With its solar panels their cleanest in years, NASA’s decade-old Mars Exploration Rover Opportunity is inspecting a section of crater-rim ridgeline chosen as a priority target due to evidence of a water-related mineral.
Orbital observations of the site by another NASA spacecraft, Mars Reconnaissance Orbiter, found a spectrum with the signature of aluminum bound to oxygen and hydrogen. Researchers regard that signature as a marker for a mineral called montmorillonite, which is in a class of clay minerals called smectites. Montmorillonite forms when basalt is altered under wet and slightly acidic conditions. The exposure of it extends about 800 feet (about 240 meters) north to south on the western rim of Endeavour Crater, as mapped by the orbiter’s Compact Reconnaissance Imaging Spectrometer for Mars (CRISM).
“It’s like a mineral beacon visible from orbit saying, ‘Come check this out,’” said Opportunity Principal Investigator Steve Squyres, of Cornell University, Ithaca, New York.
Some of the most important findings from Opportunity’s long mission came from combining CRISM and rover observations of a site about 2 miles (3 kilometers) farther north on the crater’s western rim. Rocks exposed there contain evidence for an iron-bearing smectite – called nontronite — as well as for montmorillonite. That site yielded evidence for an ancient environment with water that would have been well-suited for use by microbes, if Mars had any billions of years ago.
Opportunity reached the northern end of the montmorillonite-bearing exposure last month, at a high spot called “Pillinger Point.” Opportunity’s international science team chose that informal name in honor of Colin Pillinger (1943-2014). Pillinger was the British principal investigator for the Beagle 2 project, which attempted to set a research lander on Mars a few weeks before Opportunity’s January 2004 landing.
Though selected as a science destination, Pillinger Point also offers a scenic vista from atop the western rim of Endeavour Crater, which is about 14 miles (22 kilometers) in diameter.