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More Dawn at Ceres
For Ceres, timing was everything. Had the largest asteroid formed just a few million years earlier, it likely would be almost completely dry. Instead, water appears to account for about half of its volume. Most of the water is frozen, but some may be liquid.
We should learn more about that over the next few months as a spacecraft known as Dawn takes a close look at Ceres, which is also classified as a “dwarf planet.” Dawn is scheduled to enter orbit around it this week. It’ll become the first craft ever to orbit two different solar system objects beyond Earth.
Ceres is roughly 600 miles in diameter — about a quarter the size of the Moon. It’s in the asteroid belt, between the orbits of Mars and Jupiter.
Water probably was common in that zone when Ceres and the other asteroids took shape. But the first big asteroids to form also incorporated large amounts of radioactive elements from a nearby supernova. These elements heated the growing bodies and boiled off much of their water. Ceres probably formed a few million years later, after the radioactive elements had decayed, so it stayed cool enough to keep much of its water.
Today, its surface consists mainly of clay, which forms in a wet environment. And a space telescope discovered wisps of water vapor around Ceres, suggesting that water may be squirting into space from below ground. So Dawn could see geysers or other evidence of water on the surface of this intriguing little world.
Script by Damond Benningfield, Copyright 2015