Jupiter's heart is dissolving

Even the mighty can lose heart. New calculations suggest that Jupiter's rocky core is dissolving like an antacid tablet plopped in water.

The work could help explain why its core appears smaller and its atmosphere richer in heavy elements than predicted.

Giant planets like Jupiter and Saturn are thought to have begun their lives as solid bodies of rock and ice. 

When they grew to about 10 times the mass of Earth, their gravity pulled in gas from their birth nebula, giving them thick atmospheres made mainly of hydrogen.

Curiously, some studies have suggested that Jupiter's core may weigh less than 10 Earths, while the core of its smaller sibling Saturn packs a bigger punch at 15 to 30 Earths. Last year, researchers led by Shu Lin Li of Peking University in China offered a grisly explanation – a rocky planet bigger than Earth slammed into Jupiter long ago, vaporising most of the giant planet's core.

That scenario could also explain another mystery – why Jupiter's atmosphere contains a higher fraction of heavy elements than the sun, whose composition is thought to mirror that of the nebula that gave birth to the solar system's planets.

Now Hugh Wilson and Burkhard Militzer of the University of California, Berkeley, suggest a competing – though no less macabre – explanation: Jupiter's core has gradually been dissolving since its formation 4.5 billion years ago.

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