Mars rover finds odd rock resembling a jelly doughnut

Scientists are stumped as to how a rock resembling a jelly doughnut mysteriously appeared on the surface of Mars as if out of nowhere, as discovered by NASA's Opportunity rover.

The rover, which landed on Mars in 2004, took an image earlier this month of the peculiar rock, which was white around the outside and dark red in the middle. The rock was not present in earlier images of the same spot, located at the rim of Endeavour Crater.

Chief NASA scientist Steve Squyres has a likely explanation. He said in a presentation last week that one of Opportunity's wheels probably kicked up the rock, which then slid into its field of view.

Early testing of the "jelly" section of the rock revealed characteristics unlike any other rock the rover has discovered during its decade on Mars. The rock is high in sulfur and magnesium, and scientists are still trying to figure out why.

Either way, the rock, dubbed "Pinnacle Island," is providing an unexpected science bonus.

"Much of the rock is bright-toned, nearly white," NASA said in a statement on Tuesday. "A portion is deep red in color. Pinnacle Island may have been flipped upside-down when a wheel dislodged it, providing an unusual circumstance for examining the underside of a Martian rock."

Opportunity landed on Mars in January 2004 on what was intended to be a three-month mission, but the rover ended up outstaying its original mission and has explored the planet for 10 years.

Another rover, Curiosity, touched down on the opposite side of the Red Planet in 2012 to search for evidence of habitable environments in Mars’ past.

Al Jazeera and wire services