Opportunity rover’s Mars mystery rock puzzles NASA scientists

Where did this bright Martian rock come from?

With NASA's Opportunity rover wintering right now, just sunning itself on the rim of Endeavor Crater, the rover's handlers here on Earth probably didn't expect much excitement. However, they were in for a surprise over the past week, when pictures taken showed that a fist-sized rock suddenly appeared right next to its location.

As seen in the pictures above, the image on the left was taken on Sol 3528, or Opportunity's 3528th day on Mars, which equates to Dec. 26, 2013. The image on the right was taken on Sol 3540, or Jan. 7, 2014. Sometime between those two days, that rock suddenly made an appearance.

"It's about the size of a jelly doughnut," said Steve Squyres, the Opportunity team's lead scientist at Cornell University, according to Discovery News. "It was a total surprise; we were like, 'Wait a second, that wasn't there before, it can’t be right. Oh my God! It wasn't there before!' We were absolutely startled."

[ Related: Scientists eager for mission to search for life on Jupiter’s moon, Europa ]

Twitter user Midnight Planets posted colourized versions of the before and after photographs, which show off the details of the images a little better:

(By the way, if you're interested in this kind of thing, the Planetary Society's Emily Lakdawalla posted some great courses on how to do such image processing here.)

The scientists named the rock Pinnacle Island (since pretty much anything interesting there earns itself a nickname), and the speculation began. Is it a piece of ejecta kicked up by a nearby meteorite impact? Is it a meteorite, itself? Is it simply a local rock knocked out of place by the rover?

Squyres is fairly sure he has the answer, since the team just had Opportunity turn in place during the time between the two pictures.

"So my best guess for this rock … is that it's something that was nearby," he told Discovery News. "I must stress that I'm guessing now, but I think it happened when the rover did a turn in place a meter or two from where this rock now lies."

"You think of Mars as being a very static place and I don't think there's a smoking hole nearby so it's not a bit of crater ejecta," he added. "I think it's something that we did … we flung it."

Squyres has good reason to believe this too. Although Opportunity is doing remarkably well for nearing the 10th anniversary of the start of its three-month mission, one of its wheels is stuck — it can't rotate right or left. So, as it was executing this turn on the bedrock it's currently resting on, the wheel would have skittered across the surface, and that could have easily dislodged Pinnacle Island from where it was before. This would seem to be supported by a newly processed image by Midnight Planets, which appears to show a place where the rock may have come from (click here).

[ More Geekquinox: Time-lapse video 'Ancients' reveals the awesome splendour of our night sky ]

Opportunity's team is taking advantage of the ... well ... opportunity, that this rock has given it.

"It obligingly turned upside down, so we're seeing a side that hasn't seen the Martian atmosphere in billions of years and there it is for us to investigate," he told Discovery News. "It's just a stroke of luck."

Geek out with the latest in science and weather.
Follow @ygeekquinox on Twitter!