Isn't the protoplanet beautiful?! Dawn sure thinks so! Vesta is the second most massive object in the asteroid belt, with Ceres being the first, so it's a big deal to see such wonderful surface features on this asteroid. Ground-based telescopes have been trying to get a good picture of Vesta forever, but nothing was as good until Dawn arrived.
"We are beginning the study of arguably the oldest extant primordial surface in the solar system," said Dawn principal investigator Christopher Russell from the University of California, Los Angeles. "This region of space has been ignored for far too long. So far, the images received to date reveal a complex surface that seems to have preserved some of the earliest events in Vesta's history." No spacecraft has ever visited the asteroid belt before, so this is a first for the whole earth. NASA has accomplished much, but nothing this significant yet. It was the first space exploration group to launch a craft to visit the asteroid belt, which is very impressive.
Here, you can view Vesta's size relative to other major asteroid bodies in the asteroid belt. Click on the picture to make it larger; if you can't do that: 21 Lutetia is on top (very massive), two under that is 243 Ida and moon Dactyl, and under that is 433 Eros, just naming the famous, well-known asteroids.
As people are still in awe of Dawn's arrival after traveling over 1.7 billion miles for four years, you have to admit Dawn did make good time. Being the first spacecraft to ever make the largest propulsive acceleration of any spacecraft, Dawn made a change of velocity of more than 4.2 miles a second, on account of its high-tech ion-powered engines.
"Dawn slipped gently into orbit with the same grace it has displayed during its years of ion thrusting through interplanetary space," said Marc Rayman, Dawn chief engineer and mission manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "It is fantastically exciting that we will begin providing humankind its first detailed views of one of the last unexplored worlds in the inner solar system."
Dawn will keep on approaching Vesta for about three weeks, looking for hypothetical moons, observing surface features and properties. NASA writes, "In addition, navigators will measure the strength of Vesta's gravitational tug on the spacecraft to compute the asteroid's mass with much greater accuracy than has been previously available. That will allow them to refine the time of orbit insertion."
Dawn will leave Vesta in July 2012, making its way to minor-planet 1 Ceres in February of 2015. More of Dawn is here, along with Dawn's 'journal.' More of Dawn at Astronomical Events Calender is Here.