Stephen Eikenberry 21 Feb 2019 AST 2037 Life on Mars Stephen Eikenberry 21 Feb 2019 AST 2037

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

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

Why Mars? Seasonal variations and polar caps

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 (??)

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 !!

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

Mars Atmosphere Mostly CO2 (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, CO2 freezes (dry ice)

Polar Caps: Redux So … could polar caps be dry ice instead of H20? 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 CO2 ice But … most of the seasonal variation is in dry ice

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 … ?

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!

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

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

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

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

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

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 Sojourner Highly successful mission which sent back lots of pictures of the Martian landscape 1999 Mars Polar Lander failed to make contact

Volcanism on Mars Largest volcanoes in the solar system are here Shield volcanoes None 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. Olympus Mons on Tharsis slope

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

https://www.nasa.gov/image-feature/frost-avalanche-on-mars

What happened to the water? 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 Remains frozen for a billion years Volcanic activity heats large regions of the surface Melts the permafrost Flash floods create outflow channels Volcanic activity slows down and water refreezes