[meteorite-list] New Ceres Views as Dawn Moves Higher

[Ron Baalke]

http://www.jpl.nasa.gov/news/news.php?feature=6678

New Ceres Views as Dawn Moves Higher
Jet Propulsion Laboratory
November 18, 2016

The brightest area on Ceres stands out amid shadowy, cratered terrain 
in a dramatic new view from NASA's Dawn spacecraft, taken as it looked 
off to the side of the dwarf planet. Dawn snapped this image on Oct. 16, 
from its fifth science orbit, in which the angle of the sun was different 
from that in previous orbits. Dawn was about 920 miles (1,480 kilometers) 
above Ceres when this image was taken -- an altitude the spacecraft had 
reached in early October.

Occator Crater, with its central bright region and secondary, less-reflective 
areas, appears quite prominent near the limb, or edge, of Ceres. At 57 
miles (92 kilometers) wide and 2.5 miles (4 kilometers) deep, Occator 
displays evidence of recent geologic activity. The latest research suggests 
that the bright material in this crater is comprised of salts left behind 
after a briny liquid emerged from below, froze and then sublimated, meaning 
it turned from ice into vapor.

The impact that formed the crater millions of years ago unearthed material 
that blanketed the area outside the crater, and may have triggered the 
upwelling of salty liquid.

"This image captures the wonder of soaring above this fascinating, unique 
world that Dawn is the first to explore," said Marc Rayman, Dawn's chief 
engineer and mission director, based at NASA's Jet Propulsion Laboratory, 
Pasadena, California.

Dawn scientists also have released an image of Ceres that approximates 
how the dwarf planet's colors would appear to the human eye. This view, 
produced by the German Aerospace Center in Berlin, combines images taken 
from Dawn's first science orbit in 2015, using the framing camera's red, 
green and blue filters. The color was calculated based on the way Ceres 
reflects different wavelengths of light.

The spacecraft has gathered tens of thousands of images and other information 
from Ceres since arriving in orbit on March 6, 2015. After spending more 
than eight months studying Ceres at an altitude of about 240 miles (385 
kilometers), closer than the International Space Station is to Earth, 
Dawn headed for a higher vantage point in August. In October, while the 
spacecraft was at its 920-mile altitude, it returned images and other 
valuable insights about Ceres.

On Nov. 4, Dawn began making its way to a sixth science orbit, which will 
be over 4,500 miles (7,200 kilometers) from Ceres. While Dawn needed to 
make several changes in its direction while spiraling between most previous 
orbits at Ceres, engineers have figured out a way for the spacecraft to 
arrive at this next orbit while the ion engine thrusts in the same direction 
that Dawn is already going. This uses less hydrazine and xenon fuel than 
Dawn's normal spiral maneuvers. Dawn should reach this next orbit in early 
December.

One goal of Dawn's sixth science orbit is to refine previously collected 
measurements. The spacecraft's gamma ray and neutron spectrometer, which 
has been investigating the composition of Ceres' surface, will characterize 
the radiation from cosmic rays unrelated to Ceres. This will allow scientists 
to subtract "noise" from measurements of Ceres, making the information 
more precise.

The spacecraft is healthy as it continues to operate in its extended mission 
phase, which began in July. During the primary mission, Dawn orbited and 
accomplished all of its original objectives at Ceres and protoplanet Vesta, 
which the spacecraft visited from July 2011 to September 2012.

Dawn's mission is managed by NASA's Jet Propulsion Laboratory 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/mission

More information about Dawn is available at the following sites:

http://dawn.jpl.nasa.gov

http://www.nasa.gov/dawn

News Media Contact
Elizabeth Landau
Jet Propulsion Laboratory, Pasadena, CA
818-354-6425
elizabeth.landau at jpl.nasa.gov

2016-297