Want to Make a Diamond? Slam an Asteroid Into the Earth!

[Thomas the Tank Engine]

 

A big asteroid impact is one of nature’s more terrifying events. A chunk of rock and metal comes screaming out of the sky, slamming into the ground 20 times faster than a rifle bullet, exploding with the energy of a multimegaton nuclear bomb, creating a blast wave that incinerates everything for kilometers around.

 

But they’re not all bad. They make diamonds.

 

Yes, seriously. The idea is that the huge pressures and heat generated when the asteroid hits the ground are so powerful they can make diamonds out of carbon. Some evidence of this has been found, but until now the science has been shaky. A team of scientists from around the globe has just published new results, though, showing that diamonds can indeed be formed in just this way, and let me be honest: There is nothing about this story that isn’t totally cool. Lasers! X-rays! Asteroid impacts! Precious gems!

 

So yes, first, let’s talk diamonds for a minute. You may already know diamonds are a form of carbon. When you think of carbon you probably picture a soft, black material like coal. That’s amorphous carbon, where the atoms are connected together all willy-nilly. There’s no real overall structure to the substance.

 

 

Graphite is another form of carbon, where the atoms bond together to form interconnected hexagons in flat sheets (different structures using the same elements are called allotropes). Graphite is surprisingly strong along the plane of each individual sheet, but the sheets themselves slide around on top of each other easily.

 

 

Diamonds are a third form of carbon, where the atoms come together to bond in the form of interconnected tetrahedra (like the corners of a four-sided triangular pyramid). A diamond is essentially a gigantic carbon molecule, and the bonds are strong in all three dimensions. That’s why diamonds are so hard; the bonds are very tough to break. Terrestrial diamonds form when carbon under the Earth’s crust is subjected to high pressure and temperature, allowing the atoms to assemble in the tetrahedral pattern.

 

Diamonds come in different forms, too. One is called lonsdaleite, named after crystallographer Kathleen Lonsdale. It has a slightly different structure, with the tetrahedra connected in a zig-zaggy hexagonal shape; this was shown back in 2014. Lonsdaleite is not thought to occur inside the Earth naturally. It’s been found in meteorites, though, like Canyon Diablo—the remnants of a nickel-iron asteroid that slammed into the Arizona desert 50,000 or so years ago.

 

 

Well, maybe. The diamond crystals found in the meteorites aren’t pure, and the identification of them has been controversial. Scientists have tried to create lonsdaleite in the lab in the past but haven’t been totally successful.

 

Until now. This is the second incredible part of this story. And it has LASERS!

 

To attempt the creation of lonsdaleite, the researchers fired two high-powered lasers into a sample of graphite. By high power, I mean gigawatt lasers, which is a lot. They only fire them in pulses lasting 10 nanoseconds, but still. That graphite sample knows who’s boss after that.

 

 

 

 

 

 

 

 

 

Read the rest: http://www.slate.com/blogs/bad_astronomy/2016/03/17/asteroid_impacts_create_tiny_diamonds.html