NATS 1311 - From the Cosmos to Earth Differences Between Venus and Earth 1.Venus rotation rate is...

NATS 1311 - From the Cosmos to Earth

Differences Between Venus and Earth

1. Venus rotation rate is very slow and in retrograde direction.

2. Venus surface consists of 1 plate; earth has 9 plates.

3. Venus has little or no magnetic field.

4. Venus' atmosphere pressure is 90 times that of earth.

5. Dominant gas in the Venus atmosphere is carbon dioxide.

6. Venus' surface temperature is 900° F.

7. Venus has very little water vapor in its atmosphere.

8 Venus has a very strong greenhouse effect.

9. There is no water on Venus' surface.

10. Venus has a very dense cloud cover.


Venus

Cloud covered, thick atmosphere - carbon dioxide - greenhouse affect - surface temperature near 900ºF - rains sulfuric acid


Surface features unknown because of heavy cloud cover until the Magellan spacecraft mapped surface with radar. The surface of Venus is covered with abundant lava flows and tectonic features, along with a few large impact craters. In the following images dark and light areas correspond to how well radio waves are reflected, not visible light. Nonetheless, geological features stand out well.

Images of Venus’ SurfaceRussians probes actually landed on Venus four times in the 70’s - probes lasted up to two hours before failure. NASA’s Pioneer Venus sent probe into atmosphere - had on-board instrument (mass spectrometer) built at UTD.

Venera 13


Two of Venus' relatively rare impact craters

Shield volcanoes like this one are common on Venus.

Radar Images of Venus’ Surface

Tectonic forces have fractured and

twisted the crust in this region.

Circular cracks and volcanic bumps make up a corona, probably caused by pressure of a mantle plume below.


Venus orbit tilted 3.4º to the ecliptic

Transits of Venus only occur in pairs about 8 years apart every ~120 years.

Transit occurred in 2004 - next in 2012

Edmund Halley one of few to observe first transit in 1677 after invention of telescope - called upon future astronomers to observe subsequent transits.

Captain Cook traveled to Tahiti to observe transit of 1769 in an attempt to estimate the distance from the Earth to the Sun using triangulation and the parallax effect - discovered Hawaii on the way.

Measurements not very accurate: - intense sunlight filtering through Venus' atmosphere fuzzed the edge of the disk and decreased the precision with which Cook could time the transit- his measurements disagreed with those of ship's astronomer Charles Green, who observed the transit beside Cook, by as much as 42 seconds.

Venus Transits


- Cook and Green also observed the "black drop effect." When Venus is near the limb of the sun - the critical moment for transit timing - the black of space beyond the Sun's limb seems to reach in and touch the planet - made it hard to say just when the transit began or ended.

- a problem for observers elsewhere - observations of Venus' 1769 transit from 76 points around the globe not precise enough to set the scale of the solar system. Astronomers didn't manage that until the 19th century when they used photography to record the next pair of transits.


Venus Transit of the Sun


Earth

Only known world on which humans can live without

protective covering - only known oasis of life.


The Moon

Earth is the first planet with a moon - surprisingly large compared to Earth - major mystery of the solar system


Mars

The last of the terrestrial planets. A world of wonders with extinct volcanoes that dwarf the largest mountains on Earth, a great canyon that runs nearly 1/5 of the way around the planet, polar caps of frozen carbon dioxide and water ice, and dried up river beds


Mars

Comparison of Venus, Earth and Mars

Parameter Venus Earth Mars

Distance from Sun (AU) .72 1.00 1.52 (million KM) 108 150 228

Sidereal Period (year) (earth days) 225 365 687

Rotation Period (day) (earth days) -243 1.00 1.03

Direction of rotation Retrograde Direct Direct

Equatorial Diameter 0.96 1.00 0.53

Escape velocity (km/Sec.) 10.3 11.2 5.0

Inclination of axis 3 23.5 25.2

Seasons No Yes Yes


Mars

Comparison of Venus, Earth and Mars

Parameter Venus Earth Mars

Surface Temperature 480C (900F) 15C(60F) -60C(-76F)

Surface atmospheric pressure 90 1 1/200

(atmospheres)

Atmospheric gases CO2 N2, O2 CO2

Cloud cover Total Partial Rare

Surface Solid 3/4 water Solid

Number of satellites 0 1 2


Moons of Mars - Captured Asteroids?

Phobos - 13 km across

Diemos - 8 km across


60 km

Olympus Mons - largest shield volcano in the solar system - three times as high as Mt. Everest - 600 km across

Dried up river bed?


Life on Mars?

Mars is the only planet on which we have searched for life

• Early Mars may have been similar to early Earth

• Conclusive evidence that free-flowing water existed on Mars at one time

• Has all the chemical ingredients necessary for life as well as energy from sunlight and now dormant volcanoes

• CO2 atmosphere

• May have significant amounts of subsurface ice - residual volcanic heat may create pockets of liquid water where life could exist

• Microbacteria developed in labs can survive simulated Martian conditions


Viking Landers

Viking 1 and Viking 2 landed on Mars in 1976 - specific mission to look for life. Equipped with robotic arms to scoop up soil samples and deposit them in a closed container for treatment. Arms pushed aside rocks to get at shaded soil less likely to have been sterilized by UV light.


Viking Life Detection Experiments on Mars

Living organisms alter their environment - they breathe, eat, grow, and produce waste

Three experiments were designed to detect signs of living organisms by treating soil samples in a closed environment (a container):



Gas exchange -

• Looked for changes in the atmosphere caused by metabolism of

organisms in the soil.

• Soil sample fed nutrient in a carbon dioxide (CO2) atmosphere.

• Organisms eat nutrients and release gases like CO2, methane,

oxygen and hydrogen into the container.

• Some gases were found but were thought to be due to chemical

reactions between the nutrient water and the soil.



Labeled release -

• Looked for CO2 breathed into the atmosphere

• Soil sample fed radioactive nutrient

• Organisms would release radioactive CO2 into the container

• Some gases were found but were thought to be due to the chemical reactions between the nutrient and

the soil



Pyrolytic release -

•Looked for radioactive carbon in soil sample

•Soil sample in radioactive CO2 atmosphere illuminated by ultraviolet light to simulate sunlight

•Soil sample then heated to 650°C to decompose any growth material in the soil

•Soil contained some radioactive carbon - did not represent life

Conclusion:

Some positive results found in each experiment. However, not sufficient to confirm life as we know it Explanation - unusual chemical activity

NATS 1311 - From the Cosmos to EarthFossil Life in Meteorites

Possible fossil life found in meteorite discovered in Antarctica - hotly debated - Meteorite came from Mars - air trapped in rock matches known Martian atmosphere

• Age of meteorite 4.5 billion years - solidified shortly after Mars formed - resided on Mars throughout period when Mars may have been warmer and wetter• Ejected from Mars 16 million years ago by large meteor impact• Landed on Earth 13,000 years ago in Antartica• Well preserved: not exposed to water erosion or industrial contaminants


• While on Mars, meteorite was infiltrated by water - carbonate mineral globules formed in water• About 3.6 billion years old - when Mars was warmer and liquid water may have existed - older than impact (asteroid?) that launched meteorite into space• Oxygen and carbon in globules contain isotopes characteristic of Mars• Showed presence of polycyclic aromatic hydrocarbons (PAM) unlike any on earth - associated with life• Iron rich materials characteristic of fossil remains


Pictures of meteorite taken with electron microscope reveal shapes that look much like nanobacteria in existence on Earth - fossils of microscopic life on Mars? Hotly contested - other scientists claim they are mineral formations.


Carbonate globules are the key to biogenic activity on Mars • Globules formed in fractures of rock in liquid water • Globules are younger than the rock • Globular features resemble earth microorganisms, earth biogenic

carbonate structures and microfossils•Globules contain PAH's

CONCLUSION:

Alternative explanations exist for each globular phenomenon

taken individually

Collectively, they are evidence for primitive life on Mars


The Phoenix Mission to MarsThe Phoenix Mission to Mars

• Launched on August 4, 2007.Launched on August 4, 2007.

• Arrived on May 25, 2008.Arrived on May 25, 2008.

• Lander with arm and scoop to dig a trench in the surface to look for water Lander with arm and scoop to dig a trench in the surface to look for water and examine the soil chemistry

• Target landing site: 68º north in lowlands.Target landing site: 68º north in lowlands.

• Region expected to harbor significant amount of waterRegion expected to harbor significant amount of water


Landed in the Martian Arctic at approximately 68 degrees N latitude, 233 degrees E longitude (Earth equivalent: NW Territories, Canada)

Phoenix is exploring the farthest northern region of any Mars mission to date.


Mars surface covered with tiny rocks and pebbles and displaying polygon shaped formations. Polygons 1 to 2 meters across.Photo taken with Surface Stereo Imager.


Dust Devil Sol 104


Phoenix Instruments

• Mars Descent Imager (MARTI)

• Surface Stereoscopic Imager (SSI)

• Robotic Arm Camera (RAC)

• Microscopy, Electrochemistry and Conductivity Analyzer (MECA)

• Meteorological Station (MET)

• Thermal Evolved Gas Analyzer (TEGA)


Phoenix spacecraft at Lockheed Martin in Denver


TEGA is a combination of -

T - Thermal Analyzer - 8 high-temperature ovens - University of Arizona

EGA - Mass spectrometer – University of Texas at Dallas

TEGA, Thermal and Evolved Gas Analyzer


TEGA ovens


Spacecraft robotic arm digs trench in surface.

Robotic arm deposits selected martian ice and soil samples in each of eight single- use ovens.

Each oven has a trap door that must be opened to admit a sample.

Screen behind door prevents larger particles form entering oven.

A vibrator shakes the screen to coax soil particle to pass through into the oven.

TEGA, Thermal Analyzer


Scoop dumping martial soil into a TEGA oven


Samples are heated up to 1000 degrees C.

Some materials in the sample undergo phase transitions from solids to liquids to gases as they are heated in an oven.

Other materials decompose into their constituent parts.

These processes require more energy input to the oven than is necessary to raise its temperature.

Oven is a differential calorimeter.

The energy input to the oven is carefully measured to identify these phase transitions and decompositions of the samples.



TEGA, Thermal and Evolved Gas Analyzer

50

40

30

20

10

0

Differential Power (mW)

403020100-10Temperature (°C)

Water ice meltingWater evaporation

Calorimeter trace of melting and vaporization of H2O


Gases released by heating the martian surface materials are transported via a carrier gas, nitrogen, to the mass spectrometer for analysis.

From the energy requirements and the composition of the evolved gases, the identification of the martian materials is possible.

Goal: determine mineralogy of surface and sub-surface materials.Compare the mineralogy of Mars to that of earth.



Evolved Gas AnalyzerEvolved Gas Analyzer

UT Dallas experiment: Evolved Gas AnalyzerUT Dallas experiment: Evolved Gas Analyzer

• Magnetic sector mass spectrometer.Magnetic sector mass spectrometer.

- Serves as the analyzer for the gas effluents from the Thermal Analyzer (TA).

- Performs measurements of atmospheric constituent abundances and isotopic ratios.


Polygon formation thought to result from seasonal expansion and contraction of ground/ice mixture as temperatures change.

Exhibit central mounds and perimeter troughs.

Trough depths range from 1 cm to 10s of cms.Trough formation process involves cryoturbation - frost churning.

Similar features seen in earth’s permafrost arctic regions.


Robotic Arm: Rasping the Ice

QuickTime™ and aMPEG-4 Video decompressor

are needed to see this picture.

Left digging site called Humpty Dumpty.Right digging site called Wonderland.


Soils dumped on oven 4 exterior surface did not pass through screen into oven.Required vibrating screen for 6 sols for soil to drop into oven.Soils dried out. No water detected in soil sample.


Three small chunks of ice seen in shadow area of picture from Sol 20 are gone by Sol 24.

Trench is Dodo


There appear to be two types of ice on Mars.

1.Relatively pure white ice deposit found in Dodo- Goldilocks trench on edge of Humpty Dumpty polygon. 5 cm beneath dry top soil.

2.Hard layer, whitish material containing significant amounts of soil found 5 cm down in Snow While trench in center of polygon Wonderland.

Hard layer is too hard to scrape.Likely it is densely cemented by water ice. In 1 or 2 sols whitish material disappeared leaving behind loose dirt. Ice appears to have a very high sublimation rate.Material then looks like surface material that is loose dirt.


How did we discover water on Mars?

The hard white material in the Snow White loosened by a rasp on Robotic Arm scoop.

Spectroscopic data confirmed presence of water ice.

Material scooped up from Wicked Witch, bottom of Snow white trench, early one morning, coldest part of day, and quickly deposited on TEGA oven No. 0.


Wicked Witch material placed in oven and heated up to 35 degrees C (95 degrees F), well above the melting temperature of ice.Something in the sample melted at 0 degrees C (32 F) which was identified as frozen water.


Water in sample in oven number 0 identified by 3 methods:

1. Additional power to oven at 0 degrees C, the melting point of frozen water.

2. Pressure increase in the manifold that captured the gases evolved from the oven that occurred at 0 degrees.

3. The mass spectrum from the evolved gas analyzer. Water chemical formula is 2 atoms of hydrogen linked to 1 atom of oxygen - H2OThis molecule has a mass of 18 units on the atomic mass scale. This identifies it as water vapor.


Calcium carbonate has been found in soil samples from the trenches.

Both TEGA and MECA data confirm finding.

TEGA- High temperature release of CO2 from an oven run came from decomposition of CaCO3.Wet Chemistry Lab, WCL, of MECA found calcium at the concentration expected from calcium carbonate.

Presence of calcium carbonate requires the presence of liquid water sometime in the past.


Lidar data show ice crystals, like snow, falling from clouds on Sol 99 at an altitude of about 3 to 4 km.

Curved tracks seen in the clouds indication wind blowing the particles.

These are water based flakes, not CO2 (dry ice).Temperature of clouds too high to be CO2.

The crystals evaporate before hitting the ground.

Clouds, ground fog and frost seen regularly in the morning now as temperature is dropping.

NATS 1311 - From the Cosmos to Earth Differences Between Venus and Earth 1.Venus rotation rate is...

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