The Science of Sustainability

Treasure from the Sky

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To those who know rocks, this chondrite meteorite could not be mistaken for an Earthly stone. Photos by Andrew Alden

The other week I mentioned, in talking about concretions, that people can be fixated on the idea that they have found a dinosaur egg or meteorite. This last week meteorites featured in two news stories, one excitingly true and the other almost certainly bogus.

The exciting story was about a set of meteorites recovered in the desert of Morocco, a few months after their fall from space had been recorded. That doesn't happen very often—once meteors arrive in the atmosphere, their unguided trajectory means that a rather large area must be searched to find them. What was extraordinary was that these rocks were from Mars, certified as such this week by an expert scientific panel.

Meteorite hunting has become a cottage industry in the Sahara Desert, where conditions are ideal for space rocks to be preserved and for practiced observers to spot them. The locals who found the new Martian rocks sold them to dealers, who in turn marked up the price to almost a thousand dollars per gram even before the meteorites were formally certified as Martian.

Meteorites are most easily found in two places on Earth, the Sahara and Antarctica. In the case of Antarctica, they fall on the ice cap, where no other rocks exist at all. Movements of the ice can concentrate these meteorites, including the rarest stones from Mars and the Moon, in certain areas that are surveyed regularly and exclusively by scientists. That's good for science. For its part, the Sahara is good for the rest of us who can acquire these rarities for our own pleasure. And scientists can still study Saharan stones because meteorite hunters must donate pieces of their finds to a museum to qualify for authentication, without which the stones have no value. It's a tidy system with little impact on the environment.

The California deserts are also promising places for meteorite hunters. At least one Martian stone has already come from the Mojave. Meteorite hunting is simple in principle, yes, but far from a casual hobby. First you acquire a very intimate knowledge of the rocks that belong there, and then you examine approximately a million rocks to find one that doesn't belong there. And with that, you start to learn about meteorites. I love rocks inordinately, but I think I would still go mad. Dr. Randy Korotev is a genuine meteorite expert at Washington University who gets torrents of email from would-be meteorite finders. On his excellent "What to Do" page, he says that of over 2000 serious inquiries over the years, only eight people had real meteorites.

Easier to dream of fabulous wealth falling into your back yard. That dream, fed by an extremely rare handful of true stories, can blind people to the obvious. And that leads me to the Castro Valley man who got a reporter to feature his story in the San Jose Mercury News last week. His story did not even point to a meteorite, let alone prove it. He said he responded to his dog's barking and found a fresh pit in his back yard with a smoking, red-hot stone in it. That scenario is a old urban legend about meteorites that is never true. He said he talked to experts from Lawrence Livermore National Lab, who had him hold a magnet against the stone and try to cut off a piece of it. He claimed that after finding it both non-magnetic and hard enough to break a hacksaw blade, those experts told him that was positive evidence. None of that is what an expert would say. And the object he showed a photographer had a silvery color and finish (which could not be iron because it was non-magnetic), and a multiply-layered structure that is very common in Earth rocks. In short, it looked nothing like a fresh meteorite and everything like an ordinary metamorphic rock. But he was fervent enough in his belief to fool a reporter, and at least one editor, into running the story anyway.

This is the back side of the chondrite shown at the top. Note the dark fusion crust and the hollows, called regmaglypts, carved by erosion in passing through the Earth's atmosphere. And a magnet sticks to it because it has small grains of iron metal throughout it.

Easier to save up some of your birthday money and buy a nice little meteorite at a rock show from a large, well-run dealership. My advice is to wait until the afternoon of the last day for the best price; dealers hate to pack up their inventory. That's how I got my 1/3-pound chunk of meteoritic nickel-iron from the Sikhote-Alin fall. There's nothing like the feeling of this ancient space metal in your hand.

The Sikhote-Alin fall occurred in eastern Siberia in 1947. Specimens like this are readily available.

I've written more about Martian and lunar meteorites on my About.com site. I also have a photo gallery there. Dr. Tony Irving has a deep and erudite page on Martian meteorites.

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Category: Astronomy, Geology

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Andrew Alden

About the Author ()

Andrew Alden earned his geology degree at the University of New Hampshire and moved back to the Bay Area to work at the U.S. Geological Survey for six years. He has written on geology for About.com since its founding in 1997. In 2007, he started the Oakland Geology blog, which won recognition as "Best of the East Bay" from the East Bay Express in 2010. In writing about geology in the Bay Area and surroundings, he hopes to share some of the useful and pleasurable insights that geologists give us—not just facts about the deep past, but an attitude that might be called the deep present. Read his previous contributions to QUEST, a project dedicated to exploring the Science of Sustainability.
  • Mrmichaelcasey

    Keep on rockin'.

  • MarianneJKeenan

    This is very interesting as I didn't think that rocks as far away from Mars could make it to Earth. The iron meteorites are beautiful. You can see from their texture that they have gone through a liquid state. I wonder if that is because they have transitioned through such high temperatures enough to go through a liquid state? Something like what lava goes through. Lava comes from the inner core of the earth and reaches a cooler temperature and sometimes even makes contact with ocean water resulting in a solid stone. I enjoyed reading this article.

  • http://twitter.com/GabrielRoybal Gabriel Roybal

    hard to imagine