Jupiter swallowed a super-Earth

JUPITER might have secured its position as the solar system's mightiest planet by killing an up-and-coming rival, new simulations suggest. The work could explain why the planet has a relatively small heart, and paints a grisly picture of the early solar system, where massive, rocky "super-Earths" were snuffed out before they could grow into gas giants.

Jupiter and Saturn are thought to have begun life as rocky worlds with the mass of at least a few Earths. Their gravity then pulled in gas from their birth nebula, giving them dense atmospheres.

In this picture, all gas giants should have cores of roughly the same size. Yet spacecraft-based gravity measurements suggest Jupiter's core weighs just two to 10 Earth masses, while Saturn's comes in at 15 to 30.

New simulations by Shu Lin Li of Peking University in China, and colleagues, may explain why. They calculated what would happen when a super-Earth of 10 times the mass of our planet slammed into a gas giant. The rocky body flattened like a pancake when it hit the gas giant's atmosphere, then barrelled into the giant's core about half an hour later. The energy of the collision could have vaporised much of the core.

via Jupiter swallowed a super-Earth - space - 11 August 2010 - New Scientist.