NASA craft snaps pic of distant asteroid target

AP News
Posted: May 11, 2011 2:22 PM
NASA craft snaps pic of distant asteroid target

A NASA spacecraft hurtling toward a massive asteroid has snapped a picture of its target, the first of many before it slips into orbit.

The Dawn craft took the image last week when it was 752,000 miles away from the asteroid Vesta, which appeared as a tiny bright speck surrounded by stars.

Launched from Cape Canaveral, Fla., in 2007, Dawn is due to arrive at Vesta in July to circle the asteroid. The encounter will take place about 120 million miles from Earth.

The craft carries cameras and instruments to study the asteroid surface from orbit. After a yearlong investigation, Dawn will head toward an even bigger asteroid, Ceres, arriving in 2015.

Vesta and Ceres are the largest bodies in the crowded asteroid belt between Mars and Jupiter. Images by the Hubble Space Telescope reveal they are geologically diverse.

Vesta, about the size of Arizona, is rocky and dry and appears to have a surface of frozen lava. Scientists look forward to peering into the asteroid's south pole that's home to a giant crater measuring 285 miles across and 8 miles deep. Many of the meteorites found on Earth came from the impact that created the crater.

Texas-size Ceres, on the other hand, is icy and may possess frost-covered polar caps.

Vesta and Ceres are believed to have evolved in different parts of the solar system more than 4 1/2 billion years ago, around the same time as the formation of the rocky planets including Mercury, Venus, Earth and Mars. Studying them should help scientists learn more about the early solar system.

Previous spacecraft have visited smaller asteroids before, circling and even landing on them. But Dawn is attempting to be the first to rendezvous with two asteroids in the same mission.

The craft is powered by ion engines instead of rocket fuel, making the trip more fuel-efficient and allowing it to cruise between the asteroids and lower itself to about 120 miles above the surface to study them in depth.

The $357 million project is managed by NASA's Jet Propulsion Laboratory.