Washington, May 23 : The Mars Exploration Rover Spirit has found deposits of pure silica on the Red Planet, which is similar to hot spring deposits seen at the Yellowstone National Park in the US.
According to planetary scientists working with data collected by the rover's Miniature Thermal Emission Spectrometer (Mini-TES), a mineral-scouting instrument, the Martian deposits have been found around hydrothermal vents like those in Yellowstone National Park.
They have concluded that deposits of nearly pure silica discovered by the rover in Gusev Crater on Mars formed when volcanic steam or hot water (or maybe both) percolated through the ground.
The silica finding turns a spotlight on an important site that may contain preserved traces of ancient Martian life.
"On Earth, hydrothermal deposits teem with life and the associated silica deposits typically contain fossil remains of microbes," said Jack Farmer, professor of astrobiology in ASU's School of Earth and Space Exploration.
"But we don't know if that's the case here, because the rovers don't carry instruments that can detect microscopic life," he added.
"What we can say is that this was once a habitable environment where liquid water and the energy needed for life were present," he said.
The silica discovery unfolded in slow motion as Spirit emerged from hibernation after its second Martian winter, surveying an area of exposed soil called the Tyrone site.
The Tyrone soil proved rich in sulfate minerals, a phenomenon seen by Spirit at other locations in the Columbia Hills, where Spirit has been exploring since late 2004.
"While parked next to Tyrone, we used the Mini-TES to look at some nearby light-toned and knobby outcrops," said Steven Ruff, a faculty research associate at ASU's Mars Space Flight Facility. "It wasn't clear what we were seeing in the knobby outcrops because they were contaminated with dust and wind-blown soil. But I thought they might be silica-rich," he added.
Additional surveys with Mini-TES identified other outcrops, similarly contaminated but likewise hinting at silica.
"We aimed Mini-TES at the trench and it showed a clear silica spectrum. This prompted us to drive back to it, where the rover's Alpha Particle X-Ray Spectrometer told us the white soil was more than 90 percent silica," according to Ruff. "That's a record high for silica on Mars," he added.
According to Farmer, hydrothermal systems generally precipitate silica and other minerals as heated groundwater rises, cools, and gives off dissolved gases.
"If there were organisms living there, our terrestrial experience shows that microbes can easily be entrapped and preserved in the deposits," he said.
Both Ruff and Farmer say that if there was once a Martian biosphere, the deposits around fumaroles and hot springs are ideal places to start hunting for it.