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Download Orbital distance 1.52 AU Orbital period 1.88 years Rotation period
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Chapter 11: Mars Mars Visuals Fig11.1 (1907), 11.2 simple_mars_spin.avi vital statistics Orbital distance 1.52 AU Orbital period 1.88 years Rotation period 24.6 hours Axial tilt 25º Known Satellites 2 Mass 0.11 x MEarth Radius 0.53 x REarth Density 3.94 Surface Gravity 0.38 g Global Temp 210 K Escape Velocity 5 km/s 1 (earth’s 11.2 km/s) Mars focus of much speculation [11ex1.jpg ] “signs of life discovered on Mars” ~late 1800’s Lowell Observatory Surface [fig 11.2,4] Craters [fig 11.3,5,6] Meteorites from Mars (from impacts) relatively young meteorites (1.3 B vs. normal 4.5B) impact→vaporization of subsurface ice = launch! Volcanoes [Fig 11.7] volcanic flow has erased much of older cratering [11f08.jpg] Tharsis bulge (continent sized bulge ~ 10 km high) contains largest known volcanoes in Solar System [fig 11.8,9] Volcanic activity widespread up until ~ 2.5 B years ago some activity continuing [table 11.2] crustal motion evident [fig 11.10,11-13] Valles Marineris (chasm system) possible early period of plate tectonic activity 2 Channels [fig 11.15-19, (old) 11ex2.jpg] water flow! but standing water is not possible runoff channels: river systems probably originating from groundwater outflow channels: catastrophic flooding due to sudden release of large amounts of water Some outflow channels may be young Polar regions Permanent Ice caps mostly water ice in northern cap [fig 11.22] carbon dioxide ice in southern cap [mars_south_cap_PIA02393.jpg]) Seasonal fluctuations in size of caps evaporation and freezing of dry ice southern cap fluctuations (currently, but watch precession) most severe [fig 11.21] Erosion and Sediments deposited [mars_erosion_*.jpg] due to seasonal variation in climate 3 Mars (continued) Viking Landers surface: rocky surface, rolling hills [fig 11.23-25] similar soil composition at both sites dust storms disperse material rich in iron (rust→ red coloring) Pathfinder/Sojourner Signs of erosion [fig 11.26] Spirit and Opportunity exploration [fig 11.27-30] further evidence of past water [mars_layered_rock_PIA05495.jpg, fig 11.31] Phoenix Mars Lander [fig 11.32,33 phoenix_scrape.jpg] icy soil subsurface ice (like permafrost) 4 atmosphere thin (less than 1% earth’s atmospheric pressure) 95% carbon dioxide, with some nitrogen and argon seasonal variations in pressure as ice caps grow/shrink [fig 11.36] not enough water vapor and surface water to drive Earth-type storm systems frequent dust storms [fig 11.37] erosion sand dunes few thin clouds (water vapor) thin morning ice “fog” [fig 11.38] 5 Martian Interior “middle weight” mass, size → little compression compared to earth →density 3.940 x water cooled faster than Venus, Earth but more slowly than Mercury, Moon considerable iron on surface, in core less iron overall than earth → trend towards decreasing iron content in planets with increasing distance from the sun Thermal history: accretion, radioactive heating,expansion (forming Valles Marineris), heat loss augmented by volcanic flow weak magnetic field presents puzzle Water on Mars? ample evidence (erosion) but not on surface now as liquid hydrogen detection [fig11.41] some trapped as ice beneath surface (permafrost [fig11.40]) 6 Climate history water from outgassing → thicker carbon dioxide atmosphere carbon dioxide absorbed in surface rocks, but not recycled (lack of crustal activity) → depletion of atmosphere comet/asteroid impacts → heating, melting of subsurface ice → runoff Life on mars? no organic molecules detected on surface by landers experiments to detect biological activity inconclusive chemically active, not biologically active Methane concentrations detected in atmosphere (not necessarily biological) Meteorite from Mars: new evidence, not (yet?) conclusive Face on Mars? http://mars.jpl.nasa.gov/mgs/msss/camera/images/4_6_face_release/ fertile human imagination! 7 Evolution of Terrestrial Planets Formation by accretion heating via impacts and radioactive heating differentiation iron core rocky exterior cooling, continued evolution crustal activity 8
