LOS ANGELES — Scientists are abuzz about a coal-colored rock from Mars that landed in the Sahara desert: A yearlong analysis revealed it's quite different from other Martian meteorites.
Not only is it older than most, it also contains more water, tests showed. The baseball-size meteorite, estimated to be 2 billion years old, is strikingly similar to the volcanic rocks examined on the Martian surface by the NASA rovers Spirit and Opportunity, which found water-bearing minerals.
"Here we have a piece of Mars that I can hold in my hands. That's really exciting," said Carl Agee, director of the Institute of Meteoritics and curator at the University of New Mexico who led the study published online Thursday in the journal Science.
Most space rocks that fall to Earth as meteorites come from the asteroid belt, but a number can be traced to the moon and Mars.
Scientists believe an asteroid or some other large object struck Mars, dislodging rocks and sending them into space. Occasionally, some plummet through Earth's atmosphere.
About 65 Martian rocks have been recovered on Earth, mostly in Antarctica or the Sahara. The oldest dates back 4.5 billion years to a time when Mars was warmer and wetter. About half a dozen Martian meteorites are 1.3 billion years old and the rest are 600 million years or younger.
The latest meteorite NWA 7034 — nicknamed "Black Beauty"— was donated to the University of New Mexico by an American who bought it from a Moroccan meteorite dealer last year.
Researchers performed a battery of tests on the meteorite and based on its chemical signature confirmed that it was blasted to Earth from Mars. At 2.1 billion years old, it's the second-oldest known Martian meteorite that formed from a volcanic eruption.
There's also evidence that it was altered by water. Though the amount released during heating was small — 6,000 parts per million — it was still much more than other Martian meteorites.