[meteorite-list] Cold, Dry and Lifeless - A New Take on Mars (and True Color?)

[j.divelbiss at att.net]

Maybe this answers my Mars color question. The opening paragraph says...

"New research on a green mineral that degrades easily in water and is
present over much of the Martian surface is fuelling debates over the
history of water and the current existence of life on the Red planet."

JD



-------------- Original message from Ron Baalke <baalke at zagami.jpl.nasa.gov>: -------------- 


> 
> 
> http://www.newscientist.com/article.ns?id=dn7463 
> 
> Cold, dry and lifeless - a new take on Mars 
> Maggie McKee 
> New Scientist 
> June 3, 2005 
> 
> New research on a green mineral that degrades easily in water and is 
> present over much of the Martian surface is fuelling debates over the 
> history of water and the current existence of life on the Red planet. 
> 
> One study reveals that a region rich in the mineral olivine - which 
> suggests it is has been "dry" for about 3 billion years - is actually 
> four times larger than previously thought. That adds to a growing body 
> of evidence suggesting Mars was mostly cold and dry - and not warm and 
> wet - in the past. 
> 
> The second study asserts that subsurface reactions of olivine and water 
> could produce enough methane to account for recent observations of the 
> gas in the atmosphere, removing the need to invoke living microbes to do 
> the job. 
> 
> Olivine forms at very high temperatures and is one of the first minerals 
> to crystallise out of molten rock. But at lower temperatures and in the 
> presence of water, it is thermodynamically "unhappy and breaks down 
> really quickly into other minerals", says Phil Christensen, a geologist 
> at Arizona State University in Tempe, US. 
> 
> He and colleague Victoria Hamilton of the University of Hawaii in 
> Honolulu, US, have used infrared images taken with NASA's Mars Odyssey 
> spacecraft to show that the olivine-rich rocks on the flank of the 
> volcano Syrtis Major cover a surface area of 113,000 square kilometres - 
> about half the size of the UK. 
> 
> Higher resolution 
> 
> That is nearly four times larger than the estimate made by NASA's Mars 
> Global Surveyor (MGS) spacecraft. The difference has been attributed to 
> Odyssey's ability to resolve details as small as 100 metres across, a 
> 30-fold improvement over MGS. Christensen and Hamilton's study is 
> published in the journal Geology (vol 33, p 433). 
> 
> The rocks, at a latitude of 20° north of the planet's equator, appear to 
> have formed through successive lava eruptions about 3 billion years ago. 
> "To keep olivine around so long suggests this area of Mars may not have 
> seen a lot of water or a warm climate," Hamilton told New Scientist. 
> 
> That finding differs markedly from the recent discoveries made by the 
> Mars rovers of minerals that form in the presence of water. But 
> Christensen says such discoveries represent rare flooding events lasting 
> for weeks or months and that for most of the planet's 4.5 billion-year 
> history, any water has been locked in ice. 
> 
> "I am not a proponent of the idea that Mars had oceans in the past," 
> says Christensen. He says mineral mapping from orbit reveals most of the 
> planet is covered in volcanic rocks, which "shows most of Mars hasn't 
> seen much water". Scientists have failed to find minerals such as 
> carbonates and clays that form in oceans on Earth, he says. 
> 
> "I'm moving in the direction of 'cold and dry' more and more," agrees 
> Hamilton. "But there are other scientists headed in the other direction, 
> thinking Mars was warmer and wetter. It is an ongoing discussion." 
> 
> Making methane 
> 
> The discovery of more olivine on the surface of Mars also supports the 
> argument that underground reserves of the mineral could produce methane, 
> says geologist Mukul Sharma of Dartmouth College in Hanover, New 
> Hampshire, US. He and colleague Chris Oze detail their proposal in the 
> journal Geophysical Research Letters (vol 32, L10203). 
> 
> Olivine tends to sink when it crystallises from magma, which "implies at 
> some depth there has to be a lot more olivine than you see on the 
> surface," says Sharma. The team says there is enough olivine in the top 
> 10 kilometres of the crust to explain the recent detections of methane 
> in Mars's atmosphere - if there are stores of liquid water underground, 
> as many scientists suspect. 
> 
> Water reacts with a common, iron-rich form of olivine by producing 
> hydrogen gas, which then combines with carbon dioxide to produce 
> methane. The gas could then leak to the surface through gullies. 
> 
> "The easiest way to produce all the methane people have observed is by 
> the reaction of olivine with water," Sharma told New Scientist. Other 
> researchers have proposed that microbes might be a continuous source of 
> the gas, which is easily destroyed by sunlight in the atmosphere. 
> 
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