On Mars, A Rock Appears Where There Wasn't One Before

Nicknamed Pinnacle Island, a fist-sized rock appeared in front of the Mars rover Opportunity a few days ago, and NASA isn't sure where it came from.

Scientists overseeing the Mars rover Opportunity, which landed on the red planet 10 years ago this month, are baffled by their latest discovery: a small rock.

Nicknamed Pinnacle Island, the fist-sized rock first appeared in front of the rover a few days ago, but earlier panoramic images of the area showed bare bedrock—no sign of the object before.

"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," NASA Mars Exploration Rover lead scientist Steve Squyres told Discovery News.

Photographs of the site from two different sols, or Martian days. The one on the left, from sol 3528, shows bedrock, while sol 3540 features the mysterious rock.Image: NASA/JPL-Caltech

Because Opportunity hadn't rolled over that area with its six wheels, NASA is currently trying to figure out where Pinnacle Island came from. There are two prominent theories: that the rover flipped the rock or that it landed there after a nearby meteorite impact (the latter is considered less likely).

Squyres hypothesizes that it was Opportunity's doing because it turned in place about a meter or two from the location of the rock. He says the rover's front right steering actuator could be to blame. Because the actuator has stopped working, it's possible it caused the ground to "chatter," propelling the rock out of place.

Still, this is just an educated guess. There's an ongoing investigation to determine the origin of Pinnacle Island.

[Image: Flickr user USDAgov]