Diamonds form when carbon — the same stuff in your graphite pencil — is put under such intense heat and pressure that the carbon atoms are pushed into a special lattice formation. This makes it incredibly strong, but also changes it from opaque to completely transparent. We have ample evidence of the fact that diamonds form here on Earth, and scientists have speculated in the past that they may form deep down inside 'ice giant' planets like Uranus and Neptune as well.
Now, two scientists — Mona Delitsky of California Specialty Engineering and Kevin Baines of the University of Wisconsin-Madison — have teamed up to compare a new model of the temperatures and pressures inside planets to the conditions needed for diamond to form. Their results show that it's actually possible inside the atmospheres of Jupiter and Saturn, and it would happen much higher up in their atmosphere than on Uranus and Neptune.
What they propose is that lightning in the planet's upper atmosphere can form carbon by splitting apart methane molecules, and these carbon atoms could then clump together to form soot particles. This soot 'rains' down towards the centre of the planet, and along the way it's heated to incredible temperatures and crushed by the immense weight of all the atmosphere pushing down from above, forming what they call 'diamond hail'. It would continue to fall after that, until the temperatures were high enough to melt the diamonds, forming liquid diamond raindrops.
"We know that inside the clouds on Saturn is pure carbon," Baines told Weather.com. "There’s gravity there so obviously those solid carbon particles have to rain down. So we just said when they get down deep enough they should turn into diamonds. It all kind of just fell naturally from thunderstorms on Saturn."
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Injecting a little speculative fiction into this idea in the book Alien Seas: Oceans in Space, Delitsky and Baines suggest that robots could harvest these diamonds. This wouldn't be a money-making venture, though. Their idea is that the diamonds could be used to produce ships that could venture down into the extreme environments of these massive gas giant planets to mine resources, like helium-3 for fusion power.
(Images courtesy: Michael Carroll, Mona Delitsky, Kevin Baines)
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