Leonard Nimoy takes us on a fascinating robotic space probe to the very beginnings of our Solar System in this brilliantly animated 13-minute glimpse of NASA's Dawn mission scheduled to launch in July 7th. The movie features a look into the planning, instrumentation and technological challenges of this one-of-a kind mission into the heart of the doughnut-shaped asteroid belt between and Jupiter.
“I think of Dawn as two journeys,” says UCLA's Christopher Russell, who proposed the mission to NASA. (Russell, UCLA professor of geophysics and space physics, has spent 15 years working on NASA’s Dawn mission). “One is a journey into space. This is analogous to what ancient explorers did, who knew there was unexplored territory and wanted to discover what was there. We’re going to explore a region for the first time to find out what the conditions are today.
“Dawn is also a journey back in time. The asteroids Ceres (image) and Vesta have been altered much less than other bodies. The Earth is changing all the time; the Earth hides its history, but we believe that Ceres and Vesta, formed more than 4.6 billion years ago, have preserved their early record.
They’re revealing information that was frozen into their ancient surfaces. By looking at the surface and how it was modified by the bombardment of meteoroids, we will get an idea of what the early conditions of Ceres and Vesta were and how they changed. So Dawn is a history trip too. We’re going back in time to the early solar system.”
Dawn is scheduled to fly past by April 2009, and after more than four years of travel, the spacecraft will rendezvous with Vesta in 2011. The spacecraft will orbit Vesta for approximately nine months, studying its structure and composition. In 2012, Dawn will leave for a three-year cruise to Ceres. Dawn will rendezvous with Ceres and begin orbit in 2015, conducting studies and observations for at least five months.
“Evidence indicates it has substantial water or ice beneath its rocky crust,” Russell said. “Our instruments on board will be able to determine whether there is water.”
Dawn is expected to bring high-resolution images of previously unseen worlds to the public, including, perhaps, mountains, canyons, craters and ancient lava flows.
Dawn, which will orbit as close as 125 miles from Ceres and Vesta, is the first purely scientific mission designed to be powered by an advanced NASA technology known as ion propulsion. Unlike chemical rocket engines, ion engines accelerate their fuel nearly continuously, giving each ion a tremendous burst of speed. The fuel used by an ion engine is xenon, a gas also used in photo-flash units, which is more than four times heavier than air. This results in a xenon atom with a positive charge — a xenon ion. The xenon ions shoot out the back of the engine at a speed of 78,000 miles per hour.
At full throttle, the ion engine consumes 2,300 watts of electrical power and produces 1/50th of a pound of thrust — about the same pressure as a sheet of paper resting on the palm of a hand, and far less thrust than is produced by even small chemical rockets. This engine, for a given amount of fuel, can gradually increase a spacecraft’s velocity 10 times more than can a conventional rocket powered by liquid or solid fuel.
Dawn will be the first spacecraft to orbit two targets. At least 100,000 asteroids inhabit the asteroid belt, a reservoir of leftover material from the formation of our solar-system planets 4.6 billion years ago. Dawn also will be the first satellite to tour a dwarf planet. The International Astronomical Union named Ceres one of three dwarf planets in 2006. Ceres is round like planets in our solar system, but it does not clear debris out of its orbit as our planets do.
To prepare for the Dawn spacecrafts visit to Vesta, about the size of Arizona, astronomers used Hubble's Wide Field Planetary Camera 2 to snap new images of the asteroid. Astronomers mapped Vesta's southern hemisphere, a region dominated by a giant impact crater formed by a collision billions of years ago. The crater is 456 kilometers across, which is nearly equal to Vesta's 530-kilometer diameter. If Earth had a crater of proportional size, it would fill the Pacific Ocean basin.
Posted by Casey Kazan.
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