LJ wrote:
I think you'll agree that some of the Odyssey data will help point in one direction or the other regarding the past/current water situation on Mars, which in turn has a bearing on the possiblity of past or current life.

Alex writes:
Again, "hopefully." While 2001 Mars Odyssey (at least THEMIS) will "Follow the Water" as it were, I would not be surprised by an unambiguous or even null result, especially with regards to the (still mysterious) issue of the lack of carbonates. Even if, as is as likely as not, THEMIS (with its order-of-magnitude-higher-than-TES spatial resolution) returns a negative result for carbonates or other aqueous minerals (excepting, of course, the hematite deposits), I do not think the issue will die. At any rate, 2001 Mars Odyssey is a *geochemical* mapping mission; any data it returns that tends to support the water-based (and by extension, exobiological) models, would to be sure, help advance the issue of "Life on Mars", but would not be anything truly astounding. That said, who really knows? Serendipity is one of the joys of science.

LJ wrote:
In that vein, given the indication already from Odyssey that there may be hydrogen near the surface away from the poles, are there any other reasonable
materials that could bear hydrogen, other than water?

Alex writes:
For plausible models based on what we know about Mars, water is indeed the most probable agent to account for the (relatively high) HEND readings. This in itself is nothing surprising because almost all scientists concede that some degree of water ice or other hydrates may be present in the soil at near polar latitudes. What will be interesting, at least to me, upon release of the HEND results, is the spatial extent of the hydration in the uppermost soils *away* from the poles, which will help to constrain some of the near-surficial models in determining the degree of dessication as a function of latitude.

Alex R. Blackwell
University of Hawaii