“This is our first glimpse ever at conditions on ancient Mars that clearly show us a chemistry that would have been suitable for life,” Steven W. Squyres, the principal investigator for Opportunity, said at a news conference last week at a meeting of the American Geophysical Union.
Opportunity could be sitting on rocks chock-full of organic molecules but the rover and the scientists back on Earth would never know. Unlike Curiosity, Opportunity is not carrying instruments that can detect those kinds of molecules.
But the scientists are not complaining. Everything from Opportunity over the past eight years has been a bonus for a mission that was to have ended long ago.
Opportunity landed on Mars in January 2004, for what was supposed to be a three-month mission. Yet the rover continues operating in good condition.
Its twin rover, Spirit, died in 2010, stuck in a sand trap and unable to point its solar arrays in the correct direction to survive winter, outliving its planned lifetime by almost six years.
Last year, Opportunity arrived at a 14-mile-wide crater named Endeavour, where NASA’s Mars Reconnaissance Orbiter has spotted clays from above. Clays generally form in the presence of water.
This was followed with an image mosaic collected by the Microscopic Imager (MI) and then a placement of the Alpha Particle X-ray Spectrometer (APXS) for an overnight integration.
On Sol 3151 (Dec. 4, 2012), the rover moved just 9 inches (23 centimeters) to reach some new surface targets.
The clay signal pointed to a hill, which the scientists named after Jacob Matijevic, an engineer on the rover team who died this year.
As Opportunity approached, “We started seeing things that looked really, really different,” Dr. Squyres said.
The most common rock there was light-coloured, fine-grained, very soft, and nothing like any that Opportunity had come across before.
“It is right in the sweet spot of where the clay signature is present,” Dr. Squyres said. “It has got to be the clay-bearing stuff.”
But when the rover looked at the elements in the rock, it was the same mix of elements in a typical Martian rock. “What’s unusual is that it’s not unusual,” Dr. Squyres said. “This puzzled us at first. I was expecting something dramatic and instead what you see here kind of looks like average Mars.”
Another instrument could have identified minerals in the rock, but the radioactive cobalt it relies on has long decayed away.
If Curiosity were at the Endeavour crater, its instruments could directly look for the carbon-based molecules known as organics that are the building blocks of life.
Unfortunately, Curiosity, which landed in August, is more than 5,000 miles away exploring a different crater where clays have also been spotted from orbit and it is still months away from reaching Matijevic.
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