Rover's find: Hot springs once ran on Mars

A broken wheel of the Mars rover Spirit dug this trench in the frozen
ground near the equator, revealing a deposit of silica.

(azcentral) -- Discovery made when broken wheel scratches planet's surface

As the Phoenix Mars Mission prepares to land Sunday, a hobbled brother craft already on the planet has discovered deposits from ancient hot springs.

The finding is significant in the ongoing search for signs of life on Mars.

"We certainly haven't discovered life, but we have discovered a location that we can describe as potentially habitable sometime in Mars' ancient past," said Steve Ruff, a faculty research associate at Arizona State University and co-author of the paper published in today's Science journal.

The Phoenix mission, led by the University of Arizona, will look for signs of a habitable environment in the northern polar region of Mars. The ancient hot springs were found near the planet's equator.

Scientists, including two at ASU, believe the deposits formed from volcanic steam or hot-water springs, similar to those at Yellowstone National Park.

The golf-cart-size rover named Spirit made the discovery by accident when a broken front wheel scraped a shallow trench and uncovered a bright-white substance. An ASU infrared instrument aboard the rover confirmed the material was almost pure silica, a mineral that can form when hot water reacts with rocks. Spirit's instruments aren't sophisticated enough to detect life, but its finding could guide a planned 2009 Mars rover mission.

The twin rovers Spirit and Opportunity are exploring the ancient deserts near the equator. Their main goals are to investigate the planet's geological history and understand what role water played in its development. Scientists are interested in water because it is a basic requirement for life.

Spirit made the discovery despite showing signs of wear. The rover must travel in reverse because one of its six wheels is broken, and thick dust coats the solar panels that supply power to the craft. Last summer, a severe dust storm starved both rovers and nearly ended their lives.

Spirit and Opportunity were expected to operate for three months, but they have lasted for more than four years. They move at turtle speed, stopping every 10 seconds or so to evaluate their locations and avoid potential hazards. Dust storms also can cause engineers to park the rovers until it's safe to continue. Since landing in the 100-mile-wide Gusev Crater, Spirit has logged 4.7 miles.

The rovers are the only missions operating on the Martian surface, although on Sunday, they are scheduled to be joined by the Phoenix mission. Scientists have identified the polar plains as having a good chance of revealing a habitat suitable for life because the icy terrain preserves geological history. Unlike the rovers, Phoenix is a stationary craft that will use a nearly 8-foot robotic arm to dig into the ice, scoop up samples and transfer them to an onboard chemistry lab.

ASU scientists said the timing of the Science article is coincidental to the Phoenix landing. A research team from six universities, NASA and two museums have spent the past year analyzing data from the silicon-filled trench.

The research relied on an ASU infrared instrument aboard the rover called the Mini-Thermal Emission Spectrometer, known as Mini-TES, to detect the silica deposits. ASU's Ruff oversees daily operations of Mini-TES, which was designed by ASU Professor Phil Christensen.

The silica is Spirit's most important discovery to date, said ASU Professor Jack Farmer, who co-wrote the paper. The rover previously had found hints of water, uncovered meteorites and photographed dust devils.

Spirit may make more discoveries. NASA officials announced last fall that the rovers would continue their missions, possibly through 2009.