Diamonds from space came from long-lost planet
Gems discovered in Sudan provide evidence of an early planet that roamed the solar system, and clues about how Earth was formed
A giant space rock that crashed to Earth a decade ago is from a long lost planet that roamed the early Solar System, according to new research.
Diamonds found in the Almahata Sitta meteorite originated 4.5-billion years ago on a mysterious world bigger than Mercury, scientists have said.
The planet existed just a few million years after the birth of the sun and was destroyed in an epic cosmic collision. It backs a theory that large “proto-planets” provided the building blocks for Mars, Mercury, Venus and Earth.
Tens of these growing, or embryonic, worlds between the size of the moon and Mars are believed to have crashed into each other, forming the rocky planets we see today.
The Almahitta Sitta – named after the place in Sudan where witnesses saw it explode in the sky – is an extremely rare type of meteorite known as an ureilite. These were thought to be remnants of proto-planets, but analysis of previously discovered ones had failed to turn up any evidence – until now.The Swiss-led team used a powerful scanning technique called transmission electron microscopy to examine tiny crystals embedded within diamonds in the meteorite.
As well as being extremely valuable, the gemstone is commonly used by scientists to provide a tantalising window into the formation of planets.
The study, published in the journal Nature Communications, showed the diamonds must have formed at pressures above 20 gigapascals. This is a measure of billions of tons of rock pushing down from above – crushing forces so high they must have happened in a Mercury- to Mars-sized proto-planet.
It would have been in the first 10 million years of the Solar System, said the researchers.Dr Farhang Nabiei, of the Earth and Planetary Science Laboratory in Switzerland, said: “Planetary formation models show terrestrial planets are formed by the accretion of tens of moon- to Mars-sized planetary embryos through energetic giant impacts.
“However, relics of these large proto-planets are yet to be found. Ureilites are one of the main families of meteorites and their parent body is believed to have been catastrophically disrupted by an impact during the first 10 million years of the Solar System,” Nabiei said.
“Here we studied a section of the Almahata Sitta ureilite using transmission electron microscopy, where large diamonds were formed at high pressure inside the parent body.“We discovered chromite, phosphate and sulfide inclusions embedded in the diamond. The composition and morphology of the inclusions can only be explained if the formation pressure was higher than 20 gigapascals.
“Such pressures suggest that the ureilite parent body was a Mercury- to Mars-sized planetary embryo.”
The researchers said these types of meteorites are the last remnants of this lost planet. Nearly 50 fragments of the 83-ton asteroid were collected from the desert in northern Sudan where it fell in October 2008. The bus-sized lump of rock was first detected by astronomers in the US and made headlines as it was tracked by telescopes around the world.
It eventually disintegrated in the atmosphere above the Nubian desert, posing no threat to human life. An extensive ground search turned up 47 meteorite fragments for analysis.
The historic event – the first time such an object has been followed in this way – will boost our chances of avoiding a future catastrophe like the asteroid strike that wiped out the dinosaurs.
It was travelling at an estimated 44,641km/h until it disappeared into the planet’s shadow and was then observed as it exploded in a fireball as bright as a full moon.
Said Nabiei: “Although this is the first compelling evidence for such a large body that has since disappeared, their existence in the early Solar System has been predicted by planetary formation models.
“This study provides convincing evidence the ureilite parent body was one such large ‘lost’ planet before it was destroyed by collisions.”
– © The Daily Telegraph