[meteorite-list] Rover Gives NASA an 'Opportunity' to View Interior of Mars

[Ron Baalke]

Jan. 21, 2010

Dwayne Brown 
Headquarters, Washington 
202-358-1726 
dwayne.c.brown at nasa.gov 

Guy Webster 
Jet Propulsion Laboratory, Pasadena, Calif. 
818-354-6278 
guy.webster at jpl.nasa.gov 

MEDIA ADVISORY: 10-016

ROVER GIVES NASA AN "OPPORTUNITY" TO VIEW INTERIOR OF MARS

PASADENA, Calif. -- NASA's Mars exploration rover Opportunity is 
allowing scientists to get a glimpse deep inside Mars. 

Perched on a rippled Martian plain, a dark rock not much bigger than a 
basketball was the target of interest for Opportunity during the past 
two months. Dubbed "Marquette Island," the rock is providing a better 
understanding of the mineral and chemical makeup of the Martian 
interior. 

"Marquette Island is different in composition and character from any 
known rock on Mars or meteorite from Mars," said Steve Squyres of 
Cornell University in Ithaca, N.Y. Squyres is principal investigator 
for Opportunity and its twin, Spirit. "It is one of the coolest 
things Opportunity has found in a very long time." 

During six years of roving, Opportunity has found only one other rock 
of comparable size that scientists conclude was ejected from a 
distant crater. The rover studied the first such rock during its 
initial three-month mission. Called "Bounce Rock," that rock closely 
matched the composition of a meteorite from Mars found on Earth. 

Marquette Island is a coarse-grained rock with a basalt composition. 
The coarseness indicates it cooled slowly from molten rock, allowing 
crystals time to grow. This composition suggests to geologists that 
it originated deep in the crust, not at the surface where it would 
cool quicker and have finer-grained texture. 

"It is from deep in the crust and someplace far away on Mars, though 
exactly how deep and how far we can't yet estimate," said Squyres. 

The composition of Marquette Island, as well as its texture, 
distinguishes it from other Martian basalt rocks that rovers and 
landers have examined. Scientists first thought the rock could be 
another in a series of meteorites that Opportunity has found. 
However, a much lower nickel content in Marquette Island indicates a 
Martian origin. The rock's interior contains more magnesium than in 
typical Martian basalt rocks Spirit has studied. Researchers are 
determining whether it might represent the precursor rock altered 
long ago by sulfuric acid to become the sulfate-rich sandstone 
bedrock that blankets the region of Mars that Opportunity is 
exploring. 

"It's like having a fragment from another landing site," said Ralf 
Gellert of the University of Guelph, in Ontario, Canada. Gellert is 
lead scientist for the alpha particle X-ray spectrometer on 
Opportunity's robotic arm. "With analysis at an early stage, we're 
still working on some riddles about this rock." 

The rover team used Opportunity's rock abrasion tool to grind away 
some of Marquette Island's weathered surface and expose the interior. 
This was the 38th rock target Opportunity has ground into, and one of 
the hardest. The tool was designed to grind into one Martian rock, 
and this rock may not be its last. 

"We took a conservative approach on our target depth for this grind to 
ensure we will have enough of the bit left to grind the next hard 
rock that Opportunity comes across," said Joanna Cohen of Honeybee 
Robotics Spacecraft Mechanisms Corp., in New York, which built and 
operates the tool. 

Opportunity currently is about 30 percent of the way on a 12-mile trek 
begun in mid-2008 from a crater it studied for two years. It is en 
route toward a much larger crater, Endeavour. The rover traveled 3.3 
miles in 2009, farther than in any other year on Mars. Opportunity 
drove away from Marquette Island on Jan. 12. 

"We're on the road again," said Mike Seibert, a rover mission manager 
at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "The year 
ahead will include lots more driving, if all goes well. We'll keep 
pushing for Endeavour crater but watch for interesting targets along 
the way where we can stop and smell the roses." 

Since landing on Mars in 2004, Opportunity has made numerous 
scientific discoveries, including the first mineralogical evidence 
that Mars had liquid water. After working 24 times longer than 
originally planned, Opportunity has driven more than 11 miles and 
returned more than 133,000 images. JPL manages the rovers for NASA's 
Science Mission Directorate in Washington. 

For more information about the rovers, visit: 

http://www.nasa.gov/rovers 
	
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