Diamonds From Outer Space Formed Inside a Long-Lost Planet

Diamonds that fell to Earth inside a meteorite may contain the remnants of our solar system's first planets, protoworlds that were lost billions of years ago to extreme bombardments and collisions.

What's new?

If humans could peer back in time, the solar system we call home would be unrecognizable during its first 10 million of existence. That's because astronomers think swarms of protoplanets — balls of gas, dust, and rock about the size of Mercury or Mars — once swirled around our young sun.

Eventually, these objects collided and broke apart or were pushed out of the solar system entirely. Their remains make up the eight planets we see today as well as the asteroids and other rocky debris whirling around the sun.

However, it's been challenging to find space rocks that carry evidence of their past lives as planets. Now, an analysis published today in Nature Communications suggests that diamonds trapped in a rare meteorite called a ureilite show evidence of these early worlds.

How did they find it?

“Normally we talk about telescopes [to study space]. Here we are talking about the past, so it's different. Here we use the electron microscope,” says study author Farhang Nabiei from the École Polytechnique Fédérale de Lausanne, a research institute in Switzerland.

Nabiei began by examining a piece of ureilite that fell in Sudan's Nubian Desert in 2008. This meteorite holds tiny diamonds, which have long been touted by researchers as the perfect casings to preserve minerals, because they're capable of withstanding extreme pressure. Last month, for example, a diamond from deep within Earth yielded a never-before-seen type of mineral.

The electron microscope revealed that the diamonds in the meteorite do house specific iron- and sulfur-bearing minerals that most likely formed at pressures greater than 20 gigapascals. For comparison, the average human man exerts about 14,000 pascals when he walks, and a gigapascal is equivalent to a billion pascals.

“It is the first time that we found inclusions in extraterrestrial diamonds,” Nabiei says.

Why it Matters

According to the study authors, the minerals could only have formed at such great pressures if they originated inside large, planet-size objects, like the protoplanets thought to have populated our early solar system.

“[The find] proves the theories about the formation of our solar system,” says Nabiei.

Of the meteorites collected on Earth, 480 can be classified as ureilites, and Nabiei plans to use more of the extraterrestrial material to unlock the potential cosmic history hidden inside.

“[Ureilites] can give us a better idea of the formation and evolution of planets in the early solar system,” he adds.