NASA Mars Rover Finds Mineral Vein Deposited by Water

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Dec. 7, 2011

Steve Cole 
Headquarters, Washington                                    
202-358-0918 
stephen.e.cole@xxxxxxxx 

Guy Webster/Alan Buis 
Jet Propulsion Laboratory, Pasadena, Calif. 
818-354-6278/818-653-8339 
guy.webster@xxxxxxxxxxxx / alan.d.buis@xxxxxxxxxxxx 

RELEASE: 11-403

NASA MARS ROVER FINDS MINERAL VEIN DEPOSITED BY WATER

WASHINGTON -- 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, 
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), 16 to 20 inches 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 have 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 minerals combined with sulfur either leached from the 
rocks or introduced as volcanic gas, and 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. 

"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." 

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. 

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, visit: 

http://www.nasa.gov/rovers 

	
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