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Meteorite case closed?

The scientific verdict is finally in on the fireball that fell last month in Peru: The good news is that it really was a meteorite - and not some sort of underground gas explosion, as skeptics had thought. The bad news is that the Desaguadero Meteorite (to use its proposed new name) is a garden-variety space rock. And for most scientists, that's a cosmic yawner.

"There aren't many scientists who study this kind of meteorite, because they're so common," said Harold Connolly, the expert who analyzed samples recovered from the impact site. And although the collector who provided him with the samples has said the meteorite may have weighed as much as 10 tons, Connolly himself told me "we may never know" what's left of the rock that sparked an international incident.

Delores Hill / LPL / Univ. of Ariz.

A crossed polarized-light image shows a sample of
the Peru meteorite, spanning about a tenth of an
inch. The object in the center is a relict chondrule,
which is characteristic of an ordinary chondrite.

The flap began on Sept. 15 when Peruvians in a remote Andean village saw a flash in the sky and felt the ground shake from an impact. When they went out to investigate what happened, they saw a bubbling crater, partly filled with water, and smelled a sickening odor.

The story sparked debate around the world - with some saying that the blast crater couldn't have been caused by a meteorite impact. Skeptics initially speculated that the villagers came across and went out in search of the fireball and came across a gas explosion. Even though the evidence for a meteorite mounted over the weeks that followed, one expert at NASA told me privately that he was still unconvinced because there was no authoritative analysis of debris from the site.

Now there is: This week, Connolly told me that he had completed his analysis of samples brought back from the site by meteorite hunter Michael Farmer, and that the samples are ordinary chondrites - a class that accounts for about 85 percent of the meteorites found on Earth. Connolly said the Peruvian samples represent a relatively common subclass of chondrite, an H4/5.

Different types of chondrites, like the Tagish Lake meteorite that fell to earth in 2000, are highly prized by scientists because they preserve the primitive stuff of the solar system. The Desaguadero Meteorite and its ilk, however, suffer too much heating during their space travels to be valuable in that way, Connolly said.

"Once you start heating them up, as in type H4, H5, H6, then you begin to lose all these signs of protoplanetary processes," he said. "It's certainly great science, but it's just not something I'm interested in."

He said the rock was also "fairly friable" - crumbly, in layman's terms - and that means the rock could have broken up on impact. Farmer thought there might be a 10-ton meteorite underground, but Connolly said that estimate was based on what size of rock would be required to make the wide crater seen after impact.

"To be perfectly honest with you, there is no way to know how much of the material is left," Connolly told me. "There's probably a considerable amount of material, but I honestly have no idea at this point whether we're talking an order of many, many kilos or on the order of tons. We may never know."

Connolly is a professor at Kingsborough College and also works with the University of Arizona's Lunar and Planetary Laboratory as well as the American Museum of Natural History. He's also editor of the authoritative Meteoritical Bulletin, and he told me that the lab's findings have been vetted by the Meteoritical Society's Nomenclature Committee.

The meteorite doesn't yet appear in the society's meteorite database - which may be because Connolly and his colleagues want to check with scientists in Peru about what they've found and whether it makes sense to name the meteorite after Desaguadero, a Peruvian town close to the crater.

"As a society, we're still attempting to communicate with some of our colleagues in Peru," Connolly told me this week.

Down in Peru, some are talking about preserving what's left of the meteorite crater - and investigating the methods Farmer and other collectors used to get their samples. And scientists will still want to get samples for research. Connolly, for instance, noted some "unusual shock features" on the meteorite that would be worth studying.

Urban legends will no doubt continue to swirl around the case of the smelly space rock as well. Currently, the leading explanation for the smell is that sulfurous compounds in the meteorite reacted with water to produce a rotten-egg smell, and that the effect was compounded by hysteria.

For collectors, then, the biggest value of the Desaguadero Meteorite may well be that they have a colorful story to go with their piece of the rock.