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Hint of water in asteroid belt

- Dwarf planet with volcanoes spewing jets of water

Jan. 22: Astronomers have spotted what they say could be jets of water spewed by volcanoes on Ceres, the largest asteroid in the solar system, in observations that provide the first evidence for water in the asteroid belt.

A team of European and US astronomers detected signatures of water vapour thrice between October 2012 and March 2013 near the surface of Ceres, a 960-km wide dwarf planet and member of the asteroid belt between the orbits of Mars and Jupiter.

Their observations, using the European Space Agency’s Herschel space telescope, suggest that sites in the mid-latitude regions of the asteroid released at least three kilograms of water per second on each of these three occasions.

“This may not sound like a lot of water, but this is the first time we’re seeing water in the asteroid belt,” Michael Kueppers, a German astronomer at the European Space Astronomy Centre in Spain, told The Telegraph over telephone.

Kueppers and his colleagues have described their observations of water vapour from Ceres in a paper that will appear in the journal Nature tomorrow. “Most of the water vapour is likely to escape into space, but some of it may fall back onto the surface,” Kueppers said.

Their findings question a classical picture of the solar system in which planetary bodies in the inner solar system, including the asteroids, are believed to have formed as dry rocky worlds at the origin of the solar system, while almost all ice was concentrated in the outer planets and the distant comets.

The water vapour observations suggest that Ceres may have reservoirs of water stored as ice either close to its surface or deep in its interior. Although the mechanism for the intermittent emergence of water vapour is not clear, either of two processes may explain it.

“Heat from the Sun may evaporate ice close to the surface which will then emerge as geysers — this is a process similar to what we see on comets,” Kueppers said. “The other hypothesis assumes that Ceres has some internal residual heat leftover from its formation which causes stored water-ice to spew out water vapour just as molten rock in terrestrial volcanoes.”