September 27, 2007 (LPAC)--At sunrise today, NASA launched the Dawn spacecraft, now embarked on a three billion mile journey to carry out the first intensive study of the two largest bodies in the belt of asteroids, thought to be an exploded planet, which is situated between Mars and Jupiter. While other craft have flown by a variety of asteroids, Dawn will spend nine months orbiting Vesta, in 2011, and a similar amount of intensive study time at the object of Karl Gauss' affection--Ceres--in 2015.

More is currently known about Vesta, because, program scientist David Lindstrom explained, 5% of the meteorites that fall to Earth come from that asteroid. It is a dense body, believed to be solid rock, is oval in shape, and about 320 miles in diameter. It was discovered in 1807 by Heinrich Willhelm Olbers, and is believed to have crystallized into a solid body about 4.5 billion years ago.

Ceres, the largest asteroid, and characterized as a dwarf planet, is round in shape, and contains one quarter of all of the mass in the asteroid belt. Its density is lower, and scientists surmise that rather than being composed of solid rock, there may be water ice under its rocky crust. It was discovered in 1801 by Giuseppe Piazzi.

Dawn will reach the orbit or Mars in 2009, and use that planet for a gravity assist, to kick it into the asteroid belt. Upon entering the asteroid belt it will rendezvous with the Orbit of Ceres, first discovered by Carl Friedrich Gauss.