Life on Mars Stephen Eikenberry 12 October 2010 AST

Life on Mars?? Mars has long been a “favorite” location for extra-terrestrial life 2

Why Mars? Mass ~0.1 Earth-mass Radius ~0.6 Earth radius Axis tilt 3

Why Mars? Seasonal variations and polar caps 4

Martian “Seasons” Darkening spreads from pole towards equator as summer comes This is opposite of on Earth (summer “spreads” from equator towards poles) But … if water availability limits plant growth, as poles warm, liquid water spreads from poles towards equator As plants grow, reflectivity of planet surface decreases (??) 5

Water on Mars Polar caps seem to indicate water (??) Schiaparelli finds “canals” (!) Apparently, not just plant life on Mars, but intelligent beings with large-scale irrigation for agriculture !! 6

Hold on a second … Other people see similar shapes on Mars … but no “canals”! 7

Mars Atmosphere Mostly CO 2 (OK …) About 0.6% of the atmospheric pressure of Earth (!) Temperatures can reach about 65  F But, mostly more like -150  F At those temps, CO 2 freezes (dry ice) 8

Polar Caps: Redux So … could polar caps be dry ice instead of H 2 0? YES!! In fact, the albedo (reflectivity) of the caps is too high for water ice, but matches dry ice nicely Also, we can measure temps when caps recede/grow  too cold for water, but matches dry ice Now … there IS water ice on the caps too, under the layer of CO 2 ice But … most of the seasonal variation is in dry ice 9

Seasons: Redux The “darkening” spread from poles to equator is probably due to dry ice “melting” (reducing the albedo of that region) But … dry ice doesn’t melt – it sublimates (goes straight from solid to vapor form) Still disappears and changes albedo What else … ? 10

Canals: Redux Closer inspection (with photographs!): no evidence for canals In fact, at this low pressure, water sublimates as well  no liquid water on the surface of Mars! 11

12 Mars Overview Slightly smaller than EarthSlightly smaller than Earth Rotation period is 24.6 hours - close to EarthRotation period is 24.6 hours - close to Earth Equator inclined at 24 degrees - close to EarthEquator inclined at 24 degrees - close to Earth Very little atmosphere - 1/150 the pressure of EarthVery little atmosphere - 1/150 the pressure of Earth CO2 (95.3%),nitrogen (2.7%), argon, oxygen, CO, water vaporCO2 (95.3%),nitrogen (2.7%), argon, oxygen, CO, water vapor Two very small moonsTwo very small moons

13 Mars – Space Craft Exploration 1965 – Mariner 4, 6 and 7 “fly by” Mars1965 – Mariner 4, 6 and 7 “fly by” Mars 1971 – Mariner 9 orbits and maps Mars in detail1971 – Mariner 9 orbits and maps Mars in detail 1976 – Viking 1 lands on Mars1976 – Viking 1 lands on Mars 1997 – The Mars Pathfinder places a small rover on Mars1997 – The Mars Pathfinder places a small rover on Mars 2004-present: Mars rovers2004-present: Mars rovers

14 Mars’ Surface Polar ice caps – frozen CO2Polar ice caps – frozen CO2 Northern hemisphere is rolling volcanic planesNorthern hemisphere is rolling volcanic planes Southern hemisphere is heavily cratered highlandsSouthern hemisphere is heavily cratered highlands Like lunar maria but largerLike lunar maria but larger Few craters – young (3 billion yrs old)Few craters – young (3 billion yrs old) Older (4 billion yrs old)Older (4 billion yrs old)

15 The Tharsis Bulge is the major geographically feature on Mars Roughly the size of North America Lies on the equator 10km high Less heavily cratered Young (2-3 billion yrs) Wide depressions (valleys) lie to east and west

16 Valles Marineris runs for almost 4000 km along the Martian equator (one-fifth of the way around the planet!) 120 km across at its widest 7 km deep in places our Grand Canyon would easily fit into one of its side "tributary" cracks NOT caused by water - due to stretching and cracking when Tharsis bulge formed

17 Analysis of rocks on Mars show they are iron rich - iron in the soil and oxygen in the atmosphere produce iron oxide RUST Mars Pathfinder robot SojournerMars Pathfinder robot Sojourner Highly successful mission which sent back lots of pictures of the Martian landscapeHighly successful mission which sent back lots of pictures of the Martian landscape 1999 Mars Polar Lander failed to make contact1999 Mars Polar Lander failed to make contact

18 Volcanism on Mars Olympus Mons on Tharsis slope Largest volcanoes in the solar system are hereLargest volcanoes in the solar system are here Shield volcanoesShield volcanoes None are known to be currently active but eruptions occurred 100 million years agoNone are known to be currently active but eruptions occurred 100 million years ago Mars has a surface gravity only 40 percent that of Earth, and its volcanoes rise roughly 2.5 times as high because of this.

19 Water on Mars? Yes – but long ago Runoff channels Found in southern highlandsFound in southern highlands Extensive river systems (like Earth)Extensive river systems (like Earth) Carried water from highland to valleysCarried water from highland to valleys About 4 billions years ago Mars had a thicker atmosphere, warmer surface, and liquid water. Outflow channels Caused by floodingCaused by flooding Found at the equatorFound at the equator Formed about 3 billions year agoFormed about 3 billions year ago

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21 Remains frozen for a billion years Remains frozen for a billion years Volcanic activity heats large regions of the surface Volcanic activity heats large regions of the surface Melts the permafrost Melts the permafrost Flash floods create outflow channels Flash floods create outflow channels Volcanic activity slows down and water refreezes Volcanic activity slows down and water refreezes What happened to the water? 4 billion years ago - Martian climate begins to change 4 billion years ago - Martian climate begins to change Running water (that formed runoff channels) freezes into permafrost (water ice just below surface) and polar caps Running water (that formed runoff channels) freezes into permafrost (water ice just below surface) and polar caps

22 The Moons of Mars Mars has two very small moons Mars has two very small moons discovered in 1877 PhobosPhobos – 28 x 20 km DeimosDeimos – 16 x 10 km Less dense than our Moon or other terrestrial worldLess dense than our Moon or other terrestrial world Probably not made of the same material as MarsProbably not made of the same material as Mars Origin – captured asteroids