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| The Inquisitor |
Voyage to the Giant Asteroidshttp://science.nasa.gov/headlines/y2007/15jun_dawn.htm?list723902June 15, 2007: The asteroid belt between Mars and Jupiter is like the solar system's cluttered old attic. The dusty, forgotten objects there are relics from a time long ago, each asteroid with its own story to tell about the solar system's beginnings. These are stories planetary scientists want to hear. Much is still unknown about our solar system's distant past. We learn the basic story in school: A vast disc of gas and dust around the sun slowly gathered into larger and larger chunks, eventually forming the planets we know today. But how exactly did this happen, and why did it produce the kinds of worlds that it did, including a certain blue planet well-suited for life? To answer these questions, NASA plans to launch a robotic probe named Dawn. Its mission: Fly to two giant asteroids, Ceres and Vesta, and explore them up close for the first time. Liftoff is scheduled for July 2007. Vesta, for starters Dawn's first stop is Vesta—an asteroid that may implicate ancient supernovas in the solar system's birth. Telescopic observations of Vesta and studies of meteorites believed to have come from Vesta suggest that the asteroid may have been partially molten early in its history, allowing heavy elements like iron to sink and form a dense core with a lighter crust on top. "That's interesting--and a bit puzzling," says Chris Russell, Principal Investigator for Dawn at the University of California, Los Angeles. Melting requires a source of heat such as gravitational energy released when material comes together to make an asteroid. But Vesta is a small world—"too small," he says--only about 530 km across on average. "There would not have been enough gravitational energy to melt the asteroid when it formed." |