TESTING THE SOLAR-ELECTRIC PROPULSION THRUSTER

FROM: NASA

The Engine Burns Blue

This image shows a cutting-edge solar-electric propulsion thruster in development at NASA's Jet Propulsion Laboratory, Pasadena, Calif., that uses xenon ions for propulsion. An earlier version of this solar-electric propulsion engine has been flying on NASA's Dawn mission to the asteroid belt.

This engine is being considered as part of the Asteroid Initiative, a proposal to robotically capture a small near-Earth asteroid and redirect it safely to a stable orbit in the Earth-moon system where astronauts can visit and explore it. This image was taken through a porthole in a vacuum chamber at JPL where the ion engine is being tested.

Image credit: NASA/JPL-Caltech

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.

THE DRY ICE OF MARS

Photo:  Mars South Pole.  Credit:  NASA.
FROM: NASA
NASA Orbiter Observations Point to 'Dry Ice' Snowfall on Mars

PASADENA, Calif. -- NASA's Mars Reconnaissance Orbiter (MRO) data have given scientists the clearest evidence yet of carbon dioxide snowfalls on Mars. This reveals the only known example of carbon dioxide snow falling anywhere in our solar system.

Frozen carbon dioxide, better known as "dry ice," requires temperatures of about minus 193 degrees Fahrenheit (minus 125 Celsius), which is much colder than needed for freezing water. Carbon dioxide snow reminds scientists that although some parts of Mars may look quite Earth-like, the Red Planet is very different. The report is being published in the Journal of Geophysical Research.

"These are the first definitive detections of carbon dioxide snow clouds," said the report's lead author Paul Hayne of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif. "We firmly establish the clouds are composed of carbon dioxide -- flakes of Martian air -- and they are thick enough to result in snowfall accumulation at the surface."

The snow falls occurred from clouds around the Red Planet's south pole in winter. The presence of carbon dioxide ice in Mars' seasonal and residual southern polar caps has been known for decades. Also, NASA's Phoenix Lander mission in 2008 observed falling water-ice snow on northern Mars.

Hayne and six co-authors analyzed data gained by looking at clouds straight overhead and sideways with the Mars Climate Sounder, one of six instruments on MRO. This instrument records brightness in nine wavebands of visible and infrared light as a way to examine particles and gases in the Martian atmosphere.

The data provide information about temperatures, particle sizes and their concentrations. The new analysis is based on data from observations in the south polar region during southern Mars winter in 2006-2007, identifying a tall carbon dioxide cloud about 300 miles (500 kilometers) in diameter persisting over the pole and smaller, shorter-lived, lower-altitude carbon dioxide ice clouds at latitudes from 70 to 80 degrees south.

"One line of evidence for snow is that the carbon dioxide ice particles in the clouds are large enough to fall to the ground during the lifespan of the clouds," co-author David Kass of JPL said. "Another comes from observations when the instrument is pointed toward the horizon, instead of down at the surface. The infrared spectra signature of the clouds viewed from this angle is clearly carbon dioxide ice particles and they extend to the surface. By observing this way, the Mars Climate Sounder is able to distinguish the particles in the atmosphere from the dry ice on the surface."

Mars' south polar residual ice cap is the only place on Mars where frozen carbon dioxide persists on the surface year-round. Just how the carbon dioxide from Mars' atmosphere gets deposited has been in question. It is unclear whether it occurs as snow or by freezing out at ground level as frost. These results show snowfall is especially vigorous on top of the residual cap.

"The finding of snowfall could mean that the type of deposition -- snow or frost -- is somehow linked to the year-to-year preservation of the residual cap," Hayne said.

JPL provided the Mars Climate Sounder instrument and manages the MRO Project for NASA's Science Mission Directorate in Washington.

THIRD KEPLER CATALOG CONTAINS 1,091 NEW PLANET CANDIDATES

The following excerpt is from the NASA website:

"Since science operations began in May 2009, the Kepler team has released two catalogs of transiting planet candidates. The first catalog (Borucki et al, 2010),released in June 2010, contains 312 candidates identified in the first 43 days of Kepler data. The second catalog (Borucki et al, 2011), released in February 2011, is a cumulative catalog containing 1,235 candidates identified in the first 13 months of data.

Today the team presents the third catalog containing 1,091 new planet candidates identified in the first 16 months of observation conducted May 2009 to September 2010. These are the same candidates that the team discussed at the Kepler Science Conference held at NASA Ames Research Center in December 2011.

Here are the highlights of the new catalog:
Planet candidates smaller than twice the size of Earth increased by 197 percent, compared to 52 percent for candidates larger than twice the size of Earth.
Planet candidates with orbital periods longer than 50 days increased by 123 percent, compared to 85 percent for candidates with orbital periods shorter than 50 days.
Since the last catalog was released in February 2011, the number of planet candidates identified by Kepler has increased by 88 percent and now totals 2,321 transiting 1,790 stars.

The cumulative catalog now contains well over 200 Earth-size planet candidates and more than 900 that are smaller than twice Earth-size. Of the 46 planet candidates found in the habitable zone, the region in the planetary system where liquid water could exist, ten of these candidates are near-Earth-size.

The number of planetary systems found with more than one planet candidate also has increased. Last year, 17 percent, or 170 stars, had more than one transiting planet candidate. Today, 20 percent, or 365, stars have more than one.

"With each new catalog release a clear progression toward smaller planets at longer orbital periods is emerging, " said Natalie Batalha, Kepler deputy science team lead at San Jose State University in California. "This suggests that Earth-size planets in the habitable zone are forthcoming if, indeed, such planets are abundant."

Nearly 5,000 periodic transit-like signals were analyzed with known spacecraft instrumentation and astrophysical phenomena that could masquerade as transits, which can produce false positives. The most common false positive signatures are associated with eclipsing binary stars- a pair of orbiting stars that eclipse each other from the vantage point of the spacecraft.

The Kepler space telescope identifies planet candidates by repeatedly measuring the change in brightness of more than 150,000 stars in search of planets that pass in front, or "transit," their host star. Kepler must record at least three transits to verify a signal as a planet.

The findings are published in the "Planetary Candidates Observed by Kepler III: Analysis of the First 16 Months of Data". The catalog is available at the Kepler data archive at the Space Telescope Science Institute and can be downloaded from theNASA Exoplanet Archive.

NASA's Ames Research Center in Moffett Field, Calif., manages Kepler's ground system development, mission operations and science data analysis. NASA’s Jet Propulsion Laboratory, Pasadena, Calif., managed the Kepler mission's development.

Ball Aerospace and Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

The Space Telescope Science Institute in Baltimore archives, hosts and distributes Kepler science data. Kepler is NASA's 10th Discovery Mission and is funded by NASA's Science Mission Directorate at the agency's headquarters in Washington "