Exploring the roots of creation

On July 16, NASA’s Dawn spacecraft, managed by the Jet Propulsion Laboratory in La Cañada Flintridge, is expected to reach the orbit of an asteroid protoplanet that scientists hope may hold clues about the formation of the planets and the evolution of the solar system.

Vesta became forever relegated to asteroid status when its slow journey to becoming a planet was thwarted by the explosive force of Jupiter’s creation. Since then, the 329-mile-diameter body has remained trapped among other cosmic remnants of an asteroid belt that stretches from Mars to Jupiter.

Planetary scientists believe that, had its voyage been unimpeded, Vesta likely would have become a planet potentially similar to Earth or Mars, with an interior of a different composition than its surface.

Until now, the only images of Vesta came courtesy of the Hubble Space Telescope, which provided unclear renderings of light and shadow that implied a diverse topography. But Dawn — equipped with framing cameras, a visible and infrared mapping spectrometer and a gamma ray and neutron detector — will give new insight into Vesta’s surface, geology and chemical composition.

“The Dawn team is going to, over the next year, enable us to get a bird’s-eye view of this new world,” said Jim Adams, NASA’s deputy director of planetary science, in a news briefing held Thursday to update the public on the status of the mission, which began with a September 2007 launching. “Until now, it’s only been a fuzzy blob. The Dawn team will put a face on that fuzzy blob.”

As of the briefing, the Dawn spacecraft was a mere 96,000 miles from the sun. This relatively near approach to Vesta comes after four years, 1.7 billion miles of space travel and two laps around the sun, according to Bob Mays, JPL’s Dawn project manager.

Once it reaches Vesta’s orbit, Dawn will complete a series of revolutions around the asteroid at differing altitudes, studying the surface closely at low altitudes and gathering topographical data at high altitudes as the sun moves across the asteroid’s surface. At its closest, it will approach to 120 miles above Vesta’s surface.

After one full year, when the craft has sent the last of the Vesta data back to Earth, Dawn will prepare for a voyage to Ceres, a dwarf planet within the asteroid belt. Its anticipated arrival in 2015 will make it the first spacecraft to rendezvous with two bodies in the solar system in a single mission, Mays said.

Carol Raymond, Dawn deputy principal investigator at JPL, explained the hope that Dawn will affirm the presence of a metallic core on Vesta and give a glimpse into the unique history of a protoplanet.

“As we explore Vesta, we take a virtual journey back in time to the beginning of the solar system,” Raymond said at the briefing. “We’re literally on the edge of our seats, waiting for this data to come in.”

For more information on the Dawn project, including up-to-date images of the asteroid Vesta, visit www.nasa.gov/dawn.

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