Ceres is the dwarf planet that resides in the asteroid belt, making it the largest object in the area. For those of you who just heard about Ceres, it is not new. Back when it was discovered in 1801, it used to be a planet. Then after a slew of discoveries in the asteroid belt like Vesta, Juno, Pallas, they decided that they were different enough to be labeled asteroids. Then came 2006, and due to discovery of an object larger than Pluto, Eris, and other large Kuiper belt objects, they changed the definition. Ceres was upgraded to the status of dwarf planet because it was round, and revolved around the sun, but did not count as a full planet because it failed to clear the orbit, which is clear since Ceres resides in the asteroid belt.
Now the question is, how did the water get there from Ceres? Well, it is thought that whenever Ceres gets somewhat closer to the sun in its orbit, a jet of water is released in certain areas. The reason they believe that is that the four times they observed Ceres, they didn’t see any water signature once. Not only that, as it was rotating and moving along the orbits, the signals changed, and they believe the likely area of emission are dark spots that they have observed on the surface. While they aren’t sure about this a hundred percent, once the space probe Dawn arrives, they will be able to confirm their findings.
The really cool aspect of this discovery is the blurring between asteroids and comets. Comets are icy objects, and they are the ones that release jets of water vapor. While Ceres itself is more asteroid like, more rock like, its mixture with ice gives it a comet like behavior sometimes. So overall, Ceres has a mix of really interesting features. It is large and massive enough to be planet like, it has asteroid like compositions, and it has its icy bits like comets.