While looking for a safe place to weather the cold Martian winter, the rover Opportunity spied a subtle yet intriguing feature on the edge of the giant Endeavour crater: a bright vein of light-toned rock piercing the ruddy, rocky surface of a large rise called Cape York.

Seen above running horizontally at center, in an image colored by Stuart Atkinson, the vein (dubbed “Homestake”) may prove to be hard evidence of phyllosilicates — minerals formed in the presence of a watery environment. If this is the case then this chance discovery would mean that Opportunity, after nearly eight years on Mars, has literally stumbled upon the “Holy Grail” of its entire mission!

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Data from the Mars Reconnaissance Orbiter has already identified the region around Endeavour Crater as containing phyllosilicates, specifically iron- and magnesium-rich clays known as “smectites”. These minerals are sure signs of past water… most likely salty water that could have been highly conducive to the development of life.

Identifying chemical signatures from orbit is one thing, though… finding and studying actual outcroppings of phyllosilicates at ground level is something else entirely. And this is precisely what the MER team has been hoping Opportunity will do at Endeavour.

The first discovery of veins like this back in August raised their hopes.


“This is a real triumph of geology,” said Steve Squyres, Mars Exploration Rover principal investigator at Cornell University. “We saw these veins as we crossed from the Meridiani plains into the Noachian terrain back in August. We’ve kept those in mind as a very important thing we wanted to look at, but we were so focused on getting into the Noachian and new terrain that we made that the highest priority, figuring that we would get the veins later.”

It looks like “later” is now.

A closer look at Homestake with Opportunity’s microscopic camera shows a bright surface gouged by linear scratches. This view, a composite of three separate images also by Stu Atkinson, gives a closer look:

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The MER team hasn’t officially stated what they believe the vein may be composed of but they definitely sound intrigued.

“These are different than anything from anything we’ve ever seen with either rover, a completely new thing on Mars, never seen anywhere,” Squyres said. “And we’re pretty charged up about it.”

In the meantime the rest of us will have to wait for further information.

Opportunity is now facing its fifth Martian winter and the MER team must soon plan driving maneuvers to place it at a prime location to weather the long months of frigid temperatures and reduced sunlight. Most importantly it will need to find a north-facing slope that will position it at a ten- to fifteen-degree angle, to take best advantage of the available sunlight on its already dusty solar panels. While this potential discovery is undoubtedly exciting, Opportunity’s ultimate survival must take precedence.

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Once the six-month-long Martian winter is over, Opportunity can resume exploration of the area around Cape York, an area that has already proven itself to hold promises of many never-before-seen features.

“All the rocks we’re seeing here are completely different than Opportunity has ever seen and different significantly than the rocks Spirit saw as well,” said Bruce Banerdt, MER project scientist at JPL. “So we’re already picking up new geology and new rocks and new petrology that no one’s ever encountered yet on the Martian surface. It’s all great stuff. There is a lot of activity going on and the science team is really jazzed right now.”

Find out more in the Mars Exploration Rover 2011 Update on The Planetary Society blog, and keep up with Opportunity’s progress on Stu Atkinson’s blog The Road to Endeavour.

Image credits: NASA/JPL-Caltech. Edited by Stu Atkinson.