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Water, water everywhere, and quite a lot in space. It seems that, from believing just
a few short years ago that we had a monopoly on the wet stuff here on Earth, the solar
system is teeming with water. Not just on comets, but on Mars, on several moons, and
now on Ceres, the smallest dwarf planet and largest asteroid in the solar system.
Ceres is just under 1,000km in diameter - significantly smaller than our moon, but images from the
Herschel space Observatory, taken before it shut down in April 2013, showed two outgassings
on the surface of the planet. Outgassings of water vapour.
The amounts being emitted are on the small scale - around 6kg a second, but they are
highly unusual for an asteroid.
Scientists aren't yet sure what's causing the outgassing. The two most likely options
are either that the dwarf planet, which lies between Mars and Jupiter, is being heated
by the sun, OR that there is some geothermal activity or energy present in the core.
The answer may come soon - Nasa's ion-drive powered Dawn probe is currently ambling towards
the asteroid having already made a stop at Vesta. Once there, it will gather highly detailed
images and map the planetoid, and may answer some of the questions posed by this latest
discovery.