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Life on Mars


Life on Mars Stephen Eikenberry 12 October 2010 ... The Mars Pathfinder places a small rover on Mars 2004-present: Mars rovers * Mars Surface Polar ice caps ... – PowerPoint PPT presentation

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Title: Life on Mars

Life on Mars
  • Stephen Eikenberry
  • 12 October 2010
  • 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

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
  • 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 doesnt 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
  • 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
  • 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?
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

What happened to the water?
  • 4 billion years ago - Martian climate begins to
  • 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
  • Melts the permafrost
  • Flash floods create outflow channels
  • Volcanic activity slows down and water refreezes

The Moons of Mars
  • Mars has two very small moons discovered in 1877
  • Phobos 28 x 20 km
  • Deimos 16 x 10 km
  • Less dense than our Moon or other terrestrial
  • Probably not made of the same material as Mars
  • Origin captured asteroids