A rock that has suddenly and inexplicably appeared right in front of the Opportunity rover on Mars, has left scientists baffled.
The small rock, about the size of a jelly doughnut, was not yet in any of the images taken by the rover's panoramic camera (or pancam) taken on sol 3528 (a sol refers to a Martian day, which Is equivalent to roughly 24 hours and 40 minutes). On sol 3540, however, the rock appeared on the images. The camera database for the pancam is being maintained by the Jet Propulsion Laboratory in California, and staffers who work there had nicknamed the rock, 'Pinnacle Island."
Scientists have theories on where the rock may have come from. The first theory says that the rover, while maneuvering, could possibly have caused the rock to flip over. Another theory, which scientists say is less likely, is that the rock came from a nearby meteor impact event.
Steve Squyres, lead scientist of the NASA Mars Exploration Rover, explained how the rover itself might have caused the rock to tumble into place. Each of the rover's six wheels had an actuator, and Opportunity's front right steering has stopped working at the time. This meant that if that wheel turns against a rock it will cause a significant jitter that's strong enough to disturb the rock from where it used to be, and make it topple over to the spot where it was eventually spotted by the camera.
"So my best guess for this rock ... is that it's something that was nearby," said Squyres. "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."
"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. It's just a stroke of luck," Squyres explained. "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, I think it's something that we did ... we flung it." He also said that investigation on what made Pinnacle Island move to its current location is still ongoing.
The NASA Jet propulsion Laboratory recently commemorated the tenth year after twin rovers Spirit and Opportunity landed on Mars. Spirit lasted about six years on Mars before it got stuck in a sand trap in Gusev Crater and eventually succumbed to the elements. It stopped transmitting in March 2010 and its mission was declared lost. It was Spirit that sent to earth some of the most crucial initial findings about Mars.
Opportunity, on the other hand, is still up and running, and has traveled nearly 23 miles on Mars so far. It is kept company by a new arrival - rover Curiosity.
