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NASA's 'Robotic Emissary' Reveals New Details of Asteroid

In this image, obtained by Dawn's framing camera, a peak at Vesta's south pole is seen at the lower right. The grooves in the equatorial region are about 10 kilometers wide. The image was taken on July 24, 2011, from a distance of about 5,200 kilometers

NASA's Dawn spacecraft is about 188 million kilometers from Earth. And in a matter of days, it will begin gathering information about the giant asteroid Vesta. The spacecraft already has returned vivid and surprising images of the asteroid since it successfully maneuvered into a low orbit around Vesta last month.

Dawn is on a mission filled with historic firsts. It is the first spacecraft to orbit an asteroid in the main asteroid belt between Mars and Jupiter. It is the first to use ion propulsion, a gentle and progressive means of acceleration that provides greater speeds than any other technology. Dawn also is slated to become the first spacecraft to orbit two solar system bodies in addition to Earth.

But Dawn's chief engineer and mission manager, Marc Rayman, says there is something more that captures his imagination.

"What I think is really exciting about this is that, after two centuries of observing this fuzzy little blob of light among the stars, Earth now has a robotic emissary in orbit at Vesta," said Rayman.

Dawn is sending back images that show the asteroid in greater detail than scientists have ever seen.

Christopher Russell of the University of California, Los Angeles is the Dawn principal investigator. He says the new images show Vesta's surprisingly varied surface.

"Bright areas, dark areas," said Russell. "We see dark material that we never expected on there, you know. What is causing those craters with the black streaks going down them? I haven't seen anything like that before."

The stark black and white images show numerous craters, ridges and elongated grooves on Vesta - the second most massive object in the asteroid belt. The Dawn science team is working to determine the significance of Vesta's distinct features, such as the large grooves around the asteroid's equatorial region. Mission team members say they expect that studying Vesta's features will keep them busy for years.

Beginning this month, Dawn will map the mineral composition and features of Vesta's surface, collect information about Vesta's gravity field, and peer into a deep, massive crater that might provide a view into the asteroid's interior.

After Dawn spends a year orbiting Vesta, the spacecraft will travel to the dwarf planet Ceres. Vesta will arrive there in February 2015.

Scientists say they hope that by studying the two largest bodies in the asteroid belt, they will better understand the history of our solar system.