NASA Mars Rover Finds Mineral Vein Deposited by Water
NASA's Mars Exploration Rover Opportunity has found bright veins of a mineral, apparently gypsum, deposited by water.
PASADENA, Calif. -- NASA's Mars Exploration Rover  Opportunity has found bright veins of a mineral, apparently gypsum, deposited  by water. Analysis of the vein will help improve understanding of the history  of wet environments on Mars."This tells a slam-dunk story that water flowed through  underground fractures in the rock," said Steve Squyres of Cornell  University, Ithaca, N.Y., principal investigator for Opportunity. "This  stuff is a fairly pure chemical deposit that formed in place right where we see  it. That can't be said for other gypsum seen on Mars or for other water-related  minerals Opportunity has found. It's not uncommon on Earth, but on Mars, it's  the kind of thing that makes geologists jump out of their chairs."The latest findings by Opportunity were presented Wednesday  at the American Geophysical Union's conference in San Francisco.The vein examined most closely by Opportunity is about the  width of a human thumb (0.4 to 0.8 inch, or 1 to 2 centimeters), 16 to 20  inches (40 to 50 centimeters) long, and protrudes slightly higher than the  bedrock on either side of it. Observations by the durable rover reveal this  vein and others like it within an apron surrounding a segment of the rim of  Endeavour Crater. None like it were seen in the 20 miles (33 kilometers) of  crater-pocked plains that Opportunity explored for 90 months before it reached  Endeavour, nor in the higher ground of the rim.Last month, researchers used the Microscopic Imager and  Alpha Particle X-ray Spectrometer on the rover's arm and multiple filters of  the Panoramic Camera on the rover's mast to examine the vein, which is  informally named "Homestake."   The spectrometer identified plentiful calcium and sulfur, in a ratio  pointing to relatively pure calcium sulfate.Calcium sulfate can exist in many forms, varying by how much  water is bound into the minerals' crystalline structure. The multi-filter data  from the camera suggest gypsum, a hydrated calcium sulfate. On Earth, gypsum is  used for making drywall and plaster of Paris.Observations from orbit had detected gypsum on Mars  previously. A dune field of windblown gypsum on far northern Mars resembles the  glistening gypsum dunes in White Sands National Monument in New Mexico."It is a mystery where the gypsum sand on northern Mars  comes from," said Opportunity science-team member Benton Clark of the  Space Science Institute in Boulder, Colo. "At Homestake, we see the  mineral right where it formed. It will be important to see if there are  deposits like this in other areas of Mars."The Homestake deposit, whether gypsum or another form of  calcium sulfate, likely formed from water dissolving calcium out of volcanic  rocks. The calcium combined with sulfur that was either leached from the rocks  or introduced as volcanic gas, and it was deposited as calcium sulfate into an  underground fracture that later became exposed at the surface.Throughout Opportunity's long traverse across Mars'  Meridiani plain, the rover has driven over bedrock composed of magnesium, iron  and calcium sulfate minerals that also indicate a wet environment billions of  years ago. The highly concentrated calcium sulfate at Homestake could have been  produced in conditions more neutral than the harshly acidic conditions  indicated by the other sulfate deposits observed by Opportunity."It could have formed in a different type of water  environment, one more hospitable for a larger variety of living  organisms," Clark said.Homestake and similar-looking veins appear in a zone where  the sulfate-rich sedimentary bedrock of the plains meets older, volcanic  bedrock exposed at the rim of Endeavour. That location may offer a clue about  their origin.Opportunity and its rover twin, Spirit, completed their  three-month prime missions on Mars in April 2004. Both rovers continued for  years of extended missions and made important discoveries about wet  environments on ancient Mars that may have been favorable for supporting  microbial life. Spirit stopped communicating in 2010. Opportunity continues  exploring, currently heading to a sun-facing slope on the northern end of the  Endeavour rim fragment called "Cape York" to keep its solar panels at  a favorable angle during the mission's fifth Martian winter."We want to understand  why these veins are in the apron but not out on the plains," said the  mission's deputy principal investigator, Ray Arvidson, of Washington University  in St. Louis. "The answer may be that rising groundwater coming from the  ancient crust moved through material adjacent to Cape York and deposited  gypsum, because this material would be relatively insoluble compared with  either magnesium or iron sulfates."NASA launched the next-generation Mars rover, the car-sized Curiosity, on Nov. 26. It is slated for arrival at  the planet's Gale Crater in August 2012. NASA's Jet Propulsion Laboratory, a  division of the California Institute of Technology in Pasadena, manages the  Mars Exploration Rover Project for the NASA Science Mission Directorate in  Washington. For more information about the rovers, visithttp://www.nasa.gov/roversandhttp://marsrovers.jpl.nasa.gov.  You can follow the project on Twitter athttp://twitter.com/MarsRoversand  on Facebook athttp://www.facebook.com/marsrovers.