PSI Scientist Describes Wind-Driven Rovers in Chapter of New Mars Book

Jan. 11, 2010 - Wind-driven research platforms that could roll like tumbleweeds across the surface of Mars are the subject of a 38-page book chapter written by Kim Kuhlman and her colleagues.

Kuhlman, a senior scientist with the Tucson-based Planetary Science Institute, is the lead author on "Tumbleweed: A New Paradigm for Surveying the Surface of Mars for In-situ Resources." The chapter appears in "Mars: Prospective Energy and Materials Resources," published today by Springer Publishing Co.

Tumbleweeds are lightweight, inexpensive vehicles that can carry a variety of instruments and cover large swaths of terrain as winds push them across the landscape. They are designed to bridge the gap between large-scale surveys done by orbital platforms and intensive, small-scale research conducted by rovers, Kuhlman said.

The vehicles, some of which resemble beach balls on steroids, are based on well-developed and tested technology, Kuhlman added.

An inflatable Tumbleweed was tested in Greenland in 2003 and in Antarctica in 2004 by the Jet Propulsion Laboratory. The latest version, deployed in Greenland in 2004, covered more than 200km across an ice sheet on a four-day run. During that time, it communicated via the Iridium satellite network to a ground station at the JPL. The Tumbleweed gathered data on temperature, pressure, and its GPS location.

Since Tumbleweeds are light and relatively inexpensive, several could fly on one mission, and they could hitch rides on larger missions, she noted.

Other scientists who contributed to the chapter include: Alberto Behar, Jack Jones, Max Coleman and Daniel W. Wilson, of the Jet Propulsion Laboratory; Penelope Boston, of New Mexico Tech; Jeffrey Antol, Gregory Hajos and Warren Kelliher, of NASA Langley Research Center; Ronald Crawford, of the University of Idaho; Lynn Rothschild, of the NASA-Ames Research Center; Martin Buehler, of Decagon Devices; and Greg Bearman, of Snapshot Spectra.

The Jet Propulsion Laboratory's six-foot tumbleweed rover took a seven- day, 80-mile journey across Antarctica in 2004. Credit: NASA

PSI Receives $2.5 Million NASA Grant to Archive Asteroid and Dust Data

Jan. 5, 2010 - The Tucson-based Planetary Science Institute has received a NASA grant of nearly $2.5 million to continue archiving data relating to asteroids and space dust.

PSI has been part of NASA's Planetary Data System (PDS) effort to preserve, organize and make mission data available to the scientific community since the PDS was formed in the early 1990s.

The grant, which runs for five years, will fund PSI work on the Asteroid/Dust Subnode of the PDS Small Bodies Node, said Donald R. Davis, a PSI senior scientist who is the principal investigator on the project. The Small Bodies Node is one of a half dozen groups in PDS, and each group includes additional Subnodes, such as the one administered by PSI.

"NASA established PDS as a long-term archive for data collected on planetary missions," Davis explained. "NASA's Planetary Science Division spends more than a billion dollars each year to acquire data, and the PDS is the primary way in which this data is made available to the scientific community, both for immediate analysis and for future use."

There's a lot more to archiving than simply tossing data into a computer file and noting where it is, Davis explained. Data must be archived in a way that makes it easy to retrieve and scientifically useful.

"We make sure the data is well described so that scientists ten, 15 or even 50 years from now can understand how it was taken, the instrument used, the spacecraft and the mission objectives," Davis said. "All of this has to be adequately described and documented. Without this background, a bunch of tables, numbers or images are much less useful. We also include published papers that are based on a particular dataset."

PSI has developed an On-Line Archiving Facility (OLAF) that guides mission scientists in preparing their datasets for inclusion in the Asteroid/Dust Subnode. The data and its accompanying support material is then peer reviewed and any weaknesses in the dataset are referred back to the researcher or researchers for further clarification before the data is added to the archive.

All this generally takes place quickly because researchers can apply for NASA funding to analyze the data only after it has been archived in PDS, Davis explained. "So it's important that the data gets in, gets validated and gets peer reviewed in a timely manner," he said.

PSI also is developing a Data Ferret that will make it much easier for a scientist to sift through the increasingly voluminous holdings in the Asteroid/Dust Subnode to find what he or she is looking for.

This tool, which should be operational sometime in 2010, will allow a scientist to query the archive using standard scientific terms, rather than computer-specific terminology. The Data Ferret will then search through the holdings and return a list of datasets, which the scientist can ask the Data Ferret to further sift and refine.

The Small Bodies Group also includes ground-based observations in the archive to make it even more useful, Davis said. "A mission can tell you an awful lot about a single body, but you really want to be able to extrapolate that to the entire population of thousands of comets, millions of asteroids, and endless amounts of space dust," he said. "We're really interested in populations, not just individuals visited by missions, and the larger datasets in small bodies are taken primarily by ground-based observations."

The group also is including data gathered by amateur astronomers, who have the knowledge and sophisticated equipment -- CCDs and half-meter class telescopes, for instance -- to do professional quality work. Nearly all the data on asteroid light curves, for instance, is now collected by amateur astronomers, Davis noted.

All of this effort to preserve data in a scientifically useful archive will be as important in the future as it is now. "After all, there is no use-by date on scientific data, and researchers frequently want to re-examine old data as new theories and data analysis techniques are developed," Davis explained.

Reprocessing data with modern data-reduction techniques can lead to new discoveries, he noted. In addition, comparing current observations with previous ones identifies changes that have occurred, which gives scientists new insights into processes working on solar system bodies.

Fifty years from now, this data will form a priceless archive to help future generations in their quest to understand the solar system and their place in it, Davis said.

Trough Deposits on Mars Point to Complex Hydrologic Past

Dec. 15, 2009 - Catherine Weitz, a senior scientist at the Tucson-based Planetary Science Institute, has reported new evidence for multiple, water-related geologic processes on Mars.

She and her colleagues studied light-toned deposits (LTDs) within troughs of the Noctis Labyrinthus region in western Valles Marineris using data gathered by three Mars Reconnaissance Orbiter (MRO) instruments: the High Resolution Imaging Science Experiment (HiRISE) camera, the Context Camera (CTX) and the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM).

Weitz presented the research results today during a morning session of the American Geophysical Union Conference in San Francisco, Calif.

"We analyzed ten troughs containing well-exposed LTDs, and we found a lot of variability that we didn't expect to see," she said. "We found that each of the troughs with LTDs has a unique mineralogy, and, therefore, the processes occurring in each trough were very localized."

Weitz and her team identified various types of clays, hydrated silicas, and sulfates in these small basins, which are typically 30 to 100 kilometers across. One LTD included dozens of beds of varying thickness, brightness, color and erosional structure, suggesting that significant amounts of water once existed there. In addition, sulfates were mixed with clays within the deposits, indicating that ph levels may have fluctuated between acidic and alkaline conditions.

Another LTD is buried several meters beneath wind-deposited material and is only exposed in the trough's upper walls, indicating it is older than the trough. In still another area, clays are buried beneath younger plains along the trough floor, while in the same trough, but a few kilometers away, there are exposures of hydrated silica and calcium sulfate.

The wide variability in deposits and mineralogy in these and the other basins suggests a complex hydrologic history, including multiple events in some troughs, Weitz said.

"Clearly, these areas were affected by water," she added. "In some cases there had to be multiple events. But we don't know how much water was involved or whether it was always a flowing liquid."

"It might have been groundwater coming from Tharsis, the large volcanic complex to the west," she said. "There could have been active volcanism that produced water by melting snow, ice, or underground, hydrothermal processes. These little basins could then have filled or partially filled with some of that water. Another possibility is that material was already in several of the troughs, perhaps as volcanic ash or lava flows, and some kind of hydrothermal activity may have altered these pre-existing deposits."

Weitz and her colleagues identified LTDs using the wide-range CTX camera that covers about a 30 km swath at a spatial resolution of 6 meters per pixel. Then they zeroed in on the areas of interest using HiRISE visible light images that cover about a 5-km-wide area with a resolution of about 26 centimeters per pixel.

Finally, the corresponding CRISM data -- in the visible and near infrared regions -- revealed the hydrated minerals within each LTD.

"It's great to have these complementary data sets," Weitz said. "Together, the synthesis of these three datasets provides valuable morphologic and mineralogic information needed to interpret the geologic setting and origin of the light-toned deposits within the troughs of Noctis."

The LTDs both pre-date and post-date trough formation and occurred between the Noachian (4.6 to 3.5 million years ago) and Amazonian (1.8 billion years ago to the present) eras. The sediments in the LTDs could have formed at the bottom of lakes or pools, but materials also could have been deposited by the wind or fallen as volcanic ash and then been altered by water.

Noctis Labyrinthus is a region of Mars that's located between the volcanic Tharsis upland and Valles Marineris, a huge system of canyons.

Those working with Weitz on the research include Janice Bishop, of SETI Institute/NASA Ames; Leah Roach, of Frontier Technology; Ralph Milliken, of the Jet Propulsion Laboratory/Caltech; and J. Alexis Rodriguez, of the Planetary Science Institute.

This HiRISE camera false-color image shows dozens of beds within a light-toned deposit located in a trough in the Noctis Labyrinthus region of Mars. CRISM spectra suggest a general sulfate mineralogy for the light-toned deposit. However, the beds differ in brightness, color, thickness, and erosional properties, suggesting that many compositions may be present here but are too thin to be resolved. The arrows on this image point to an upper, dark-toned, blocky unit that has covered the older light-toned deposit. Photo Credit: NASA/Jet Propulsion Laboratory/The University of Arizona. [Full resolution image]

PSI Researcher Delighted that LCROSS Confirms Lunar Prospector Findings

Dec. 7, 2009 - When the LCROSS rocket stage slammed into Cabeus crater on October 9, creating an impact plume of material that had not seen sunlight for possibly billions of years, it conclusively proved that water ice exists in the dark recesses of the moon's polar craters.

The LCROSS findings delighted William Feldman, a senior scientist at the Tucson-based Planetary Science Institute. "What got me excited is that everything we said is right, which is a nice feeling."

In 2001, Feldman was the lead author on a paper in the Journal of Geophysical Research entitled Evidence for Water Ice Near the Lunar Poles, which was based on neutron spectrometer data that he and his instrument team gathered during NASA's 1998 Lunar Prospector mission. Feldman was working at Los Alamos National Laboratory at the time, and came to PSI in 2006.

The paper's conclusions were subsequently confirmed by an extensive series of computer simulations conducted by David Lawrence, of the Johns Hopkins University Applied Physics Laboratory, and his co-workers. This work was published in the Journal of Geophysical Research in 2006.

As early as 1961, scientists speculated that water ice could be hidden in the deep recesses of lunar polar craters that never see daylight. These are some of the coldest spots in the solar system, and water from comet and meteorite impacts could freeze and remain for billions of years.

Researchers using radar on the 1994 Clementine spacecraft thought they saw signatures for water in their data, but the results were controversial, especially when others, using Earth-based radar, found similar signatures in measurements taken near the moon's mid-latitude regions, which are exposed to sunlight.

Feldman and his team didn't measure water directly, but their data showed evidence for inordinately large amounts of hydrogen in some craters. Other phenomena, such as the solar wind and outgassing could account for relatively high levels of hydrogen, "but there was a sufficient amount in some of these craters that it would be hard to understand if it came only from the solar wind or through other processes," Feldman said. "So in our paper we didn't call it 'evidence for hydrogen,' but 'evidence for water'."

Not everyone agreed, and some controversy surrounded the paper. But, when NASA went looking for water on the moon with the LCROSS mission, it headed for the Cabeus crater, about 62 miles from the moon's south pole, that Feldman's Lunar Prospector team had identified as having the maximum hydrogen signature among all the high-latitude craters surveyed.

"This is a big, permanently shaded crater," Feldman said. "In fact, you can't even see it from the Earth because it has a rim that hides it. It takes a satellite to see it."

"When we converted the hydrogen signal to the amount of water ice in the regolith, we found that it was only about 1.5 percent by weight," Feldman added. "That's the reason the radar researchers really couldn't see it. There aren't large enough deposits of high-grade water ice to create the signal needed to identify ice with radar."

So it turns out that Feldman and the Lunar Prospector team showed the first experimental evidence for water on the moon, which has now been conclusively confirmed by the LCROSS mission.

"There's a lot of interest in water on the moon right now," Feldman said. "And there is more to be learned. The whole story is not in yet."



This image, taken by the LCROSS visible-light camera, shows the ejecta plume from the LCROSS rocket stage at about 20 seconds after impact. Credit: NASA

The Planetary Science Institute is a private, nonprofit corporation founded in 1972 and dedicated to solar system exploration. It is headquartered in Tucson, Arizona.

PSI scientists are involved in numerous NASA and international missions, the study of Mars and other planets, the Moon, asteroids, comets, interplanetary dust, impact physics, the origin of the solar system, extra-solar planet formation, dynamics, the rise of life, and other areas of research. They conduct fieldwork in North America, Australia and Africa. They also are actively involved in science education and public outreach through school programs, children's books, popular science books and art.

The Institute's researchers are based in 15 states, the United Kingdom, France, Russia, Switzerland and Australia.