Solar system’s most volcanic body to go dormant

By | June 20, 2009

Jupiter's massive size, coupled with Io's close orbital distance to the planet, expose the moon to powerful gravitational forces. These forces constantly deform the moon, generating the heat that powers its volcanism. Similar, but less powerful, 'tidal' forces are thought to power geysers of water vapour erupting from Saturn's icy moon Enceladus (Illustration of Jupiter and Io: V Lainey/IMCCE-Paris Observatory)The most volcanically active body in the solar system has just received a death sentence. Jupiter’s moon Io, whose surface erupts with active volcanoes, will one day become dormant, a new study analysing more than 100 years of observations suggests.

Io, which is about the size of Earth’s moon and is Jupiter’s closest large satellite, is covered with lava flows and dozens of active volcanoesMovie Camera (see image).

The heat for this activity comes from the fact that the moon travels on an elongated path around Jupiter, and therefore feels the giant planet’s gravity at different strengths along its orbit. This varying pull causes its body to deform, producing bulges that move its surface up and down by an estimated 10 metres per orbit. This generates heat that powers the moon’s volcanism.

But it will not always be so, according to a new study led by Valéry Lainey of the Paris Observatory in France.

Out of resonance

If Io were Jupiter’s only satellite, the planet’s intense gravity would eventually pull the nearby moon into a circular orbit.

The reason it travels on an elliptical path instead is because of special gravitational interactions with its nearest large sister moons, Europa and Ganymede. For every orbit that Ganymede makes, Europa makes two and Io four – a type of gravitational relationship called a Laplace resonance.

But Lainey and colleagues have found that the moons are, in fact, moving out of their resonance – Europa and Ganymede are gradually drifting away from Jupiter, while Io is moving towards the planet.

The team came to these conclusions after carrying out numerical calculations of Io’s orbital motion and plugging in observations of Io, Europa and Ganymede taken between 1891 and 2007.

via Solar system’s most volcanic body to go dormant – space – 18 June 2009 – New Scientist.

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