Cosmic rock found in farmer’s field

When two amateur meteorite hunters met with Randy Korotev at Washington University in St. Louis last January, to show him their latest purchase, they had no idea the cosmic rock would be worth up to $850,000. Yet it is, scientists announced today (November 10, 2011).

The rock is a pallasite meteorite, weighing 17-kilograms, found in 2006 near Conception Junction (population 202) in northwest Missouri. These meteorites consist of green olivine crystals embedded in an iron-nickel matrix – like cherries in a pie. The rock type is so odd in appearance, so different from earthly rocks, that it was the first type of rock to be identified as extraterrestrial.

In fact, the pallasite is named for Peter Pallas, a German naturalist who first described one in 1749.

Not only are they beautiful, they are rare. The Conception Junction meteorite is only the 20th pallasite found in the United States so far.

In its sliced and polished state, the meteorite is worth about $200 a gram. For comparison, the most common meteorites sometimes sell for as little as $2 or $3 a gram and pieces of the first lunar meteorite found by a private collector went for $40,000 a gram, Korotev said.

The meteorite’s story

In 2006, a farmer found a meteorite buried in a hillside in the Missouri town of Conception Junction (population 202). The farmer, who has asked to remain anonymous, had sawed off the end of the stone, revealing an interior impossible to mistake for that of a terrestrial rock.

In 2009, Karl Aston, a St. Louis chemist and amateur meteorite hunter and collector, heard about the rock and joined with friends to buy it.

To determine what kind of stone they had on their hands, the collectors brought the rock to Randy Korotev, who was well known among meteorite enthusiasts for his website about identifying space rocks.

Korotev is a research professor in Earth and planetary sciences and an expert in lunar meteorites. He identified the stone as of a fragment of an asteroid. His lab also analyzed crystals within the rock to help identify its body of origin, eventually referring the meteorite hunters to the University of California, Los Angeles (UCLA), for analysis of the metal in which the crystals are embedded.

The stone has since received the official name Conception Junction on Aug. 27, 2011.

Meteorite prices depend on the type of the stone, its condition (some are unstable in Earth’s atmosphere), the story that comes with it (one fetched by a dog commanded a higher price than usual) and many other factors.

Clues to planet formation

Conception Junction was probably once part of an asteroid that orbited the sun in the asteroid belt between the planets Mars and Jupiter. The gas giant Jupiter played havoc in this zone, preventing material from the primordial solar nebula from coalescing into planets.

Much of the asteroid belt’s original mass has been lost since the solar system formed, some fragments, like the Conception Junction meteorite, finding their way into Earth-crossing orbits.

Today, pallasites are thought of as miniature models of planet formation that provide clues to what lies beneath our feet. They are thought to be fragments of asteroids large enough to produce sufficient heat early in their history to partially melt and separate into a metal core and a rocky exterior. They come from the lower mantle of these differentiated bodies and contain both metal from the core and olivine from the mantle.

Pallasites are thought to represent material from the boundary between the asteroid’s metal core and the olivine of its lower mantle.

The boundary between Earth’s mantle and core is probably similar. Korotev said:

We can’t break the Earth open. We can’t go down there and sample the rock, but we’ve got these pieces of broken asteroids that land on Earth, and they’re made of the same stuff, they’re just a lot smaller.

Bottom line: A meteorite found in a farmer’s field in 2006 is worth up to $850,000, scientists including Randy Korotev at Washington University in St. Louis announced today (November 10, 2011). The Conception Junction meteorite was probably once part of the asteroid belt. It is a rare and very beautiful example of a pallasite meteorite.

Via Washington University in St. Louis

November 10, 2011

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