Scientists are confirming a recent and rare invasion from Mars: meteorite chunks from the red planet that fell in Morocco last July.
This is only the fifth time scientists have confirmed chemically Martian meteorites that people witnessed as they fell. The fireball was spotted in the sky six months ago, but the rocks were not discovered on the ground in North Africa until the end of December.
This is an important and unique opportunity for scientists trying to learn about Mars' potential for life. So far, no NASA or Russian spacecraft has returned bits of Mars, so the only Martian samples scientists can examine are those that come here in meteorite showers.
Scientists and collectors of meteorites are ecstatic, and already the rocks are fetching big money because they are among the rarest things on Earth, rarer even than gold.
A special committee of meteorite experts, including some NASA scientists, confirmed the test results Tuesday. They certified that 15 pounds (7 kilograms) of meteorite recently collected came from Mars. The biggest rock weighs more than 2 pounds (1 kilogram).
Astronomers think millions of years ago something big smashed into Mars and sent rocks hurtling through the solar system. After a long journey through space, one of those rocks plunged through Earth's atmosphere, splitting into smaller pieces.
Most other Martian meteorite samples sat around on Earth for millions of years, or at the very least for decades, before they were discovered, which makes them tainted with Earth materials and life. These new rocks, while still probably contaminated because they have been on Earth for months, are purer.
The last time a Martian meteorite fell and was found fresh was in 1962. All the known Martian rocks on Earth add up to less than 240 pounds (110 kilograms).
The new samples were scooped up by dealers from those who found them. Even before the official certification, scientists at NASA, museums and universities scrambled to buy or trade these meteorites.
"It's a free sample from Mars. That's what these are, except you have to pay the dealers for it," said University of Alberta meteorite expert Chris Herd, who heads the committee that certified the discovery.
He already has bought a chunk of meteorite and said he was thrilled just to hold it, calling the rock "really spectacular."
One of the crucial decisions the scientists made Tuesday was to connect these rocks officially to the fiery plunge witnessed by people and captured on video last summer. The announcement and the naming of these meteorites -- called Tissint -- came from the International Society for Meteoritics and Planetary Science, which is the official group of 950 scientists that confirms and names meteorites.
Meteorite dealer Darryl Pitt, who sold a chunk to Herd, said he charges $11,000 to $22,500 an ounce and has sold most of his supply already. At that price, the new Martian rock costs about 10 times more than gold.
"It's scientifically invaluable," Herd said. "These are really beautiful specimens. It's a rare type, so fresh and aesthetically pleasing."
Several of the world's top experts in meteorites, including those who work for NASA, told The Associated Press that they were sure this was a piece of Mars. Tony Irving of the University of Washington is the scientist who did the scientific analysis on the rocks and said there is no doubt that they are from the red planet.
Scientists can tell when meteorites are from Mars because they know what the Martian atmosphere is made of, thanks to numerous probes sent there. The chemical signature of the rocks and the Martian air match, Irving said. Another clue is that because planets like Mars are more geologically active, its rocks tend to be much younger -- millions of years old instead of hundreds of millions or more -- than those from the moon or asteroids.
Most of the Martian rocks on Earth have been around for centuries or longer and have been found in Antarctica or the desert. They look so similar to dark Earth rocks that if they fell in other places, such as Maryland, they would blend right in and never be discovered, Irving said.
Jeff Grossman, a NASA scientist who is the Meteoritical Society's database editor, said there is a higher probability of finding "something interesting" from Mars on these rocks because they fell so recently. However, six months is a long time for Earthly contamination to take root, he said.
Herd said the first thing he would do with the rocks would be to rinse them with solvents to try to get rid of earthly contamination and see what carbon-based compounds are left.
A Martian meteorite that was buried in Antarctica made news in 1996. NASA scientists theorized that the rock, found in 1984, showed signs of traces of life from Mars, fossils of what seemed to be lifelong forms. Even the White House made an announcement about it as the first sign of life outside of Earth. Years of study since then have led much of the astronomy world to conclude that there was not enough evidence to support the claim.
Because known Martian meteorite falls happen only once every 50 years or so -- 1815 in France, 1865 in India, 1911 in Egypt and 1962 in Nigeria -- this is a once-in-a-career or even one-in-a-lifetime event.
"It's incredibly fresh. It's highly valuable for that reason," said Carl Agee, director of the Institute of Meteoritics and curator at the University of New Mexico. "For someone who knows their Martian, this is a beauty. It's gorgeous."