Ceres has always been believed to have an icy, rocky surface and now new evidence finally confirms that this is true. Scientists using the Herschel Space Telescope have detected ice on the surface and water vapor in the dwarf planet’s atmosphere. The study was led by Michael Küppers of the ESA and the results were published in Nature.
Ceres is the largest and roundest body within the main asteroid belt which exists between the orbits of Mars and Jupiter. First discovered in 1801, Ceres was classified as a planet. It would later be reclassified as the first named asteroid by Sir William Herschel. In 2006, the meeting of the International Astronomical Union voted on specific definitions for different planetary bodies, resulting in yet another reclassification of Ceres, this time as a dwarf planet. This was the same meeting that reclassified Pluto to dwarf planet status as well. Ceres has only about 1% of the mass of the moon with an estimated surface area about the size of Argentina.
Though Ceres has always been believed to have ice on the surface, it has never actually been shown before. The researchers used the Herschel Space Telescope to study radiation deflecting off of Ceres and found that the wavelength indicated the presence of water vapor. Not only does the dwarf planet have ice, it has a lot of it. Researchers believe that surrounding its rocky core is a mantle of ice so thick, it could very well hold more water than Earth does.
The plumes of water vapor are a bit of a mystery to the astronomers and has raised a lot of questions about how they appear. It could be that part of the dwarf planet’s orbit brings it slightly closer to the sun, which warms up the ice and then vents off as steam, though there could be radioactivity within the core that causes the sublimated water to be expelled. Water vapor does not appear to be venting all the time and the amount coming out does not seem to be held constant. The vents do not appear sporadically and appear to be restricted to two separate areas. At maximum, the vents were observed to release about 6 kilograms (13.2 pounds) of water per second.
In 2007, NASA launched the Dawn space probe with a mission of studying Ceres and Vesta, a large asteroid. Dawn will study the geology, chemical composition, and atmospheres of these two proto-planets in order to better understand planetary formation. The spacecraft is expected to rendezvous with the dwarf planet in February of 2015. This is incredibly good timing, as scientists won’t really have to wait long to take up close measurements and follow up with these preliminary observations. Information collected from Dawn will help researchers understand how water was distributed throughout the solar system, and how it ended up on a planet capable of retaining it as a liquid: the prerequisite for life as we know it.