Long winter nears, but there may yet be life in Mars rovers
With their third Martian winter fast approaching, the twin rovers patrolling opposite sides of the Red Planet are showing distinct signs of age, even as they uncover fresh evidence that the planet was once hospitable to rudimentary life forms.
In fact, Spirit made one of its most significant discoveries because of its deteriorating health.
While dragging an inoperable wheel as it investigated a region called Home Plate this year, the rover uncovered a sub-surface strain of almost pure silica, possible evidence that Mars may have been home to hot springs like those found at Yellowstone National Park.
“This soil popped up bright as snow,” said Cornell University astronomer Steve Squyres, who manages the science instruments on Spirit and its twin, Opportunity.
After turning around and analyzing the soil with an X-ray spectrometer, the rover found the soil was nearly pure silica.
“This shows us a side of Mars we haven’t seen before,” Squyres said during a presentation at the American Geophysical Union conference in San Francisco this week.
The rovers, which landed on Mars in 2004 for what was supposed to be a three-month mission, have previously uncovered evidence that at one time, probably billions of years ago, Mars was home to lakes and possibly seas.
The silica shows evidence of a new set of environmental conditions, Squyres said.
Scientists are divided over whether the silica evidence indicates an ancient hot spring or a fumarole, a geologic opening caused by acidic steam rising through cracks in the planet’s surface. Fumaroles are common in volcanic areas on Earth such as Hawaii and Iceland.
“The jury is still out,” Squyres said.
“The point is, whether it’s one or the other, the potential for habitability is the same. You can go to hot springs and fumaroles on Earth, and both are teeming with life.”
Such formations might even preserve fossils, scientists said.
How long ago the deposits were laid down, however, is unknown, Squyres said.
Squyres said the rover scientific team would like to pursue the investigation, but they are running out of time. The long Martian winter is about to set in and the rovers must be parked where they get the most sunlight to help them weather the freezing temperatures and blowing dust.
Both rovers recently endured a planetwide dust storm that virtually blocked out the sun. Spirit’s solar panels are caked with so much dust that it looks like it just crossed the finish line in an off-road desert race. The dust, which rover project manager John Callas compared to military camouflage, has cut the rover’s performance to 42%, approaching the rover’s safety margin.
Callas said Spirit’s drivers were scrambling “because we’re losing sunlight.”
The list of maladies afflicting the rovers includes Spirit’s balky wheel and problems operating the grinding tool on both rovers. Opportunity is struggling with a bent brush on a grinding tool, difficulties using a thermal spectrometer and a gimpy robotic arm.
Despite these troubles, Opportunity, which is exploring Victoria Crater on the other side of the planet, has covered seven miles of the Martian surface.
“The rovers are in very good health considering they are almost 4 years old,” Callas said.
The threat in the near term is greatest for Spirit. “This is going to be a challenging winter for Spirit,” Callas said. “There is a good chance we could lose the vehicle.”
