Constrainingtheaccretionregionsofmeteoritesviaastrochemicalmodellingofprotoplanetarydisks
JonRamsey,SørenFrimann,ElishevahvanKooten,TommasoGrassi
SusanneWampfler,JesK.Jørgensen,MartinBizzarroCentreforStarandPlanetFormation,
NaturalHistoryMuseumofDenmarkandtheNielsBohrInsitute,
UniversityofCopenhagen
November9,2017
TheBeginning
Thisprojectspringsfrom"AdivergentheritageforcomplexorganicsinIsheyevolithicclasts"synergy
project(vanKootenetal.,2017,GCA,205,119).
IsheyevoisaCH/CBcarbonaceouschondritewithtwonoticeably
differentlithologiesbutacontinuoustransitionbetweenthetwo.
Itcontainspristinelithicclaststhatcanbecategorisedaseitherhydrated(H)or
weaklyhydrated(A).
TheA-clastsare -enriched( )relativetotheH-
clasts( ).
Thereare hotspotsreaching .
fortheA-clastsand
fortheH-clasts.
15N 15N/N = 0.004 − 0.00615N/N = 0.0039 − 0.0043
15N/N ∼ 0.022
D/H = (1.1 − 1.3) × 10−4 D/H = (1.2 − 1.6) × 10−4
Imagecredit:D.Weir'smeteoritestudies.com
Imagecredit:ElishevahvanKooten
IsotopicTrendsinIsheyevo
vanKootenetal.(2017)
increasinghydration←−−−−−−−−
A-clasts:orange;H-clasts:blue.
δ15N = ( − 1) × 100015N/Nmeas15N/Nair
Canweconstraintheaccretionregionsofmeteoriteparentbodies?
TounderstandIsheyevo,onecaninvoke
heterogeneousaccretion.
Perhapstheaccretionofthedifferentlithologies
occurredatdifferentspace-timesintheSolar
System.
Howcanweplaceconstraints?
Let'suseChemistry!
Isotopicratiosarecommonlymeasuredinmeteorites.
Wewillassumethatvolatilesendupinmeteoriteparent
bodiesviafreeze-out.
Approach
HowcanwelearnaboutthechemicalstructureofthePPD?1. Radiativetransfer:Hyperion(http://www.hyperion-rt.org)
Dustradiativetransferincl.isotropicscatteringandinternalviscousheating(singlegrainsize;nosettling).
Temperature-dependentmeanopacitiesfromSemenovetal.(2003),Fergusonetal.(2005).
Dustsublimationisaccountedforintheopacities.
HardworkcourtesyofSørenFrimann.
2. Non-equilibriumchemisitry:KROME(http://kromepackage.org)
TheKIDAdatabasenetworkisused(http://kida.obs.u-bordeaux1.fr/),modifiedfor , ,isotopefractionation(Roueffetal.,
2015),iceaccretion/thermaldesorption(Charnley,Rodgers&Ehrenfreund2001;Rodgers&Charnley,2003)andsimplified
photochemistry.
Thenetworkis"isotopologised"( ,butnot );isotopologizedreactionratesdeterminedby
"statisticalapproach"(Millaretal.,1989).
Bindingenergiesforthermaldesorption"scraped"fromtheliterature.
Thereare1341chemicalspecies(including56icespecies)andmorethan53400reactions.
TheDOCMAKEtoolisusedtoexplorethenetwork,examinereactionratesandproduceintegratedphotochemicalrates(with
cross-sectionsfromtheLeidendatabase).
15N D
D,D2, D3, 15N 15N2, D4
3.Theglue:SLiPPD(SnowLinesinProtoplanetaryDisks)Pythonpackage.
https://bitbucket.org/perrybothron/slippd
SetsupandinvokesHyperionandKROMEinsuccessionorindividuallyinserialorinparallel(MPI).
Visualisationandanalysisscriptsareprovided.
Foragivennetwork,youcancalculatethechemicalfluxesofreactionsoverarangeofdensitiesandtemperatures.
BetweenRTiterations,hydrostaticequilibriumisre-calculatedandthedensityadjusted.
Itwillbecomepubliconceapaperissubmitted(alsothechemicalnetwork).
ParameterisedDiskStructure
Internalviscousheatingisincluded:
Constantgas-to-dustratioof100.
Dustsublimationaccountedforvia
temperature-dependentopacities.
ρ(R, z) = ρ0 ( )−2.3exp(− )
exp[− ( )2]
R0
RRR0
12
zh(R)
Γvisc = αPΩKep94
α = 10−3
Mdisk = 0.01M⊙,M∗ = 1.0M⊙
Teff = 4339K, R∗ = 1.78R⊙
TheMiddle:PreliminaryResults
After2.5Myrofchemicalevolution
InitialconditionsarefromBrudereretal.(2009).
Nowwithisotopologisedinitialabundances
Freeze-outtimescale
Desorptiontimescale
∝ n−1T −1/2
∝ exp(−Eb/T)
D-bearingmolecules
-bearingmolecules15N
More!
Inthemidplane
TheEnd(fornow)
Thevariationof and ratiosindifferenticespeciesasafunctionofradiusisnotsimple.
RecallthevaluesinIsheyevo:
A-clasts: ; .
H-clasts: ; ;
Hotspots: .
Overall,theresultsareinreasonableagreementwiththerangeofSolarSystemmeasurements,including
theIsheyevoclasts,butwedonotreachthehotspotvalues.
WishListWhatwoulddustsurfacechemistrydo?
ViaLIME,generatesyntheticobservationsfordifferentdisks.
Addheatingandcoolingtotemperaturecalculation(CRheating,photoelectricheating,etc.).
D/H 15N/N
15N/N = 0.004 − 0.006 D/H = (1.1 − 1.3) × 10−4
15N/N = 0.0039 − 0.0043 D/H = (1.2 − 1.6) × 10−4
15N/N ∼ 0.022
Thankyouforyourattention!
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