Ceres is, by most astronomers’ accounts, both a dwarf planet and an asteroid. It’s neither fish nor fowl, in other words, but—depending on whether the structure of an average solar system includes more planets than asteroids, or vice versa—it may actually be more representative of cosmic habitats than Earth is. We just don’t know yet.
What we do know is that there is considerable evidence that Ceres has an underground ocean, which exobiologists have historically taken to be a good indicator that a planet or moon may contain life. Our reasoning behind investigating Enceladus, Ganymede, and Europa is certainly predicated on the idea that where there is water, life may follow.
But we’re still not entirely sure we’re dealing with a liquid ocean here. That all boils down to two questions: (1) What is the chemical composition of the ocean, and (2) What is its temperature? We can’t answer either question yet (that blurry image in the header above is our best photograph yet of Ceres, taken by the Hubble Space Telescope, and tells us little about its surface features). We know enough to know that the surface temperature of Ceres is well below freezing, but if Ceres is geologically active (it probably isn’t, but it could be), it could easily be much warmer—hospitably warmer, even—underground.
We’ll get a better look at Ceres in February 2015 when the DAWN Mission arrives at Ceres, give us a better idea of the dwarf planet’s composition and features. Unless DAWN finds that Ceres is surprisingly bland, it will remain on the short, but growing, list of celestial objects in our solar system that host underground water in some form and could therefore also host some form of life.