As we’ve learned from our recent explorations of Mars, there’s really not a whole lot going on there. Yes, there are geological processes at work, but most of them move at a nearly imperceptible pace. So that's why after nearly ten years of Martian rover exploration, NASA scientists were surprised to see a rock suddenly “appear” in front of the Mars Rover last week.

You can see the rock in the images above. The image on the left shows the area in front of Opportunity on Sol 3528. The image to the right was taken 12 Martian days later and is almost identical—except for a rock the size of a donut that had unexpectedly shown up

NASA announced the discovery of the rock at an event at Caltech in Pasadena this past Thursday night, dubbing the rock “Pinnacle Island.” “It’s about the size of a jelly doughnut,” NASA Mars Exploration Rover lead scientist Steve Squyres told 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.”

Unless someone has figured out a way to punk Opportunity all the way from Earth, mission scientists can come up with just two explanations for the sudden appearance of Pinnacle Island: a really close call with a meteor or something Opportunity did. It’s possible that the mystery rock came from a nearby meteor strike, with the force of impact blowing Pinnacle Island off the surface to land in front of Opportunity. Squyers thinks it’s far more likely that Opportunity somehow moved the rock during maneuvers.

“So my best guess for this rock... is that it’s something that was nearby,” Squyers 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.”

One of Opportunity’s steering actuators has stopped working, so when the rover made a recent turn, the skidding of the affected wheel atop the bedrock may have bumped the mystery rock, sending it a few feet through the Martian atmosphere to land in front of the rover.

However the rock got there, NASA is going to study the heck out of it. According to Squyers, the side facing up hasn't been exposed to the Martian atmosphere for "billions of years," so researchers may be able to learn something new from its appearance.