“We have in our hands a piece of a former planet that was spinning around the sun before the end of the formation of today’s solar system,” said Philippe Gillet, who has aPhD in Geophysics at Université de Paris VII and now works at the Federal Institute of Technology in Lausanne, Switzerland and an author of the paper that was published in Nature Communications. And surprise, surprise it has diamonds embedded inside. This is a remarkable find, and the story behind it is amazing and begins more than a decade ago.
In 2008, a car-sized asteroid named TC3 exploded above the Nubian Desert last October and although it was small compared to the dinosaur-killing, civilization-ending objects that still orbit the sun. But that didn’t stop it from having a huge impact among scientists, and the reason is that TC3 spotted asteroid in space before falling to Earth. “Any number of meteorites have been observed as fireballs and smoking meteor trails as they come through the atmosphere,” says Douglas Rumble of the Carnegie Institution’s Geophysical Laboratory, a co-author of the paper. “It’s been happening for years. But to actually see this object before it gets to the Earth’s atmosphere and then to follow it in – that’s the unique thing.”
And then on top of Scientist discovered diamonds insideTC3 which is a ureilite, or a type of rare meteorite that has contains different types of minerals and in this case they found diamonds. The New York Times reports that “The nano-sized gems were much larger than any meteorite diamond that had been previously found, according to Dr. Gillet. Upon further inspection the team noticed that the diamonds were far from crystal clear. They were riddled with tiny imperfections, called inclusions, made of chromite, phosphate and iron-nickel sulfides. Those flaws made the diamond extraordinary.”
“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. “It has a chemistry which has no equivalent in the solar system today, in terms of planets,” he said.
And that lead scientists to believe thatTC3may have come from a destroyed planet that orbited our sun billions of years ago, and scientists say it may be the first time anyone has recovered fragments from one of our solar system’s so-called “lost” planets. According to the NY Times, “And because the chemistry of the inclusions did not match what is known on planets in today’s solar system, they think the diamonds came from a protoplanet that existed between 4.54 and 4.57 billion years ago. That protoplanet most likely collided with another planet and expelled debris that ended up in the asteroid belt, where it wandered for billions of years before plunging to Earth.”
The asteroid, known as 2008 TC3, was first sighted October 6, 2008, by telescopes of the automated Catalina Sky Survey near Tucson Arizona. Numerous observatories followed its trajectory and took spectrographic measurements before it disappeared into the Earth’s shadow the following day. A recovery team led by Peter Jenniskens of the SETI Institute in California and Muawia Shaddad of the University of Khartoum then searched for meteorites along the projected approach path in northern Sudan. They recovered 47 fragments, one of which was selected for preliminary analysis by laboratories, including the Carnegie Institution’s Geophysical Laboratory.
According to paper that was published in Nature Communications. entitled “A large planetary body inferred from diamond inclusions in a ureilite meteorite.” This is how they sum it up in the abstract.
Asteroid 2008 TC3 fell in 2008 in the Nubian desert in Sudan1, and the recovered meteorites, called Almahata Sitta, are mostly dominated by ureilites along with various chondrites2. Ureilite fragments are coarse grained rocks mainly consisting of olivine and pyroxene, originating from the mantle of the ureilite parent body (UPB)3 that has been disrupted following an impact in the first 10 Myr of the solar system3. High concentrations of carbon distinguishes ureilites from all other achondrite meteorites3, with graphite and diamond expressed between silicate grains.
Planetary formation models show that 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 achondritic 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. 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 (Fe,Ni)-sulfide inclusions embedded in diamond. The composition and morphology of the inclusions can only be explained if the formation pressure was higher than 20 GPa. Such pressures suggest that the ureilite parent body was a Mercury- to Mars-sized planetary embryo.
There are three mechanisms suggested for diamond formation in ureilites: (i) shock-driven transformation of graphite to diamond during a high-energy impact4, (ii) growth by chemical vapor deposition (CVD) of a carbon-rich gas in the solar nebula5, and (iii) growth under static high-pressure inside the UPB6. Recent observation7 of a fragment of the Almahata Sitta ureilite (MS-170) revealed clusters of diamond single crystals that have almost identical crystallographic orientation, and separated by graphite bands. It was thus suggested that individual diamond single crystals as large as 100 μm existed in the sample, which have been later segmented through graphitization7. The formation of such large single-crystal diamond grains along with δ15N sector zoning observed in diamond segments7 is impossible during a dynamic event8,9 due to its short duration (up to a few seconds10), and even more so by CVD mechanisms11, leaving static high-pressure growth as the only possibility for the origin of the single-crystal diamonds.
Owing to their stability, mechanical strength and melting temperature, diamonds very often encapsulate and trap minerals and melts present in their formation environment, in the form of inclusions. In terrestrial diamonds, this has allowed to estimate the depth of diamond formation, and to identify the composition and petrology of phases sampled at that depth. Therefore, diamonds formed inside the UPB can potentially hold invaluable information about its size and composition.