December 23, 2005 | David F. Coppedge

Mars Water Evidence Evaporates

The strongest evidence for water from the Mars rovers has been called into question.  Scientists from the University of Colorado at Boulder believe that the observations of sulfates and concretions are better explained by fumaroles in volcanic ash deposits (see also EurekAlert).  Their paper in Nature1 explains that the model means high temperatures: “Consequently, the model invokes an environment considerably less favourable for biological activity on Mars than previously proposed interpretations.”  Another paper in the same issue of Nature2 by scientists from University of Arizona and Los Alamos proposes rapid turbulent flows caused by meteor impacts produced the deposits, not periods of long-standing water as was previously assumed.  The report by Robert Roy Britt on included a response from Steve Squyres, principal investigator for the Mars Exploration Rovers.  He said he always contended that the water was primarily underground, but thought that alternative views are good for science.  The rovers, by the way, both celebrated their “One Martian Year Anniversary” recently (about twice as long as an Earth year).  Both rovers are still going strong (see JPL press release).  Opportunity recovered from a shoulder injury not long ago.  Engineers were able to get the robotic arm working again.  The MER Website has posted some more “special effects” images in which the rovers are placed into the scene.  This one of Opportunity on Burns Cliff would make a nice Christmas stocking stuffer.
    In other Mars news, the first results of the MARSIS instrument (Mars Advanced Radar for Subsurface and Ionospheric Sounding) on the European orbiter Mars Express were published in Science.3  The radar instrument can penetrate the surface for up to a kilometer.  Researchers found an underground impact basin 250 kilometers in diameter, and probed the northern polar ice deposits in this first-ever survey of the 3rd dimension of Mars.

1McCollom and Hynek, “A volcanic environment for bedrock diagenesis at Meridiani Planum on Mars,” Nature 438, 1129-1131 (22 December 2005) | doi:10.1038/nature04390.
2Knauth, Burt and Wohletz, “Impact origin of sediments at the Opportunity landing site on Mars,” Nature 438, 1123-1128 (22 December 2005) | doi:10.1038/nature04383.
3Picardi et al., “Radar Soundings of the Subsurface of Mars,” Science, 23 December 2005: Vol. 310. no. 5756, pp. 1925 – 1928, DOI: 10.1126/science.1122165.

Remember the optimistic claims that Opportunity had found evidence for long-lasting surface water?  Remember how the astrobiologists immediately jumped to the conclusion that Mars probably had good conditions for life?  (They’re still doing it; see the 11/29 JPL press release).  It was interesting to hear that the concretions or “blueberries” that seemed to clinch the argument for water have another explanation; they are apparently expected in an impact scenario, when a meteorite strike causes a short-term flood or “base surge” that can travel hundreds of kilometers from the impact site.  It may be possible that the H2O on Mars is subsurface ice that might liquefy during an impact event, only to freeze or vaporize quickly afterward.  Whatever they eventually decide, Mars doesn’t have to be lively to be interesting.

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