Diamonds found in meteorites on Earth may have come from an ancient long-dead planet the size of Mercury or Mars, the first potential known relics from these lost worlds, a new study finds.

Scientists examined a ureilite, a kind of meteorite that is rich in carbon and sometimes even possesses diamonds. More than 480 ureilites have been discovered so far, says study lead author Farhang Nabiei, a materials scientist and electron microscopist at the Swiss Federal Institute of Technology in L