Asteroid and Meteorite Impacts on Earth Create Bizarre Diamonds

Asteroids and meteorites can slam into planets, generating immense heat and pressures. Now, scientists have taken a closer look at these impacts and found that they may actually create a form of diamond called lonsdaleite.

For years, researchers have wondered whether creating diamonds with asteroids and meteorites would result in a different kind of diamond. Yet it seems that this latest study reveal that lonsdaleite is actually a structurally disordered form of ordinary diamond.

"So-called lonsdaleite is actually the long-familiar cubic form of diamond, but it's full of defects," said Peter Nemeth, one of the researchers, in a news release.

So how does lonsdaleite form? About 50 years ago, scientists first reported that a large meteorite in northern Arizona contained a new form of diamond with a hexagonal structure. Intrigued by this diamond, scientists labeled it lonsdaleite. Since then, the form of diamond has been used as an indicator of ancient asteroidal impacts on Earth, including those linked to mass extinctions.

The scientists examined the lonsdaleite that was first discovered 50 years ago. More specifically, they used advanced electron microscopes to study samples.

"Most crystals have regular repeating structures, much like the bricks in a well-built wall," said Peter Buseck, one of the researchers. "Defects are intermixed with the normal diamond structure, just as if the wall had an occasional half-brick or longer brick or row of bricks that's slightly displaced to one side or another."

In other words, it seems that lonsdaleite is a regular diamond with an unusual structure. By being subjected to shock or pressure, lonsdaleite has defects within its structure.

The findings have implications for other studies, which presume that lonsdaleite is a separate type of diamond. The reality is that it's a regular diamond, even if it does have structural defects.

The findings are published in the journal Nature Communications.