Icy World Found Inside Asteroid

Science News Magazine ^ | 9-30-2005 | Ron Cowen

[blam]

Icy world found inside asteroid

Ron Cowen

New observations of Ceres, the largest known asteroid, suggest that frozen water may account for as much as 25 percent of its interior. If this is true, the volume of ice on Ceres would be greater than that of all the fresh water on Earth.

CERES SERIES. This sequence of Hubble images reveals a bright spot of unknown origin on Ceres during a quarter-turn of the asteroid's 9-hour rotation. Thomas, et al., NASA

The evidence comes from Hubble Space Telescope images showing that the 930-kilometer-wide asteroid is smooth and almost perfectly round. Simulations show that a body as massive as Ceres can have that shape and texture only if materials inside it have separated into layers of higher– and lower-density compounds. A period of heating and cooling, such as that experienced by the solar system's rocky inner planets, could have caused light material to move toward the asteroid's surface and denser material to sink.

In the Sept. 8 Nature, Peter Thomas of Cornell University and his colleagues suggest that the outer, low-density material is probably ice because Ceres' surface shows signs of water-bearing minerals and because the asteroid's overall density is lower than that of Earth's rocky crust. The proposed ice layer would lie just beneath a thin crust of clay and carbon-rich compounds and above a rocky core, the researchers say.

Ceres is one of several hundred thousand bodies that lie in the main asteroid belt between Mars and Jupiter. The layering provides new evidence that Ceres is a case of arrested development. It's "an embryonic planet" halted by Jupiter's gravity from packing on additional material to become a full-fledged planet, says study coauthor Lucy McFadden of the University of Maryland in College Park.

Next year, NASA plans to launch a mission called Dawn, which will orbit Ceres in 2015 and then move on to Vesta, the second-largest known asteroid.

[SunkenCiv]

an oldie, and another one (':

NASA Restarts Canceled Asteroid Mission - DAWN
AP on Yahoo | 3/27/06 | Alicia Chang - ap
Posted on 03/27/2006 3:40:16 PM EST by NormsRevenge
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[SunkenCiv]

Largest Asteroid May Be 'Mini Planet' With Water Ice
Science Daily
Sept 2005

Observations of 1 Ceres, the largest known asteroid, have revealed that the object may be a "mini planet," and may contain large amountsof pure water ice beneath its surface. The observations by NASA's Hubble Space Telescope also show that Ceres shares characteristics of the rocky, terrestrial planets like Earth. Ceres' shape is almost round like Earth's, suggesting that theasteroid may have a "differentiated interior," with a rocky inner core and a thin, dusty outer crust... Ceres is approximately 580 miles (930 kilometers) across, about thesize of Texas. It resides with tens of thousands of other asteroids inthe main asteroid belt... Pluto, our solar system's smallest planet, is 14 times more massive than Ceres.