Saturn, Jupiter may harbor diamonds in different forms

Traci Watson | Special for USA TODAY

There is something in the sky with diamonds, and not only a girl named Lucy.

New research suggests solid diamonds are scattered deep inside both Jupiter and Saturn. Planetary experts have long thought that Uranus and Neptune boast diamonds in their depths, but no one knew whether the same was true for their solar-system neighbors. Now there's evidence Jupiter and Saturn also harbor hidden treasure, scientists said Tuesday at a meeting in Denver.

"We don't want to give people the impression that we have a Titanic-sized diamondberg floating around," says planetary scientist Mona Delitsky of California Specialty Engineering, a consulting firm. "We're thinking they're more like something you can hold in your hand."

Only the outer parts of the planets would contain solid diamonds. Closer to the planets' core, temperatures are so high that the gems would melt into droplets of liquid diamond, a mysterious substance that may have some of the internal structure of the familiar jewel. That could lead to diamond "rain," which could form small pools of molten diamond. On Neptune and Uranus, by contrast, lower temperatures mean that diamonds stay solid.

"Diamonds are forever on Uranus and Neptune, but not on Jupiter and Saturn," quips Delitsky's colleague Kevin Baines of the University of Wisconsin-Madison.

Any diamonds on Jupiter and Saturn originated with a decidedly less glamorous material: methane gas, which wafts out of landfills and sewers on Earth and is found in the atmosphere on the solar system's two biggest planets. During storms, lightning blasts apart some of the methane on both Jupiter and Saturn, creating fluffy, jet-black soot much like the stuff that floats out of a fireplace.

Delitsky and Baines decided to trace the fate of that soot as it sinks downward. They relied in part on new calculations by other scientists of conditions deep inside the planets. They also took advantage of recent data showing how carbon – the building block of both soot and diamonds – reacts to high temperatures and pressures.

Their work shows that the sinking soot first turns into graphite, a form of carbon used in pencils. As the bits of graphite continue their journey to the center of the planet, the growing pressure and temperature squeeze and heat them into specks of solid diamond floating in a sea of helium and hydrogen. That transformation takes place at roughly 5,000 degrees on Saturn and nearly 7,000 degrees on Jupiter – many times hotter than the temperature at which diamonds are forged inside the Earth.

The new results, presented at the annual meeting of the American Astronomical Society's Division for Planetary Sciences, are plausible, says Scott Edgington, deputy project scientist of NASA's Cassini spacecraft, which has orbited Saturn since 2004. It's also possible that there are diamonds in the middle of Venus and Mars, he says.

To find out, "we would have to go and drill for them," he says. "Who knows? Maybe this will give DeBeers the opportunity to send missions to Saturn to go find diamonds."