Dawn Reveals Secrets of Giant Asteroid Vesta
Findings from Dawn reveal new details about the giant asteroid Vesta, including its varied surface composition, sharp temperature changes and clues to its internal structure.
PASADENA, Calif. - Findings from NASA's Dawn spacecraft reveal new  details about the giant asteroid Vesta, including its varied surface  composition, sharp temperature changes and clues to its internal structure. The  findings were presented today at the European Geosciences Union meeting in  Vienna, Austria, and will help scientists better understand the early solar  system and processes that dominated its formation.Images from Dawn's framing camera and visible and infrared mapping  spectrometer, taken 420 miles (680 kilometers) and 130 miles (210 kilometers)  above the surface of the asteroid, show a variety of surface mineral and rock  patterns. Coded false-color images help scientists better understand Vesta's  composition and enable them to identify material that was once molten below the  asteroid's surface.Researchers also see breccias, which are rocks fused during impacts  from space debris. Many of the materials seen by Dawn are composed of iron- and  magnesium-rich minerals, which often are found in Earth's volcanic rocks.  Images also reveal smooth pond-like deposits, which might have formed as fine  dust created during impacts settled into low regions."Dawn now enables us to study the variety of rock mixtures making  up Vesta's surface in great detail," said Harald Hiesinger, a Dawn  participating scientist at Münster University in Germany. "The images  suggest an amazing variety of processes that paint Vesta's surface."At the Tarpeia crater near the south pole of the asteroid, Dawn imagery  revealed bands of minerals that appear as brilliant layers on the crater's  steep slopes. The exposed layering allows scientists to see farther back into  the geological history of the giant asteroid.The layers closer to the asteroid's surface bear evidence of  contamination from space rocks bombarding Vesta. Layers below preserve more of  their original characteristics. Frequent landslides on the slopes of the  craters also have revealed other hidden mineral patterns."These results from Dawn suggest Vesta's 'skin' is constantly  renewing," said Maria Cristina De Sanctis, lead of the visible and  infrared mapping spectrometer team based at Italy's National Institute for  Astrophysics in Rome.Dawn has given scientists a near 3-D view into Vesta's internal  structure. By making ultra-sensitive measurements of the asteroid's  gravitational tug on the spacecraft, Dawn can detect unusual densities within  its outer layers. Data now show an anomalous area near Vesta's south pole,  suggesting denser material from a lower layer of Vesta has been exposed by the  impact that created a feature called the Rheasilvia basin. The lighter, younger  layers coating other parts of Vesta's surface have been blasted away in the  basin.Dawn obtained the highest-resolution surface temperature maps of any  asteroid visited by a spacecraft. Data reveal temperatures can vary from as  warm as minus 10 degrees Fahrenheit (minus 23 degrees Celsius) in the sunniest  spots to as cold as minus 150 degrees Fahrenheit (minus 100 degrees Celsius) in  the shadows. This is the lowest temperature measurable by Dawn's visible and  infrared mapping spectrometer. These findings show the surface responds quickly  to illumination with no mitigating effect of an atmosphere."After more than nine months at Vesta, Dawn's suite of instruments  has enabled us to peel back the layers of mystery that have surrounded this  giant asteroid since humankind first saw it as just a bright spot in the night  sky," said Carol Raymond, Dawn deputy principal investigator at NASA's Jet  Propulsion Laboratory in Pasadena, Calif. "We are closing in on the giant  asteroid's secrets."Launched in 2007, Dawn began its exploration of the approximately  330-mile-wide (530-kilometers) asteroid in mid-2011. The spacecraft's next  assignment will be to study the dwarf planet Ceres in 2015. These two icons of  the asteroid belt have been witness to much of our solar system's history.Dawn's mission is managed by JPL for NASA's Science Mission Directorate  in Washington. Dawn is a project of the directorate's Discovery Program,  managed by NASA's Marshall Space Flight Center in Huntsville, Ala. UCLA is  responsible for overall Dawn mission science. Orbital Sciences Corp. in Dulles,  Va., designed and built the spacecraft. The German Aerospace Center, the Max  Planck Institute for Solar System Research, the Italian Space Agency and the  Italian National Astrophysical Institute are international partners on the  mission team. The California Institute of Technology in Pasadena manages JPL  for NASA.To view the new images and for more information about Dawn, visit:http://dawn.jpl.nasa.gov.