The 'Diamond asteroid' points to a long-lost planet

Using transmission electron microscopy and electron energy-loss spectroscopy, the team analysed the Almahata Sitta diamonds to see what these mineral inclusions were.

Then students from the University of Khartoum searched for fragments, eventually recovering more than 600 pieces from the 83-tonne asteroid.

Instead, they were traced inside a small asteroid that crashed into Earth over the Nubian Desert in October 2008.

Almost 50 fragments of the 83-tonne asteroid were collected from the Nubian desert where it fell. The explosion from the 13-foot-wide (4 meters) body shot fragments all over the desert below.

But, as The Washington Post says: "That is not even the coolest thing about Almahata Sitta". The space rock is classified as ureilite, a type of rare meteorite that has embedded within it several different types of minerals.

The unanswered question, so far, has been the planetary origin of 2008 TC3 ureilites.

Specifically, the diamonds must have formed at 20 gigapascals, which is the kind of pressure found deep within a planet the size of Mars or Mercury - but the meteorites come from neither of these planets or any other planet that we know of for that matter.

Researchers from France, Germany and Switzerland, headed by Farhang Nabei, of the Earth Science Laboratory and Planets of the Swiss Institute of Physics of the Swiss Federal School of Lausanne (EPFL), who published the publication in Nature Communications, used modern scientific methods and electronic microscopes to analyze in depth the meteorite.

They discovered chromite, phosphate and iron-nickel sulfide embedded in the diamond, with compositions and morphologies that could only have occurred under greater pressure than 20 gigapascals - almost 200,000 times that of sea level atmospheric pressure. They seem to have been formed inside bodies that no longer exist.

That means that the diamonds had to be formed toward the centre of an object large enough to produce the requisite amount of pressure and heat. This level of internal pressure can only be explained if the planetary parent body was a Mercury- to Mars-sized planetary "embryo", depending on the layer in which the diamonds were formed.

Many planetary and lunar scientists believe that it was a collision between Earth and a Mars-sized planet that led to the formation of our moon. The study shows us that the ureilite parent body was once a largely lost planet which was destroyed by collisions.

The diamonds in the meteorite have tiny crystals inside them that would need great pressure to form, said one of the study's co-authors, Philippe Gillet.

  • Valerie Cook