|Portion of a trough in the Nili Fossae region of Mars in an enhanced-color image from taken from NASA's Mars Reconnaissance Orbiter in 2007. The area revealed the strongest carbonate signature ever found. (NASA/JPL-Caltech/University of Arizona )|
A team of scientists believe there may be more patches of carbonates on Mars than originally thought. These minerals form in water and are indicators of a planet's wet history.
Only a few patches of carbonates have been discovered on Mars, but many more could be hidden beneath layers of iron oxide.
"The plausibility of life on Mars depends on whether liquid water dotted its landscape for thousands or millions of years," said leading author Janice Bishop, a NASA planetary scientist, in a press release.
"It's possible that an important clue, the presence of carbonates, has largely escaped the notice of investigators trying to learn if liquid water once pooled on the Red Planet."
Since desert regions on planet Earth have extremely dry conditions like Mars, field experiments on desert rocks and soil can yield information for comparison.
When Bishop and colleagues investigated carbonate rocks covered with layers of iron oxides in the Mojave desert, they realized this rusty coating could be hiding carbonates on Mars.
"When we examined the carbonate rocks in the lab, it became evident that an iron oxide skin may be hindering the search for clues to the Red Planet's hydrological history," said co-author Chris McKay in the release.
"We found that the varnish both altered and partially masked the spectral signature of the carbonates."
In the Mojave, the varnish was found to conceal blue-green algae that are resistant to dehydration.
"The organisms in the Mojave Desert are protected from deadly ultraviolet light by the iron oxide coating," McKay said. "This survival mechanism might have played a role if Mars once had life on the surface."
During previous explorations of Mars, a motorized grinding tool was needed to remove the rusty coating on rocks so other instruments could gather data. The Mars Reconnaisance Orbiter (MRO) identified an area called Nili Fossae with high carbonate levels, but other abundant areas of carbonates might not have been detected due to this iron oxide coating.
"To better determine the extent of carbonate deposits on Mars, and by inference the ancient abundance of liquid water, we need to investigate the spectral properties of carbonates mixed with other minerals," Bishop concluded.
The paper was published in the July 1 edition of the International Journal of Astrobiology.