[meteorite-list] NASA to Begin Attempts to Free Sand-Trapped Mars Rover

[Ron Baalke]

Nov. 12, 2009

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 

RELEASE: 09-263

NASA TO BEGIN ATTEMPTS TO FREE SAND-TRAPPED MARS ROVER

PASADENA, Calif. -- NASA will begin transmitting commands to its Mars 
exploration rover Spirit on Monday as part of an escape plan to free 
the venerable robot from its Martian sand trap. 

Spirit has been lodged at a site scientists call "Troy" since April 
23. Researchers expect the extraction process to be long and the 
outcome uncertain based on tests here on Earth this spring that 
simulated conditions at the Martian site. 

"This is going to be a lengthy process, and there's a high probability 
attempts to free Spirit will not be successful," said Doug 
McCuistion, director of the Mars Exploration Program at NASA 
Headquarters in Washington. "After the first few weeks of attempts, 
we're not likely to know whether Spirit will be able to free itself." 

Spirit has six wheels for roving the Red Planet. The first commands 
will tell the rover to rotate its five working wheels forward 
approximately six turns. Engineers anticipate severe wheel slippage, 
with barely perceptible forward progress in this initial attempt. 
Since 2006, Spirit's right-front wheel has been inoperable, possibly 
because of wear and tear on a motor as a result of the rover's 
longevity. 

Spirit will return data the next day from its first drive attempt. The 
results will be assessed before engineers develop and send commands 
for a second attempt. Using results from previous commands, engineers 
plan to continue escape efforts until early 2010. 

"Mobility on Mars is challenging, and whatever the outcome, lessons 
from the work to free Spirit will enhance our knowledge about how to 
analyze Martian terrain and drive future Mars rovers," McCuisition 
said. "Spirit has provided outstanding scientific discoveries and 
shown us astounding vistas during its long life on Mars, which is 
more than 22 times longer than its designed life." 

In the spring, Spirit was driving backward and dragging the inoperable 
right front wheel. While driving in April, the rover's other wheels 
broke through a crust on the surface that was covering a 
bright-toned, slippery sand underneath. After a few drive attempts to 
get Spirit out in the subsequent days, it began sinking deeper in the 
sand trap. Driving was suspended to allow time for tests and reviews 
of possible escape strategies. 

"The investigations of the rover embedding and our preparations to 
resume driving have been extensive and thorough," said John Callas, 
project manager for Spirit and Opportunity at NASA's Jet Propulsion 
Laboratory in Pasadena, Calif. "We've used two different test rovers 
here on Earth in conditions designed to simulate as best as possible 
Spirit's predicament. However, Earth-based tests cannot exactly 
replicate the conditions at Troy." 

Data show Spirit is straddling the edge of a 26-foot-wide crater that 
had been filled long ago with sulfate-bearing sands produced in a hot 
water or steam environment. The deposits in the crater formed 
distinct layers with different compositions and tints, and they are 
capped by a crusty soil. It is that soil that Spirit's wheels broke 
through. The buried crater lies mainly to Spirit's left. Engineers 
have plotted an escape route from Troy that heads up a mild slope 
away from the crater. 

"We'll start by steering the wheels straight and driving, though we 
may have to steer the wheels to the right to counter any downhill 
slip to the left," said Ashley Stroupe, a JPL rover driver and Spirit 
extraction testing coordinator. "Straight-ahead driving is intended 
to get the rover's center of gravity past a rock that lies underneath 
Spirit. Gaining horizontal distance without losing too much vertical 
clearance will be a key to success. The right front wheel's inability 
to rotate greatly increases the challenge." 

Spirit has been examining its Martian surroundings with tools on its 
robotic arm and its camera mast. The rover's work at Troy has 
augmented earlier discoveries it made indicating ancient Mars had hot 
springs or steam vents, possible habitats for life. If escape 
attempts fail, the rover's stationary location may result in new 
science findings. 

"The soft materials churned up by Spirit's wheels have the highest 
sulfur content measured on Mars," said Ray Arvidson a scientist at 
Washington University in St. Louis and deputy principal investigator 
for the science payloads on Spirit and Opportunity. "We're taking 
advantage of its fixed location to conduct detailed measurements of 
these interesting materials." 

Spirit and its twin rover landed on Mars in January 2004. They have 
explored Mars for five years, far surpassing their original 90-day 
mission. Opportunity currently is driving toward a large crater 
called Endeavor. 

NASA's JPL manages the rovers for NASA's Science Mission Directorate 
in Washington. 

For updates about Spirit's progress, visit: 

http://www.nasa.gov/rovers 
	
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