Dwarf planet has water

Artist’s portrayal of water vapor being spewed by the dwarf planet Ceres. 

Ceres — the largest asteroid in the solar system — has water.

It’s not really a surprise. For three decades, astronomers have suspected that this “dwarf planet” might host water. But proving it was challenging. Michael Küppers with the European Space Agency (ESA) in Villanueva de la Cañada, Spain, and his colleagues now claim success.

The celestial body sits 270 million kilometers (nearly 168 million miles) from Earth in the asteroid belt between Mars and Jupiter. And Küppers’ team measured Ceres spewing at least 6 kilograms of water per second from two spots on its surface. It’s about 100 times more than scientists had been expecting. Both water-vapor sources are in mid-latitude regions. That means they are far from Ceres’ poles, which the astronomers note should be “where ice would be most stable.”

 The researchers don’t know the source of the water but have some ideas. It could be ice that sort of vaporizes directly to a gas. Or — more provocatively — the water may be erupting from ice volcanoes. Like geysers, they would spew water, not the molten rock that Earth’s volcanoes do.

The researchers described their findings early (and online) Jan. 23 in the journal Nature.

Ceres’ vapors were confirmed with an instrument aboard ESA’s Herschel Space Observatory. It viewed the asteroid in far infrared light (wavelengths not visible to the unaided eye) on four occasions between late 2011 and early 2013. With the use of computer analyses, the researchers attempted to home in on the regions responsible for shedding most of the water vapor.

Confirming Ceres has water also supports the idea that icy bodies, such as comets, may have migrated into the asteroid belt as the solar system was forming.