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01101001
2005-Sep-18, 11:13 PM
Jack Farmer has got a nice 3-part series about Mars going on. The first two parts are:

Deciphering Mars: Follow the Water (http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=1709) September 12


We not only have to follow [Mars water] in the past on the surface, but because liquid water is unstable on the surface of Mars today, if we're going to look for liquid water today, we're going to have to go into the subsurface. So we're looking in the past for ancient deposits for evidence of past water, and in the subsurface for active environments where we might actually have biology going on. Deciphering Mars: The Current Decade (http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=1712) September 15


If liquid water's around today, it may exist several kilometers below the surface as a global groundwater system. The question is, How can we begin to address the idea of a subsurface hydrosphere on Mars? Well, the Mars Global Surveyor, in particular the Mars Orbital Camera, has provided some compelling evidence: images of fluid seeps on the polar-facing slopes at high latitudes.
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One suggestion was that these seeps could have been sites for the escape of hydrothermal brines, or brines that were really saline and were able to maintain their fluidity, even at low temperatures. Recently, Phil Christensen, of Arizona State University, put on the table the idea that during low-obliquity periods a lot of ice and snow moved to these latitudes, that at the base of those snow accumulations there was the potential for basal melting and that the flow of water beneath the ice packs carved these features. Both hypotheses are still on the table right now, probably along with a few others. We don't know for sure what this is telling us, but one thing it does tell us is that probably there has been liquid water at the surface of Mars very recently in martian history. And where you've got water, you've got the potential for habitability.

With the Odyssey mission, we've had another insight, which has come from the Gamma Ray Spectrometer. We've learned that large areas, across broad range of latitudes, show evidence for very high hydrogen concentrations in the upper 35 to 50 centimeters of regolith, implying the presence of either water or hydrated minerals. Probably most of this is ground ice. This is a really exciting find, because during obliquity changes that we know have occurred during martian history, these become potential environments for the melting of surface water, for the formation of habitable zones just beneath the surface.

01101001
2005-Sep-26, 07:15 AM
Jack Farmer has got a nice 3-part series about Mars going on. The first two parts are:

Deciphering Mars: Follow the Water (http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=1709) September 12

Deciphering Mars: The Current Decade (http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=1712) September 15Part 3 of 3 is up.

Deciphering Mars: The Future (http://www.astrobio.net/news/modules.php?op=modload&name=News&file=article&sid=1724) September 26


Continue the Search for Evidence of Past Life. [...] Explore for Ancient Hydrothermal Habitats. [...] Search for Present Life. [...] Explore the Evolution of Mars.
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So, to summarize, what have we learned? Mars has had a prolonged aqueous history with widespread surface water during its early period, and hints of a subsurface hydrosphere through much of its younger history, possibly up to the present time. What do we need to know? We still have a lot to learn about the availability of basic nutrients and energy sources in both surface and subsurface environments, essential information for reliable assessment of habitability.