyboardthatisoftenused.2. Wipetheswabcarefullyacrosstheagarplatebeingcarefulnottodisruptthesurfaceofthe
agar.3. Replacethelid,tapeattwopointsandlabelattheedgewithamarkerpen.4. Repeatsteps1-3foranotherareaonthekeyboard.5. UsingtheUVcleaningdevice,cleanthekeyboardbyholdingitabout2cmawayfromthe
surfacefor10-20secondsineacharea.6. Repeatsteps1-4forthesametwoareasonthekeyboard.7. Incubatetheagarplatesat20⁰Cfor48hours.
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Discussion:
Thepicturesbelowshowthesamplestakenbeforethekeyboardwascleaned.
Thepicturesbelowshowthesamplestakenafterthekeyboardwascleaned.
UVlighthassufficientenergytobreakapartorganicmolecules,includingDNA.BecauseDNAisdamagedbyUVlight,cellsarepreventedfromreproducingandthisreducesthecolonycountforareasthathavereceivedUVtreatment.
Youcancountthenumberofcoloniesoneachplatebydividingitintosectorsusingamarkerpen.Ahandlenscanthenbeusedtoscrutiniseeachsectorforbacterialcoloniesandthemarkerpenusedtostrikethrougheachcolonyasitiscounted.CountthenumberofcoloniesvisiblebeforeandafterUVexposure.
Onceyouhaveobtainedsomenumericaldata,youshouldthenconsiderrepeatingtheinvestigationseveraltimes(poolingclassroomdata)andanalysingtheresultsusinganappropriatestatisticaltest(e.g.95%confidencelimitsand2xstandarderror)–thiswilldeterminewhetherthereisanysignificantdifferenceinthenumberofbacterialcoloniesbeforeandafterUVexposure.
Figures1-4–above
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Backgroundinformation-Mars
LIFEONMARS?THEVIKINGLABELEDRELEASEEXPERIMENT*
GILBERTV.LEVINandPATRICIAANNSTRAAT
BiosphericsIncorporated,Rockville,MD20852,U.S.A.1977
Vikingradiorespirometry("LabeledRelease"[LR])experimentsconductedonsurfacematerialobtainedattwositesonMarshaveproducedresultswhichonEarthwouldclearlyestablishthepresenceofmicrobialactivityinthesoil.However,twofactorsonMarskeepthequestionopen.First,theintenseUVfluxstrikingMarshasgivenrisetoseveraltheoriespostulatingtheproductionofhighlyoxidativecompounds.Suchcompoundsmightberesponsiblefortheobservedresults.Second,themolecularanalysisexperimenthasnotfoundorganicmatterintheMarssurfacematerial,andtherefore,doesnotsupportthepresenceoforganisms.However,sensitivitylimitationsoftheorganicanalysisinstrumentcouldpermitasmanyasonemillionterrestrialtypebacteriatogoundetected.
TerrestrialexperimentswithUVirradiationofMarsAnalogSoildidnotproduceMarstypeLRresults.Gammairradiationofsilicageldidproducepositiveresults,butnotmimickingthoseonMars.Thelifequestionremainsopen.
TheVikingLabeledRelease(LR)Experiment(LevinandStraat,1976)hasobtainedresultsconsistentwiththepresenceofmicrobiallifeonMars.IntheLRexperiment,adiluteaqueoussolutionofsimple,uniformlylabeledcarboncompoundsisappliedtoasampleofsoilinasealedtestcell.Theheadspaceatmosphereinthechamberismonitoredfortheappearanceofradioactivegas.Apositiveresponseistestedforbiologicallabilitybyrepeatingtheexperimentafterheatingaduplicateportionofthesampleto160°Ctosterilizeit.Testsconductedwithterrestrialsoilscontainingviablemicroorganismsinvariablyproducepositiveresponsesand,underfavorableenvironmentalconditions,gasevolutionplottedasafunctionoftimerevealstheclassicmicrobialgrowthcurvewithlag,exponentialandstationaryphasesclearlydefined.
PriortoVikinglaunch,acarefullycontrolledLRexperimentwasconductedinasisterinstrumenttothoseflowntoMars.Theatmosphericcompositionandpressure,thewatervaporcontentandthetemperatureofthetestcellcontainingaCaliforniasoilwitharichmicrobialpopulationwerecontrolledtosimulateconditionsanticipatedwithinthetestcellonMars.Theresultsoftheactiveand
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controlcyclesarepresentedinFig.1asthecumulativeevolutionofradioactivegasoverMartiansols(1sol=24.6h).AtthepointindicatedinFig.1,asecondaliquotoftheradioactivenutrientwasinjectedontothesoilwhichimmediatelyproducedafreshradiorespirometricresponse.Inthecontrolsequence,aduplicateportionofthissoilwasheatedto160°Cfor3handpermittedtocoolpriortonutrientinjection.AsseeninFig.1,essentiallynogasevolved.
*PresentedattheFifthInternationalConferenceontheOriginofLife,Kyoto,Japan,April5-10,1977.
Asofthiswriting,twoactivecyclesoftheLRexperimenthavebeenperformedateachofthetwoMarslandersitessome4000milesapart.Allfouractivecycleshaveyieldedpositive,andsurprisinglysimilar,resultsupontheirfirstinjections.However,ratherthanproducingadditionalgas,subsequentinjectionsineachcyclehaveallproduceddiminutionsintheaccumulatedquantityofradioactivegasalreadyevolved.Typicalresults,thoseforVL-1,Cycle3,arepresentedinFig.2.Duringthislongincubation,atotalofthreenutrientinjectionsweremade.Thefirstproducedastrongpositiveresponse,butthesecondandthirdwerefollowedbyadeclineintheamountofradioactivegasevolvedbythefirst,indicatingadrasticchangeorlossoftheactiveagentinthesoilsometimepriortothesecondinjection.
Figure5–below
5
Fig.3summarizesthecurrentfirstinjectiondataatVikingLander1.TwoactivecyclesandonecontrolcyclearepresentedonascalecomparabletothatusedinFig.1topermitreadycomparisonoftheMarsandEarthresults.Similarly,thecurrentfirstinjectionresultsatVikingLander2aresummarizedinFig.4tothesamescale.
ComparisonoftheresultsfromallfourMarsactivecyclestotheresultsobtainedfromterrestrialsoilundersimulatedMarsconditions,Fig.1,showsthat,withrespecttothefirstinjection,theresponsesaresimilarinmagnitudeoverthetimespanmeasured.TheshapesofthefirstinjectionportionsoftheactivecyclecurvesonMarsandonEarthdifferinthattheMarsresponsesapproachplateauearlierinthetimecourse.Nonetheless,thesimilarityamongallfouractivetestsonMarsisstriking.Thisisdespitethefactthatoneoftheexperiments,VL-1,Cycle3,wasconductedonasampleobtainedbymovingarockwhichhadprotecteditfromUVradiationformanythousandsofyears.Itisinterestingtonotethat,whiletheMarsdatafailtoshowevidenceofexponentialgasevolution,fromwhichgrowthmightbeinferred,neitherdotheterrestrialmicroorganismsundertheimposedMartianconditions.The160°Cpreheatedcontrolsamplesproducedsimilar,lowlevelresultsonEarthandMars.
AlthoughtheLRresultsareconsistentwiththepresenceoflifeonMars,otherfactorspreventtheindicatedconclusionatthistime.ExperimentersfortheothertwoVikinglifedetectionexperiments,PyrolyticReleaseandGasExchange,havestated(Horowitz,1977)thattheirexperimentshaveproducednoconfirming
Figure6–below
Figure7–below
6
evidence.Also,theMolecularAnalysisExperiment(Biemann,1977)hasfoundnoevidenceoforganicmatterintheMartiansurfacematerial.However,thesensitivitythresholdforthisexperimentcouldpermit106terrestrialtypebacteriatogoundetectedprovidedtheywerenotaccompaniedbyorganicdebrismanytimestheirownmassasisgenerally,ifnotalways,thecaseinterrestrialsoils(Biemann,1977).
VarioushypothesesthatexoticMartianconditions,principallythehighUVflux,couldproduceactivestatesorhighlyoxidativecompoundsintheMarssurfacematerialledtospeculations(LevinandStraat,1976)thatphysicalorchemicalprocessesmightfalselyindicatethepresenceoflife.TheearlyreceiptofapositiveactivecycleandanegativecontrolfromtheLRexperimentonMarsintensifiedspeculationonthesehypotheses.
Withintheseverelimitationsofthespacecraftinstrument,theauthorsattemptedvariationsintheLRexperimentsoonafterthepositiveresultsonMarsinanattempttoresolvethedilemma.Thecontrolpretreatmenttemperaturewasdroppedto50°C(actuallyapprox.51.5°C)(LevinandStraat,inpress)onthetheorythatmicroorganismsonMarswouldbeseverelydamagedevenat50°C,atemperaturebeyondtheirexperience,butthatphysicalorchemicalphenomenoncausingthebreakdownofthenutrientwasfarlesslikelytobedegradedbythisrelativelymildtreatment.TheresultsshowninFig.4forVL-2,Cycle2,indicatesevereattenuationoftheLRreaction.However,thestrangekineticsarousedsuspicionthattheLRinstrumenthadmalfunctioned.Aseriesofengineeringtestsremotelyconductedontheinstrumentfailedtodetectanymalfunctionandasubsequentactivecycle,Cycle3,Fig.4,produceda"normal"activeLRcurveforMars.Nonetheless,thesignificanceofthereducedresponsefollowingheatingto50°Crequiredthattheeffectbeconfirmed.Accordingly,Cycle4,inwhichafreshsamplewaspreheatedtoonly46°C(LevinandStraat,inpress),wasconducted.TheresultsconfirmedthemajorreductionintheLRresponseachievedbymildheatingalthough,thistime,thestrangekineticswerenotevident.(Therelativelyminorfluctuationsintheradioactivitycurvescorrelatewithtemperaturechangesimposedonthetestcellbythelander'stemperaturecontrolmechanismasitreactstothediurnaltemperatureswingonMars.)
7
SimultaneouswiththeattemptstoresolvethelifeissueonMars,theauthorsundertookaseriesoflaboratorysimulationexperiments.Theexperimentsreportedhereinwerecomplementarytothe"undertherock"experimentconductedonMarsinthattheysoughttodeterminewhetherexposureofsoiltoradiationmightmimictheLRresults.A"worstcase"testofthetheoriesthationizingradiationofoxygen-richmineralsmightactivatesitescapableofdegradingoneormoreoftheorganicsubstrates(LevinandStraat,1976)comprisingtheLRmediumwaseffectedthroughtheirradiationofpuresilicagelwithgammaraysemittedfromacobalt-60source.SilicagelwasselectedbecauseitwasalmostpureSiO2forwhichconsiderableevidencehasbeencited(Zelleretal.,1970;Zeller,1976)concerningitsactivationbysolarfluxprotonsorharder,ionizingradiation.Moreover,SiO2,intheformofsilicagel,wouldprovideenormoussurfaceareatocontacttheLRmedium.Davisonsilicagel,grade950*wasselectedforuse.Itstypicalchemicalanalysisonapercentdryweightbasisis:99.85%SiO2;ironasFe2O3,0.005%;sodiumasNa2O,0.004%;calciumasCaO,0.018%;titaniumasTiO2,0.058%;andzirconiumasZrO2,0.030%.Surfaceareaisgivenas700m2/g.Maximumtotalvolatilecontentat1750°F(954.4°C)is6.5%.
Sampleswerepreparedinthefollowingmanner.Samples(0.5g)ofthesilicagelwereplacedintoeither7mlglassampoulesor1.5mlquartzampoules.Allampouleswerethenheattreatedat160°Cforthreeormorehoursundercontinuouslymaintainedvacuum.OneatmosphereofC02wasintroduceduponcoolingandtheampoulesweresealed.Theampouleswerethenheatsterilizedat160°Cforaminimumof2.5h.Theglassampouleswerethenpackedindryiceandreceived0.83Mradofcobalt-60gammairradiation.TheyweremaintainedindryiceduringshipmenttotheBiosphericslaboratorywheretheywereimmediatelyplacedinacoldroommaintainedat4°C.Thepurposeofthecoldtreatmentwastominimizehypothesized(DanielliandPlumb)temperatureinducedannealingsofanydisjunctionsordefectsinthesilicagelproducedbytheirradiation.
Figure8–below
8
Thesilicagelinquartzampouleswastreatedinthesamemannerasjustdescribedfortheglassampoules.ThesesampleswerethenSubjectedtoUVirradiation.TheUVsourceconsistedof10Rayonett,2,537Ålamps(15wattsperlamp)arrangedina10inchdiametercircle.Theampouleswereplacedontheirsidesformaximumsurfaceexposureofthesilicagelandwerestationedatthebottomcenterofthecircleoflamps.Theywereirradiatedcontinuouslyfor14daysatapprox.25°C.Thephysicalconstraintsmadeitimpossibletomaintainthesesamplesindryiceduringirradiation.However,immediatelyafterirradiation,theywerepackedindryicewheretheyweremaintainedduringshipmenttoBiosphericsandintroductionintothe4°Ccoldroom.
*DavisonSilicaGelSelectiveAdsorptionGrades,TechnicalBulletin,AdsorbentsDepartment,DavisonChemicalGradeCo.
PriortoconductingLRexperiments,oneseteachofduplicateampoulesexposedtogammaandUVradiationweregiventhefollowingrespectiveheattreatmentsfor3h:4°C,50°C,and160°C.AllheatedsampleswerethenreturnedtothecoldroomwhereLabeledReleaseexperimentswereconducted.Eachampoulewasbrokenandthesilicagelcontentstransferredasepticallytosterilizedglassvialsof25cccapacity.0.1mlofVMlflight-typeLabeledReleasemediumwaspipettedontoeachportionofsilicagel.Absorbentpads(20mmdiameter,No.470,SchleicherandSchuell)placedinsidetheglassvialscrewcap,werequicklymoistenedwithtwodropsofafreshlyprepared,saturatedsolutionofBa(OH)2.Thesecapswereimmediatelyscrewedontocollectevolved14CO2.Incubationwasmaintainedatthe4°Ctemperatureoftheroom.Asacontrolagainstcontaminationandacheckonthenoiselevelofthemedium,duplicateportionsofthesterileVMlalonewereincubated.Atintervalsrangingfrom15mininitiallytoamaximumofonceperdaytowardtheendoftheexperiment,theglassvialcapswereremovedandimmediatelyreplacedwithfreshonescontainingBa(OH)2moistenedpads.Allpadsexposedforthecollectionofradioactive14CO2weretransferredtoplanchets,driedandcountedforradioactivityinagasflowcounter.
Theresults,adjustedforinstrumentsensitivityandscaledtopermitdirectcomparisonoftheMarsandEarthresults,arepresentedinFig.5.Fig.5Apresentsthedataonevolvedradioactivityfromnon-irradiatedsilicagelsubjectedtothevariousheattreatments.AllsamplesofsilicagelevolvedanamountofgaswithinthetypicalsterilecontrolrangefortheLabeledReleaseexperiment.Nosignificantdifferencesareattributedtotheheattreatments.Theresultsofthegammairradiatedsamples,however,Fig.5B,showthatgammairradiationhasapronouncedeffectonthenon-biologicalactivityofthesilicagel.ThesamplesapproachtheactivitylevelsseenforterrestrialorganismsunderMartianconditionsinFig.1andfortheMarsdatapresentedinFigs.3and4.Allfigureshavebeendrawntoapproximatelythesamescaletofacilitatevisualcomparison.The160°Cheatingofthesilicagelsignificantlyattenuateditsresponse.However,themagnitudeoftheeffectdoesnotapproachthatonMarswherethe160°Cpreheattreatmentvirtuallyeradicatedtheresponse.Althoughtheduplicatesforthenon-heatedsamplesandthesamplesheatedto50°Coverlap,theremaybeaslight(approx.10%)reductioninsilicagelreactivityfollowingheatingat50°C.Again,however,theeffectdoesnotapproachthemagnitudeoftheresponse
9
attenuationcausedbyheatingtheMarssampleto50°C.
ResponsesfromtheUVirradiatedsamplesarepresentedinFig.5C.AllareessentiallywithintherangeofcontrolresponsescharacterizingheatsterilizedsoilstestedintheLRexperiment.
Upontheconclusionoftheexperiment,0.5mlofdistilledwater(pH6.3,unbuffered)wasthenaddedtoeachremainingportionofthesampleanditspHdetermined.TheresultsarepresentedinTable1.Theremaininghalfofeachsamplewasplatedontrypticase-soyagartocheckforsterility.Thematerialwasshakenoutoftheglassvialinwhichithadbeenincubatedanddispersedontheagarplatebyagitatingtheplate.Afterincubatingatroomtemperatureforfourdays,allplateswerenegativeforcolonies.
Figure9–below
Figure10–below
10
Anidenticalsetofexperimentswassimultaneouslyperformedonaportionof
theMarsanalogsoil(Clarketal.)preparedbytheVikingInorganicAnalysisTeam
inaccordancewithX-rayfluorescenceanalysesperformedonMars.The
compositionoftheMarsanalogsoilispresentedinTable2.Theresultsofthis
experimentarepresentedinFig.6.Initsnon-irradiatedcondition,theMars
analogsoil,Fig.6,producedgasevolutioninsignificantlygreaterquantitiesthan
didnon-irradiatedsilicagel.Thereisessentiallynodifferencebetweenthenon-
heatedMarsanalogsoilsampleandthesamplepreheatedto50°C.The
magnitudeoftheresponsesapproach50%ofthoseobtainedfromMars.The
apparentdiminutioninresponseofthesamplepreheatedto160°Cmaybean
artifactinthattheveryearlyportionofthecurveshowsthisresponseexceeding
theotherspriortoasharpbreakintheslopewhichmayreflectagasleakor
otherlossofthatday'scollection.Fig.6BshowsthatexposureoftheMarsanalog
soiltogammairradiationdidnotincreaseitsreactivitywithVM1.Norisany
significantattenuationinresponseattributabletotheheattreatmentindicated.
However,allresponsesareabovenormalcontrollevelsfortypicalsterilizedsoils
examinedintheLRexperiment.UVirradiationoftheMarsanalogsoil,asshown
inFig.6C,resultedinadiminutioninallresponsesproducingresultsat,ornear,
thenormalsterilizedsoilcontrollevels.
Figure11–Pleaseseebelow
11
ThepHofeachportionoftheMarsanalogsoilwasdeterminedinthesamemannerasforthesilicagelsamples.TheresultsareshowninTable3.SterilitytestswereperformedonallportionsofMarsanalogsoilattheterminationoftheLRexperimentidenticallyasdescribedforthesilicagel.Allplateswerenegative.
Discussion
ThegammaradiationlevelsinthevicinitiesoftheVikingspacecraftonMarshavenotyetbeenmeasured.However,theymustbelowinthatthebackgroundlevelsmonitoredbytheLRradioactivitydetectorscorrespondextremelycloselytothegammalevelsanticipatedfromtheradioisotopicthermoelectricgenerators(RTGs)carriedoutbytheVikinglanders.Anyexternalgammacontributiontothebackgroundreadingsmust,therefore,beminor.ThebackgroundlevelfortheflightLabeledReleaseinstrumentonEarth,withouttheinfluenceoftheRTGs,isapprox.10cpm.Thus,the0.83MradgammadoseadministeredtothesilicagelandMarsanalogsoilsamplesrepresentsanaccumulateddoseoveralongperiodoftimeonMars.ThiscombinationofaseveregammadoseadministeredtoasubstancehighlysusceptibletosustainingdefectsdidcauseasignificantreleaseofradioactivegasfromtheVMlapproximatingthatoftheLRMarsresponseinmagnitude,butnotinkinetics.PretreatmentoftheirradiatedsilicagelatelevatedtemperaturesresultedindecreasedLabeledReleaseactivityfollowing
Figure12–Pleaseseebelow
Figure13–Pleaseseebelow
12
nutrientinjection.ThisisevocativeoftheLRMarsdata,butthetemperatureeffectonsilicagelisgreatlymutedwithrespecttothatonMars.
TheUVfluxincidenttothesurfaceofMarshasbeenestimated(Glasston,1968)at2X10-4Wcm-2.Currentestimates(Shorthill,pers.comm.)indicatethatonly50%ofthisUVfluxreachestheMartiansurface,yieldingafluxatthesurfaceof10-4wattsor103ergssec-1.BasedonanestimatedUVdoseof10,000µWcm-2,or105ergssec-1,incidenttothesamplesfromtheirradiationarray,theUVirradiationgiventhesamplesexceedsthatonMars,byapproximatelytwoordersofmagnitude.TheLRresponseproducedbyUVirradiatedMarsanalogsoilisevenlessthanthatproducedbynon-irradiatedMarsanalogsoil.Thus,theresultsofthesetwotestsoftheMarsanalogsoilmakeitunlikely,iftheMarsanalogsoilisafaithfulrepresentation,thatultravioletirradiationisresponsiblefortheresultsobtainedonMarsintheLRinstrument.Whilethepositiveresponseofthenon-irradiatedMarsanalogsoilanditspossiblepretreatmenttemperaturedependencyareofinterest,thefactthatitscapabilitytoproducegasfromVMlisUV-labilemakesitanunlikelyexplanationoftheMarsresults.Theanalogsoiltestedcontainedalpha-Fe2O3.Recently,ithasbeensuggested(Oyama,VikingBiologyTeam)thatepsilon-Fe2O3mightbetheformonMarsandthatitmightreactwithorganiccompounds.Accordingly,theVikingInorganicAnalysisTeamispresentlypreparinganotherMarsanalogsoil,similartothefirst,butcontainingepsilon-Fe2O3.TheauthorsplantotestthismaterialforpossibleactivityintheLRexperiment.
Conclusions
1. TheVikingLabeledReleaseExperimenthasproducedevidenceforlifeonMars.However,non-terrestrialsoilchemistrymaybemimickingabiologicalresponse.Allhypothesesrequirefurtherstudybeforeaconclusioncanbereached.
2. IntensegammairradiationofsilicagelcausesevolutionofgaswhentheLRVMlmediumisappliedtoit.TheamountofgasevolvedapproachesthatobservedintheLRexperimentonMars.However,whilesomepretreatmenttemperaturedependencywasobservedinthesilicagel,theeffectsarenotasgreatasthoseobservedintheMarsexperiments.This"worstcase"testisextremeinthatthegammalevelsonMarsdonotapproachthedosageappliedinthetest.However,thereactionisofsufficientinterestthatitwillbeexploredfurtheranditspossiblerelevancy,totheLRMarsresultsstudied,perhapsasananalogoflong-termexposuretothesolarwind.
3. NosignificanteffectwasobservedintheLRexperimentwhensilicagelwasirradiatedbyUVlight.
4. Non-irradiatedMarsanalogsoilproducesaresponseintheLRexperiment.Theresponsemayshowsomeslightpretreatmenttemperaturedependency,butnotofthemagnitudeobservedonMars.
5. GammairradiationoftheMarsanalogsoilhadnoapparenteffectintheLRexperiment.
6. UVirradiationoftheMarsanalogsoilreducedtheLRresponsetowellwithinthosenormallyobservedfromsterilizedsoils.ItisthusunlikelythattheMars
13
resultscanbeattributedtoafactorintheMarsanalogsoil.
Conclusions3and6inconjunctionwiththeLRMarsdataobtainedfromthe"undertherock"sampletendtoeliminateUVradiationascausativeoftheLabeledReleaseresponse.
UpdatedversionsoftheMarsanalogsoil(includingepsilon-Fe2O3)willbetestedwithandwithoutgammairradiationintheLabeledReleaseTestStandardsModule(TSM)(LevinandStraat,1976)wheretheycanbemaintainedundersimulatedMarsconditionsthroughouttheincubationperiod.TheeffectofadditionalinjectionsofnutrientcanbestudiedintheTSMforcomparisonwiththeMarsresults.
14
RISKASSESSMENT Overallrisk(providedsafetyproceduresarefollowed)=LOW
Substance Hazard CommentBacterialcolonies
BIOHAZARD
Agarplateswillcontainnumerousbacterialcoloniesathighconcentrations.Theymustremainclosedatalltimes,andsealedviatwostripsofsellotapeeithersideofthedish–incubateatatemperaturenohigherthan20°C.Cottonswabsusedtosampledifferentareasshouldbedisposedofinthedisinfectantsolutionprovided.Agarplatesshouldbedisposedofinanautoclaveafteruse.
UVlight HAZARD UVlightisdamagingtoskincellsandalsocellsoftheretina.ExposuretoUVlightfromthesterilisingprobeshouldbepreventedatalltimes
Cottonswab
LOWHAZRAD
Possiblyharbourspathogenicmicrobesafterbeingusedforsampling.However,theconcentrationsofmicrobeswilllikelybeatalowlevelpriortoincubationonagar.Cottonswabshouldbedisposedofusingthesterilesolutionprovided.
Additionalcomments:
• Washhandsthoroughlybeforeandafterprocedureandwearlatexglovesifavailable
• Agarplatesshouldbesealedwithonlytwostripsofsellotapeateithersideoftheplate,topreventanaerobicconditionsdevelopingandpathogenicbacteriabeinggrown.
• Undernocircumstancesshouldtheagarplatesbeopenedonceincubationhasbegun.
• Agarplatesmustbedisposedofusinganautoclaveattheendoftheinvestigation
• EnsurethattheUVprobeisswitchedoffwhennotinusetopreventaccidentalexposuretoUVlight
Incaseofaccident/incident:
••
ExposuretoUVlightExposuretobacterialcolonies
Dependingonthelengthoftimethattheexposurewasfor,seekmedicaladvice.Ifskincontact,immediatelywashaffectedareawithsoapandwarmwater.Antisepticsolutionsorwipesmayalsobeusedtocleanaffectedarea.Re-sealanyagarplatethathasbecomeexposedandarrangefordisposalviaautoclave.Seekmedicaladvice.
15
ImageReferences:
Figures1-4-OwnedbyChristopherCarr–AuthorofClassroomActivity#2
Figure5-GILBERTV.LEVINandPATRICIAANNSTRAAT(1977)LIFEONMARS?THEVIKINGLABELEDRELEASEEXPERIMENT*[WWW]Copyright:Elsevier/North-HollandScientificPublishers,Ltd.http://mars.spherix.com/lifemars/lifemars.htm[03/12/2012]
Figure6-GILBERTV.LEVINandPATRICIAANNSTRAAT(1977)LIFEONMARS?THEVIKINGLABELEDRELEASEEXPERIMENT*[WWW]Copyright:Elsevier/North-HollandScientificPublishers,Ltd.http://mars.spherix.com/lifemars/lifemars.htm[03/12/2012]
Figure7-GILBERTV.LEVINandPATRICIAANNSTRAAT(1977)LIFEONMARS?THEVIKINGLABELEDRELEASEEXPERIMENT*[WWW]Copyright:Elsevier/North-HollandScientificPublishers,Ltd.http://mars.spherix.com/lifemars/lifemars.htm[03/12/2012]
Figure8-GILBERTV.LEVINandPATRICIAANNSTRAAT(1977)LIFEONMARS?THEVIKINGLABELEDRELEASEEXPERIMENT*[WWW]Copyright:Elsevier/North-HollandScientificPublishers,Ltd.http://mars.spherix.com/lifemars/lifemars.htm[03/12/2012]
Figure9-GILBERTV.LEVINandPATRICIAANNSTRAAT(1977)LIFEONMARS?THEVIKINGLABELEDRELEASEEXPERIMENT*[WWW]Copyright:Elsevier/North-HollandScientificPublishers,Ltd.http://mars.spherix.com/lifemars/lifemars.htm[03/12/2012]
Figure10-GILBERTV.LEVINandPATRICIAANNSTRAAT(1977)LIFEONMARS?THEVIKINGLABELEDRELEASEEXPERIMENT*[WWW]Copyright:Elsevier/North-HollandScientificPublishers,Ltd.http://mars.spherix.com/lifemars/lifemars.htm[03/12/2012]
Figure11-GILBERTV.LEVINandPATRICIAANNSTRAAT(1977)LIFEONMARS?THEVIKINGLABELEDRELEASEEXPERIMENT*[WWW]Copyright:Elsevier/North-HollandScientificPublishers,Ltd.http://mars.spherix.com/lifemars/lifemars.htm[03/12/2012]
Figure12-GILBERTV.LEVINandPATRICIAANNSTRAAT(1977)LIFEONMARS?THEVIKINGLABELEDRELEASEEXPERIMENT*[WWW]Copyright:Elsevier/North-HollandScientificPublishers,Ltd.http://mars.spherix.com/lifemars/lifemars.htm[03/12/2012]
Figure13-GILBERTV.LEVINandPATRICIAANNSTRAAT(1977)LIFEONMARS?THEVIKINGLABELEDRELEASEEXPERIMENT*[WWW]Copyright:Elsevier/North-HollandScientificPublishers,Ltd.http://mars.spherix.com/lifemars/lifemars.htm[03/12/2012]
1
WeAreAliens!–Classroomactivity3(Biology)
What’syourlimit?
Background:
PhysicalconditionsonotherplanetsandmoonsareunlikelytobewithinthesamerangesasthatexperiencedbyEarth.However,asignificantdegreeofvariancefrom‘ideal’rangesmaybetolerableforasmallnumberoforganismsknownasextremophiles.Theseareorganismswhichcanwithstand(andeventhrive)inextremeenvironmentsonEarth,includingthoseoftemperature,pHandsalinity.Thisinvestigationlooksattheeffectsofsubjectingalivingorganism(yeast)tosomeextremeconditionsandobservingchangestoratesofreaction–indicatingtherangesatwhichitcansurvive.TheinvestigationisaimedmainlyattheupperendofKS3orKS4.However,itispossibletoadapttheinvestigationintoaformmoresuitableforKS5ifrequired.
Curriculumareascovered:
• Respiration• Cellbiology• Enzymes&ratesofreaction• HowScienceWorks–collecting,analysing(viastatisticaltests)andinterpretingdata
Equipmentlist:
• Emptywaterbottles(250ml)• Balloons• Driedyeastgranules• Glucose• Whitevinegar• Wateratdifferenttemperatures–hot,warmandcold• Markerpen• AndrewsSalts(dissolveinwatertocreateanalkalinesolution)• Salt(tocreatesolutionsofdifferentsalinities)
Method:
Theinvestigationinvolvessubjectingsomepre-preparedyeastsamplestodifferentconditionsoftemperature,pHandsalinity.Amixtureofyeastandglucoseishydratedwithwaterinsideabottle,withaballoonplacedonthetoptogaugetheamountofcarbondioxideproduced,andhenceactivityoftheyeast.Thetasksheetsthatfollowgivefulldetailsofthemaininvestigationsbutitisimportanttonotethefollowingdetailsregardingtheinitialsetupofapparatus:
• Youwillneedtofirstsetupseveralbottleseachcontainingtwoteaspoonsofglucoseandfourteaspoonsofyeast.Eachgroupintheclasswillneedthreebottles.
• Thebottlescanbepre-markedwithlinesthatshowapproximatevolumesofwaterorothersolutionsrequired.
• Theyeast,glucoseandwatermustbefirmlyshakenforabout30secondsbeforetheinvestigationcommences.
2
• Theresultsoftheinvestigationarenotinstantaneous–youwillneedtoplanforatleast30minuteswhileballoonsbecomeinflatedbycarbondioxideproducedfromtheyeast.Thiswouldbeagoodtimeforstudentstoanswerquestionsonthetasksheetsandfeedbacktheirpredictionstothewholeclass.
• Theinvestigationhasplentyofscopefordevelopments,refinementsandimprovements–studentsshouldbeencouragedtocarryoutanevaluationaftertheinvestigationisover.
Discussion:
Afterabout30minuteshaselapsed,askeachgrouptocometothefrontoftheclassandholdtheirbottlesup(withpartiallyinflatedballoons).Askeachgrouptodescribethedifferencesbetweentherelativeamountsofballooninflationandthenexplainusingtheirknowledgeofenzymes,cells,ratesofreactionand/orosmosis:
Temperature–warmtemperaturewillshowgreatestrateofinflation,duetoenzymesinyeastbeingclosesttotheiroptimumtemperature.Coldtemperatureswillshowlittleinflationduetoreducedkineticenergyandhenceratesofreaction.Hottemperatureswillshowlittleinflationduetodenaturationofsomeenzymes.
pH–theenzymesinyeastgenerallyhaveoptimumvaluesclosetopH7.Therewillbelittleinflationinacidicoralkalineconditionsduetothedenaturationoftheseenzymes.
Salinity–theadditionofsaltlowersthewaterpotentialofthesolutioninthebottle.Themoresaltadded,thelowerthewaterpotentialbecomesresultinginwaterlossfromyeastcells(andtheirsubsequentdeath).Inflationoftheballoonswilllikelydiminishasmoreandmoresaltisadded.
3
Meettherecordbreakers...
Finishthelessonwithadiscussionontheextremeconditionsthatlifehasbeenknowntowithstand:
Notethatalltheseorganismsarebacterial–morecomplexlifeformsaresimplytoocomplicatedtowithstandtheseenvironments(themorecomplexsomethingis,themorethereistogowrong!).Findinglifeexistinginextremeenvironmentsmaybepossible,butitisunlikelytoanythingotherthansimplemicro-organisms.
4
FurtherexamplesofEarthlyextremophiles
Cold–TheMcMurdoDryValleysinAntarcticaaresomeofthecoldest,driestdesertsonEarth,withaverageannualtemperaturesof-20oC(-4oF)andlessthan10centimetres(4inches)ofprecipitationayear.Scientistshavefoundbacteriainliquidwaterpocketsembeddedabouttwelvefeetdeepin“solid”lakeice.Someofthesebacteriausechemicalnutrientsfromparticlesofdirtintheiceanduseenergyfromsunlightforphotosynthesis.
Hot–LargeconcentrationsofmicrobesthriveinYellowstoneNationalPark’sGrandPrismaticSprings,ahotspringwithwatertemperaturesupto90oC(188oF).OtherhotspringsinYellowstoneareextremelyacidic,yetarehometomanydifferentkindsofbacteriaandmicrobes.Manyofthesemicrobesusechemicalnutrientsinthewatersandenergyfromsunlightforphotosynthesis.
Deepunderground–Scientistshavediscoveredbacterialivingingroundwater5kilometresbelowthesurfaceindeepgoldminesoftheWitwatersrandBasininSouthAfrica.Thesemicrobesthriveincavitiesandcracksinrocks.ScientistsarealsoareinvestigatinglifewithinandbelowpermafrostinnorthernCanada.
Bottomofthesea–Scientistshavefoundabundantlifeclusteredaroundhydrothermalventsontheoceanfloor,includingbacteria,mussels,clams,shrimp,andgianttubewormsthatcanreachtenfeetinlength.Waterpouringoutoftheventsinthecompletedarknessthousandsoffeetunderthesurfaceoftheseacanreachtemperaturesof113-120oC(235-248oF).Thehighpressureskeepthewaterfromboiling.Bacteriausechemicalsinthevent’swater,primarilyhydrogensulfide,astheirenergysourceinsteadofsunlight.Othercreaturessurvivebyeatingthebacteriaoreachother.
HighAcidity–ThewaterintheRioTintoinsouthwesternSpainisveryacidic,aresultofchemicalreactionsbetweenthewater,andironandsulfurmineralsintheground.Theriverhasadeepredcolor,likewine,becauseofirondissolvedinthewater.Microbeslivinginthewaterusechemicalreactionswithironandsulfurmineralstogeneratetheenergytheyneed.ProductsfromthesemetabolicreactionscontributetothelowpHintheenvironment.Manyalgaeandfungialsoliveintheacidicwaters.
Source:NASA
5
TasksheetYouareinvestigatingtheeffectofpHontherateof
respirationinyeast.Youwillneedtoworktogetherasateamtoensure
thateachexperimenttakesplaceatthesametime,sothatyourresultscanbecompared
Collectthreeofthebottlesthathavebeenpre-
preparedwithyeastandsugarandcollectthreeballoons
Youwillnowneedtovaryakeyvariabledepending
onyourgroup:VaryingpHCollectsomewarmwaterfromawaterbathandaddthistoyourbottlesuntilitreachesthefirstblacklineon
thesideofthebottle.Shakethebottlewelltomixthecontents.• Addasmallvolumeofvinegartoyourfirstbottleuntilthewaterlevelreachesthesecondblackline.Shake
againandwhenyouarereadytostart,immediatelyattachtheballoontotheendofthebottle.• Addasmallvolumeofsodiumbicarbonatesolutiontoyoursecondbottleuntilthewaterlevelreachesthe
secondblackline.Shakeagainandwhenyouarereadytostart,immediatelyattachtheballoontotheendofthebottle.
• Addasmallvolumeofwarmwaterfromawaterbathtoyourthirdbottleuntilthewaterlevelreachesthe
secondblackline.Shakeagainandwhenyouarereadytostart,immediatelyattachtheballoontotheendofthebottle.
Onceyouhavesetthebottlesup,youwillneedtoleavethemtostandforatleast20minutes.Youshouldthen
beabletomakesomecomparisonsbetweenthedifferentbottlesThinkaboutit...............1. Whichbottlesshowedthegreatestrateofrespirationandwhichshowedtheleast?2. WhatsortofpHconditionsdoyouthinkyeastisadaptedtolivein?3. DoyouhaveenoughdatatoestablishtherangeofpHvaluestowhichyeastis
tolerant?Howcouldyouimprovetheinvestigationtogiveamoreaccurateestimateoftherangeoftolerances?
4. ExplainwhychangesinpHwouldaffecttherateofrespirationinyeast5. Whatwasthepurposeofaddingmorewatertoyourthirdbottle?
Figure1–above
Fig.2–above
6
TasksheetYouareinvestigatingtheeffectoftemperatureontherateof
respirationinyeast.Youwillneedtoworktogetherasateamtoensurethateach
experimenttakesplaceatthesametime,sothatyourresultscanbecompared
Collectthreeofthebottlesthathavebeenpre-preparedwithyeast
andsugarandcollectthreeballoonsYouwillnowneedtovaryakeyvariabledependingonyourgroup:VaryingtemperatureYouareprovidedwithcold,warmandhotwaterinthreedifferent
waterbaths.Youshouldnotethetemperaturesofthewaterusingthethermometersprovided.
• Addasmallvolumeofcoldwaterfromthecoldwaterbathtoyourfirstbottleuntilthewaterlevelreaches
thesecondblacklineonthebottle.Shakethebottlewellandwhenyouarereadytostart,immediatelyattachtheballoontotheendofthebottle.
• Addasmallvolumeofwarmwatertoyoursecondbottleuntilthewaterlevelreachesthesecondblackline.
Shakeagainandwhenyouarereadytostart,immediatelyattachtheballoontotheendofthebottle.• Addasmallvolumeofhotwater(CARE!)fromawaterbathtoyourthirdbottleuntilthewaterlevelreaches
thesecondblackline.Shakeagainandwhenyouarereadytostart,immediatelyattachtheballoontotheendofthebottle.
Onceyouhavesetthebottlesup,youwillneedtoleavethemtostandforatleast20minutes.Youshouldthen
beabletomakesomecomparisonsbetweenthedifferentbottlesThinkaboutit...............1. Whichbottlesshowedthegreatestrateofrespirationandwhichshowedtheleast?2. Whatsortoftemperatureconditionsdoyouthinkyeastisadaptedtolivein?3. Doyouhaveenoughdatatoestablishtherangeoftemperaturevaluesto
whichyeastistolerant?Howcouldyouimprovetheinvestigationtogiveamoreaccurateestimateoftherangeoftolerances?
4. Explainwhychangesintemperaturewouldaffecttherateofrespirationin
yeast5. Doyouthinkthatthesurfacetemperatureofaplanetwouldhaveany
implicationsaboutthelikelihoodoffindinglifethere?Explainyouranswer
Figure3–above
Fig.2–above
7
TasksheetYouareinvestigatingtheeffectofsalinityontherateof
respirationinyeast.Youwillneedtoworktogetherasateamtoensurethateach
experimenttakesplaceatthesametime,sothatyourresultscanbecompared
Collectthreeofthebottlesthathavebeenpre-preparedwith
yeastandsugarandcollectthreeballoonsYouwillnowneedtovaryakeyvariabledependingonyour
group:VaryingsalinityCollectsomewarmwaterfromawaterbathandaddthistoyourbottlesuntilitreachesthesecondblacklineon
thesideofthebottle.Shakethebottlewelltomixthecontents.• Addtwoteaspoonsofsalttoyourfirstbottle.Shakewellsothatthesaltdissolvesandwhenyouareready
tostart,immediatelyattachtheballoontotheendofthebottle.• Addsixteaspoonsofsalttoyoursecondbottle.Shakewellsothatthesaltdissolvesandwhenyouare
readytostart,immediatelyattachtheballoontotheendofthebottle.• Donotaddanysalttoyourthirdbottle.Shakewellandwhenyouarereadytostart,immediatelyattach
theballoontotheendofthebottle.Onceyouhavesetthebottlesup,youwillneedtoleavethemtostandforatleast20minutes.Youshouldthen
beabletomakesomecomparisonsbetweenthedifferentbottlesThinkaboutit...............1. Whichbottlesshowedthegreatestrateofrespirationandwhichshowedthe
least?2. Whatsortofsalinityconditionsdoyouthinkyeastisadaptedtolivein?3. Doyouhaveenoughdatatoestablishtherangeofsalinityvaluestowhichyeast
istolerant?Howcouldyouimprovetheinvestigationtogiveamoreaccurateestimateoftherangeoftolerances?
4. Explainwhychangesinsalinitywouldaffecttherateofrespirationinyeast
Fig.2–above
Figure4–above
8
RISKASSESSMENT Overallrisk(provided
safetyproceduresare
followed)=LOW
Substance Hazard CommentYeast
BIOHAZARD
Yeastisamicro-organismthatshouldnotbeingestedorallowedto
entercutsorabrasionsonskinsurfaces.Thoroughwashingofhands
beforeandafteruseisgenerallytheonlyprecautionrequired.
Vinegar LOWHAZARD Weakacid,requiringeyeprotectiontobeworn.Maindangercomes
fromsquirtingoutofthebottleaspressurebuildsduetocarbon
dioxideproduction
Sodiumbicarbonatesolution
LOWHAZARD
Weakalkali,requiringeyeprotectiontobeworn.Maindangercomes
fromsquirtingoutofthebottleaspressurebuildsduetocarbon
dioxideproduction
Hotwater>70°C HAZARD Dangerofscalding.Eyeprotectionmustbewornwhilehandling.
Teachertoarrangeforhotwatertobepouredintoseparatebeakers
whichstudentscanthenuse
Additionalcomments:
• Careshouldbetakenwhenbottlesareshakentohydrateyeast–makesurebottlecapsarefullyscrewedonto
preventanypossibleejectionofthecontents
• Eyeprotectionmustbewornthroughoutthepractical,particularlywhenremoving,inspectingoraddingballoonsaspressure
canbereleasedsuddenlycausingthecontentsofthebottletobeejected
Incaseofaccident/incident:
••••
IntheeyeSwallowedScaldsSpiltonskinorclothing
Floodtheeyewithgently-runningtapwaterfor10minutes.Seeadoctor.
Donomorethanwashoutthemouthwithwater.Donotinducevomiting.Sipsofwatermayhelpcool
thethroatandhelpkeeptheairwayopen.Seeadoctor.
Runaffectedareaundercoldwaterforatleasttenminutesandpossiblylongerdependingonextenton
theinjury.Applyasteriledressingandseeadoctorifblisteringoccurs.
Removecontaminatedclothing.Drenchtheskinwithplentyofwater.Ifalargeareaisaffectedor
blisteringoccurs,seeadoctor.
9
ImageReferences:
Figure01-LUXInnovateLtd(2009)Assessmentoferosionsusceptibility[WWW]LUXDSAvailable
from:http://luxds.com/web/index.php?option=com_content&task=view&id=31[04/12/2012]
Figure01-ELMHURST(dateunknown)pHScale–IntroductionandDefinitions[WWW]Availablefrom:http://www.elmhurst.edu/~chm/vchembook/184ph.html[04/12/2012]
Figure02-TOON,MARK(2012)Stickmanhandsonhipslookpuzzledclipart[WWW]MarkToonAvailablefrom:http://www.marktoon.co.uk/cartoons/stickmen/stickman-hands-on-hips-looks-puzzled-clipart.gif[04/12/2012]
Figure03-REIGNOVERUS(09-07-2010)Thesightsofsummer[WWW]Availablefrom:
http://reignover.us/2010/07/[04/12/2012]
Figure04-Land_Fish(04-10-2004)Re:Refractometer@swingarmSGtesters[WWW]Postby–
Land_FishAvailablefrom:http://www.3reef.com/forums/water-chemistry/refractometer-swingarm-sg-testers-32759.html[04/12/2012]
WeAreAliens!–Classroomactivity4(Biology)Cells1. Firstlabelthetwocellsbelowasplantoranimal2. Nowaddtheselabels
nucleuscytoplasmchloroplastcellwallcellmembranevacuole
3.Fillinthetablebelowbylistingthepartsfoundin plantandanimalcells.
Plantcell Animalcell
4.Usecolourstomatchthepartwithitsjob
Part Job
Nucleus Helpstoprovidesupportandcontainscellsap
Cytoplasm Absorbslightenergyforphotosynthesis
Membrane Carriesgeneticinformation
Cellwall Providessupport
Vacuole Manychemicalreactionsoccurhere
Chloroplast Controlsthemovementofsubstancesinandoutofthecell
5.Herearetwostudentmodelsofcells
a) Aretheyplantoranimalcells?b) Addasmanylabelsasyoucan
1
WeAreAliens!–Classroomactivity5(Biology)MakingModelCells
Thecellisthesmallestunitoflifeandalthoughwedon’tknowexactlywhentheyfirstappearedonEarthweknowthatlifearrivedaremarkablyshorttimeafterthebirthoftheplanet.FormanymillenniasinglecelledorganismsweretheonlyformoflifeonEarthandit’sthistypeoflifethatastrobiologistsarelookingforelsewhereinthesolarsystem.Inthisfunactivity,wallpaperpasteisusedtobuildmodelcells.It’sverygoodforhelpingstudentstoappreciatewhatcellsarelikeandisverymemorable.
Equipment• Wallpaperpaste(ensureit’sthealmostcolourlesssortratherthanthetypebasedon
starch)• Smallsealableplasticbags(sandwichbagsareOKbutratherbig.Smallerbagsare
readilyavailableonline.Forexampleyoucanget10003”bagsherefor£6amazonlink)
• Waterproofpen(s)
Tomakemicrobes• Cotton• String• lengthsofwool
Tomakeplantcells• Greentiddlywinks/counters
(chloroplasts)• {Redtiddlywinks/counters
(mitochondria)}• Clingfilm(vacuole)• Marbles(nucleus)
PracticaltipsThewallpaperpasteneedsmakingupbeforethelessonandshouldonlybedispensedbytheteacherunlessyouwantalotofmess.Followtheinstructionsonthepacketbutmakeitupusingthesmallestamountofwaterspecified(ieasifhangingheavypaper).Ifyouwanttoidentifythecellslater,ensurestudentwritetheirnamesonthebagsbeforetheyarefilled.Usethewaterproofpensforthis.Tomakeamodelmicrobe:
1. AddsomelengthsofcottontotheplasticbagtorepresenttheDNAstrands.Youcouldalsoaddsomecottonloopstorepresentplasmids.
2. Theteacheraddsagooddollopofwallpaperpaste
3. Squeezeouttheairandsealthebag.Whentheoutsideofthebagisdry,youmaywanttoensureitstayssealedbyaddingsellotape
4. Usingsellotape,fixalengthofwooltotheoutsideofthebagtorepresentflagella
5. Addseveralshortlengthofthisstringtorepresentpillli
6. Youcanevenusealayerofwallpaperpasteontheoutsideofthebagtorepresentabacterialcapsule.
Figure1–above
2
Tomakeamodelplantcell:
1. Carefullyrunsomewaterintoa“saggy”pieceofclingfilmandthentwistthecornerstogethertomakea“bubble”ofwater.Youmaywanttoaddsellotapetohelpsealit.
2. Placetheclingfilmbubble,marbleandseveralgreentiddlywinks,intoaplasticbag.Ifappropriatetoyourspecificationyoucanalsoaddredtiddlywinks
3. Teacheraddsagooddollopofwallpaperpaste,thensealthebagtofinishthemodelcell
FollowupworkMatchthepartofthemodeltowhatitrepresentsinarealmicrobe
Plasticbag cytoplasmCottonthread cellmembraneWallpaperpaste flagellumWool pilliString chromosome
Matchthepartofthemodeltowhatitrepresentsinarealplantcell
Marble vacuoleGreentiddlywinks cytoplasmWallpaperpaste membranePlasticbagcell chloroplastsClingfilm nucleus
Theonepartofthecellthatwasmissingwasthe__________(cellwall)Thereisalsoasimplereinforcementworksheetoncellsforstudentstocomplete
Figure2–above
3
Takingitfurther(takenfromtheUniversityofUtah’slearngeneticswebsite)SomeoftheoldestcellsonEartharesingle-cellorganismscalledbacteria.FossilrecordsindicatethatmoundsofbacteriaoncecoveredyoungEarth.Somebeganmakingtheirownfoodusingcarbondioxideintheatmosphereandenergytheyharvestedfromthesun.Thisprocess(calledphotosynthesis)producedenoughoxygentochangeEarth'satmosphere.Soonafterward,newoxygen-breathinglifeformscameontothescene.Withapopulationofincreasinglydiversebacteriallife,thestagewassetforsomeamazingthingstohappenThereiscompellingevidencethatmitochondriaandchloroplastswereonceprimitivebacterialcells.Thisevidenceisdescribedintheendosymbiotictheory.Howdidthistheorygetitsname?Symbiosisoccurswhentwodifferentspeciesbenefitfromlivingandworkingtogether.Whenoneorganismactuallylivesinsidetheotherit'scalledendosymbiosis.Theendosymbiotictheorydescribeshowalargehostcellandingestedbacteriacouldeasilybecomedependentononeanotherforsurvival,resultinginapermanentrelationship.Overmillionsofyearsofevolution,mitochondriaandchloroplastshavebecomemorespecializedandtodaytheycannotliveoutsidethecell.ImageReferences:Figure01-RUIZ,MARIANA(dateunknown)GramStainandBacterialCellWallStructure[WWW]Availablefrom:http://tamiport.hubpages.com/hub/Gram-Stain-and-Bacterial-Cell-Wall-Structure#slide2149066[06/12/2012]Figure02-9AREVISION(dateunknown)Thesearethethingsthatplantsneedforphotosynthesis[WWW]Availablefrom:http://9arevision.wikispaces.com/plants[04/12/2012]Figure03-UTAHLEARNGENETICS(dateunknown)EndosymbioticOriginofChloroplastsandMitochondria[WWW]UtahLearnGenetics–EducationAvailablefrom:http://www.uic.edu/classes/bios/bios100/lectures/cells.htm[04/12/2012]
Figure3–above
1
WeAreAliens!–Classroomactivity1(Chemistry)LivingintheFreezer
Thecellsofplants,animalsandbacterialivinginlowtemperatureenvironmentsonEarthoftencontainantifreeze
proteinstopreventtheirbodyfluidsfromfreezing.
Ifthere’slifeanywhereelseinoursolarsystem,it’slikelythatittoowillhavetocopewithcoldconditionsand
needsomesortofantifreeze.
Youcandemonstratetheeffectthatfreezingwaterhasoncellsbydisplayingstrawberries(andotherfruitand
veg)aftertheyhavebeeninthefreezer.Theicecrystalsthatformhavealargervolumethanliquidwaterthey’re
madefromandtheresultingexpansionbreaksopencellwallsresultingin“soggy”strawberries
Inthisactivity,studentsplanandcarryoutanexperimenttofindouttheeffectofanantifreezeonthemelting
pointofwater.Theaimoftheexperimentisconceptuallysimple,allowingstudentstodeveloptheirplanningand
practicalskills.
Theymayalreadyknowthat“grit”containingrocksalt(impuresodiumchloride)isspreadonroadsinthewinter
tostopiceforming.Liquidantifreezesarealsoaddedtothewaterinthecoolantsystemandscreenwashbottles
ofcarstopreventwaterfromfreezingoverthewinter.
Therearetwodifferentmethodsthatcouldbeused.Dependingonthetimeyouhaveavailable,youmightliketo
steerstudentstowardsoneortheother.
1. Findingtheconcentrationneededtostopwaterfromfreezinginadomesticfreezer.Different
concentrationsofantifreezeandusedtofillanicecubetrayandthenplacedinafreezer.Thenext
lesson,studentscanviewtheicecubesandseewhichconcentrationsremainliquid.
2. Findingouthowlongicecubesmadewithdifferentconcentrationsofantifreezetaketomelt.Thelonger
theytaketomelt,thelesseffectivetheantifreeze.Studentsshoulddevisetheirownmethodfor
determiningthemelttimebutsuitablemethodsinclude,placingthecubeinabeakerofwaterandtiming
howlongittakestodisappearandplacingtheicecubeinafunnelheldover10cm3measuringcylinder
andmeasuringthevolumeofwaterproducedinacertaintime.Tosavetime,heicecubescouldbemade
upreadybytechnicians
Usingeitherofthemethodsabove,analternativeinvestigationistodeterminewhichantifreezeismosteffective.
Antifreezestotryinclude:
• Rocksalt
• Puresodiumchloride
• Calciumchlorideirritant
• Potassiumchloride
• Ethan-1,2-diol(ethyleneglycol)(thisistheactiveingredientincommercial
antifreezes)harmful
• Commercialantifreeze
• IMS/IDA/ethanolhighlyflammableandharmful
• Windscreenwasherfluid(oftencontainsethanol)
2
RiskAssessment-refertoCLEAPShazchemcardsandcarryoutyourownriskassessment.
EquipmentListwillvarydependingupontheexactmethodstudentschoosebutitlikelytoinclude
• Oneormoreantifreezes(seeabove)
• Icecubetrays
• Accesstoafreezer
• Foodcolourings
• Measuringcylinders
• Distilledwater
• Balance
• Funnels
• Beakers
• (thermometers–formeasuringwatertemperatureifmeltingicecubes)
PracticalHints
Whenmakingupsolutionsofliquidantifreezes,studentscoulduse10cm3measuringcylinders.
10cm3water =0%antifreeze
9.5cm3water+0.5cm
3antifreeze =5%antifreeze
9cm3water+1cm
3antifreeze =10%antifreeze
8cm3water+2cm
3antifreeze =20%antifreeze
Andsoon
Whenmakingupsolutionsofsolidantifreezesthen%concentrationsareworkedoutmosteasilyw/v(weightfor
volume)
100cm3water =0%antifreeze
100cm3water +5gsalt =5%antifreeze
100cm3water +10gsalt =10%antifreeze
Andsoon
Commercialantifreezesolutionsareoftencolouredandconcentrationscanbeseenbyjudgingthedepthof
colour.Ifstudentsmakeuptheirownicecubes,itisrecommendedthattheyusearowofthetrayforsuccessive
concentrations.Indeliblepenscanbeusedtomarkthetrayswithnamesetc.
Ifmakingupicecubeswithdifferentsaltconcentrations,itcansavealotofconfusioniffoodcolouringisalso
addedtothewater.So,forexample,5%cubesareyellow,10%cubesaregreenetc.
Domesticfreezersusuallyoperateatabout-20oCbutyoumaybeabletogetthemcolderiftheyhavean
adjustablethermostat.Ifyouhavetheoptionof“fastfreeze”youmaybeabletogetdowntoabout-26oC
Followupwork
Adataanalysisworksheetisincludedthatrequiresstudentstodrawabargraphthatincludesnegativenumbers
andinterpretthedataitshows.
Extension
Youcouldgoontoinvestigatetheeffectofanantifreezeontheboilingpointofwater.Studentsmaybesurprised
tofindthatsaltraisestheboilingpointofwater.
1
WeAreAliens!–Classroomactivity1(Chemistry)Antifreezes Name
______________________________(graphpaperrequired)
Anti-freezeliquid
A B C D
FreezingPoint(°C) 10 -6 0 -15
Drawabargraph(ongraphpaper)toshowthisdata.
Beforeyoustart,thinkaboutwherethehorizontalaxisshouldbe.
Useyourgraphorthetabletocompletethiswork.
1. Liquid______hasthelowestfreezingpoint.
2. Liquid______hasthehighestfreezingpoint.
3. Liquid______couldbewater.
4. Liquid______wouldbeuselessasanantifreeze.
5. Liquid______wouldmakethebestantifreeze.
6. LiquidCwillmeltat______°C
7. IfliquidsBandCweremixed,thefreezingpointwouldbeabout_____°C
8. IfliquidsAandDweremixed,thefreezingpointwouldbeabout_____°C
9. Onewinterdaythetemperatureis-2°C.
Liquids______and______wouldactuallybesolidsonthisday.
10. TheaveragetemperatureonMarsis-55°C.
ExplainwhynoneoftheseliquidswouldbeanygoodasanantifreezeonMars
11. EnceladusisamoonofSaturn.Thispictureshowsaplume
oficeandwatergushingintospace.Scientistshave
discoveredthatthewatercontainssalt.Explainwhythis
mighthelpkeepthewateraliquid.
__________________________________________
__________________________________________
__________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
1
WeAreAliens!–Classroomactivity6(Chemistry)UsingUVbeadstoinvestigatereactionrates
OverviewTherateofachemicalreactionishighlydependentontemperature;oftena10oriseintemperaturewilldoubleareactionrate.Thechemicalreactionsthattakeplaceinlivingcellsarenowexception,indeedmanyorganismregulatetheirtemperatureveryaccuratelyforthisreason.Inthisexperimentstudentswillexplorehowratedependsontemperatureinaverydirectmannerwithoutthecomplicationofmeasuringchemicalreactantsoftheirproducts.PhotochromicbeadscontainaUVsensitivepigment.WhenplacedunderUVlightorsunlighttheychangefromcolourlesstocoloured.Oncethelightsourceisremovedtheircolourgraduallyfadesuntiltheyarecolourlessagain.Thereactionisreversibleandrepeatable.Thereturntothecolourlessformprovidesareactionwhichcanbesafelyinvestigatedexperimentally.ThebeadscanalsobeusedasasimpleUVradiationdetector.Manyschoolswillalreadyhaveasupplyofthesebeadsbutifnottheyareavailablefrommindsetsonline.co.ukforaround£6.50for100eitherinsinglecoloursormixed.ScientificConceptsThedyemoleculesinUVreactivebeadsconsistoftwolargeflatconjugatedsystemsorchromophoresthatareatrightanglestooneanother.TheyabsorbradiationonlyintheUVpartofthespectrumandthedyeremainscolourless.WhenUVlightexcitesthecentralcarbonatom,thetwosmallerchromophoresformonelargeconjugatedsystem.Thischromophoreislargeenoughtoshifttheabsorptionintothevisiblepartofthespectrumandthedyebecomescoloured.Bychangingthesizeofthetwoconjugatedsectionsofthemolecule,differentwavelengthsareabsorbedanddifferentdyecolourscanbeproduced.Heatfromthesurroundingsprovidestheactivationenergyneededtoreturnthecolouredformofthemoleculebacktoitslowerenergycolourlessform.
Itisthereactionthatproducesthecolourlessformthatismosteasilyinvestigatedinthisscenario.However,thereisscopeforfurtherspacerelatedwork.Starsemitawiderangeofelectromagneticradiationincludingultraviolet.OnEarthweareprotectedfrommuchofthisradiationbyouratmosphere,howeverinspaceoronotherworldstheremaybenosuchprotection.Complexorganicmoleculeswillabsorbandhencebeeffectedbythisradiation.Inmanyspaceenvironmentsmoleculesareexposedtoshortwavelengthradiationandlowtemperaturesandthisreactionprovidesamodelforthetypeofreactionsthatcanleadtotheformationoflifeprecursormoleculessuchastheaminoacidsfoundinmeteoritesandcomets.
Figure1–Pleaseseeabove
2
DescriptionofActivityAnumberofbeadsareexposedtoUVlight,eitherfromaUVlamporsunlight.IthelpstokeepthebeadscoolwhilebeingexposedtotheUV.Placingtheminabeakerwithsomecrushedicewillachievethis.Oncefullycolouredtheyarequicklyremovedfromthelightsourceandimmediatelyplacedinabeakerofwateratapre-settemperature.ThetimeforthebeadstofadetothesameshadeassomereferencebeadsnotexposedtoUVisrecorded.Thisisdoneoverarangeoftemperatures.Thebeakershouldbeplacedonawhitetileorpapertofacilitatejudgingwhenthecolourhascompletelyfaded.Atemperaturerangefrom20°Cto50°Cprovidesasuitablerangesothewatercouldcomefromhotandcoldtaps.IfaUVsourceisunavailablethenthebeadscanbestoredintheircolouredstateforseveraldaysinafreezer.
AtKeyStage4theactivitycouldbeusedtoinvestigatetheeffectoftemperatureonrateofreactionwithstudentsplottinggraphsof1/timeagainsttemperature.StudentscoulduseExceltotryandfitalinetothedataandtolinkthefindingstocollisiontheoryandtheconceptofactivationenthalpy.Alternativelytheprovidedresultssheetcouldbeusedtospeedthingsup.TeachingResourcesUVbeads,stopwatches,beakers,thermometers(0-50°Careidealbutanywilldo),whitetilesandasourceofhotandcoldwatere.g.kettleorhottap.AUVlampmaybeneededonadullwintersday.UVtorch£9.99fromAmazonUVBeadsfrom mindsetsonline.co.uk HealthandSafetyThebeadsmayrepresentachokinghazardforverysmallchildren.Careshouldbetakenwithhotwaterandglassware.AssociatedDigitalResourcesWAL_Chemistry_06_Results.docx
ExtraResources
WAL_Chemistry_06_VennDiagram_Worksheet.docx
TheVenndiagramactivityworkswellatKS4alongsidethisactivity.Itisausefuldiagnostictoolrevealingmisconceptionsinstudents(andteachers)understandingofcollisiontheory.ItcanbescaledupsoeachstudenthasanA5printoutastatementandtheVennDiagramischalkedontheground.Throughdiscussionthestudentsmustarrangethemselvesinthecorrectlocationsonthediagram.
Figure2–Pleaseseetotheleft
InvestigatingtheEffectofTemperatureontheRateofaChemicalReactionFortemperaturebetween7°Cand57°Candtimesover5s.
temp/°C temp/K time/s rate=1/time/s-1
Conclusion
QWhendoesTemp/°C=time/s?
T/K280 290 320310300 330
0.20
0.15
0.10
0
0.05
rate/s
-1
increasedconcentrationofdissolvedreactant
increasedconcentrationofdissolvedproduct
increasedsurfaceareaofsolidcatalyst
increasedtemperatureofreactants
demandthechemicalsreactfasterorelse….
givingthereactionverbalencouragement
greatervolumeofreactingsolution
usefreshlymadeupsolutions
smallerparticles(lumps)ofsolidreactant
increasedsurfaceareaofsolidreactant
presenceofsuitableenzyme
increaseconcentrationofdissolvedcatalyst
stirwell addacatalyst
useapowderinsteadofalump
buymoreexpensivechemicals
shake writetoyourMPanddemandaction
increasedpressureofgaseousreactants
increasesizeofreactionvessel
addacatalystandincreasetheconcentrationofthe
reactants
additionofsubstancethatreducesactivationenergy
increasedsurfaceareaofsolidreactant
carryouttheexperimentatahighertemperature
usemoreconcentratedreactants
stareatthereactioninamenacingfashion
largersurfaceareaandahighertemperature
Shinelightonthereactionmixture
Morefrequentcollisions
Greaterproportion
ofcollisions
aresuccessful
1
WeAreAliens!–Classroomactivity7(Chemistry)UsingUVReactiveBeadstofindActivationEnthalpy
OverviewTherateofachemicalreactionishighlydependentontemperature;oftena10oriseintemperaturewilldoubleareactionrate.Thechemicalreactionsthattakeplaceinlivingcellsarenowexception,indeedmanyorganismregulatetheirtemperatureveryaccuratelyforthisreason.Inthisexperimentstudentswillexplorehowratedependsontemperatureinaverydirectmannerwithoutthecomplicationofmeasuringchemicalreactantsoftheirproductsandusetheirresultstocalculatetheactivationenthalpyforthereaction
PhotochromicbeadscontainaUVsensitivepigment.WhenplacedunderUVlightorsunlighttheychangefromcolourlesstocoloured.Oncethelightsourceisremovedtheircolourgraduallyfadesuntiltheyarecolourlessagain.Thereactionisreversibleandrepeatable.Thereturntothecolourlessformprovidesareactionwhichcanbesafelyinvestigatedexperimentally.ThebeadscanalsobeusedasasimpleUVradiationdetector.Theyareavailablefrommindsetsonline.co.ukforaround£6.50for100eitherinsinglecoloursormixed.
AtKeyStage5theactivitycouldbeusedtoestablishtheactivationenergy/enthalpyforthereactionusingtheArrheniusequation.Thereactionisalsoaniceexampleofareversiblereactionwherethepositionofequilibriumcanbeshifted.ThebeadscouldbeusedtointroducetheideaofequilibriumconstantandLeChatelier’sprinciple.InvestigatingwhetherdifferentcolouredbeadshavedifferentactivationenergiescouldformthebasisofanA2chemistryinvestigation.Theresultssheetcanbeusedasisormodifiedtoprovidedifferentiation.ScientificConceptsThedyemoleculesinUVreactivebeadsconsistoftwolargeflatconjugatedsystemsorchromophoresthatareatrightanglestooneanother.TheyabsorbradiationonlyintheUVpartofthespectrumandthedyeremainscolourless.WhenUVlightexcitesthecentralcarbonatom,thetwosmallerchromophoresformonelargeconjugatedsystem.Thischromophoreislargeenoughtoshifttheabsorptionintothevisiblepartofthespectrumandthedyebecomescoloured.Bychangingthesizeofthetwoconjugatedsectionsofthemolecule,differentwavelengthsareabsorbedanddifferentdyecolourscanbeproduced.Heatfromthesurroundingsprovidestheactivationenergyneededtoreturnthecolouredformofthemoleculebacktoitslowerenergycolourlessform.
Figure01
2
Starsemitawiderangeofelectromagneticradiationincludingultraviolet.OnEarthweareprotectedfrommuchofthisradiationbyouratmosphere,howeverinspaceoronotherworldstheremaybenosuchprotection.Complexorganicmoleculeswillabsorbandhencebeeffectedbythisradiation.
Thisprovidesaspacebasedcontextforthereaction.Forexamplethepigmentmoleculesinthebeadscouldbeusedinanastronaut’seyeprotectionvisor(asinphotochromicsunglasses)withthestudentsinvestigatinghowthevisorwouldbeareeffectedbytemperature.
Inmanyspaceenvironmentsmoleculesareexposedtoshortwavelengthradiationandlowtemperaturesandthisreactionprovidesamodelforthetypeofreactionsthatcanleadtotheformationoflifeprecursormoleculessuchastheaminoacidsfoundinmeteoritesandcomets.
Thebeadsprovideaexperimentallysimplewaytoestablishtheactivationenthalpyforareaction.ThetheorybehindthisisbrieflyoutlinedbelowstartingwiththeBoltzmanndistributionofenergystates.
Forachemicalreactiontooccurreactantparticlesmustcollidewithacertainminimumkineticenergyinorderforareactiontooccur,thatis,theactivationenergy.Inacollectionofmoleculesattemperature,Tthefractionofmolecules,NhavinganenergygreaterthanEisgivenby,N=e-E/kTwherekistheBoltzmannconstant.
IfEaistheactivationenergypermoleofmolecules(i.e.inkJmol-1)theAvogadroconstant,LmustbeintroducedtocompensategivingN=e-Ea/LkT .SinceLk=R,whereRisthegasconstant,N=e-Ea/RT
Therateofthereactionwilldependonthecollisionrate(combinedwithstericfactors)andonthefractionofmoleculeswithenoughenergytoreacti.e.rate=collisionrate× fraction.SubstitutingtheexpressionforNgivestheArrheniusequation,rate=collisionrate× e-Ea/RTandtakingnaturallogsofbothsidesgives,ln(rate)=ln(collisionrate)–Ea/RTwhichcanbewrittenas
ln(rate)=–(Ea/R)× (1/T)+ln(collisionrate)Thisintheformofanequationofastraightline(y=mx+c)whereyisln(rate)andxis1/T.Thegradientis–Ea/Randtheinterceptisln(collisionrate).Soagraphofln(rate)vs1/Twillhaveagradientof–Ea/R.(R=8.31JK-1mol-1)
DescriptionofActivityAnumberofbeadsareexposedtoUVlight,eitherfromaUVlamporsunlight.IthelpstokeepthebeadscoolwhilebeingexposedtotheUV.Placingtheminabeakerwithsomecrushedicewillachievethis.Oncefullycolouredtheyarequicklyremovedfromthelightsourceandimmediatelyplacedinabeakerofwateratapre-settemperature.ThetimeforthebeadstofadetothesameshadeassomereferencebeadsnotexposedtoUVisrecorded.Thisisdoneoverarangeoftemperatures.Thebeakershouldbeplacedonawhitetileorpapertofacilitatejudgingwhenthecolourhascompletelyfaded.Atemperaturerangefrom20°Cto50°Cprovidesasuitablerangesothewatercouldcomefromhotandcoldtaps.IfaUVsourceisunavailablethenthebeadscanbestoredintheircolouredstateforseveraldaysinafreezer.
3
ln(rate)
1/T
-Ea/R
Fromthetemperaturesandtimesitispossibletocalculatetheactivationenergyforthereactionfromthegradientofagraphofln(rate)against1/temperature.Therateisjustgivenby1/timeandTisthetemperatureinK.
Thetableandgraphbelowgivetypicaltimes.Agraphofln(rate)against1/Tforthisdatahasagradientof-9908K.Sincethegradient=-Ea/RitfollowsthatEa=gradientxR(8.31JK-1mol-1)whichgivesavalueforEaof82.3kJmol-1.EainkJmol-1canalsobeestablishedfromjusttwotimes,t1andt2recordedattemperatures,T1andT2usingtheequation.
!" = 8.31 ×!" !!
!!1000× 1
!! −1!!
SampleDataforPurpleBeadsTemp/°C time/s 1/TK-1 ln(rate)
21 180 0.00340 -5.19329 70 0.00331 -4.24833 48 0.00327 -3.87136 36 0.00324 -3.58438 29 0.00322 -3.36740 24 0.00319 -3.17844 16 0.00315 -2.77345 14 0.00314 -2.63948 10 0.00312 -2.303
y=-9908x+29
-5.200
-4.700
-4.200
-3.700
-3.200
-2.700
-2.2000.00310 0.00315 0.00320 0.00325 0.00330 0.00335 0.00340 0.00345
ln(rate)
1/TK-1
4
Basedonthedatafromthetrialexperimentaboveitispossibletogenerateamathematicalmodelfortherelationshipbetweentemperatureandtime.Timeinseconds=1/(EXP((-9908/(Temperaturein°C+273))+28.51))Anextensionactivitymightbetoinvestigatedeviationsfromsuchamodel.TeachingResources
UVbeads,stopwatches,beakers,thermometers(0-50°Careidealbutanywilldo),whitetilesandasourceofhotandcoldwatere.g.kettleorhottap.AUVlampmaybeneededonadullwintersday.UVtorch£9.99fromAmazonUVBeadsfrom mindsetsonline.co.uk HealthandSafetyThebeadsmayrepresentachokinghazardforverysmallchildren.Careshouldbetakenwithhotwaterandglassware.AssociatedDigitalResourcesWAL_Chemistry_07_ChemistryOfUVReactiveBeads_Information.xlsx
Excelfilewithsampledata
WAL_Chemistry_07_ChemistryOfUVReactiveBeads_Information.pptx
PowerPointSlide
ExtraResources WAL_Chemistry_07_VennDiagram_Worksheet.docx
TheVenndiagramactivityworkswellatKS4andKS5alongsidethisactivity.Itisausefuldiagnostictoolrevealingmisconceptionsinstudents(andteachers)understandingofcollisiontheory.ItcanbescaledupsoeachstudenthasanA5printoutastatementandtheVennDiagramischalkedontheground.Throughdiscussionthestudentsmustarrangethemselvesinthecorrectlocationsonthediagram.Alsosee
PhotochromismAminoAcidsinMeteoritesComplexMoleculesinSpace
CalculatingtheActivationEnthalpyforaChemicalReactionFortemperaturebetween20°Cand50°Candtimesbetween5sand240s
temp/°C temp/K 1/temp/K-1 time/s 1/time/s-1 ln(1/time)
gradient=∆!∆! =
= ______________K Ea=gradientx-8.31Jmol-1K-1=_______________kJmol-1
QWhendoesTemp/°C=time/s?
1/T/10-3K3.0 3.1 3.43.33.2 3.5
-1.5
-2.5
-3.5
-5.5
-4.5
ln(1/tim
e)
1
increasedconcentrationofdissolvedreactant
increasedconcentrationofdissolvedproduct
increasedsurfaceareaofsolidcatalyst
increasedtemperatureofreactants
demandthechemicalsreactfasterorelse….
givingthereactionverbalencouragement
greatervolumeofreactingsolution
usefreshlymadeupsolutions
smallerparticles(lumps)ofsolidreactant
increasedsurfaceareaofsolidreactant
presenceofsuitableenzyme
increaseconcentrationofdissolvedcatalyst
stirwell addacatalyst
useapowderinsteadofalump
buymoreexpensivechemicals
shake writetoyourMPanddemandaction
2
increasedpressureofgaseousreactants
increasesizeofreactionvessel
addacatalystandincreasetheconcentrationofthe
reactants
additionofsubstancethatreducesactivationenergy
increasedsurfaceareaofsolidreactant
carryouttheexperimentatahighertemperature
usemoreconcentratedreactants
stareatthereactioninamenacingfashion
largersurfaceareaandahighertemperature
Shinelightonthereactionmixture
Morefrequentcollisions
Greaterproportionofcollisions
aresuccessful
1
WeAreAliens!–Classroomactivity8(Chemistry)Couldlifeexistinthisicecore?Answersheet
NotalllifeonEarthrespiresaerobicallyusingglucoseasanenergysource.Therearemanytypesof
bacteriathatrespireusinginorganicmoleculeseitherwithorwithoutoxygen.Herearesome
examples.
1. Theequationbelowshowsarespiration(redox)reactioncarriedoutbysocallediron
bacteria.
H2O+Fe2O3→2Fe(OH)2+O2
water+iron(III)oxide→iron(II)hydroxide+oxygen
a. GivetheoxidationstateoftheironinFe2O3 +3
andFe(OH)2 +2
b. GivetheoxidationstateoftheoxygeninH2O -2
andO20
c. Whatisactingasthereducingagent? water
2. Thepurplesulfurbacteriaareoftenfoundinhotspringsorstagnantwater.Unlikeplants
theydonotusewaterastheirreducingagent,andsodonotproduceoxygen.Insteadthey
usehydrogensulfide,whichisoxidizedtoproducegranulesofelementalsulfur.Thisinturn
maybeoxidizedtoformsulfuricacid.Thesebacteriathriveissulphuricacidlakes.
a. Bybalancinghydrogenwithhydrogenions,writeanelectricallybalancedequationforthe
oxidationofhydrogensulphide(H2S)toelementalsulphur
H2Sà2H++S+2e
-
b. Explainwhythisreactionisoxidation
Hydrogenhasbeenremoved,oxidationstateofsulphurhasincreasedfrom-2to0
3. Biologicalnitrogenfixationoccurswhenatmosphericnitrogenisconvertedtoammoniaby
anenzymecallednitrogenaseThereactionis:
N2+8H++8e
−→2NH3+H2
a. Explainwhythisisaredoxreactionandnametheoxidisingagent
Nitrogenisoxidisedfrom0to+3,hydrogenisreducedfrom+1to0sobothreductionand
oxidationhavetakenplace.Theoxidisingagentishydrogen.
Sowhatdoyouthink,couldlifeexistonEuropaorEnceladus?
Howmuchwouldyoubepreparedforgovernmentstospendinordertofindout?
1
WeAreAliens!–Classroomactivity8(Chemistry)IceCoreAnalysisOnEarth,whereverthere’swaterthere’slife,evenifmuchofthatwaterisfrozen.Ourownsolarsystemcontains
anumberofsuchenvironments,whichastrobiologistsarekeentoexplore.Inthisactivitystudentswillanalyseice
coresthathavecomefromfrozenworldssuchasEuropa,oneofJupiter’smoonsandEnceladus,amoonof
Saturn.TheaccompanyingPowerPointwithpicturesofthesemoonscouldbeusedtofurthersetthescene.
Thecompositionoftheicecorecanbemodifiedtomatchparticularspecificationsortomatchtheresources
availableindifferentschools.Thedetailsprovidedinthisactivityarespeculativeandarenotintendedto
accuratelyrepresentthecompositionofparticularmoons!
ChemistryCoveredAnintroductiontoinorganiccompoundsincludingtheformulaeofnaturallyoccurringcompounds.
Acids,basesandneutralisationreactionsincludingacid-basetitrations.
Oxidationstatesandredoxreactionsincludingaredoxtitration.
OutlineofPracticalActivityStudentsaregivensamplesoficepurportedtobefromEnceladus/Europaonwhichtheycarryoutthefollowing
activitiesoverasequenceoflessons:
• Meltthesample,recordthevolumeandfilterit.
• Examinethesolidsrecoveredusingalowpowermicroscopyandidentifymineralspresent.
• Performqualitativetestsonthemeltwatertodiscovertheidentityofdissolvedions.
• Titrateaknownvolumeofthemeltwateragainstsodiumhydroxidetocalculatetheconcentrationofthe
acidpresent.
• Titrateaknownvolumeofthemeltwateragainstmanganate(VII)ionstodeterminetheconcentrationof
iron(II)
MakingtheIceCoresMakeupasolutionofapproximately0.05moldm
-3iron(II)sulphateinapproximately1moldm
-3sulphuricacid.To
thisbaseaddaselectionofmineralfragments,producedbysmashingupcheapmineralsampleswithahammer.
Tomakethecores,usethecylindricalicetraysnowreadilyavailableforcoolingdrinksbottles.(suitabletrayhere
atAmazonfor£3.50)Ensurethateachcorecontainssomeofthemineralfragments.Alternatively,makeupa
largeblockoficeusingalargeice-creamcontainerorsimilarandprovidestudentswithsamplesoficeobtained
bysmashingthelargeblockwithahammer.Itispossibletogetthemineralfragmentsdistributedthroughoutthe
icecoresbymakingupthecoresfromcrushedfrozensolutionandicecoldsolution.Thiswillpreventthemineral
grainsfromsinking.
Ifdesired,addothersaltsolutionsforstudentstoperformqualitativeanalysison.
Onlyverysmallamountsofmineralsamplesarerequiredastheywillbeviewedusingamicroscope.Youmay
wishtomixthefragmentsyouobtainwithfinesand(amineralitself)tomakethemeasiertohandle.
Mineralsamplessuitableforthiscanbeobtainedcheaply(95peach)fromukge.co.uk/uk/small-minerals.asp
Itisrecommendedthatyouobtainarangeof5or6minerals,ideallyalldifferentcolourstoaididentification.
Suitablemineralsinclude:
• Pyrite
• Malachite
• Quartz
• Galena
• Amethyst
• Chrysocolla
Studentswillneedabout30-40cm3ofsolution(about4standardicecubes)
2
RiskAssessmentWhenworkingwithicecubespreviouslystudentsmayhavetriedtodropthemdownthenecksofotherstudents.Theyshouldbewarnedthattheseare“acid”cubesandshouldbenotbehandled.1moldm-3sulphuricacid irritant0.05moldm-3iron(II)sulphate lowhazardMineralsamples lowhazardwhenhandledinthisformbutgalenaistoxicand,asa
precaution,studentsshouldwashtheirhandsbeforeleavingthelab.0.1moldm-3sodiumhydroxidesolution irritant1moldm-3hydrochloricacid irritant0.2moldm-3silvernitrate irritant0.5moldm-3bariumchloride harmfulUniversalindicator flammablePhenolphthaleinindicator flammable0.001moldm-3potassiummanganate(VII)lowhazard
EquipmentListRecordingandMineralIdentification
• Beakers• CylindricalicecubetraysORandcontainertomakealargeblockofice• Accesstofreezer• Iron(II)sulphate• 1moldm-3sulphuricacid• Crushedmineralsamples(seebelow)• Lowpowermicroscopes(oftenthoseusedatKS3/4aremostsuitable)• Filterpaperandfunnels
QualitativeAnalysis
• Meltedicesamplefrompreviouswork• Qualitativeanalysisinformationsheet• Universalindicator• Rangeofchemicalswithwhichtocarryoutqualitativeanalysis
o 0.1moldm-3sodiumhydroxidesolutiono 0.5moldm-3hydrochloricacido 0.2moldm-3silvernitratesolutiono 0.5moldm-3bariumchloridesolutiono spills
Acid-BaseTitration
• meltedicesamplefrompreviouswork• 100cm3volumetricflask• Distilledwater• 10cm3pipette• 25cm3pipette• Burette,burettestandandclamp• Phenolphthaleinindicator• Whitetile• Funnel• 0.10moldm-3sodiumhydroxidesolution(madeupaccurately)
RedoxTitrationAsabovebutwithoutindicatorandpotassiummanganatereplacessodiumhydroxide
• 0.001moldm-3potassiummanganate(VII)solution(madeupaccurately)
3
StudentPracticalWork1. RecordingandMineralIdentificationThisisalovelyactivitythatstudentsoftenreallyenjoy.Usingamicroscopetoviewsmallmineralsamplesiscomparabletoviewinglargemineralsampleswiththenakedeye.Mostwillfindthesamplestheyviewbeautifulandwillbekeentoidentifythem.a. Placetheicesampleinaclean,drybeakeranduseaBunsenburnertomelttheice.b. Filteryourmeltedsamplecollectingthefiltrateinameasuringcylinder(choosethemostappropriatesize
available).Makesurethatallthesolidendsupbeingtransferredtothefilterpaper.c. Recordthevolumeofsolutionyouobtain.Transferyoursolutiontothecontaineritwillbestoredinandlabel
itclearly.Youwillneeditagainlater.d. Examinethecontentsofthefilterpaperwithamicroscopeusingalowpowerlens.e. Usethemineralidentificationsheettotryandidentifythemineralsamplesyoufind.2. QualitativeAnalysisYoumaywishtoadaptthispartoftheanalysistomatchyourownspecificationornottocarryoutthispartofthepracticalatall.
Studentsareprovidedwithaninformationsheetthatdetailsarangeofqualitativeanalyticaltests.Theirtaskistocarryoutthetests,decidewhichionsarepresentandsuggesttheformulaeofsomedissolvedsaltswhichmaybepresent.
TheyshouldalsouseuniversalindicatortofindthepHofthesolution.Warnstudentstoonlyusesmallamountsoftheirsolution.Theyshouldleaveatleast20cm3forfurtheranalyticalwork.3. Acid–BaseTitration
Thisisastandardacid-basetitrationsetinanovelcontext.Theendpointofthetitrationisthefirstpermanentappearanceofpink.
a. Usinga10cm3pipette,transfer10.00cm3ofyoursampleintoa100cm3volumetricflask.b. Usingdistilledwater,makethesolutionuptothemarkandshakewell.Younowhavea1in10dilutionofyour
originalsample.c. Usingapipettetransfer20/25cm3ofyoursampleintoaconicalflaskandaddafewdropsofphenolphthalein
indicator.d. Setupaburetteandfillitwith0.10moldm-3sodiumhydroxidesolution.e. Carryoutthetitrationuntilyouhaveatleasttwoconcordantresults.4. RedoxTitrationManganate(VII)ionsareusedheretodeterminetheconcentrationofiron(II)ionspresentintheicecore.Manganate(VII)isaddedtothesamplefromaburetteandisdecolourisedimmediately.Assoonasallthereducingagent(Fe2+ions)isusedup,thesolutionintheconicalflaskgoespalepinkduetothepresenceofMnO4
-ions.Theendpointofthetitrationisthefirstpermanentappearanceofthispalepinkcolour.Noindicatorisrequiredasthemanganate(VII)isself-indicating.
a. Usinga10cm3pipette,transfer10.00cm3ofyoursampleintoa100cm3volumetricflask.b. Usingdistilledwater,makethesolutionuptothemarkandshakewell. Younowhavea1in10dilutionofyouroriginalsample.c. Usingapipettetransfer20/25cm3ofyoursampleintoaconicalflask.d. Setupaburetteandfillitwith0.001moldm-3potassiummanganate(VII)solution.e. Carryoutthetitrationuntilyouhaveatleasttwoconcordantresults.
1
WeAreAliens!–Classroomactivity8(Chemistry)IceCoreAnalysis
1. MineralIdentification
a. Placetheicesampleinaclean,drybeakeranduseaBunsenburnertomelttheice.b. Filteryourmeltedsamplecollectingthefiltrateinameasuringcylinder(choosethemost appropriatesizeavailable).Makesurethatallthesolidendsupbeingtransferredtothefilterpaper.c. Recordthevolumeofsolutionyouobtain.Transferyoursolutiontothecontaineritwillbestoredin andlabelitclearly.Youwillneeditagainlater.d. Examinethecontentsofthefilterpaperwithamicroscopeusingalowpowerlense. Usethemineralidentificationsheettotryandidentifythemineralsamplesyoufind.
Volumeofsolution cm3
Briefdescriptionincludingcolour Possiblename Possibleformula
2. QualitativeAnalysis
Usetheinformationsheetstocarryouttestsonyousampleofmeltwater.Makesureyoukeepatleast20cm3ofsampleforthenexttwoexperiments.Usethesetablestorecordyourpositiveresults
CationsPresent AnionsPresent
ColourwithUniversalIndicator EstimatedpH
2
Usingyourqualitativeanalysisresults:
Suggestwhatacidcouldbepresent Suggesttheformulaofsomepossibledissolvedsalts
3. Acid–BaseTitration
Youareusingsodiumhydroxideofknownconcentration(intheburette)tofindouttheconcentrationofacidinyouricesample.Theendpointofthetitrationisthefirstpermanentappearanceofpink.a. Usinga10cm3pipette,transfer10.00cm3ofyoursampleintoa100cm3volumetricflask.b. Usingdistilledwater,makethesolutionuptothemarkandshakewell.Younowhavea1in10dilutionofyouroriginalsamplec. Usingapipettetransfer20/25cm3ofyoursampleintoaconicalflaskandaddafewdropsof phenolphthaleinindicatord. Setupaburetteandfillitwith0.10moldm-3sodiumhydroxidesolutione. Carryoutthetitrationuntilyouhaveatleasttwoconcordantresults
Titre/cm3Rough 1 2 3 mean
Yourmeltwatersamplecontainssulphuricacid(H2SO4).Inthistitration,itwasneutralisedbysodiumhydroxidesolution.i. Writeabalancedequationfortheneutralisation
ii. Youused0.10moldm-3sodiumhydroxidesolution.Useyourtitremeantocalculatethenumberofmolesofsodiumhydroxideyouadded.
iii. Useyourequationfromitoworkoutthenumberofmolesofsulphuricacidthatmusthavebeenpresentintheconicalflask.
iv. Youhadeither20or25cm3ofacidinyourconicalflaskatthestartofthetitration.Useyouranswer fromiii.tocalculatetheconcentrationofthesulphuricacidpresent
v. Thesolutionintheconicalflaskwasa1in10dilutionofyourmeltwater.Calculatetheconcentrationofsulphuricacidintheoriginalice.
3
4. RedoxTitration
Inthistitrationpurplemanganate(VII)ionsareusedtodeterminetheconcentrationofiron(II)ionspresentintheicecore.Manganate(VII)isaddedtothesamplefromaburetteandisdecolourisedimmediately.Assoonasallthereducingagent(Fe2+ions)isusedup,thesolutionintheconicalflaskgoespalepinkduetothepresenceofMnO4
-ions.Theendpointofthetitrationisthefirstpermanentappearanceofthispalepinkcolour.Noindicatorisrequiredasthemanganite(VII)isself-indicating.a. Usinga10cm3pipette,transfer10.00cm3ofyoursampleintoa100cm3volumetricflask.b. Usingdistilledwater,makethesolutionuptothemarkandshakewell.Younowhavea1in10dilutionofyouroriginalsample.c. Usingapipettetransfer20/25cm3ofyoursampleintoaconicalflask.d. Setupaburetteandfillitwith0.001moldm-3potassiummanganate(VII)solution.e. Carryoutthetitrationuntilyouhaveatleasttwoconcordantresults.
Titre/cm3Rough 1 2 3 mean
YourmeltwatersamplecontainedFe2+ionswhichreactedwithMnO4
-ions.Theequationforthereactionisbelow.
8H++5Fe2++MnO4-à4H2O+5Fe3++Mn2+
i. Usetheequationtotellyouwhichelementwasoxidised. Givethebeforeandafteroxidationstatesforthiselement.
ii. Whichelementwasreduced?Givethebeforeandafteroxidationstatesforthiselement.
iii. Youadded0.001moldm-3potassiummanganate(VII)(KMnO4)solutiontotheflask. Useyourtitretocalculatethemeannumberofmolesofmanganateionsadded.
iv. Usetheequationgivenabovetoworkoutthenumberofmolesofiron(II)thatthemanganitereactedwith.
v. Youhadeither20or25cm3ofironsolutioninyourconicalflaskatthestartofthetitration. UseyouranswerfromivtocalculatetheconcentrationoftheFe2+present.
vi. Thesolutioninyourconicalflaskwasa1in10dilutionfromyourmeltwater. Calculatetheconcentrationofironintheoriginalice.
4
Couldlifeexistinthisicecore?
NotalllifeonEarthrespiresaerobicallyusingglucoseasanenergysource.Therearemanytypesofbacteriathatrespireusinginorganicmoleculeseitherwithorwithoutoxygen.Herearesomeexamples.1. Theequationbelowshowsarespiration(redox)reactioncarriedoutbysocalledironbacteria. H2O+Fe2O3→2Fe(OH)2+O2 water+iron(III)oxide→iron(II)hydroxide+oxygena. GivetheoxidationstateoftheironinFe2O3andFe(OH)2
b. GivetheoxidationstateoftheoxygeninH2OandO2c. Whatisactingasthereducingagent?2. Purplesulphurbacteriaareoftenfoundinhotspringsorstagnantwater.Unlikeplantstheydonotusewater
astheirreducingagent,andsodonotproduceoxygen.Insteadtheyusehydrogensulphide,whichisoxidizedtoproducegranulesofelementalsulphur.Thisinturnmaybeoxidizedtoformsulphuricacid.Thesebacteriathriveissulphuricacidlakes.
a. Bybalancinghydrogenwithhydrogenions,writeanelectricallybalancedequationfortheoxidationofhydrogensulphide(H2S)toelementalsulphur.b. Explainwhythisreactionisoxidation.
3. Biologicalnitrogenfixationoccurswhenatmosphericnitrogenisconvertedtoammoniabyanenzymecallednitrogenase.Thereactionis: N2+8H++8e−→2NH3+H2 Explainwhythisisaredoxreactionandnametheoxidisingagent.Sowhatdoyouthink,couldlifeexistonEuropaorEnceladus?Howmuchwouldyoubepreparedforgovernmentstospendinordertofindout?
WeAreAliens!–Classroomactivity8(Chemistry)-Mineral Information
Turquenite Blacktourmaline Pyrite Sodalite Tigereye Galena Malachitecalciumborosilicate
hydroxide acomplexsilicate ironsulphide sodiumaluminiumsilicate
silicondioxidewithtracesofiron leadsulphide coppercarbonate
hydroxideCa2B5SiO9(OH)5 (Ca,K,Na,)
(Al,Fe,Li,Mg,Mn)3(Al,Cr,Fe,V)6(BO3)3(Si,Al,B)6O18(OH,F)4
FeS2 (Na4Al3(SiO4)3Cl) SiO2 PbS Cu2CO3(OH)2
Amethyst Calcite Rosequartz Quartz Rhodonite Chrysocollasilicondioxidewithtracesoftitaniumor
manganesecalciumcarbonate
silicondioxidewithtracesoftitaniumor
manganesesilicondioxide manganesesilicate copperandaluminiumsilicate
SiO2 CaCO3 SiO2 SiO2 MnSiO3 (Cu,Al)2H2Si2O5(OH)4·nH2O
TestsforAnionsAnion Symbol Test Positiveresult
Bromide Br- Addsilvernitratesolution
Paleyellowprecipitateformswhichdissolvesslightlyinammoniasolution.
Carbonate CO32- Adddilute
hydrochloricacidEffervescence(fizzing)isseenandcarbondioxideisgivenoff
Chloride Cl- Addsilvernitratesolution
Thickwhiteprecipitateformswhichdissolvesinammoniasolution.
Iodide I- Addsilvernitratesolution
Paleyellowprecipitateformswhichdoesnotdissolveinammoniasolution.
Sulphate SO42- Addbariumchloride
solution. Whiteprecipitateforms.
TestsforCationsSodiumhydroxidetestCation Formula ObservationsAluminium Al3+ Whiteprecipitatewhichdissolveswhenmoresodium
hydroxideisaddedCalcium Ca2+ Whiteprecipitatewhichdoesnotdissolvewhenmore
sodiumhydroxideisaddedMagnesium Mg2+ Whiteprecipitatewhichdoesnotdissolvewhenmore
sodiumhydroxideisaddedCopper Cu2+ BlueprecipitateIron(II) Fe2+ GreenprecipitateIron(III) Fe3+ Brown(rust)precipitateLithium Li+ NoprecipitateSodium Na+ NoprecipitatePotassium K+ NoprecipitateAmmonium NH4
+ Noprecipitate
Flametest:SoakaspillinthesolutiontobetestedandplacethespillintheblueflameofaBunsenburnerCation Formula FlamecolourLithium Li+ RedSodium Na+ OrangePotassium K+ LilacCalcium Ca2+ BrickredBarium Ba2+ LightgreenCopper Cu2+ Blue-green
TestsforAnionsAnion Symbol Test Positiveresult
Bromide Br- Addsilvernitratesolution
Paleyellowprecipitateformswhichdissolvesslightlyinammoniasolution.
Carbonate CO32- Adddilute
hydrochloricacidEffervescence(fizzing)isseenandcarbondioxideisgivenoff
Chloride Cl- Addsilvernitratesolution
Thickwhiteprecipitateformswhichdissolvesinammoniasolution.
Iodide I- Addsilvernitratesolution
Paleyellowprecipitateformswhichdoesnotdissolveinammoniasolution.
Sulphate SO42- Addbariumchloride
solution. Whiteprecipitateforms.
TestsforCationsSodiumhydroxidetestCation Formula ObservationsAluminium Al3+ Whiteprecipitatewhichdissolveswhenmoresodium
hydroxideisaddedCalcium Ca2+ Whiteprecipitatewhichdoesnotdissolvewhenmore
sodiumhydroxideisaddedMagnesium Mg2+ Whiteprecipitatewhichdoesnotdissolvewhenmore
sodiumhydroxideisaddedCopper Cu2+ BlueprecipitateIron(II) Fe2+ GreenprecipitateIron(III) Fe3+ Brown(rust)precipitateLithium Li+ NoprecipitateSodium Na+ NoprecipitatePotassium K+ NoprecipitateAmmonium NH4
+ Noprecipitate
Flametest:SoakaspillinthesolutiontobetestedandplacethespillintheblueflameofaBunsenburnerCation Formula FlamecolourLithium Li+ RedSodium Na+ OrangePotassium K+ LilacCalcium Ca2+ BrickredBarium Ba2+ LightgreenCopper Cu2+ Blue-green
1
WeAreAliens!–Classroomactivity1(Physics)The“boilingwaterinasyringewithoutheatingit”experimentandwhyoceanscan’texiston
Marsnow–butonceuponatime,theydid!
Boilingisthelarge-scaleevaporationofaliquidintothegaseousstateand,forpurewater,
occursat100oCat1atmosphericpressure(1013.25mbor101325Pa).
Asatmosphericpressuredecreases,thetemperatureatwhichboilingoccursalsoreduces:
Figure01
Asweascendintheatmospherethedecreasingairpressuremeansthatwaterboilsat
progressivelylowertemperatures.
OnthesummitofMountEverest,whichis8,848m(29,028ft)abovesealevel-onlyslightly
lowerthanthealtitudecommercialairlinersflyat-thisfigurehasreducedfromourfamiliar
100Centigradetoaround70degreesCentigrade.
Higherstill,theconsequencesforunprotectedhumansbecomeevenmoreinsidious.At
20,000m(63,000ft)theboilingpointofwaterequalsahuman'sbodytemperature:37
degreesCentigrade.Ifweconsiderthemainconstituentofthehumanbody,therelevance
ofthisparticularpressuretohumanphysiologyandsurvivalisclear.Infact,theaeromedical
boundaryofspaceistakenasbeingatthisaltitude(63000ft),sinceafullpressuresuit
wouldbeneededforsurvival.Thepressureissolow(6%ofsea-level)thattheboilingpoint
ofwaterisbelowtheaveragehumanbloodtemperature.Theoutsidepressureislessthan
thepartialpressureofwaterinthebody.
Acommonmisconceptionisthatanunprotectedhuman'sbloodwouldstartboilinginthe
arteriesandveins,butsincetheskinisareasonablygoodpressurevesselthiswouldnotbe
thecase.
However,thedramaticoutgassingofnitrogendissolvedinthebloodstream(similarto,but
farmorerapidthantheexperiencesofdiverswhoascendtooquicklyfromdepth)coupled
withtheeffectsofexplosivedecompressionandlackofoxygenwouldresultin
unconsciousnessinseconds,anddeathwithinaminuteortwo.
2
Fromanaeromedical,orhumanphysiologyandsurvivalperspective,thisistheboundaryof
space
Martianmeandatumpressureiswellbelowthepressureequivalentatthisaltitude,and
thusafull-pressuresuitlikethosecurrentlyinuseforspacewalks(EVAs)ontheInternational
SpaceStationwouldbeneeded.
CurrentsurfaceconditionsonMarsandliquidwater
Figure2(aboveleft)Figure3(aboveright)
Atpresent,ambientpressuresaresolowthatliquidwaterpouredoutontotheMartian
surfacewouldsimultaneouslyfreezeandevaporateaway.Therearenolong-lyingareasof
liquidwateranywhereonthecurrentsurface.
Yetweseemuchevidenceofawarmer,wetterpast–whatlookslikeanancientriversystem
belowspansseveralhundredkilometres:
Figure4
Left:afrozenMartianlake?
Below:Sedimentaryrocks
photographedbyOpportunity
3
Mars–aburiedocean?
MarsOdyssey,whichhasbeenorbitingMarssinceOctober2001carriedaneutronspectrometertomeasuretheneutronfluxproducedduetothefollowing:
• High-energygalacticcosmicradiation(GCR)slamsintotheMartiansurface–
neutronsareejectedfromsurfaceatomicnuclei
• Someoftheejectedneutronfluxisupwardstowardstheorbitingspacecraftwhich
detectsthem
• Eachchemicalelementcreatesitsownuniquedistributionofneutronenergies
• Themeasuredneutronflux“signatures”allowdeterminationofthetopsurface
material’schemicalcomposition
• Hydrogeninthesoil(assumedtobeinsubsurfaceice)willeffectivelyabsorb
neutronenergyandreducetheneutronfluxthatescapesfromthesurfacetobe
detectedonorbit.
• Additiongammafluxescausedbynuclearde-excitationafterGCRinteractionswith
surfacenucleiwerealsomeasuredbythespacecraft
Thefollowingmapshowstheinferreddistributionofsubsurfaceicefromorbitaldata:
Figure5(below)
Thisdatasetisvalidforsurfacedepthsofonly1morthereabouts–yettheamountofwater
indicatedisstaggering.
MorerecentresultsfromNASA’sMarsPhoenixlanderhaveconfirmedthepresenceof
subsurfaceicewhichslowlysublimatesonexposuretosurfaceconditions.
4
Conclusion
AtpresenttheconditionsonthesurfaceofMarsaresuchthatcomplexEarthorganisms
suchasourselveswouldfinditimpossibletosurvivewithoutsignificantprotectionfromthe
extremeenvironmentalparametershighlightedinthedemonstrationfilms.
Yetallthegeologicalandobservationalevidencepointstoaplanetthatwasonce
significantlywetterandwarmer.AllovertheMartiansurfaceweseeevidenceoffeatures
associatedwithlong-standingextensivebodiesofliquidwater…..dendriticriversystems,
evidenceofcatastrophicfloodeventsandrocksthatrequirethepresenceofliquidwaterto
form.Theseimplytheplanetoncehadamuchdenseratmosphere,onethatwouldasa
consequencehavehadsignificantlyhighertemperaturesthanthosecurrentlyextant.What
happened?
Figure6(above)
Figure7(above)
Marstoday.ThisMGScompositeimageis
centredonVallisMarineris,thegiant
tectoniccrackinMars’crust.Atleftcanbe
seentheTharsisbulgewiththe
“supervolcanoes”Arsia,Pavonisand
AscraeusMons.
Thisartisticimpressionshows
whatMarsmayhavelookedlike
3.8-3.5billionyearsago(Noachian
epoch).TheNorthernhemisphere
lowlandsarecoveredbyashallow
oceanthatfillsVallisMarineris.
5
ImageReferencing:
Figure01-CHEM.PURDUE.EDU(dateunknown)Boiling;Factorsthataffectboilingpoint[WWW]PurdueeduAvailablefrom:http://www.chem.purdue.edu/gchelp/liquids/boil.html
[06/12/2012]
Figure02-VIRGINIA.EDU(2012)WateronMars:FrozenLakeinCrater[WWW]Credit:
ESA/DLR/FUBerlin(G.Neukum)
http://www.astro.virginia.edu/class/oconnell/astr121/im/ice-in-crater-Mexpress-lg.jpg
[06/12/2012]
Figure03-NASA(2012)MarsExplorationProgramAnalysisGroup(MEPAG)[WWW]Pancam
photomosaic,approximatelytruecolor:NASA/JPL/CornellAvailablefrom:
http://mepag.nasa.gov/science/1_ancient_persistent_liquid_water/index.html
[06/12/2012]
Figure04-ABOVETOPSECRET(2011)TheSearchForLife.Part2–Aretheyhere?[WWW]
Availablefrom:http://www.abovetopsecret.com/forum/thread669103/pg1[06/12/2012]
Figure05-NASA(2012)MarsExplorationProgramAnalysisGroup(MEPAG)[WWW]
Graphic:NASA/JPL/UniversityofArizonaAvailablefrom:
http://mepag.nasa.gov/science/3_Modern_Water/index.html[06/12/2012]
Figure06-NRAO(2012)Mars[WWW]Availablefrom:
http://www.gb.nrao.edu/epo/sol_sys/mars.html[06/12/2012]
Figure07-CARROLL,MICHAEL(2012)LiquidWateronMars(artisticimpression)[WWW]
PaintingbyMichaelCarrollAvailablefrom:
http://www.lpi.usra.edu/publications/slidesets/redplanet2/slide_28.html[06/12/2012]
1
WeAreAliens!–Classroomactivity2(Physics)COMETRECIPE
CometIngredientsWaterinajug(abouthalftheamountofdryice)
Binliners
DryIce(about2-3x600mlcontainerfulls)
1Spoonfulofsand1Spoonfulofcarbondust
Fewdashesofworcestersauce(organiccomponent)
Fewdashesofwhisky/redwine(optional–themethanol/ethanolcomponent)
BowlDisposalBucket
RubberGlovesWoodenSpoon
ClearscreenPolysterenecontainerfordryice
Method
1. Takeabinlineranduseittolinethebowl.
2. Addtheingredientsofyourcomet–water,sand,carbondust,worcestersauce.These
replicatethecompoundsthatrealcometsarecomposedof.Volunteersoftheaudience
canaddsomeofthese.Mixwellwithwoodenspoon.
Anoteonthesignificanceoftheingredients:
§ WATER - how comets have large amounts ofH2O, and in the past it is believed
comets could have brought water to Earth through impacts with our planet
billionsofyearsago.§ The SAND, TheCARBON,ALCOHOL, and theWORCESTER SAUCE for the organic
component.Cometshaveall theright ingredients for life,but themixture isnot
underthecorrectconditionsforlifetoexist.§ THE DRY ICE – frozen CO2, the frozen gas that holds together our comet and
sublimateswhenitinteractswiththesolarwindandsolarradiationtoformthe
comaandgastail.
3. Finallyaddthedryice.Wearingglovesfeelaroundthebinlinerandmouldthecomet
intoonelump.Don’tcompressittoohardasthecometmaybreak,allowsteamgasto
escape.
4. Whenthedemonstrationiscompletedplacethecometsinsidethebinlinerinabucket.
2
SafetyPrecautions
• Whenhandlingthedryicewearglovesandgoggles.Donottouch,swallowortastethedryice.Donotallowstudentstoonearthedryice.Givetheaudienceclearinstructionsonthehazardandthedistancetheyshouldbeseatedformthedryiceasthecometmay‘spit’
• Donotsealthedryiceintoacontainerasexplosiveoutgassingmayresult!• Transportdryiceinaplasticbaginsideabox.• Disposeofcometoutsideinawell-ventilatedareawherestudentscan’taccessit.
TheScience
DryiceisfrozenCarbonDioxide(-78.5oC,or-109.3oF),orCO2,whichisagasunderstandardtemperatureandpressure conditions. Theatmosphere contains about0.035%of this gas.CO2isagreenhousegas,whichmeansitabsorbslightatinfraredwavelengths.Anincreasein the concentration of this gas may cause an increase in the atmosphere's averagetemperature.ThehighconcentrationofCO2(>96%)intheatmosphereoftheplanetVenuscontributestothatplanet'shighaveragetemperature.
At normal atmospheric pressureon this planet, frozenCO2doesn'tmelt into a liquid, butratherevaporatesdirectly into itsgaseous form -hence thename ‘dry ice’. Thisprocess iscalledsublimationandisresponsiblefortheformationofacomet’scoma.WecanseeCO2gassublimingawayfromourcometfromwherewatervapourintheaircondensesaroundit.
1
WeAreAliens!–Classroomactivity3(Physics)Pressureandwhatit’sreallylikeonEarth,VenusandMars!
WhatdoweMeanbyPressure?
Putsimply,pressureisthemeasureofaforcespreadoverasurfacearea.Theunitof
pressure,thePascal,istheforceof1Nactingoveranareaof1squaremetre.
TheOriginofAtmosphericPressureAtmosphericpressure,whichwetakeforgranted,canhave
unusualeffects,asweseeintheglassofwaterandcard
experiment.Itscauseissimplytheweightofatmosphereabove
uswhichextendstoanaltitudeofwellover100km-the
internationallyacceptedboundaryofspace(althoughnearly
90%ofthetotalmassoftheatmosphereiswithin10kmofthe
Earth’ssurface).
Wetendtoforgetthatwearelivingatthebottomofan
“ocean”ofair.
Figure01
Atmosphericpressurevariesatagivenlocationwiththepassageofweathersystems,and
decreasesexponentiallywithaltitude.Thestandardvalueis101.325Pa(1013.25mb),also
knownas1atmosphere(atm).ThismeansthateverysquaremeteroftheEarth’ssurfaceis
sittingunder10tonnesofatmosphericmass!
Figure02–Shownabove
2
TheEffectsofAtmosphericPressureGaspressureiscausedbymomentumchangesduringthecollisionsbetweenthemoleculesoratomsthatcomposethegas,andanythingthathappenstobeintheway!Weoftenmodelthebehaviourofgasesbyconsideringthemtobe“ideal”gases.Thesearemonatomicgaseswithatotalparticlevolumewhichisnegligibleincomparisontothetotalvolumeoccupiedbythegasandwithnointerparticleinteractionsapartfromduringcollisions.TheIdealGasEquation–GCSE+levelThisisderivedbyputtingtogetherthefamiliarequationsfromthreeLawspV=constant,p/T=constantandV/T=constantforaconstantmassofidealgas;whichleadsto(ALevel)n=numberofMOLESofthegas(oneMOLEisdefinedasbeingAvogadro’snumberofsomething.Ifyouevergetstressedaboutwhatamoleis,justthinkofitasbeing6.02x1023ofsomething–beitgasmoleculesorpeople!)R=MOLARGASCONSTANT–ameasureofthekineticenergy/temperaturelinkforonemole’sworthofmolecules/particles.T=AbsolutetemperatureinKelvinForaMICROSCOPICratherthanMACROSCOPICmodel(i.e.consideringthesmallnatureofparticlesratherthanmassesofthematonce),theidealgasequationisoftenwrittenasBoltzmann’sconstantgivesusadirectlinkbetweentranslationalkineticenergyand
temperatureforasingleparticle.Themeantranslationalkineticenergyofaparticleina
2
22
1
11
TVp
TVp
=
nRTpV =
N = total absolute number of particles (rather than grouping them into moles) T = temperature in K
k = BOLTZMANN’s CONSTANT = 1.38*10-23 J/K
NkTpV =
3
systemattemperatureTis3/2kT.(Ifwestartconsideringother“degreesoffreedom”suchasmolecularROTATIONorVIBRATION,thenweaddafactorofkT/2foreachextradegreeandmodethat’sincluded.)PressureandAltitude(GCSEandALevel)Asweascendintheatmosphere,theairpressurediminishes,asthereislessweightofairabove.ALevelmodellingIfweassumeanidealgasisbehavingHYDROSTATICALLY,thenforaparticularlayerofgasatagivenaltitudethedownwardforceofitsweightandthedownwardforceexertedbypressureinthelayeraboveisequaltotheupwardforceexertedbypressureinthelayerbelow.It’spossibletoshowthatthefollowingrelationholds
ForEarth,withanapproximateatmosphericcompositionof80%N2and20%O2,wefindameanmolarmassof28.8g(N2=28,O2=32)whichneedstobeexpressedinkg.TheEarthvaluetranslatestoameanmolecularMASSof28.8timesthatofahydrogenatom=4.8x10-26kg.UsingthisequationisasstraightforwardasthemorefamiliarusesofexponentialswithregardstoTakingthesea-levelvalueforpressuregivenabove,ameanatmospherictemperatureof0oCandtheheightofMountEverestas8850m,wecanshowthatthepressureonitssummitisaboutone-thirdofthesea-levelvalue,andcalculateitinPascals.OfcoursethemodelisinaccurateinthatitassumestheatmosphereisISOTHERMAL;atthesametemperaturethroughout.Infact,asweascendintheatmosphere,temperaturedropsattheLAPSERATEof6.5oCper1000muntilwereachthecoldestpartoftheatmosphere–thetropopause(boundarybetweentroposphereandstratosphere).Abovethisaltitude,intheSTRATOSPHERE,temperatureincreaseswithaltitudeduetoincidentuVabsorptionandre-emissionatlongerwavelengthscausingatmosphericheating.
P = pressure at altitude h metres P0 = sea level pressure m = mean mass of a particle in the atmosphere
( )kTmgh0 ePP /−=
Radioactivity t0 eNN λ−=
Capacitance ( )CRt0 eVV /−=
4
Venus–Earth’s“eviltwin”Venus,namedaftertheRomangoddessoflove,probablywinstheprizefortheastronomicalobjectthatfailstoliveuptoitslabel!ItisprobablytheclosestapproximationtoHellthatwecouldenvisageanywhereintheSolarSystem.Withsurfacetemperaturesoftheorderof480C(andlittlevariationindayandnight)andasurfacepressureof90+Earthatmospheres(equivalenttonearly1000Newtonsoneverysquarecentimetre)eventhemostrobustplanetarylandershaveonlysurvivedtoreturndataforamatterofminutesor,atbest,afewhours.StepoutonVenus’ssurfacewithoutatungstenarmouredhard-shellpressuresuitandyou’dbecrushedandbakedwithinseconds!
Figure03Ourimagesofthesurfacedatebacktothe1970sand1980s.TheSovietVeneraseriesoflanderssurvivedtoreturnsurfacedata,withVeneras9,10,13and14eachreturningonepanoramicfish-eyeviewbeforesuccumbingtotheharshenvironment:
This cross-sectional pressure and temperature profile through the Venusian atmosphere highlights the exponential pressure increase with depth in the atmosphere 1 bar = 100 000N/m2
1 standard Earth atm = 1013.25mb
5
Figure04
ThisVenera13rawimage(1982)attophasbeenenhancedtobringoutfurtherdetails:
Figure05–Shownabove
TheatmosphereofMars
OnMars,theatmospherehaslessthan1%ofthesea-levelpressureonEarth.Martian
pressuresaregivenwithreferencetoaMartianimaginarysea-levelcalledthemeandatum
becauseMarshasnooceansatpresent!
Mars’atmosphereissoinsubstantialcomparedtoEarth’sthateveninMartiansummer
whereoccasionallythesurfacetemperatureinafewlow-lyinglocalesmightreach20o
C,the
lapserateintheimmediatevicinityofthesurfaceismuchlargerthanonEarth.TheMartian
atmosphere’sheatretentioncapacityissolowthateventwoorthreemetresaboveour
surfaceinmidsummer,itwouldbebelow0o
C.
MisunderstandingsaboutpressuredifferentialsandthehumanbodyThehumanbody,ifexposedtotheMartianorvacuumenvironmentunprotected,would
NOTexplode!Invacuumchamberaccidents,humanshavesurvivedexposuretovacuumof
uptooneminutewithouttheexplosionoftheinternalorgansorskinoreyeballs.The
humanskinisstrongerthanexpectedandwouldfunctiontosomedegreeasapressuresuit
forashortperiodoftime.Bloodwouldnotboilthroughtheskinbutdissolvedgasesinthe
6
bloodstreamwouldstartcascadingoutofsolution–resultinginlethalebullisminashortperiodoftime.
• Explosiveoutgassingofairfromthelungsatoverpressurescorrespondingto10N/cm2(normalatmosphericpressure)wouldbeenoughtoblastoutweakerhumanfrontteeth
• Alotofmisconceptionsconfusedivingdecompressionaccidentswithspacesuit
failures.Intheearly1980sadecompressionaccident(theByfordDolphinincident)resultedinanumberofdiversbeingexplosivelydecompressedfromapressureof9atm(900000Pa)to1atminlessthanasecond.Thisresultedintheexplosivedisintegrationofoneofthediver’sbodies.However,aspacesuitdecompressionwouldresultinapressuregradientfarlesssteepandhencethehumnanbodywouldmostlikelyretainintegrity.
• In1966JohnsonSpaceCenterengineerJamesLeBlancwastestingaspacesuitina
vacuumchamberwhenhissuitdecompressedatanequivalentaltitudeof250000ft(toallintentsandpurposesavacuum).Hislastmemorywasofthesalivaboilingoffhistongueashelostconsciousness.Thechamberwasfloodedwithairwithin14secondsandLeBlancmadeafullrecoverywithindays.
LandingonMars…….ischallenging,tosaytheleast!Thereisenoughofanatmospheretocauseram-airheatingonatmosphericentry,butnotenoughtobeabletorelyontheterminalvelocityofaerodynamicdecelerators(i.e.parachutes)deliveringthespacecraftsafelytothesurface.ThesuccessrateforMartianlandingmissionsisstillonlyjustover50%-afternearlyfourdecadesoflandingattempts,notablefailureshaveincluded:
• Mars2(1971)CrashedonMars(SovietUnion)• Mars3(1971)15secondsofdataandpartialimage(SU)• Mars6(1973)Transmissionsceasedjustbeforelanding(SU)• MarsPolarLander(1999)Enginecutoffwhilst40mabovesurface(US)• DeepSpace2(1999)Unknown(US)• Beagle2(2003)Unknown(UK2003)
SuccesseshaveincludedtheVikinglandersofthe1970s,PathfinderandtheSojournermini-rover(1997)andthespectacularUSMarsExplorationRovers(MER)–SpiritandOpportunity.Launchedin2003withanoperationalexpectancyof90Martiandays(sols),Opportunityhasnowbeenreturningdataforeightyears(Spiritfinallystoppedtransmittingin2010)andbothrovershavetransformedourunderstandingoftheMartianenvironmentandgivenustantalisingcluesastotheplanet’spasthistory.
7
MostrecentlyPhoenix(US)successfullylandedintheMartianArcticin2008andCuriosity(NASA’sMarsScienceLaboratory)iscurrentlyexploringGalecrater,havingsuccessfullylandedinthesummerof2012.Marscurrentlyhoststhreeactivespaceprobesinorbit(MarsOdyssey(NASA),MarsExpress(ESA)andtheMarsReconnaissanceOrbiter(NASA)).
Figure06–Shownabove
Theaboveimageshowsatrue-colourpanoramaoftheEndurancecraterasexploredbyMER-B(Opportunity)SurfacepressuredatafromNASA’sPathfindermission(1997)Forreference,Earth’smeanpressureis1013.25mb.
Figure07MarsGlobalSurveyor’sthermalemissionspectrometerobtainedthefollowingdataaboutsurfacetemperaturesinthesouthernhemispherefromMartianorbit:
8
Figure08The“frost”inthis1978Viking2imageisnotwatericebutrathersolidCO2thathassublimedoutoftheMartianatmosphereaswinterdrawscloser.
Figure09
FromorbitalandgroundmeasurementswecancombinedatasetstogivethefollowingoverallapproximatepictureoftheMartiansurfaceenvironment:
• Temp(Mean):-46C
• Temp(Max):-5to+20C(verytransient)
• Temp(Min):-90C
• Meansurfacepressure
=8mb
• (Earth=1013.25mb=101325Pa)
• Composition:96%CO2
Theblueskyisafalse-colourartefactfromimageprocessing.
9
ImageReferences:Figure01-ImagefromWeAreAliens!teachingresourcevideo(2012)©NSCCreative2012Figure02-(2012)©NSCCreative2012Figure03-DAILYKOS.COM(2011)GettingtoknowyourSolarSystem(3):Venus[WWW]Availablefrom:http://www.dailykos.com/story/2011/08/28/1008141/-Getting-to-Know-Your-Solar-System-3-Venus[06/12/2012]Figure04-UOREGON.EDU(dateunknown)Venera[WWW]Availablefrom:http://abyss.uoregon.edu/~js/space/lectures/lec11.html[06/12/2012]Figure05-MAHALO.COM(2010)WhatimagesdidRussianVenera13takeofVenus?How
wasVenera13abletosurviveforover30minutesonthesurfaceofVenus?[WWW]Availablefrom:http://www.mahalo.com/answers/what-images-did-russian-venera-13-take-of-venus-how-was-venera-13-able-to-survive-for-over-30-minutes-on-the-surface-of-venus[06/12/2012]Figure06-NASA(dateunknown)MarsRover“Opportunity”Images[WWW]EnduranceCratorAvailablefrom:http://nssdc.gsfc.nasa.gov/planetary/mars/mars_exploration_rovers/merb_images.html[06/12/2012]Figure07-NASA(dateunknown)MarsPathfinderMETSurfaceCalibratedData;Dataset
Description[WWW]Availablefrom:http://starbase.jpl.nasa.gov/mpfl-m-asimet-4-ddr-edl-v1.0/mpam_0001/document/srfrdrds.htm#DataSetOverview[06/12/2012]Figure08-REDORBIT(2003)MGSThermalEmissionSpectrometerImage[WWW]Availablefrom:http://www.redorbit.com/images/pic/3436/mgs-thermal-emission-spectrometer-image/[07/12/2012]Figure09-WIKIPEDIA(2012)MarsViking21i093[WWW]Availablefrom:http://en.wikipedia.org/wiki/File:Mars_Viking_21i093.png[07/12/2012]
1
WeAreAliens!–Classroomactivity4(Physics)UsingTVsandmagnetstoexplainwhyMarsistheschizophrenicworldoftheSolarSystem!Weoftenthinkofspaceasavacuum–buttheSuniscontinuallyemittingastreamofchargedparticles–thesolarwind–inalldirections.Thistorrentofhigh-energyelectronsandprotonshasthecapability,overmillionsofyears,tostripawayaplanetaryatmosphere.Thereasonitdoesn’t,inthecaseofEarth,isbecauseofourglobalplanetarymagneticfield.(CRTTVandmagnetdemo)
Figure01IfweheatapermanentironmagnettoaboveitsCURIEtemperature(about1000K)thenthermalagitationmeansthatindividualatomicdipolemomentsarerandomlyaligned–i.e.thematerialwillloseitspermanentmagneticmoment.TheinterioroftheEarthiswellabovethistemperature–therecan’tbeasolidironmagnetburiedtherethatcreatestheEarth’smagneticfield!CurrentmodellingsuggeststhatliquidcurrentsintheEarth’soutercoregenerateaplanetarymagneticfield–amechanismcalledthegeomagneticdynamo.
Figure02
2
Figure03TheinteractionbetweentheEarth’smagneticfieldandthechargedparticlesofthesolarwind(trillionsofelectriccurrents,ineffect–eachthuscreatingtheirownmagneticfield)causestheparticlestobedeflectedawayfromstrippingawaytheatmosphere.Somegetfunnelledtothepolarregions,causingtheupperatmosphericauroraewhilstothersgettrappedintheEarth’smagneticfieldoscillatingbackandforthinthefamedVanAllenradiationbelts.Figure04–Shownbelow
CurrentlyMarshasnoglobalmagneticfieldofcomparablestrengthtoEarth’s.
3
Figure05–ShownaboveHowever,weseegeologicalevidencefora“fossil”fieldinthepastfromMGS(MarsGlobalSurveyor)data:
Figure06–ShownaboveAsasmallerplanetthanEarth,Marshasalargersurfaceareatovolumeratioandsolostinternalheatquicker.Italsohadlessgravitationalself-accretionenergytostartwithandalowerinventoryofradioactivematerialsinitscorewhichprovidesextra“internalheating”.PerhapsMars’corewasoncewarmenoughtoenabletheliquidmotionnecessarywithinthecoretocreateaplanetarymagneticfield.Asideeffectofthisincreasedcoreheatwouldhavebeenpartialsurfacetectonicactivity–asevidencedbytheenormousshieldvolcanoOlympusMonsandthegianttectoniccrackofVallisMarineris.ItisasifthetectonicengineonMarswasstutteringbutneverbecamegloballyoperational.
Forreference,Earth’smagneticfieldstrengthatthesurface(awayfromthegeomagneticpoles)isapproximately5*10-4Tesla.
ThefiguresforMarsare4to5ordersofmagnitudesmaller.
4
Figure07–ShownaboveAstimewentonandtheplanet’sinteriorcooled,tectonismdiedawayandtheliquidcurrentsnecessaryinthecoretoproduceapowerfulglobalmagneticfieldceasedasthecorecooledandsolidified.Itisalsopossiblethatasequenceofgiantasteroidimpactsdestroyedtheplanetarymagneticfield.Whichevermechanismwasresponsible,theendresultwasthesame:thetenuoussolarwindwasnowabletostartdirectlyinteractingwithMars’atmosphere,strippingitawayinarelentlessprocessoverbillionsofyearswiththefinalresultbeingthebarren,dead(?)worldweobservetoday.
Figure08Couldthisbethefateofourplanet?It’scertainlyapossibilitybutcurrentestimatesgiveusatleast1.5billionyearsbeforetheeffectswouldbesodramaticonourhomeworld.Nevertheless,thishighlightsoneofthebenefitsofplanetaryexploration–unlockingthesecretsofotherworldsgivesusbetterinsightsintoourown.
HereweseethatwiththelackoftectonicplatemovementoftheMartiancrust,themagmaticplumeresponsibleforthecreationoftheOlympusMonssupervolcanocreatedamassive,550kmwidepeakreachingover20kmabovemeandatum.
ThelargestvolcanoesonEarth–theHawaiianislandchain,formedanarcduetorelativemotionoftheoceanicplateoverthemantleplume.
ObservationshaveshownthatMartianauroraarenotconfinedtoregionscoincidentwithplanetarygeomagneticpolesbutareevidentatalllatitudes.
5
Imagereferences:Figure01-AEROSPACEWEB(2012)WateronMars[WWW]Earth'smagneticfielddeflectingthesolarwindAvailablefrom:http://www.aerospaceweb.org/question/astronomy/q0230.shtml[07/12/2012]
Figure02-DISCOVERYENTERPRISE(2012)DowntotheEarth’sCore[WWW]Availablefrom:http://www.discovery-enterprise.com/2012/10/down-to-earths-core.html[07/12/2012]
Figure03-NATIONALATLAS(dateunknown)TheEarthasDynamo[WWW]Availablefrom:http://www.nationalatlas.gov/articles/geology/a_geomag.html[07/12/2012]
Figure04-ASTRO.UMD.EDU(dateunknown)EducationandOutreach;RadiationBeltstheBigPicture[WWW]Availablefrom:http://spp.astro.umd.edu/SpaceWebProj/education.htm[07/12/2012]
Figure05-UNIVERSETODAY(2008)MarsmagneticField[WWW]Availablefrom:http://www.universetoday.com/14949/mars-magnetic-field/[07/12/2012]
Figure06-COLORADO.EDU(dateunknown)MarsmagneticField;MartianVectorMagneticFieldat400km[WWW]Availablefrom:http://lasp.colorado.edu/~bagenal/3750/ClassNotes/Class19/Class19.html[07/12/2012]
Figure07-MPS.MPG.DE(2006)MantleDynamics[WWW]Availablefrom:http://www.mps.mpg.de/projects/planetary-dynamics/mantle.html[07/12/2012]
Figure08-NASA(2011)HowVitalIsaPlanet'sMagneticField?NewDebateRises[WWW]Artist'sconcept:DisappearanceoftheancientmagneticfieldmayhavetriggeredthelossoftheMartianatmosphere.CREDIT:NASAAvailablefrom:http://www.space.com/11187-earth-magnetic-field-solar-wind.html[07/12/2012]