Even before entering into orbit around the asteroid Vesta in the middle of July, NASA's Dawn spacecraft had discovered a mysterious dark spot at the asteroid's equator. Since Dawn has been taking numerous images of Vesta.
Dawn has found a dry, rocky world littered with impact craters floating in the asteroid belt between the orbits of Mars and Jupiter. It is thought the asteroid belt consists of the remnants of material that might have formed into a planet had the gravitational effects of Jupiter had prevented it, driving the material apart instead of allowing it to coalesce. Vesta might well have grown to a rocky world much like Earth or Mars had this not happened. As it is, Vesta is 330 miles across and is classified as a "protoplanet."
A number of spectacular images of Vesta are due to be released by NASA. Preliminary results suggest a number of processes have happened on Vesta during the years of its early formation.
The Dawn spacecraft will spend a year orbiting Vesta, studying it with a suite of instruments, attempting to understand how the early solar system was formed. Then the ion engines will blast the Dawn out of orbit around Vesta and will take the spacecraft to Ceres, the largest asteroid in the main belt, for a year or more of study of that celestial body starting in 2015. Ceres measures 590 miles in diameter and is thought to contain ice, making it a different type of world than Vesta.
Dawn is part of NASA's Discovery series of spacecraft, costing $466 million. Dawn was launched on Sept. 27, 2007, on a Delta II rocket, and used an ion engine, with the help of a gravity assist maneuver at Mars to make the nearly four year, over 1.7 billion mile voyage to Vesta. Dawn will study Vesta from a variety of orbits, including one at a distance of just 110 miles from the asteroid's surface.
The images taken of Vesta hitherto have been done to calibrate the cameras and other scientific instruments on board Dawn. The scientific study of Vesta now begins in earnest.
Mark R. Whittington is the author of Children of Apollo and The Last Moonwalker. He has written on space subjects for a variety of periodicals, including The Houston Chronicle, The Washington Post, USA Today, the L.A. Times, and The Weekly Standard.
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