Back in 2009 the Mars Reconnaissance Orbiter (MRO) discovered that the older, clay-bearing rocks along Endeavour's rim represented a totally new rock-type — one that could give us a glimpse of life (or lack thereof) on ancient Mars.
"The clays [we found] are not only indicative of abundant water, but also a watery environment more suitable for life," said Steve Squyres, professor of astronomy at Cornell University and the principal investigator for the science payload on NASA's Mars Exploration Rovers. Squyres and his colleagues believe this new rock-type may have once been more hospitable to life than any of the others encountered over the course Opportunity's 7-year tenure on the surface of Mars.
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