…it goes and rains diamonds.
That’s the theory put forth by planetary scientists Kevin Baines and Mona Delitsky, at the Division for Planetary Sciences conference in Denver earlier this month. They came up with it as a way of explaining the presence of soot — bits of pure carbon — in Saturn’s upper atmosphere.
Saturn’s atmosphere is mostly hydrogen, Baines said, but there’s about a half percent of methane, a molecule made up of carbon and hydrogen. During a thunderstorm, lightning can fry that methane to a crisp, releasing the hydrogen and reducing the carbon to little black bits. The researchers think those bits of soot are blown up into the ammonia clouds during the thunderstorms.
“So we have this reservoir of carbon dust and so the natural question is, what happens to the carbon dust eventually?” Baines said. “Eventually it’s going to drift on down.”
Keep in mind that “drifting down” on Saturn means falling through thousands of kilometers of atmosphere — it is a gas giant, after all. And each succeeding kilometer puts a little more pressure on the carbon. Remember what we all learned in primary school about how diamonds are made? Carbon + super high pressure + super high temperature. Saturn’s deeper atmosphere has those second two factors in plentiful supply.
So these bits of carbon float down, and just like hail in Earth’s atmosphere, they aggregate into bigger bits, and the bigger bits aggregate into chunks. The chunks get hotter and more squished the farther they fall, and after the first few hundred kilometers they’re flattened into graphite. (Hey, maybe someday in the future, humans can mine pencil lead on Saturn!)
About 2,300 kilometers into the atmosphere (3,700 miles), the pressure reaches 100,000 times that of Earth sea level, and the graphite is crushed into diamond form. At that point, you’ve got diamonds falling like hail through another 36,000 kilometers or so (22,400 miles). If future humans want to mine them, they’ll have to catch the diamonds in that layer, because after that the pressure and heat get so high that the diamonds melt. (Assuming future humans could build ships to withstand the heat and pressure, that layer shouldn’t be too constraining, since it’s nearly three times the diameter of Earth.)
It’s a very cool theory, and the even cooler part is that if diamonds can rain on Saturn, they can certainly rain on Jupiter, too.
Of course, this is just a conference presentation of unpublished material that has not been peer-reviewed. And while some scientists agree that the hypothesis makes sense and is entirely within the realm of possibility, others rain on the parade:
Dr Nadine Nettelmann, of the University of California, Santa Cruz, said further work was needed to understand whether carbon can form diamonds in an atmosphere which is rich in hydrogen and helium – such as Saturn’s.
“Baines and Delitsky considered the data for pure carbon, instead of a carbon-hydrogen-helium mixture,” she explained. “We cannot exclude the proposed scenario, but we simply have no data on mixtures in the planets. So we do not know if diamond formation occurs at all.”
Before you ask, no, I couldn’t resist that pun. I also can’t resist posting this trailer of one of the best musicals ever made, because the signature song is now stuck in my head.