NASA Announces August 4 News Briefing On MRO Science Finding |
NASA Announces August 4 News Briefing On MRO Science Finding |
Aug 3 2011, 03:55 PM
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Newbie Group: Members Posts: 10 Joined: 20-April 05 Member No.: 293 |
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Aug 4 2011, 07:49 PM
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Member Group: Members Posts: 819 Joined: 3-June 04 From: Brittany, France Member No.: 79 |
That's weird CRISM does not see anything. They argue that flows are much smaller than the CRISM pixel scale (18m). That's true for a single flow, which width scales between 0.5 and 5m, but some HiRISE pictures show 60m*60m areas covered by this dark flows. So CRISM shoud see them. And a mixture of water and salt does not change anything : there is still a strong signature of water. I'm very skeptical...
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Aug 6 2011, 12:53 AM
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Member Group: Members Posts: 715 Joined: 22-April 05 Member No.: 351 |
That's weird CRISM does not see anything. They argue that flows are much smaller than the CRISM pixel scale (18m). There's a spectral processing technique called spectral mixture analysis (SMA) which has been used in many studies (including by yours truly) to determine the sub-pixel fractional area cover of different substances. If water covers a reasonable portion of the area of a pixel, SMA should be able to tease it out. I believe SMA has been used for Mars studies, but if not, it's a well known technique. If it's not been used in this case, this suggests that the CRISM investigators have used equally good spectral techniques for teasing out fractional coverage. The lack of a water spectra suggests that (1) CRISM has been unlucky enough to look when water wasn't present, (2) there is so little water at any given time that it doesn't trigger a measurable spectral response, (3) water isn't involved. -------------------- |
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