[meteorite-list] NASA's Mars Rover Has Uncertain Future as Sixth Anniversary Nears

[Ron Baalke]

Dec. 31, 2009

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

Guy Webster/Veronica McGregor 
Jet Propulsion Laboratory, Pasadena, Calif. 
818-354-5011 
guy.webster at jpl.nasa.gov, veronica.mcgregor at jpl.nasa.gov 

RELEASE: 09-297

NASA'S MARS ROVER HAS UNCERTAIN FUTURE AS SIXTH ANNIVERSARY NEARS

PASADENA, Calif. -- NASA's Mars rover Spirit will mark six years of 
unprecedented science exploration and inspiration for the American 
public on Sunday. However, the upcoming Martian winter could end the 
roving career of the beloved, scrappy robot. 

Spirit successfully landed on the Red Planet at 8:35 p.m. PST on Jan. 
3, 2004, and its twin Opportunity arrived at 9:05 p.m. Jan. 24, 2004. 
The rovers began missions intended to last for three months but which 
have lasted six Earth years, or 3.2 Mars years. During this time, 
Spirit has found evidence of a steamy and violent environment on 
ancient Mars that was quite different from the wet and acidic past 
documented by Opportunity, which has been operating successfully as 
it explores halfway around the planet. 

A sand trap and balky wheels are challenges to Spirit's mobility that 
could prevent NASA's rover team from using a key survival strategy 
for the rover. The team may not be able to position the robot's solar 
panels to tilt toward the sun to collect power for heat to survive 
the severe Martian winter. 

Nine months ago, Spirit's wheels broke through a crusty surface layer 
into loose sand hidden underneath. Efforts to escape this sand trap 
barely have budged the rover. The rover's inability to use all six 
wheels for driving has worsened the predicament. Spirit's right-front 
wheel quit working in 2006, and its right-rear wheel stalled a month 
ago. Surprisingly, the right-front wheel resumed working, though 
intermittently. Drives with four or five operating wheels have 
produced little progress toward escaping the sand trap. The latest 
attempts resulted in the rover sinking deeper in the soil. 

"The highest priority for this mission right now is to stay mobile, if 
that's possible," said Steve Squyres of Cornell University in Ithaca, 
N.Y. He is principal investigator for the rovers. 

If mobility is not possible, the next priority is to improve the 
rover's tilt, while Spirit is able to generate enough electricity to 
turn its wheels. Spirit is in the southern hemisphere of Mars, where 
it is autumn, and the amount of daily sunshine available for the 
solar-powered rover is declining. This could result in ceasing 
extraction activities as early as January, depending on the amount of 
remaining power. Spirit's tilt, nearly five degrees toward the south, 
is unfavorable because the winter sun crosses low in the northern 
sky. 

Unless the tilt can be improved or luck with winds affects the gradual 
buildup of dust on the solar panels, the amount of sunshine available 
will continue to decline until May 2010. During May, or perhaps 
earlier, Spirit may not have enough power to remain in operation. 

"At the current rate of dust accumulation, solar arrays at zero tilt 
would provide barely enough energy to run the survival heaters 
through the Mars winter solstice," said Jennifer Herman, a rover 
power engineer at NASA's Jet Propulsion Laboratory in Pasadena, 
Calif. 

The team is evaluating strategies for improving the tilt even if 
Spirit cannot escape the sand trap, such as trying to dig in deeper 
with the wheels on the north side. In February, NASA will assess Mars 
missions, including Spirit, for their potential science versus costs 
to determine how to distribute limited resources. Meanwhile, the team 
is planning additional research about what a stationary Spirit could 
accomplish as power wanes. 

"Spirit could continue significant research right where it is," said 
Ray Arvidson of Washington University in St. Louis, deputy principal 
investigator for the rovers. "We can study the interior of Mars, 
monitor the weather and continue examining the interesting deposits 
uncovered by Spirit's wheels." 

A study of the planet's interior would use radio transmissions to 
measure wobble of the planet's axis of rotation, which is not 
feasible with a mobile rover. That experiment and others might 
provide more and different findings from a mission that has already 
far exceeded expectations. 

"Long-term change in the spin direction could tell us about the 
diameter and density of the planet's core," said William Folkner of 
JPL. He has been developing plans for conducting this experiment with 
a future, stationary Mars lander. "Short-period changes could tell us 
whether the core is liquid or solid," he said. 

In 2004, Opportunity discovered the first mineralogical evidence that 
Mars had liquid water. The rover recently finished a two-year 
investigation of a half-mile wide crater called Victoria and now is 
headed toward Endeavor crater, which is approximately seven miles 
from Victoria and nearly 14 miles across. Since landing, Opportunity 
has driven more than 11 miles and returned more than 132,000 images. 

For more information about the rovers, visit: 

http://www.nasa.gov/rovers 
	
-end-