Mars Crater Shows Its (False) Colors: Big Pic

Oct. 31, 2011 -- This could be the iridescent "mother of pearl" found on the inner surface of an oyster shell -- vivid olive green and purple shimmering in the sunlight. However, this image isn't of this planet; it's a satellite observation of the Martian surface.

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Using observational data from two instruments on board NASA's Mars Reconnaissance Orbiter (MRO) -- the High Resolution Imaging Science Experiment (HiRISE) and Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) -- this composite image is approximately 500 meters wide, detailing the central uplift in the middle of a much larger impact crater.

Inside large, complex impact craters, a central uplift feature may occur over long periods of time -- gravity acts on the crater rim, forcing material upward in the center of the crater. As a result, sub-surface minerals may be uncovered and scientists analyzing this image believe the colorful rocks exposed in the central peak may be evidence of mineral variations caused by water activity in the early history of Mars -- when the Red Planet was a lot wetter.

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According to SETI planetary scientist Adrian Brown, a scientist working with CRISM data, the minerals seen here are likely indicative of the presence of clays. Unfortunately, we cannot know exactly what minerals are present from this image alone.

"It's impossible to say what minerals might be here from HiRISE," Brown said in an email to Discovery News. "It's particularly difficult because of the false color nature of the image to tell what is causing this."

"Because we are covering the 0.4-1.0 micron range, this is the region where electronic transitions happen in iron and other minerals. Often this will be associated with clays in HiRISE images only based on the fact that they are often targeted and are generally quite bright minerals (think Kaolinite or Mica)."

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So, if this color variation is due to different types of clays, how did they get there?

"There would be two possibilities of why clays might be in a central peak," Brown continued. "1) They were there before the impact. This looks possible because there is layering that is exposed and on its side to my eye."

"2) It was altered in the heat of the impact and in combination with some nearby water hydrothermal activity took place that ran through the central peak."

Brown is keen to point out that it is very hard to make any conclusions as to the nature of this feature, however. Although satellite imagery is great for spotting regions of interest, the thorough analysis can only begin when geologists' boots are on the ground.

"I think we have to land the ship and walk around to find out," he said.

ANALYSIS: Why Explore Mars?

Although sending human geologists to Mars is a long way off, we actually have a robotic Mars geologist being readied for launch. And guess what it will be studying when it lands?

NASA's Mars Science Laboratory "Curiosity" is scheduled to blast off from Cape Canaveral in November and it will touch down on Mars inside Gale Crater on Aug. 6, 2012. It just so happens that Gale Crater also has a fascinating central uplift region ripe for study. Mission planners hope Curiosity will be able to read the history of Mars' watery past as the wheeled rover makes its trek up the peak.

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-- by Ian O'Neill.

Image credit and hi-res photos: NASA/JPL/University of Arizona