Page 12 September 13, 2012 Looking Up Dawn Spacecraft Leaves Asteroid Vesta for Trek to Dwarf Planet Ceres By Bob Eklund two colossal impacts in the last two billion than a typical asteroid.” managed by NASA’s Marshall Space Flight NASA’s Dawn spacecraft is on track to years. Without Dawn, scientists would not Vesta, with a mean diameter of 326 miles, Center in Huntsville, Alabama. become the first probe to orbit and study two have known about the dramatic troughs does not have enough gravity to make it UCLA is responsible for the overall Dawn distant solar system destinations in order to sculpted around Vesta, which are ripples entirely spherical—hence its somewhat mission science. Orbital Sciences Corp. help scientists answer questions about the from the two south polar impacts. irregular appearance. Ceres is three times of Dulles, Virginia designed and built the formation of our solar system. The spacecraft “We went to Vesta to fill in the blanks of as large, with a diameter of 950 miles. spacecraft. The German Aerospace Center, left the giant asteroid Vesta on September 4 our knowledge about the early history of Designated a “dwarf planet” (as is Pluto), the Max Planck Institute for Solar System to start its two-and-a-half-year journey to the our solar system,” said Christopher Russell, Ceres is composed of both rock and ice and Research, the Italian Space Agency and the dwarf planet Ceres. Dawn’s principal investigator, based at the has enough gravity to make it very nearly a Italian National Astrophysical Institute are Dawn began its three-billion-mile odyssey University of California Los Angeles (UCLA). perfect sphere. part of the mission’s team. to explore the two most massive objects in “Dawn has filled in those pages and more, The mission to Vesta and Ceres is managed Text, images and video: the main asteroid belt in 2007. It arrived at revealing to us how special Vesta is as a by NASA’s Jet Propulsion Laboratory for http://www.nasa.gov/mission_pages/dawn/ Vesta in July 2011 and will reach Ceres in survivor from the earliest days of the solar the agency’s Science Mission Directorate news/dawn20120830.html • early 2015. Dawn’s targets represent two icons system. We can now say with certainty that in Washington. Dawn is a project of the of the asteroid belt that have been witness to Vesta resembles a small planet more closely directorate’s Discovery Program, which is much of our solar system’s history. To make its escape from Vesta, the spacecraft will spiral away as gently as it arrived, using a special, hyper-efficient system called ion propulsion. Dawn’s ion propulsion system uses electricity to ionize xenon to generate thrust. The 12-inch-wide ion thrusters provide less power than conventional engines, but can maintain thrust for months at a time. “Thrust is engaged and we are now climbing away from Vesta atop a blue-green pillar of xenon ions,” said Marc Rayman, Dawn’s chief engineer and mission director, at NASA’s Jet Propulsion Laboratory in Pasadena. “We are feeling somewhat wistful about concluding a fantastically productive and exciting exploration of Vesta, but now have our sights set on dwarf planet Ceres.” Dawn’s orbit provided close-up views of Vesta, revealing unprecedented detail about the giant asteroid. The mission revealed that Vesta completely melted in the past, forming a layered body with an iron core. The spacecraft also revealed the scarring from titanic collisions Vesta suffered in its This image of NASA’s Dawn spacecraft and the giant asteroid Vesta is an artist’s concept. Dawn arrived at Vesta on July 15, 2011 PDT (July 16, 2011 EDT) and is set to depart on Sept. 4, 2012 PDT (Sept. southern hemisphere, surviving not one but 5, 2012 EDT). Image credit: NASA/JPL-Caltech. A better commute? It’s about time. Starting Fall 2012, Metro ExpressLanes will save you time in tra;c on the I-110 freeway. They’re toll-free for carpools, vanpools and motorcycles. Solo drivers have the choice to use ExpressLanes by paying a toll. All you need to use ExpressLanes is a FasTrak account and transponder in your car. Pre-order your FasTrak® now at metroexpresslanes.net. lacmta ©2012 ml 12-2215
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