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Mardi, 20 Décembre 2011 18:55

Jupiter's Solid Core May Be Liquifying Itself

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Jupiter's Solid Core May Be Liquifying Itself

By Duncan Geere, Wired UK

Think climate change is bad? Things are rather worse in the outer solar system. Jupiter’s rocky central core may well be dissolving into liquid.

The gas giant, which is twice as massive as all of the other planets orbiting the Sun put together, has a central core comprised of iron, rock and ice. It sits in the center of the planet, submerged in a fluid of hydrogen and helium under intense pressures about 40 million times greater than atmospheric pressure on Earth, and temperatures around 16,000 degrees kelvin — hotter than the surface of the Sun.

As such, we can’t recreate those conditions experimentally on Earth. But that hasn’t stopped planetary scientists Hugh Wilson and Burkhard Militzer of the University of California, Berkeley, giving it a go. They’ve performed quantum mechanical calculations to try and work out how one of the key ingredients of the core — magnesium oxide — responds in such an extreme situation.

They found that under these intense pressures and temperatures, the magnesium oxide has very high solubility, meaning that it’s likely to be dissolving into liquid. The exact rate of the erosion isn’t known, but the pair had earlier predicted that the ice in the core is also dissolving. That means that Jupiter’s core is likely to be smaller now than it was when the planet formed.

The research has been detailed in a paper submitted to Physical Review Letters, in which Wilson and Militzer say that the work has substantial implications for working out how to simulate these types of planets. “For large exoplanets exceeding Jupiter’s mass, higher interior temperatures promote both solubility and redistribution, implying that the cores of sufficiently large super-Jupiters are likely to be completely redistributed,” it reads.

We’ll be able to find out more in 2016, when NASA’s Juno spacecraft arrives at the gas giant and begins to measure its gravitational field.

Image: NASA/ESA/E. Karkoschka (U. Arizona) [high-resolution]



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