Reading: Chapter 6 Lecture 9. A Biological Tour of the Solar System

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

reading: Chapter 6

Lecture 9. A Biological Tour of the Solar System

6 Key Properties of Life

1. Has Order/Structure2. Reproduction3. Growth & Development4. Energy Utilization5. Response to the Environment6. Evolutionary Adaptation

Pervasiveness of Life

Snow algae on glacierSierra Nevada, CA

Earth life extraordinarily successfulNatural selection & evolution

--> adaptabilityOrganisms found EVERYWHERE

glaciers & permafrosthot springshydrothermal ventsdesert rockscloudsdeep sea sedimentssoils

Five Things You Need to Have Life

1. Stable Environmentbe able to adapt to changes

2. Liquid water-20˚C to 121˚C

3. Energy SourceO2 and carbohydratesoxidant (O2) and reductant (sugars)

4. Carbon Sourcecarbohydratessometimes different from an energy source

5. NutrientsThe Biogenic Elements: C, H, N, O, P, STrace Nutrients: Ca, Fe, Cu, Zn, vitamins…..some organisms need more than others

when considering thepotential for life elsewhere:





Mercury & The Moon

Similar:- pockmarked with craters- surfaces of basalt- small diameter

Mercury: 4,880 kmMoon: 3,476 km

Earth: 12,756 km- weak gravity

Mercury: 0.28gMoon: 0.17g

- lost their internal heat- no volcanism/outgassing- easy to lose atmosphere

daytime nighttime dayMercury 427˚C -168˚C 88 d.Moon 100˚C -173˚C 27 d.

Mariner 10 Spacecraft Images, 1975



6.6 billion tons of ice in the floor of perpetually dark craters at North & South Poles.

First detected by Clementine 1996 (SDI-NASA).Confirmed by Lunar Prospector 1998.

Neutron Spectrometer found presence of H atoms:

Ice can’t be primordial - has to be more recent.Discrete, confined, near-pure water ice deposits buried under regolith.Best guess: comet source - delivered 10-100 billion tons of water.Craters act as cold traps.

Ice on the Moon

When cosmic rays hit the Moon, neutrons are emitted back into spaceIce absorbs neutrons, re-emits at a lower energy.Look for low energy neutrons.



South Pole Aitken Basin -giant impact craterdeep basin floor, no sunlight.

Very dense planet: uncompressed:Mercury: 5.4 g/cc 5.5 g/ccMoon: 3.3 g/ccEarth: 5.5 g/cc 4.0 g/cc

60-70% by weight metal corehas a weak magnetic field (1% of Earth’s)may have lost its mantle

would have dehydrated the planetmay have ices in perpetually dark craters

largest surface feature: Caloris Basin, 1300 km impact crater

Mercury



Venus

Earth’s “sister planet”Nearly same size (12,104 km)Thick clouds0.7 AU, a little closerWith an Earth-like atmosphere

T 35˚C/95˚F1962 Mariner 2 flyby

Surface T 450˚C/850˚FDay and night T

Thick atmosphere: P 90x higher(1 km depth equivalent)

Atmosphere has concentrated sulfuricacid cloud droplets.

No magnetic field.



Terrestrial Planet Atmospheres

Venus Earth MarsCO2 96% 0.035% 95%N2 3.5 % 78% 2.7 %H2O 0.01% few % 0.03%O2 ----- 21% 0.13%

Venus’ atmosphere like Mars’.May have been similar to Earth’s early atmosphere.Earth’s atmosphere has changed significantly because of

- life (oxygen)- oceans (CO2 -----> carbonate rock)

Almost all Earth’s CO2 is either:- carbonate rock- dissolved in the oceans





Runaway Greenhouse Effect

Dense CO2 rich atmosphere.Too much of a good thing!

Venus may have once had oceans (like Earth and early Mars).Oceans could have kept low CO2 levels in the atmosphere.Somehow oceans destroyed & all CO2 in the atmosphere.

80% of solar radiation reflected back to space.10% absorbed by atmosphere.10% reaches and heats the surface.

Clouds are inhomogeneous, cumulus-type clouds.Wind speeds 260 km/hr in cloud layers

(light breeze near surface)





infrared image showinghot clouds ~30 km altitude

ESA’s Venus Express







Launched Nov. 5First spacecraft to Venus in 15 years.Orbit insertion in 63 days.Spectrometers and imagers will cover surface

and atmosphere at many wavelengths.Focused on study of the atmosphere.Look for evidence of volcanic activity.

Mars



Jupiter

methane clouds in the infrared:red: 889nm methane absorption, high cloudsgreen: 727nm methane absorption, lower cloudsblue: no absorbers, reflected from deepest cloudsGRS is relatively high in altitude (50 km) Solar composition.

142,984 km diameter.1400 Earths fit inside.Small rocky core, large atmosphere.At cloud tops, T is below freezing.P rises dramatically with depth. T increases with depth.Liquid water droplets at 100 km.Storms are swirls, bands, spots.Great red spot seen 300 years ago.Colors from different T and

composition.Lightning made by water near tops

of clouds.Rotates every 10 hours.

Rings: imaged by Galileo, 1996.shows radial structuremade of small dust grainshighly perturbed by Adrastea, Metis, and J’s magnetosphere

Core of rock (10-14 Earths) and metalhydrogen metal 40,000km deepsource of magnetic field and radio waves

Magnetic field 20x the size of the Sun.

High energy electrons trappedin Jupiter’s radiation belts emitradiation at radio wavelengths.



Chandra X-ray image shows auroral activity, charged ions of O hitting atmosphere, 2005.

Jupiter, cont.



Jupiter, cont.

model of what layers between clouddecks on Jupiter would look like

based on data from Galileo Spacecraft

Movie generated duringflyby of Cassini Spacecraft

Bands of rapidly rotating clouds.Very strong, vertical winds 600 km/hr.Winds may extend thousands of km depth.Winds driven by internal heat.Clouds at one level: CH4 and NH3 ice

another: NH3 and H2Sanother: water

Smoggy haze layers at high altitudes

Any complex organic compounds formedcarried to high T

Rise quickly to very cold T (-150˚C)

Carl Sagan: giant gas-filled sacks, regulate buoyancyWould have to be enormous - very strong winds

Saturn, Uranus120,536 km, -170˚C to 30˚CSaturn 3 clouddecks, similar to Jupiter

NH3 cloudsNH4SH cloudswater

hazes/colors: sulfurous, phosphorours polymers, organic compounds



Less H and He, more CH4 (blue color)Belts and bands harder to distinguish

hidden by CH4 cloud layerStable spots = storms

U: 51,118 kmrotates backward and is tilted 90˚T average -200˚C.

Neptune

49,532 kmBands of cloudsClouds also made of methane Hazes of snog composed of hydrocarbonsWhite clouds are very high in altitudeGreat Dark Spot - disappeared in 1994

replaced by a new one months laterWinds up to 2000 km/hrInternal heat source, radiates 2x as much

heat as it receives from the Sun.Crosses the orbit of Pluto.

Pluto

Discovered in 1930.5,913 km.Smallest planet - 1% of Earth’s mass.Largest known Kuiper Belt Object.May not be a planet.

Rotates in the opposite direction as other planets.Eccentric orbit.Orbit inclined to the plane of the solar system (17˚).

Similar to Kuiper belt objects.70% rock, 30% ices (NH3, CH4, ethane, CO)T -235 to -210˚CAtmosphere: N2, CO, and CH4, is very thinClose to sun: atmosphere is a gas, further away: freezes out.



Asteroids & Comets

Small size; lack liquid water; no atmosphere.Too small to have any internal heat to melt the ices.Perpetually frozen (except rare comet that passes by Sun).Substantial evidence of organic compounds in asteroids and comets.Meteorites contained liquid water in the past, just after formed.May have persisted for tens of millions of years.

Asteroid 951 Gaspra imaged by Galileo Spacecraft

Europa, Mars, Titan



Ice rafts on Europa, imaged bythe Galileo Spacecraft.

Hematite “blueberries” on Mars,imaged by Opportunity Rover.

Titan, imaged by AOon Keck telescope.

surface of Titan, imagedby the Huygens probe.

Ridges and pits on Europa,imaged by Galileo Spacecraft.

reading: Chapter 7

Lecture 10. Early Mars Was Once Warmer & Wetter

Documents

Reading: Chapter 6 Lecture 9. A Biological Tour of the Solar System