Once upon a time there was a planet….It had all the characteristics of a planet: a strong enough gravitational field that gave it a round shape, a history of geological formation which produced a core, mantle and crust, an atmosphere, and an orbit around the sun. Then, abruptly, a group of astronomers decided that this wasn’t enough, and it was demoted to the status of a “dwarf planet.”
We’re not talking about Pluto, however. This is Ceres, orbiting the sun in the asteroid-strewn region between Mars and Jupiter. Ceres has more in common with planets like Earth and Mars. Early images from Dawn seem to show evidence of enormous quantities of water, frozen into ice under the surface.
2015 is shaping up as the year of the dwarf planets. New Horizons is on course for its Pluto flyby, and Dawn is now in orbit around Ceres, ready to send pictures of surface features – craters, valleys and hills. The first names for these geographical features were unveiled at the recently-concluded Lunar and Planetary Science Conference in Houston, Texas.
The IAU’s Working Group for Planetary System Nomenclature has announced two themes for naming physical features on Ceres: “The theme for craters is Gods and goddesses of agriculture and vegetation from world mythology. The theme Names of agricultural festivals of the world will be used for other features.” Ceres is named for the Roman goddess of agriculture and fertility.
Planetary Society blogger Emily Lakdawalla reports that Dawn has already mapped the entire surface of Ceres, and that the major regions, or quadrants, have been provisionally named, after harvest deities from around the world. You can see her map of the regions with their new names here.
Before Ceres, the Dawn spacecraft visited Vesta, the largest object in the asteroid belt, and mapped its surface features. The differences between Ceres and Vesta will continue to fuel debate on the classification of objects in the solar system, and the place of Ceres and Pluto in this classification.