Diamond hunting in space? Dream on
By Amanda Jermyn

While here on Earth raindrops lit by sunlight may sparkle like diamonds it seems likely that on Saturn and Jupiter it really does rain diamonds. After analyzing data on these planets this was the conclusion of Mona Delitsky of California Specialty Engineering and Kevin Baines of NASAís Jet Propulsion Laboratory and the University of Wisconsin-Madison.

On Earth diamonds form naturally about 100 miles below the planetís surface when carbon is heated to about 2,000 degrees Fahrenheit under pressure of about 725 pounds per square inch. Volcanic magma then brings the molten diamond quickly to the surface, allowing it to cool down and form the precious stone used to make fine jewelry the world over.

However, on Saturn and Jupiter the process is somewhat different. The tremendous gravity generated by these planetsí large masses results in dense atmospheres that exert extreme pressure and heat. Huge lightning storms zap methane in the atmosphere, turning it into pure hydrogen and burnt carbon in the form of soot. As the soot particles fall towards the planet they clump together under the planetís pressure to form graphite, like that used to make pencils. As the graphite falls the planetís pressure continues to increase, and, in the case of Saturn, for example, at around 3,700 miles down, the pressure is so extreme that the graphite is squeezed together to form diamonds, which rain down on the planet. As they sink towards Saturnís core, at a depth of about 18,600 miles, the extreme heat and pressure transform the diamonds into molten carbon.

Diamonds are thought to form elsewhere in the universe too. Back in 2013, the exoplanet 55 Cancri e was labeled the ďdiamond planetĒ as its surface was thought likely to be covered in graphite and diamond. Researchers have also long surmised that diamonds exist in the cooler cores of the smaller gas giants, Neptune and Uranus, but it was assumed that the atmospheres of the larger gaseous planets were not suitable for diamond formation. However, using new data on temperatures and pressures exerted on Jupiter and Saturn, Baines and Delitsky were able to model how carbon would behave in these circumstances. They concluded that diamonds were likely raining down on these planets in large quantities, probably about 1,000 tons of diamonds a year.

Thinking of mining diamonds on Saturn or Jupiter any time soon? Dream on. The extreme pressure of the planetsí atmospheres would crush any spacecraft sent to the diamond-forming depths, and the diamonds themselves melt when they get close to the core. Still, itís intriguing to think that on planets not so far away itís raining diamonds.

On August 12th at 7.30pm join the Amherst Area Amateur Astronomers Association at the Amherst College Planetarium for a talk by Adam Jermyn on ďHow Stars change when they are heated externally by Pulsar Companion Stars.Ē Jermyn is a Hertz Fellow, National Science Foundation Fellow, Goldwater Scholar and Marshall Scholar currently pursuing a PhD in astrophysics at the Institute of Astronomy at the University of Cambridge. While an undergraduate at the California Institute of Technology he was the recipient of numerous research awards. The talk is free and open to the public.