Dawn's First Year at Ceres: A Mountain Emerges
NASA's Dawn mission commemorates the spacecraft's first year at Ceres with new images of a mysterious mountain.
One year ago, on March 6, 2015, NASA's Dawn spacecraft slid  gently into orbit around Ceres, the largest body in the asteroid belt between  Mars and Jupiter.  Since then, the  spacecraft has delivered a wealth of images and other data that open an  exciting new window to the previously unexplored dwarf planet."Ceres has defied our expectations and surprised us in many  ways, thanks to a year's worth of data from Dawn. We are hard at work on the  mysteries the spacecraft has presented to us," said Carol Raymond, deputy  principal investigator for the mission, based at NASA's Jet Propulsion  Laboratory, Pasadena, California.Among Ceres' most enigmatic features is a tall mountain the Dawn  team named Ahuna Mons. This mountain appeared as a small, bright-sided bump on  the surface as early asFebruary 2015from a distance of 29,000 miles  (46,000 kilometers), before Dawn was captured into orbit. As Dawn circled Ceres  at increasingly lower altitudes, the shape of this mysterious feature began to  come into focus. From afar, Ahuna Mons looked to be pyramid-shaped, but upon  closer inspection, it is best described as a dome with smooth, steep walls.Dawn's latest images of Ahuna Mons, taken 120 times closer than  in February 2015, reveal that this mountain has a lot of bright material on  some of its slopes, and less on others. On its steepest side, it is about 3  miles (5 kilometers) high. The mountain has an average overall height of 2.5  miles (4 kilometers). It rises higher than Washington's Mount Rainier and  California's Mount Whitney.Scientists are beginning to identify other features on Ceres that  could be similar in nature to Ahuna Mons, but none is as tall and well-defined  as this mountain."No one expected a mountain on Ceres, especially one like  Ahuna Mons," said Chris Russell, Dawn's principal investigator at the  University of California, Los Angeles. "We still do not have a  satisfactory model to explain how it formed."About 420 miles (670 kilometers) northwest of Ahuna Mons lies the  now-famousOccator Crater.  Before Dawn arrived at Ceres, images of the dwarf planet from NASA'sHubble Space  Telescopeshowed a prominent bright patch on the surface. As  Dawn approached Ceres, it became clear that there were at least two spots with  high reflectivity. As the resolution of images improved, Dawn revealed to its  earthly followers that there are at least 10 bright spots in this crater alone,  with the brightest area on the entire body located in the center of the crater.  It is not yet clear whether this bright material is the same as the material  found on Ahuna Mons."Dawn began mapping Ceres at its lowest altitude in  December, but it wasn't until very recently that its orbital path allowed it to view Occator's  brightest area. This dwarf planet is very large and it takes a great many orbital  revolutions before all of it comes into view of Dawn's camera and other  sensors," said Marc Rayman, Dawn's chief engineer and mission director at JPL.Researchers will present new images and other insights about  Ceres at the 47th Lunar and Planetary Science Conference, during a press  briefing on March 22 in The Woodlands, Texas.When it arrived at Ceres on March 6, 2015,  Dawn made history as the first mission to reach a dwarf planet, and the first  to orbit two distinct extraterrestrial targets. The mission conducted extensive  observations of Vesta in 2011-2012.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, Alabama. UCLA is responsible for overall Dawn mission science.  Orbital ATK Inc., in Dulles, Virginia, designed and built the spacecraft. The German  Aerospace Center, Max Planck Institute for Solar System Research, Italian Space  Agency and Italian National Astrophysical Institute are international partners  on the mission team. For a complete list of mission participants, visit:http://dawn.jpl.nasa.gov/missionMore information about Dawn is available at  the following sites:http://dawn.jpl.nasa.govhttp://www.nasa.gov/dawn