Oldest Meteorite Collection on Earth Found in One of the Driest Places

Large meteorite found in the Atacama Desert. (Image: Jérôme Gattacceca (CEREGE).
Large meteorite found in the Atacama Desert. (Image: Jérôme Gattacceca (CEREGE).

Earth is bombarded every year by rocky debris, but the rate of incoming meteorites can change over time. Finding enough meteorites scattered on the planet’s surface can be challenging, especially if you are interested in reconstructing how frequently they land.

Now, researchers have uncovered a wealth of well-preserved meteorites that allowed them to reconstruct the rate of falling meteorites over the past 2 million years. Alexis Drouard, Aix-Marseille Université, lead author of the new paper in Geology, said:

To recover a meteorite record for millions of years, the researchers headed to the Atacama Desert. Drouard says they needed a study site that would preserve a wide range of terrestrial ages where the meteorites could persist over long time scales.

Meteorite recovery campaign in the Atacama Desert (Nov. 2017). (Image: Katherine Joy, University of Manchester)

Meteorite recovery campaign in the Atacama Desert (Nov. 2017). (Image: Katherine Joy, University of Manchester)

While Antarctica and hot deserts both host a large percentage of meteorites on Earth (about 64 percent and 30 percent, respectively), Drouard says:

He adds that meteorites naturally disappear because of weathering processes (e.g., erosion by wind), but because these locations themselves are young, the meteorites found on the surface are also young, adding:

The team collected 388 meteorites and focused on 54 stony samples from the El Médano area in the Atacama Desert. Using cosmogenic age dating, they found that the mean age was 710,000 years old. In addition, 30 percent of the samples were older than 1 million years, and two samples were older than 2 million years.

The L6 ordinary chondrite El Médano 128, a 556 g meteorite recovered in the Atacama Desert. (Image: CCJ-CNRS, P. Groscaux)

The L6 ordinary chondrite El Médano 128, a 556 g meteorite recovered in the Atacama Desert. (Image: CCJ-CNRS, P. Groscaux)

All 54 meteorites were ordinary chondrites, or stony meteorites that contain grainy minerals, but spanned three different types. Drouard said:

The authors note that this is the oldest meteorite collection on Earth’s surface. Drouard says this terrestrial crop of meteorites in the Atacama can foster more research on studying meteorite fluxes over large time scales:

Meteorite with thin, dark, fusion crust in the Atacama Desert. (Image: Jérôme Gattacceca (CEREGE))

A meteorite with a thin, dark, fusion crust in the Atacama Desert. (Image: Jérôme Gattacceca (CEREGE))

Drouard adds that the team plans to expand their work, measuring more samples and narrowing in on how much time the meteorites spent in space:

Provided by: Geological Society of America [Note: Materials may be edited for content and length.]

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