Meteorite diamonds may have come from "long-lost planet"

Diamond Meteorite

Diamonds from ureilites formed inside the deceased proto-planet mesopodopsis

Their first line of evidence that the space rock was a chunk of what was originally a large planetesimal came from the size of the diamonds themselves.

In 2008, an asteroid exploded 37km above ground across the Nubian desert of northern Sudan.

Was found after the explosion, the meteor was mainly composed of coarse-grained rocks (olivine and pyroxene), which could be formed in the mantle of "planet-Bud", and the concentration of carbon in them was unusually high.

And yet, in a paper published Tuesday in Nature Communications, researchers say that within these small diamonds are chemical clues that suggest they could only have formed deep within a Mercury- or Mars-sized almost-planet that formed in the chaotic early days of the solar system. Because diamonds are forged at huge pressures and temperatures, typically deep inside the planet, the various materials that get trapped inside are quite hard to get a hold of at the surface - and diamonds can preserve them for billions of years. At first, it was believed that the diamonds formed with the shock of colliding with another body.

"The analysis of the data showed that the diamonds had chromite, phosphate, and iron-nickel sulfides embedded in them - what scientists refer to as "inclusions", EPFL explained in a news release.

Colorized electron microscopy image of the meteorite sample
Colorized electron microscopy image of the meteorite sample

Rest either went on to form bigger planetary bodies or ended up being destroyed by the sun or ejected out of the solar system. Over time, the fragments were gathered and catalogued for study into a collection named Almahata Sitta (Arabic for "Station Six", after a nearby train station between Wadi Halfa and Khartoum). He plans to seek out similar meteorites and search them for inclusions that might provide clues about their origins.

"What for a jeweler is an imperfection becomes for me something that is very useful because it tells me about the history of the diamond", said Dr. Gillet.

Diamonds are considered as one of the most precious metals on Earth. The researchers used three different types of microscopy, which characterized the mineral and chemical substance present in the diamond-bearing rocks. By examining these materials, they're able to get a picture of the early solar system. Some of these bodies were almost as big as Mars and one of them, dubbed Theia, collided with Earth to throw our moon into orbit.

The team led by Farhang Nabiei of the Ecole Polytechnique Federale de Lausanne in Switzerland was initially investigating the relationship between the diamonds and the layers of graphite surrounding them, when they realized the small pockets of material trapped inside looked far more interesting. The study shows us that the ureilite parent body was once a largely lost planet which was destroyed by collisions.


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