More water-formed clay on Mars discovered, rovers hunting it

While both Mars Exploration Rovers, Curiosity and the now 9 year old Opportunity, are traveling the surface of the red planet in search for water and clay minerals, it is data from orbit that a new study used to find surprising amounts of the water-formed mineral on Mars.

Eldar Noe Dobrea of the Planetary Science Institute, lead researcher of the study, identified the clay minerals using a spectroscopic analysis from the Mars Reconnaissance Orbiter. According to the results, clays also exist in the Meridiani plains that Opportunity already rolled over.

"It's not a surprise that Opportunity didn't find clays while exploring," commented Prof. James Wray, co-author from Georgia Institute of Technology. "We didn't know they existed on Mars until after the rover arrived. Opportunity doesn't have the same tools that have proven so effective for detecting clays from orbit."

The clay signatures near Eagle crater are very weak, especially compared to those along the rim and inside Endeavour crater. Wray said that clays could have been more plentiful in the past, but Mars' volcanic, acidic history has probably eliminated some of them.

"It was also surprising to find clays in geologically younger terrain than the sulfates," said Dobrea. Current theories of Martian geological history suggest that clays, a product of aqueous alteration, actually formed early on when the planet's waters were more alkaline. As the water acidified due to volcanism, the dominant alteration mineralogy became sulfates. "This forces us to rethink our current hypotheses of the history of water on Mars," he added.

Even though Opportunity has reached an area believed to contain rich clay deposits, the odds are still stacked against it. Opportunity was supposed to survive for only three months. It's still going strong nine years later, but the rover's two mineralogical instruments don't work anymore. Instead, Opportunity must take pictures of rocks with its panoramic camera and analyze targets with a spectrometer to try and determine the composition of rock layers.

"So far, we've only been able to identify areas of clay deposits from orbit," said Wray. "If Opportunity can find a sample and give us a closer look, we should be able to determine how the rock was formed, such as in a deep lake, shallow pond or volcanic system."

Fortunately, and also thanks to the Opportunity mission, Curiosity's instruments are better equipped to search for signs of past or current conditions for habitable life. Wray is also a member of Curiosity's science team.