Diamonds in a meteorite that crashed into Earth years ago have now given scientists a glimpse into the universe’s past. Recently, a team of scientists led by the Ecole Polytechnique Fédérale de Lausanne (EPFL) in Switzerland used transmission electron microscopy to examine the diamonds contained in a slice of the Almahata Sitta meteorite. Based on their research, the scientists think the meteorite came from a planetary embryo, between the size of Mercury and Mars, that was destroyed in a collision around 4.5 billion years ago.
Nearly a decade ago, an asteroid exploded over the Nubian Desert in Sudan. Scientists collected fragments from what’s now called the Almahata Sitta meteorite, and these fragments have yielded intriguing new information. EPFL materials scientist Farhang Nabiei told The Washington Post, “These samples are coming from an era that we don’t have any access to…This is part of the story of how we came to be.” The meteorite fragments are largely ureilites, which EPFL said are “a rare type of stony meteorite” in which nano-sized diamonds can be found.
Embedded in the diamonds were chromite, phosphate, and iron-nickel sulfides; the scientists call these inclusions, and they hold signatures of the mysterious long-lost planet. According to EPFL, the “particular composition and morphology of these materials can only be explained if the pressure under which the diamonds were formed was higher than 20 GPa (giga-Pascals, the unit of pressure). This level of internal pressure can only be explained if the planetary parent body was a Mercury- to Mars-sized planetary embryo, depending on the layer in which the diamonds were formed.”
What exactly happened to the long-lost planet? Nabiei couldn’t say for sure. Researchers think that, in the early solar system, large protoplanets pulled on others’ orbits until they coalesced, crashed, or broke up into pieces. The ureilites could have come from the same protoplanet that existed for a few million years before its demise in a collision.
Nature Communications published the research online this week; scientists from institutions in France and Germany contributed.