THE POSSIBILITIES FOR LIQUID WATER WITHIN THE UPPERMOST MARTIAN CRUST. MEPAG Special Regions Science Analysis Group, Water Subteam (D.W. Beaty, W.V. Boynton, K.L. Buxbaum, B.C. Clark, R.M. Haberle, J.W. Head, M.H. Hecht, M.T. Mellon, M.A. Meyer, G.G. Ori, D.A. Paige, J.A. Spry).

Introduction: At its meeting in November, 2005, 3. MEPAG (Mars Exploration Program Analysis Group) was asked to analyze some of the issues regarding the 4. Very deep (depth of several km) groundwater planetary protection concept of “special region”. The on Mars has been hypothesized (e.g., by Steve current definition of “special region” is “…a region Clifford). However, for the purpose of con- within which terrestrial organisms are likely to propa- straining spacecraft acitivies, this is relevant gate, or a region which is interpreted to have a high only to those cases where a natural transport mechanism between the shallow and deep sub- potential for the existence of extant martian life surface is proposed to exist. forms.” A recent NRC panel, chartered to advise NASA on forward planetary protection issues, strug- Results: The SR-SAG’s preliminary conclusion is gled with the above definition, and eventually conclud- that a logical first-order classification of Mars can be ed that it is so ambiguous that it was of no practical use made as follows: in distinguishing regions that are “special” from those 1. environments at or close to equilibrium with that are “not special.” Until a means of drawing this respect to water distinction is established, they concluded that it would be prudent to interpret all of Mars as “special.” 2. environments for which there are long-term MEPAG chartered the Special Regions Science water disequilibrium issues (e.g. glaciers, gul- Analysis Group (SR-SAG), and tasked them with lies, recent impact craters, active volcanoes, proposing an improved definition of “special region” etc.) that can be applied in a practical way, and that can be offered to planetary protection policy-setting entities 3. environments for which there are short-term for their consideration. The SR-SAG was also asked water disequilibrium issues (e.g. changes to develop a preliminary analysis of the kinds of mar- caused by spacecraft activities). tian environments (organized by geology, geomorphol- The implications for the occurrence and concentra- ogy, PVT, or any other classification system that tion of biologically available liquid water are different makes sense) that should be considered “special” and in these three situations. As of the preparation of this “non-special.” abstract, the team was still actively debating the physi- Importance of Water: It is clear that one of the cal limits to terrestrial life (including the minimum wa- essential parameters for the definiton of “special re- ter activity), the possibilities for the natural occurrence gion” is the presence of biologically available liquid of liquid water within the uppermost martian crust, and water. the scale of any water-related possibilities. Practical Limits on the Problem: The MEPAG study team is seeking clarifications that have practical Additional Information: If you have questions value to the planning and implementation of missions regarding this analysis, or have information you wish to Mars. The ‘special regions’ analysis can therefore to contribute, please contact: be simplified with the following boundary Dr. David W. Beaty, Mars Program Office (JPL), conditions /assumptions. [email protected], 818-354-7968, Dr. Karen 1. The time within which the “special” condition Buxbaum, Mars Program Office (JPL), must exist is limited to either 100 or 1000 [email protected], 818-393-1135, or years in the future (i.e., not “forever”). Dr. Michael Meyer, Mars Program Office (NASA- HQ), [email protected], 202-358-0307. 2. Spacecraft (or spacecraft components) crash- ing on Mars can inject terrestrial microbes into the martian subsurface to a maximum depth of a few meters. The maximum depth accessible to deliberate engineering (e.g., by drilling), at least for the next three decades, is a few 10s of meters. This is therefore the primary volume of concern.