MYSTERIOUS LIGHTS ON PLANET CERES

FROM:  NASA 

A cluster of mysterious bright spots on dwarf planet Ceres can be seen in this image, taken by NASA's Dawn spacecraft from an altitude of 2,700 miles (4,400 kilometers). The image, with a resolution of 1,400 feet (410 meters) per pixel, was taken on June 9, 2015.  Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

VIEWS OF CERES

 FROM:  NASA

These two views of Ceres were acquired by NASA's Dawn spacecraft on Feb. 12, 2015, from a distance of about 52,000 miles (83,000 kilometers) as the dwarf planet rotated. The images have been magnified from their original size. The Dawn spacecraft is due to arrive at Ceres on March 6, 2015. Dawn's mission to Vesta and Ceres is managed by the 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., of Dulles, Virginia, designed and built the spacecraft. JPL is managed for NASA by the California Institute of Technology in Pasadena. The framing cameras were provided by the Max Planck Institute for Solar System Research, Göttingen, Germany, with significant contributions by the German Aerospace Center (DLR) Institute of Planetary Research, Berlin, and in coordination with the Institute of Computer and Communication Network Engineering, Braunschweig. The visible and infrared mapping spectrometer was provided by the Italian Space Agency and the Italian National Institute for Astrophysics, built by Selex ES, and is managed and operated by the Italian Institute for Space Astrophysics and Planetology, Rome. The gamma ray and neutron detector was built by Los Alamos National Laboratory, New Mexico, and is operated by the Planetary Science Institute, Tucson, Arizona. Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.

THE IION THRUSTER

FROM: U.S. DEPARTMENT OF DEFENSE

by jtozer

Saturday Space Sight: Ion Thruster Sets World Record

While the Dawn spacecraftis visiting the asteroids Vesta and Ceres, NASA Glenn has been developing the next generation of ion thrusters for future missions. NASA's Evolutionar Xeon Thruster (NEXT) Project has developed a 7-kilowatt ion thruster that can provide the capabilities needed in the future.

An ion thruster produces small levels of thrust relative to chemical thrusters, but does so at higher specific impulse (or higher exhaust velocities), which means that an ion thruster has a fuel efficiency of 10-12 times greater than a chemical thruster.

The higher the rocket’s specific impulse (fuel efficiency), the farther the spacecraft can go with a given amount of fuel.

Given that an ion thruster produces small levels of thrust relative to chemical thrusters, it needs to operate in excess of 10,000 hours to slowly accelerate the spacecraft to speeds necessary to reach the asteroid belt or beyond.

The NEXT ion thruster has been operated for over 43,000 hours, which for rocket scientists means that the thruster has processed over 770 kilograms of xenon propellant and can provide 30 million-newton-seconds of total impulse to the spacecraft. This demonstrated performance permits future science spacecraft to travel to varied destinations, such as extended tours of multi-asteroids, comets, and outer planets and their moons.

Photo Credit:  NASA

HYDRATED MINERALS ON VESTA

Capturing the Surface of Asteroid Vesta

This full view of the giant asteroid Vesta was taken by NASA's Dawn spacecraft, as part of a rotation characterization sequence on July 24, 2011, at a distance of 3,200 miles (5,200 kilometers). A rotation characterization sequence helps the scientists and engineers by giving an initial overview of the character of the surface as Vesta rotated underneath the spacecraft. This view of Vesta shows impact craters of various sizes and grooves parallel to the equator. The resolution of this image is about 500 meters per pixel.

Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

FROM: NASA

Dawn Spacecraft Sees Hydrated Minerals on Giant Asteroid

WASHINGTON -- NASA's Dawn spacecraft has revealed the giant asteroid Vesta has its own version of ring around the collar. Two new papers, based on observations from the low-altitude mapping orbit of the Dawn mission, show volatile, or easily evaporated, materials have colored Vesta's surface in a broad swath around its equator.

The volatiles were released from minerals likely containing water. Pothole-like features mark some of the asteroid's surface where the volatiles boiled off. Dawn did not find actual water ice at Vesta. However, it found evidence of hydrated minerals delivered by meteorites and dust in the giant asteroid's chemistry and geology. The findings appear Thursday in the journal Science.

One paper, led by Thomas Prettyman, the lead scientist for Dawn's gamma ray and neutron detector (GRaND) at the Planetary Science Institute in Tucson, Ariz., describes how the instrument found signatures of hydrogen, likely in the form of hydroxyl or water bound to minerals in Vesta's surface.

"The source of the hydrogen within Vesta's surface appears to be hydrated minerals delivered by carbon-rich space rocks that collided with Vesta at speeds slow enough to preserve their volatile content," said Prettyman.

A complementary paper, led by Brett Denevi, a Dawn participating scientist at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., describes the presence of pitted terrain created by the release of the volatiles.

Vesta is the second most massive member of our solar system's main asteroid belt. Dawn was orbiting at an average altitude of about 130 miles (210 kilometers) above the surface when it obtained the data. Dawn left Vesta on Sept. 5 EDT (Sept. 4) and is on its way to a second target, the dwarf planet Ceres.

Scientists thought it might be possible for water ice to survive near the surface around the giant asteroid's poles. Unlike Earth's moon, however, Vesta has no permanently shadowed polar regions where ice might survive. The strongest signature for hydrogen in the latest data came from regions near the equator, where water ice is not stable.

In some cases, space rocks crashed into these deposits at high speed. The heat from the collisions converted the hydrogen bound to the minerals into water, which evaporated. Escaping water left holes as much as six-tenths of a mile (1 kilometer) wide and as deep as 700 feet (200 meters). Seen in images from Dawn's framing camera, this pitted terrain is best preserved in sections of Marcia crater.

"The pits look just like features seen on Mars, and while water was common on Mars, it was totally unexpected on Vesta in these high abundances," said Denevi. "These results provide evidence that not only were hydrated materials present, but they played an important role in shaping the asteroid's geology and the surface we see today."

GRaND's data are the first direct measurements describing the elemental composition of Vesta's surface. Dawn's elemental investigation by the instrument determined the ratios of iron to oxygen and iron to silicon in the surface materials. The new findings solidly confirm the connection between Vesta and a class of meteorites found on Earth called the Howardite, Eucrite and Diogenite meteorites, which have the same ratios for these elements. In addition, more volatile-rich fragments of other objects have been identified in these meteorites, which supports the idea the volatile-rich material was deposited on Vesta.

The Dawn mission is managed by NASA's Jet Propulsion Laboratory for the Science Mission Directorate in Washington. The spacecraft is as a project of the Discovery Program managed by NASA's Marshall Space Flight Center in Huntsville, Ala. The University of California, Los Angeles, is responsible for overall mission science. Orbital Sciences Corporation of Dulles, Va., designed and built the spacecraft.

The framing cameras that saw the pitted terrain were developed and built under the leadership of the Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany, with contributions by the German Aerospace Center (DLR) Institute of Planetary Research, Berlin, and in coordination with the Institute of Computer and Communication Network Engineering, Braunschweig. The framing camera project is funded by NASA, the Max Planck Society and DLR. The gamma ray and neutron detector instrument was built by Los Alamos National Laboratory, N.M., and is operated by the Planetary Science Institute.

NASA'S DAWN SPACECRAFT OBSERVES ASTEROID CALLED VESTA

The following excerpt is from the NASA website:
WASHINGTON -- NASA's Dawn spacecraft has revealed unexpected details
on the surface of the giant asteroid Vesta. New images and data
highlight the diversity of Vesta's surface and reveal unusual
geologic features, some of which were never previously seen on
asteroids.

Vesta is one of the brightest objects in the solar system and the only
asteroid in the so-called main belt between Mars and Jupiter visible
to the naked eye from Earth. Dawn found that some areas on Vesta can
be nearly twice as bright as others, revealing clues about the
asteroid's history.

"Our analysis finds this bright material originates from Vesta and has
undergone little change since the formation of Vesta over 4 billion
years ago," said Jian-Yang Li, a Dawn participating scientist at the
University of Maryland, College Park. "We're eager to learn more
about what minerals make up this material and how the present Vesta
surface came to be."

Bright areas appear everywhere on Vesta but are most predominant in
and around craters. The areas vary from several hundred feet to
around 10 miles across. Rocks crashing into the surface of Vesta seem
to have exposed and spread this bright material. This impact process
may have mixed the bright material with darker surface material.

While scientists had seen some brightness variations in previous
images of Vesta from NASA's Hubble Space Telescope, Dawn scientists
also did not expect such a wide variety of distinct dark deposits
across its surface. The dark materials on Vesta can appear dark gray,
brown and red. They sometimes appear as small, well-defined deposits
around impact craters. They also can appear as larger regional
deposits, like those surrounding the impact craters scientists have
nicknamed the "snowman."

"One of the surprises was the dark material is not randomly
distributed," said David Williams, a Dawn participating scientist at
Arizona State University, Tempe. "This suggests underlying geology
determines where it occurs."

The dark materials seem to be related to impacts and their aftermath.
Scientists theorize carbon-rich asteroids could have hit Vesta at
speeds low enough to produce some of the smaller deposits without
blasting away the surface.

Higher-speed asteroids also could have hit the asteroid's surface and
melted the volcanic basaltic crust, darkening existing surface
material. That melted conglomeration appears in the walls and floors
of impact craters, on hills and ridges, and underneath brighter, more
recent material called ejecta, which is material thrown out from a
space rock impact.

Vesta's dark materials suggest the giant asteroid may preserve ancient
materials from the asteroid belt and beyond, possibly from the birth
of the solar system.

"Some of these past collisions were so intense they melted the
surface," said Brett Denevi, a Dawn participating scientist at the
Johns Hopkins University Applied Physics Laboratory in Laurel, Md.
"Dawn's ability to image the melt marks a unique find. Melting events
like these were suspected, but never before seen on an asteroid."

Dawn launched in September 2007. It will reach its second destination,
Ceres, in February 2015.

"Dawn's ambitious exploration of Vesta has been going beautifully,"
said Marc Rayman, Dawn chief engineer at NASA's Jet Propulsion
Laboratory (JPL) in Pasadena, Calif. "As we continue to gather a
bounty of data, it is thrilling to reveal fascinating alien
landscapes."

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.