Researchers may have discovered direct evidence of a former sister planet that resided in our Solar System, but was obliterated during an unknown cataclysm that occurred billions of years ago. It is theorized that the Solar System may have had as many as ten such lost planets early in its history, but this new evidence takes such theories and brings them that much closer to reality.
The evidence of such a planet came from the debris recovered from asteroid 2008 TC3, in the form of nanodiamonds that were found within the fragments. The circumstances surrounding 2008 TC3 were already notable in the field of astronomy, as it is currently the only asteroid to have had its impact with the Earth predicted prior to the event: The 4.1-meter (13 foot) asteroid was spotted only 19 hours before it exploded 37 kilometers (23 miles) above Sudan’s Nubian Desert on October 7, 2008. Roughly 600 meteorites were recovered from the desert sands, with many of them being made up of a material called "ureilite", containing a comparatively high amount of carbon, typically in the form of graphite and nanodiamonds.
It is the nanodiamonds found in 2008 TC3’s remains that intrigued researchers: when analyzed with an electron microscope, it was discovered that these tiny crystals would have required a massive amount of pressure to form, to the tune of more than 20 gigapascal, meaning that 2008 TC3 was a fragment of a planet that originally had to be at least the size of Mercury or Mars.
"We’ve often wondered, what is the parent body that formed this thing?" according to physics professor Peter Brown, with Canada’s Western University. "The particularly exciting thing is, [the researchers] have a really strong case with the pressures that they’re measuring to say there really is no other way around the fact that this had to be a really big body present early in solar system history."