LOS, ANGELES/PARIS – The largest object in the asteroid belt just got more attractive. Scientists have confirmed signs of water on the dwarf planet Ceres, one of the few bodies in the solar system to hold that distinction.
Peering through the Herschel Space Observatory, a team led by the European Space Agency detected water plumes spewing from two regions on Ceres.
The observations, published in Thursday’s issue of Nature, come as NASA’s Dawn spacecraft is set to arrive at the Texas-size dwarf planet next year.
It has long been suspected that Ceres is water-rich, but previous detections have been inconclusive. This is the first definitive evidence of water on Ceres and confirms that it has an icy surface. Lead author Michael Kuppers of the European Space Agency said, “It makes Ceres a more exciting target” for exploration.
The latest finding puts Ceres in a special class of solar system objects with active plumes of water, a key ingredient for life. The company includes Jupiter’s moon Europa — where an ocean is believed to lie below thick surface ice — and Saturn’s moon Enceladus, where jets have been seen venting from the surface.
The source of the water plumes is unclear. There may be a layer of ice just below the surface that gets heated by the sun, or the plumes could be spewed by ice volcanoes.
Dawn won’t be in the best position to witness any water activity, since it will arrive at a time when Ceres is far from the sun. But it carries instruments that can detect water and it will map the dwarf planet in detail.
Launched in 2007 and powered by ion propulsion, Dawn is the first spacecraft to orbit two space rocks.
Ceres is different from Dawn’s first target, Vesta, the second-largest object in the asteroid belt between Mars and Jupiter. The zone is littered with rocks left over from the formation of the solar system 4.6 billion years ago, allowing scientists to study how Earth and the other planets evolved.
Unlike Ceres, Vesta is dry and rugged. Its scars reveal it got whacked twice by smaller asteroids. Some of the debris was cast into space and rained on Earth as meteorites.
The observation of water boosts once-derided theories that billions of years ago, rocks carrying water and carbon molecules pounded the fledgling Earth, providing it with the ingredients essential for life, said University of Central Florida astrophysicists Humberto Campins and Christine Comfort in a commentary in Nature.
“Does Ceres have a sub-surface ocean? Or are the two sources of water just isolated pockets?” France’s National Center for Scientific Research, which took part in the investigation, pondered in a statement announcing the discovery.
Ceres was first recorded in 1801 by the Italian astronomer Giuseppe Piazzi, who named it after the Roman goddess of agriculture and fertility.
Measuring 950 km across, it was initially taken to be simply a massive asteroid. Closer examination found it to be a sphere, believed to be a silicate core with an icy exterior. In 2008, the International Astronomical Union promoted Ceres to the new category of “dwarf planet,” to which it also relegated Pluto, until then considered a full-fledged planet.