Life_on_Mars - Life on Mars Stephen Eikenberry 12 October...

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Unformatted text preview: Life on Mars Stephen Eikenberry 12 October 2010 AST 2037 1 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 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) 8 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 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 Mars Overview •Slightly smaller than Earth •Rotation period is 24.6 hours Rotation close to Earth close •Equator inclined at 24 degrees Equator close to Earth close •Very little atmosphere - 1/150 Very the pressure of Earth the •CO2 (95.3%),nitrogen (2.7%), CO2 argon, oxygen, CO, water vapor argon, •Two very small moons 12 Mars – Space Craft Exploration Mars Exploration •1965 – Mariner 4, 6 and 7 “fly 1965 by” Mars by” •1971 – Mariner 9 orbits and 1971 maps Mars in detail maps •1976 – Viking 1 lands on Mars •1997 – The Mars Pathfinder places 1997 a small rover on Mars small •2004-present: Mars rovers 13 Mars’ Surface •Polar ice caps – frozen CO2 •Northern hemisphere is rolling Northern volcanic planes •Like lunar maria but larger •Few craters – young (3 Few billion yrs old) billion •Southern hemisphere is heavily Southern cratered highlands cratered •Older (4 billion yrs old) 14 The Tharsis Bulge is The the major geographically feature on Mars on •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 15 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 16 Analysis of rocks on Mars show they are iron rich - iron in the soil and oxygen in the atmosphere produce iron iron oxide iron RUST •Mars Pathfinder robot Mars Sojourner Sojourner •Highly successful mission Highly which sent back lots of pictures of the Martian landscape landscape •1999 Mars Polar Lander 1999 failed to make contact failed 17 Volcanism on Mars •Largest volcanoes in the solar system are here •Shield volcanoes •None are known to be currently active but eruptions None occurred 100 million years ago occurred Mars has a surface gravity only Mars 40 percent that of Earth, and its volcanoes rise roughly 2.5 times as high because of this. times Olympus Mons on Tharsis slope8 1 Water on Mars? Yes – but long ago Yes but About 4 billions years ago Mars had a thicker About atmosphere, warmer surface, and liquid water. atmosphere, 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 19 anche.ap/index.html 20 What happened to the water? • 4 billion years ago - Martian climate begins to change billion • Running water (that formed runoff channels) freezes into runoff freezes permafrost (water ice just below surface) and polar caps permafrost • Remains frozen for a billion years Remains • Volcanic activity heats large regions of the surface regions • Melts the permafrost Melts • Flash floods create outflow channels channels • Volcanic activity slows down and water refreezes water 21 The Moons of Mars Mars has two very small moons discovered in 1877 •Phobos – 28 x 20 km Phobos •Deimos – 16 x 10 km •Less dense than our Moon or other terrestrial world •Probably not made of the same material as Mars Origin – captured asteroids 22 ...
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This note was uploaded on 07/26/2011 for the course AST 2037 taught by Professor Eikenberry during the Fall '08 term at University of Florida.

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