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Ceres (optimized image from the Hubble Space telescope)

Today’s post topic is located in the depths of space far far away from the bats, pumpkins, and haunted deserts I have been writing about for October. The dwarf planet Ceres is located in the midst of the asteroid belt between Jupiter and Mars.  The only dwarf planet in the inner solar system, Ceres is only 950 km (590 miles) in diameter, but it is sufficiently large to have become spherical from its own gravity (and it is by far the largest asteroid). Named after Ceres (Demeter), the mythological goddess of growing things whose daughter was abducted by Hades and who gave the secrets of agriculture to humankind through the farmer Triptolemus, the dwarf planet was discovered in 1801 by Italian astronomer Giuseppe Piazzi, a Roman Catholic priest of the Theatine order.  Ceres was the first asteroid to be discovered and it comprises a third of the asteroid belt’s total mass.

A comparison of the sizes of the Earth, Moon, and Ceres

The nebular hypothesis proposes that the solar system formed as a great cloud of space dust and gas coalesced into a disk which then further coagulated into small clumps, then into planetesimals, then into moon-sized planetary embryos, and finally into planets. Ceres is one of the few (or maybe the only) planetary embryos which formed four and a half billion years ago but somehow did not get smushed together with other like bodies to form a planet or hurled off into deep space. The dwarf planet probably consists of a rocky core surrounded with an icy mantle of frozen water.  Ceres is believed to contains 200 million cubic kilometers of water–more fresh water than in all the lakes, rivers, clouds, swamps, ponds (and everything else) on Earth. The Hubble telescope has photographed several mysterious surface features on Ceres including a dark spot believed to be a crater (now informally named after Piazzi) and several bright spots, the nature of which is unknown.

Image of the bright spots on Ceres (taken by the Hubble Space telescope)

Astronomers are profoundly curious about Ceres and hope to better understand the history of the solar system by examining this surviving planetary embryo.  Additionally, the chemical makeup of Ceres is similar to that of Earth. Scientists seeking extraterrestrial life have concentrated on Europa and Mars, but Ceres is next on their short list.

Astronomers will soon have some of their answers about Ceres.  The asteroid probe Dawn is currently orbiting the asteroid Vesta–but its mission there is scheduled to end in July of 2012.  At that point Dawn will power up its ion thrusters and fly to Ceres. In February of 2015 Dawn will enter permanent orbit around the little planet and we will finally have some of our answers.

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