October 15, 2013

It rains diamonds on Saturn and Jupiter. New atmospheric data about these gas giant planets led Kevin Baines–an astronomer at the University of Wisconsin-Madison and NASA’s Jet Propulsion Laboratory–and his colleague Mona Delitsky to conclude that carbon is abundant on Saturn and Jupiter in its most dazzling crystal form–diamonds. Massive lightning storms high in the atmospheres of both planets turn methane into soot. Soot consists chiefly of particles of carbon. As the soot falls through Saturn and Jupiter’s gaseous atmospheres, it hardens into chunks of graphite and then diamond, which fall like “hail stones.” “The bottom line is that 1,000 tons (907 metric tons) of diamonds a year are being created on Saturn,” stated Baines.

Diamonds are one of the three crystalline forms of pure, solid carbon. The other forms are graphite and fullerenes (shown as a Buckminsterfullerene and carbon nanotube). (World Book illustrations by Oxford Illustrators Limited and Bensen Studios)

Baines delivered his and Delitsky’s unpublished findings last week at the American Astronomical Society’s annual Division for Planetary Sciences meeting. Analyzing the latest temperature and pressure predictions for the planets’ interiors, the two scientists concluded that stable crystals of diamond “hail down over a huge region” of Saturn in particular. “It all begins in the upper atmosphere, in the thunderstorm alleys, where lightning turns methane into soot,” stated Baines. “As the soot falls, the pressure on it increases. And after about 1,000 miles (1,600 kilometers) it turns to graphite–the sheet-like form of carbon you find in pencils.” The falling graphite hardens into diamonds, the hardest substance found on Earth. However, the diamonds eventually fall into the planets’ hot cores and melt into a liquid sea. “Once you get down to those extreme depths, the pressure and temperature is so hellish, there’s no way the diamonds could remain solid,” explained Barnes. On Saturn and Jupiter–diamonds are not forever!