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The meteorite's large diamonds and their impurities suggest they formed inside a planetary "embryo." Photo by EPFL/Hillary Sanctuary |
New analysis of a slice of a meteorite containing unusual diamonds suggest the space rock came from a long lost planet.
In 2008, an asteroid measuring 13 feet across penetrated Earth's atmosphere and exploded above Sudan, scattering rocky fragments across the Nubian Desert. The fragments were gathered and organized into the Almahata Sitta collection.
The Almahata Sitta fragments are ureilites, a kind of rocky meteorite containing clusters of tiny diamonds. Scientists believe ureilite diamonds can form three ways: under the extreme pressure triggered by a planetary collision, through chemical vapor deposition or under normal pressure conditions inside the parent body -- as most diamonds on Earth are formed.
Over the last decades, several teams of researchers have studied the Almahata Sitta collection, but until now, scientists have been unable to determine where the asteroid came from.
When researchers at the Swiss Federal Institute of Technology in Lausanne, EPFL, examined several larger diamonds inside the Almahata Sitta meteorites -- diamonds with a diameter greater than 100 microns -- they identified evidence that the asteroid 2008 TC3 came from a planetary "embryo."
Transmission electron microscopy revealed traces of chromite, phosphate and iron-nickel sulfides inside the larger diamonds. The impurities are what are known as "inclusions" and are found in Earth's diamonds, too. The discovery marks the first time inclusions have been identified inside extraterrestrial diamonds.
The presence of these particular inclusions suggest the diamonds were formed under significant pressure, roughly 20 giga-Pascals. Such levels of pressure couldn't be created by a collision; they could only be found inside a planetary body with a size between Mercury and Mars.
Planetary scientists believe the early solar system hosted many similarly sized planetary embryos. Many of these protoworlds collided, their fragments forming new planets and moons. Others were cast out of the solar system or collided with the sun.
"This study provides convincing evidence that the ureilite parent body was one such large 'lost' planet before it was destroyed by collisions [some 4.5 billion years ago]," researchers wrote in the new paper on the subject, published this week in the journal Nature Communications.
Lead researcher Farhang Nabiei hopes the study is only the beginning. There are hundreds more ureilites that could offer clues to the nature of the early solar system.
"[Ureilites] can give us a better idea of the formation and evolution of planets in the early solar system," Nabiei told National Geographic.
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