A Martian mystery: Where did that jelly doughnut rock come from?

After 10 years of wheeling around Mars, NASA’s Opportunity rover has discovered a rock shaped like a jelly doughnut that seems to have appeared out of thin Martian air.

“One of the things I like to say is Mars keeps throwing things at us,” Steven Squyres, principal investigator for the Mars Exploration Rover Mission, said in a presentation describing Opportunity’s first decade on Mars as well as the mysterious rock.

In late December, Opportunity snapped an image of a rocky outcropping on the Red Planet with no rock the size and shape of a jelly doughnut. But 12 days later, when the rover took another picture of the same area, the jelly doughnut-like rock was there.

The rock, which you can see in the image above and to the right, is colored like a jelly doughnut too. Squyres said that the doughnut part of the rock is white and the depression is bright red.

The Opportunity team has come up with two theories to explain the rock’s mysterious and sudden appearance. One idea is that Opportunity’s wheels somehow flicked the rock out of the ground and it eventually slid to the spot.

The second theory is that the rock got thrown into place when something else hit the planet, and it is in fact a piece of crater ejecta. Squyres doesn’t like the idea.

“The crater ejectera I don’t really believe,” he said.

The Opportunity team has just started to take a closer look at the rock to figure out its composition. So far, those results have been baffling. For example, they discovered that the red “jelly” part is very high in sulfur and magnesium, and that it has twice as much of the element manganese as anything they’ve ever seen on Mars.

“We’re completely confused,” Squyres said. “We’re having a wonderful time. Everyone on the team is arguing and fighting.”

He added that even 10 years after Opportunity landed on Mars, it was still making important discoveries.

“I used to have this comforting notion that no matter how long the rovers last, at some point we would get to a stage in the mission where we could sit back and fold our arms and say to ourselves ... ‘We did it ... we learned everything about Mars that we could with this vehicle, at this place,’ ” he said. “But Mars isn’t like that. Mars keeps throwing new things at us.”

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