[meteorite-list] NASA's Twin Mars Rovers Continue Exploration

[Ron Baalke]

Dolores Beasley/Gretchen Cook-Anderson
Headquarters, Washington                          February 15, 2005
(Phone: 202/358-1753/0836)

Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.
(Phone: 818/354-6278)

John Bluck
Ames Research Center, Moffett Field, Calif.
(Phone: 650/604-5026/9000)

RELEASE: 05-044

NASA'S TWIN MARS ROVERS CONTINUE EXPLORATION 

NASA's Spirit rover found a new class of water-affected rock, while 
its twin, Opportunity, finished inspecting its own heat shield and 
set a new martian driving record. The rovers successfully completed 
their three-month primary missions in April 2004 and are working on 
extended exploration missions.

"This is probably the most interesting and important rock Spirit has 
examined," said Dr. Steve Squyres of Cornell University, Ithaca, N.Y., 
principal investigator for the rovers. The rock, dubbed "Peace," is an 
exposure of bedrock in the Columbia Hills. The rock is in the Gusev 
Crater, where Spirit landed 13 months ago. "This may be what the bones 
of this mountain are really made of; it gives us even more compelling 
evidence for water playing a major role for altering the rocks here," 
Squyres added.

Peace contains more sulfate salt than any other rock Spirit has examined. 
Dr. Ralf Gellert, of Max-Planck-Institut fur Chemie, Mainz, Germany, said, 
"Usually when we have seen high levels of sulfur in rocks at Gusev, it 
has been at the very surface. The unusual thing about this rock is that 
deep inside; the sulfur is still very high. The sulfur enrichment at the 
surface is correlated with the amount of magnesium, which points to 
magnesium sulfate." 

Observations by Spirit show the rock contains significant 
amounts of the minerals olivine, pyroxene and magnetite, all of which 
are common in some types of volcanic rock. The rock's texture appears 
to be sand-size grains coated with a material loosely binding the rock 
together. Spirit's rock abrasion tool dug about 1 centimeter (0.4 inch) 
deep in two hours.

"It looks as if you took volcanic rocks that were ground into little 
grains, and then formed a layered rock with them cemented 
together by a substantial quantity of magnesium-sulfate salt," Squyres 
said. "Where did the salt come from? We have two working hypotheses we 
want to check by examining more rocks. It could come from liquid water 
with magnesium sulfate salt dissolved in it, percolating through the 
rock, then evaporating and leaving the salt behind. Or it could come 
from weathering by dilute sulfuric acid reacting with magnesium-rich 
minerals that were already in the rock. Either case involves water," 
he said.

Opportunity used its microscopic imager last week to examine a cross 
section of the heat shield that protected the spacecraft as it 
slammed into Mars' atmosphere. This is the first time experts have 
been able to examine a heat shield after it entered another 
planet's atmosphere. Engineers expect the findings to aid design 
for future missions.

"We've identified each broken piece of the heat shield. We know 
there's a lot of data there, but we still need to analyze it," said 
Ethiraj Venkatapathy of NASA's Ames Research Center, Moffett Field, 
Calif. 

Christine Szalai, a spacecraft engineer at NASA's Jet Propulsion 
Laboratory (JPL), Pasadena, Calif., said, "We are examining the 
images to determine the depth of charring in the heat shield 
material. In the initial look, we didn't see any surprises. We 
will be working for the next few months to analyze the performance of 
the heat shield," Szalai said.

Since leaving the heat shield, Opportunity has been traveling south 
to explore new sites. The rover set a single-day martian driving 
record, covering 154.65 meters (507.4 feet) on Jan. 28. 
Two days later, it drove even farther, 156.55 meters (513.6 feet). The 
first 90 meters (295 feet) of each drive was performed in blind-drive 
mode, following a route planners created from stereo images from the 
rover and maps created from orbital imagery. The rest was autonomous 
driving, with the rover choosing its own route to avoid any hazards 
it perceived in stereo images taken along the way.

"The terrain we're crossing is so flat we can see a long way ahead," 
said JPL rover planner Frank Hartman, who teamed with Jeff 
Biesiadecki to plot the drive. "Opportunity has paused for some 
trenching, but in a few days we'll put the pedal to the metal 
again."

For Images and additional information about the rovers on the 
Internet, visit:

http://www.nasa.gov/vision/universe/solarsystem/mer_main.html

For information about NASA and agency programs on the Internet, 
visit:

http://www.nasa.gov

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