| NASA's Mars Exploration Rover Spirit has found a patch of bright-toned soil so rich in silica that scientists propose water must have been involved in concentrating it.
Mars' Spirit Rover Finds More Evidence of Water
NASA's Spirit Rover on Mars has found "silica-rich soil" in Gusev Crater that scientists say is so rich that it would require water to have been present at some point.
"You could hear people gasp in astonishment. This is a remarkable discovery. And the fact that we found something this new and different after nearly 1,200 days on Mars makes it even more remarkable. It makes you wonder what else is still out there," said Steve Squyres, principal investigator for the Mars rovers' science instruments at Cornell University.
The Martian soil was analyzed by Spirit's alpha particle X-ray spectrometer, and the soil was found to contain at least 90% pure silica. The findings were announced during a teleconference between Squyres and the other rovers' team members.
Spirit did not make this discovery on purpose. One of the six wheels on the rover is no longer functioning, and whereever Spirit goes, a deep gash is left in the soil in its wake. This caused the soil to be exposed and this discovery to be made. Actually, Spirit has made other discoveries using this "method." The rover had previously found other indicators of water, such as patches of water-bearing, sulfur-rich soil and alteration of minerals.
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NASA's Mars Exploration Rover Spirit has found a patch of bright-toned soil so rich in silica that scientists propose water must have been involved in concentrating it.The silica-rich patch, informally named "Gertrude Weise" after a player in the All-American Girls Professional Baseball League, was exposed when Spirit drove over it during the 1,150th Martian day, or sol, of Spirit's Mars surface mission (March 29, 2007). One of Spirit's six wheels no longer rotates, so it leaves a deep track as it drags through soil. Most patches of disturbed, bright soil that Spirit had investigated previously are rich in sulfur, but this one has very little sulfur and is about 90 percent silica.
Spirit's panoramic camera imaged the bright patch through various filters on Sol 1,158 (April 6). This approximately true-color image combines images taken through three different filters. The track of disturbed soil is roughly 20 centimeters (8 inches) wide. Spirit's miniature thermal emission spectrometer, which can assess a target's mineral composition from a distance, examined the Gertrude Weise patch on Sol 1,172 (April 20). The indications it found for silica in the overturned soil prompted a decision to drive Spirit close enough to touch the soil with the alpha particle X-ray spectrometer, a chemical analyzer at the end of Spirit's robotic arm. The alpha particle X-ray spectrometer collected data about this target on sols 1,189 and 1,190 (May 8 and May 9) and produced the finding of approximately 90 percent silica.
Silica is silicon dioxide. On Earth, it commonly occurs as the crystalline mineral quartz and is the main ingredient in window glass. The Martian silica at Gertrude Weise is non-crystalline, with no detectable quartz.
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"This unexpected new discovery is a reminder that Spirit and Opportunity are still doing cutting-edge exploration more than three years into their extended missions. It also reinforces the fact that significant amounts of water were present in Mars' past, which continues to spur the hope that we can show that Mars was once habitable and possibly supported life."
The discovery is being called the best one yet to support the theory that Mars once had an abundance of water.
"This is some of the best evidence Spirit has found for water at Gusev," said a geochemist at NASA's Jet Propulsion Laboratory in Pasadena, California, Albert Yen, who added that this is the best indication so far that there could have been "favorable conditions" for there to have been life on Mars in the past.
There are some interactions that scientists say could have caused the silica to be deposited, but all of them include water. One is that volcanic activity, which produces acid vapors, interacted with the water inside the soil. Another theory is an ancient hot spring located in the area.
Both Spirit, and its partner rover Opportunity have both been in operation on Mars for almost 1,200 days. Both of the rovers finished their initial mission back in 2004, but both have been operating since and making new discoveries.
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