[BRIEF NOTE] Ceres, a new planet?

[rfmcdonald]

atomic_orrery, a new LJ user already of note, has pointed out that the Hubble Space Telescope's latest observations of the asteroid 1 Ceres have revealed some interesting discoveries about that largest asteroid.

The astronomers used Hubble's Advanced Camera for Surveys to study Ceres for nine hours, the time it takes the asteroid to complete a rotation. Hubble snapped 267 images of Ceres. From those snapshots, the astronomers determined that the asteroid has a nearly round body. The diameter at its equator is wider than at its poles. Computer models show that a nearly round object like Ceres has a differentiated interior, with denser material at the core and lighter minerals near the surface. All terrestrial planets have differentiated interiors. Asteroids much smaller than Ceres have not been found to have such interiors.

The astronomers suspect that water ice may be buried under the asteroid's crust because the density of Ceres is less than that of the Earth's crust, and because the surface bears spectral evidence of water-bearing minerals. They estimate that if Ceres were composed of 25 percent water, it may have more water than all the fresh water on Earth. Ceres' water, unlike Earth's, would be in the form of water ice and located in the mantle, which wraps around the asteroid's solid core.

It's fitting that, in a year when Pluto's status as a planet has been threatened by the discoveries of larger worlds in the Kuiper belt, astronomers are making the case for bodies smaller than Pluto to be considered as proto-planetary in their own right. The term "planet," it seems, is losing much of its latent meaning as a descriptor for a world of note, as worlds the size of traditional planets like the Galilean moons of Jupiter, Saturn's Titan, the Earth's Moon, and Neptune's Triton attract interest in their own right and smaller bodies stake their claims.

The possible revision of Ceres' status might bring that world to the attention of space fans. I've argued elsewhere that Ceres' relegation to the ranks of the minor planets has ensured it the neglect of astronomers and space scientists. All the established planets save Pluto have already received at least one space probe mission, and many of the large moons besides; Dawn is slated to arrive at Ceres only in 2016. A Ceres that is considered more planet-like might well attract more attention, especially since the world may be well-suited for extensive industrialization and even colonization as atomic_orrery notes. A world with abundant water ice, low gravity, and a location near the Earth could prove quite useful.