Happy Halloween! Homework #6 Due 6:00 pm today Exam #2 on Wednesday Could Mars once have been warm and soggy? And could Mars have/had life? Much has been learned from orbiters/rovers that are active today Orbiters:Mars Reconnaissance Orbiter Mars Express Mars Express Rovers:Spirit Opportunity Early Mars was similar to Earth Evidence of past water flows The current thin, cold atmosphere prohibits liquid water from being stable on the surface. The current thin, cold atmosphere prohibits liquid water from being stable on the surface. However, there is ample evidence for past water However, there is ample evidence for past water 3 flavors of flowing surface water: 3 flavors of flowing surface water: 1)Valley Networks (really old) 2)Outflow Channels (pretty old) 3)Gullies (really young) 10 km 500 km Viking Orbiter image MOLA topography Outflow Channels Formed from catastrophic release of groundwater in mid to late Martian history. Formed from catastrophic release of groundwater in mid to late Martian history. older, degraded channel system different flow paths Orbital photos from Mars Express show features similar to ice patterns seen in Antarctica: dust covered frozen sea? Sedimentary rocks Main evidence for a warm and wet ancient Mars Valley networks Valley networks Widespread highland erosion (up to a km of crust lost) Widespread highland erosion (up to a km of crust lost) Chemically weathered components of the crust Chemically weathered components of the crust Mars Exploration Rovers show clear signs of groundwater interaction and possible signs of standing bodies of water Mars Exploration Rovers show clear signs of groundwater interaction and possible signs of standing bodies of water Did the Northern Lowlands Once Contain an Ocean? Tharsis Northern plains Valles Marineris Northern plains It is quite possible! Evidence of current water flows Gullies Martian gullies are the best evidence for liquid water on Mars today. These fresh-cut features are found on the inner walls of some craters and the old runoff channels. For water to produce these features, it must have been released in a torrent, for a slow trickle will not suffice. This image shows recent gullies in a crater wall. Mars (and Venus) lost most of their water to space. For Mars, frozen water is tied up in the subsurface and polar caps Where did the water go to? Mars geologic history was once warmer and wetter than now. Mars geologic history was once warmer and wetter than now. Climate History Atmosphere warmer in the past Atmosphere warmer in the past Greenhouse effect due to CO 2 and some CH 4 Loss of CO 2 to space Loss of CO 2 to space Polar caps insufficient to account for missing CO 2 No good evidence for carbonates Loss via impacts Loss via the solar wind, which is not well deflected because of weaker magnetic field (core cools faster) Loss of H 2 O Loss of H 2 O Loss via impacts UV breaks up H 2 O and H 2 escapes easily Life on Mars??? Based upon our understanding of biology, Mars has all the necessary ingredients for life Based upon our understanding of biology, Mars has all the necessary ingredients for life Water, an energy source, and the basic elements and compounds required make life. Mars likely had a very different climate in the past that was more hospitable to life. Mars likely had a very different climate in the past that was more hospitable to life. Life on Earth is exceptionally tough (lives and survives under extreme conditions)! Life on Earth is exceptionally tough (lives and survives under extreme conditions)! Meteorite from Mars ALH84001 ALH84001 possible evidence of fossil microbes from Mars? Life on Mars? Martian Meteorite. Fossil Life? If this is life it is very small in size. Too small? Some scientists are convinced it is life. Most are still unsure. Life on Mars? It has been proven there is water ice on Mars. Probably below the surface today but a large ocean in the past. Water reasonable possibility of life but is it extinct, dormant or alive? Life on Mars today? Direct search by space probes 1976 Viking probes - inconclusive 2003 Beagle II crashed on landing Data obtained by the Mars Express probe show that water vapor and methane gas are concentrated in the same regions of the Martian atmosphere. Methane & Water! Data obtained by the Mars Express probe show that water vapor and methane gas are concentrated in the same regions of the Martian atmosphere. Must be recently made! Methane only lasts about 100 years (UV light destroys it) Life (micro-organisms) or volcanoes? If microbes are making methane in the Martian atmosphere as part of their living process, they would rely on water. Methane & Water!