Mars rover captures a mysterious rock that appeared out of nowhere

A comparison of two raw Pancam photographs from sols 3528 and 3540 of Opportunity's mission (a sol is a Martian day). Notice the "jelly doughnut"-sized rock in the center of the photograph to the right.

The Opportunity rover that has been active on Mars since 2004, according to the scientists before recent discovery, had explored all of the mars. But their views have changed since the ‘appearance’ of a mysterious rock caught by the rover.

The rover had been stuck at the same place for over a month due to bad weather conditions and photographed the same region all the time. The photographs being sent were monitored at the Jet Propulsion Library (JPL) in California. One can compare the photographs captured by the rover’s panoramic camera (Pancam) on sol 3528 of the mission and the sol 3540. While sol 3528 shows a bare bedrock, sol 3540 had a fist-sized rock. The MER scientists nicknamed it “Pinnacle Island”.

Raw images from Pancam can be viewed in the Archive. NASA issued a status report “Encountering a surprise” for this revelation.

Mars Exploration rover scientist Steve Squyres told a JPL event it seems the planet literally "keeps throwing new things at us". He also said, "We saw this rock just sitting here. It looks white around the edge in the middle and there's a low spot in the centre that's dark red - it looks like a jelly doughnut.”

"And it appeared, just plain appeared at that spot - and we haven't ever driven over that spot."

Where did the Pinnacle Island come from?

NASA has derived two possible explanations:
1) The rover must have “flipped” the rock as it maneuvered, or,
2) It might have landed there after a nearby meteorite impact.

Squyers told that the possible cause of the mystery might be the Opportunity’s front right steering actuator that has stopped working. The wheel with that actuator would when turn across the rock, it would do a jittery motion which may have flung the rock out of the place landing few feet away from the rover.
The object is currently being investigated by rover’s measuring instruments. It looks like a jelly doughnut-white around the edge in the middle and there's a low spot in the centre that's dark red.  "It's very high in sulphur, it's very high in magnesium, it has got twice as much manganese as we've ever seen in anything on Mars,” Squyres said.

"That's the beauty of this mission ... what I've realised is that we will never be finished. There will always be something tantalizing, something wonderful just beyond our reach that we didn't quite get to - and that's the nature of exploration."

Opportunity has now been roaming the planet for more than the originally planned ten years, travelling about 24 miles (38km) as on 15 January 2014. Sister rover Spirit lost to the Martian elements and stopped transmitting in March 2010.