Mars rover's first rock resembles Earthly ones

• A mystery object looks like a bit of plastic from rover wire bundles
• Scientists presented results from tests of a rock named "Jake Matijevic"
• Rover will head for a rock bed

Scientists at the controls of NASA's Curiosity rover report that its first chemistry tests of a Martian rock revealed a surprise. The Mars rock looks a lot like volcanic ones found on Earth.

In a briefing Thursday, NASA scientists said they base the observation on the rover's first laser-beam-aided chemistry tests of a Martian rock. The triangular rock dubbed "Jake Matijevic," named after a recently deceased engineer from the Jet Propulsion Laboratory in Pasadena, Calif., received about 30 small laser beam blasts aimed at revealing its interior chemistry.

Unlike the volcanic rocks spotted by past Mars rovers, the 2-foot-wide rock has a familiar chemical composition resembling ones found on Hawaii and other volcanic islands, reports team scientist Edward Stolper of Caltech. "It is a very close match in its chemical composition to ones that are unusual but are well-known on Earth," he says.

On Earth, such rocks form in volcanoes about 5 miles deep, typically in magma suffused with water, Stolper said. He said the team cannot say whether the Jake Matijevic rock formed the same way on Mars, or even what kind of asteroid impact or eruption carried it into Gale Crater, the 96-mile wide depression on Mars that the rover is exploring.

The team performed the investigation of the Mars rock as a first test of its laser chemistry sensors. It also resumed tests of the $2.5 billion rover's scoop. The sand scooping tests are similarly intended for cleaning and calibration of chemistry sensors on the end of the rover's 7-foot arm, says Chris Roumeliotis of NASA's Jet Propulsion Laboratory.

The rover has vibrated and dumped one soil sample, another first on Mars, and will take at least one more before sand is allowed to enter a test chamber on the rover arm. In the next few weeks, the rover will head for a rock bed that is expected to shed light on the geology of the rocks underlying Gale Crater.

Mission scientists report that a mysterious "bright object" spotted in a Martian sandpit that briefly delayed the rover's investigations this week is very likely a tiny bit of plastic shed from the rover itself.

"Probably it happened to fall from the rover," says Chris Roumeliotis of NASA's Jet Propulsion Laboratory in Pasadena, Calif. Plastic ties bundle electric wires on the rover, and the team has noticed flakes missing from them, he said, adding that the team doesn't expect to see such flakes delaying future operations. "We do plan to take more images of it," Roumeliotis said.