Ice shouldn't Stop Dune Movement on Mars or Earth
July 1, 2009 - Planetary scientists have monitored some Martian sand dunes for more than 30 years, and the dunes have not moved during that time, leading scientists to question whether snow and ice trapped inside the dunes might be preventing movement.
However a recent study published in "Geomorphology" shows that snow and ice are not enough in themselves to stop dune movement. While trapped ice and snow impedes movement of sand dunes in polar climates, compared to their counterparts in warmer areas, this does not entirely stop dune movement, the study shows.
This indicates that other factors are limiting dune movement, said Mary Bourke, a senior research scientist at the Tucson-based Planetary Science Institute. Bourke led the study, which covers the longest time period of any cold-climate dune migration and dune dynamics study to date.
In a paper published last year, Bourke also showed that two small dunes recently disappeared on Mars. The dunes, which were 20 meters wide (about 65 feet) and located in the north polar region of Mars, were completely eroded away over a period of 5.7 Earth years.
"This (dune disappearance) is fantastic new data, showing that sand is transported on Mars where and when the wind energy is available," Bourke said. "But the bigger, larger dunes on Mars are not moving, at least in the areas we studied."
In the most recent study, Bourke and her colleagues used vertical aerial photos and LiDAR (Light Detection and Ranging) data to estimate dune migration rates in Antarctica's Victoria Valley dune field. The photos, taken between 1961 and 2001, came from the USGS Antarctic Resource Center. These dunes are known to be covered by seasonal snowfalls and have snow and ice layers trapped inside.
Bourke found that the dunes migrated about 1.5 meters (5 feet) per year, which is small compared to the distance covered by dunes in warm deserts, which can be as high as 30-70 meters (about 100 to 230 feet) a year.
Recent images from the HiRISE camera that is orbiting Mars reveal crusted surfaces on the dunes scientists have monitored since the first Viking mission in 1975. These appear to be similar to hard-surfaced sandy deposits found in some of Earth's deserts. The dunes also have cemented layers. These could be cemented by ice or by geochemical processes.
Other factors limiting dune movement on Mars would include the planet's thin atmosphere, which requires very high wind speeds to provide the force needed to move sand, and the water and carbon-dioxide frosts that cover dunes in Mars' polar regions for 70 percent of the year, Bourke said.
But, Bourke adds, the study of dune movement in Antarctica's Victoria Valley shows that dunes in the cold weather environments found on Mars, Titan and other frozen bodies still have the potential to move, organize and evolved in the same way that dune fields do on Earth.
NASA's Mars Fundamental Research Program is funding this research under a grant entitled "Volatile-rich aeolian deposits: A field-based analogue study".
Those who worked with Bourke on the research include: Ryan C. Ewing, of the University of Texas at Austin; David Finnegan, of the U.S. Army Cold Regions Research and Engineering Laboratory; and Hamish A. McGowan, of the University of Queensland in Australia.
Cemented layers protrude from a dune in North Polar Region of Mars. This is a subset of HiRISE image PSP_001374_2650. (Image credit: NASA/Jet Propulsion Laboratory/The University of Arizona.)
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Martian Climate Was Life-Friendly More Recently Than Thought
June 30, 2009 - Warm weather near the Martian equator may have melted the ice in ice-rich soils as recently as 2 million years ago, according to a paper published yesterday in "Earth and Planetary Science Letters." This indicates that the Red Planet was warmer and more life-friendly much later in its history than previous studies show.
Matthew Balme, a research scientist with the Tucson-based Planetary Science Institute and a research fellow at the United Kingdom's Open University, discovered signs of melting permafrost in images from NASA's HiRISE (High Resolution Imaging Science Experiment) camera, which is flying aboard the Mars Reconnaissance Orbiter.
The images show that landforms once thought to be shaped by volcanism were actually modified by the expansion and contraction of ice due to freeze/thaw cycles, Balme said.
Balme studied an outflow channel that was active as recently as 2 to 8 million years ago. The channel contains polygonal patterns, branched channels, blocky debris and mound/cone formations, all of which are similar to formations found where permafrost melts on Earth.
"These observations demonstrate that ice melted near the Martian equator within the past few million years and then refroze," Balme said. "This probably happened over many freeze/thaw cycles."
Since liquid water is essential to life as we know it, this equatorial channel would be an ideal place to hunt for traces of past or present Martian life, Balme added.
Balme's research was funded by the UK's Science and Technology Facilities Council and by NASA's Mars Data Analysis Program. In addition to his post with PSI, Balme is an Aurora Fellow at the UK's Open University.
This HiRISE image shows evidence of flowing water on Mars, which occurred in recent geologic time. A cusp-shaped cliff (with narrow, spur-like headlands) divides higher terrain (bottom left) from lower terrain (upper right). A channel network leads away from a debris field underneath the cliff and terminates in hummocky debris fans. Both the upper and lower terrains are marked by a polygonal pattern of faint grooves and mounds. This terrain pattern - when found with cusp-shaped cliffs, debris fields, and channels - indicates thawing of an ice-rich permafrost landscape. Virtually identical features are seen on Earth in permafrost areas of Canada and Siberia. These features are Part of HiIRSE image PSP_009280_1905. (Image credit: NASA/Jet Propulsion Laboratory/The University of Arizona.)
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PSI Scientist and Kaguya Team Find First Conclusive Signature for Lunar Uranium
June 26, 2009 - Robert C. Reedy, a senior scientist at the Tucson-based Planetary Science Institute, is mapping the moon's surface elements using data gathered by an advanced gamma-ray spectrometer (GRS) that rode aboard the Japanese Kaguya spacecraft.
The data promise to show chemical elements on the moon that have never been identified before, and Reedy and the Kaguya GRS team already have found uranium signatures in the data, an element not seen in previous moon-mapping efforts.
The uranium results were recently announced in papers presented at the 40th Lunar and Planetary Conference and at the Proceedings of the International Workshop Advances in Cosmic Ray Science. The lead authors on those papers are Prof. Naoyuki Yamashita and Prof. Nobuyuki Hasebe respectively. Both are from Japan's Waseda University.
Earlier gamma-ray spectrometer maps from the Apollo and Lunar Prospector missions show a few of the moon's chemical elements. But the maps constructed by Reedy and the Kaguya GRS team -- using data gathered by state-of-the-art high-energy-resolution germanium detectors -- are extending the earlier results and improving our understanding of the moon's surface composition.
In addition to uranium, the Kaguya GRS data also is showing clear signatures for thorium, potassium, oxygen, magnesium, silicon, calcium, titanium and iron.
Reedy and his colleagues are using measurements from the Kaguya lunar orbiter's GRS to construct high-quality maps of as many chemical elements as possible. Kaguya was launched in September 2007 and crashed into the moon at the end of its mission on June 10 of this year.
"We've already gotten uranium results, which have never been reported before," Reedy said. "We're getting more new elements and refining and confirming results found on the old maps. Some of these comparisons are being done with lunar elemental maps made by a Lunar Prospector team headed by PSI senior scientist Tom Prettyman."
Reedy has been an official co-investigator on the Kaguya GRS team since 2007, and has received some support from the Japan Aerospace Exploration Agency (JAXA).
"Being selected as a co-investigator for a JAXA planetary mission is a great honor," Reedy said.
Reedy's continuing mapping work now is being funded for two years through NASA's SALMON program (Stand-Alone Missions of Opportunity).
"All of the work being funded is considerably improving our knowledge of the moon's composition and its origin and evolution," Reedy said. It also will help scientists locate lunar resources and help with planning for future lunar missions, he added.
In addition to Reedy, the Kaguya GRS team includes Hasebe (the GRS principal investigator); Yamashita and Yuzuru Karouji, of the Waseda University in Tokyo, Japan; and Claude d'Uston and Olivier Gasnault, of the Centre d'Etude Spatiale des Rayonnements in Toulouse, France.
PSI Senior Scientist Robert C. Reedy gave an invited talk at the Third Kaguya Science Working Team meeting in Tokyo in January. (Photo by the JAXA Kaguya Project)
Study to Assess Effects of Small Impacts on Earth's Climate
June 11, 2009 - Humans have stretched Earth's resources to the limit, and ever-expanding populations now require new technologies -- such as genetically engineered crops and alternative energy sources -- to survive.
What would happen to this delicate balance if the planet's climate changed slightly due to a smaller-sized asteroid or comet impact -- an event just large enough to cause crop failures or reduce atmospheric ozone?
That's what planetary scientist Elisabetta Pierazzo hopes to discover through research that has been funded under a new grant from the NASA Astrobiology: Exobiology and Evolutionary Biology Program.
Pierazzo, a senior scientist at the Tucson-based Planetary Science Institute, will use general circulation models (GCMs) of the Earth's atmosphere to analyze the effects of impactors between 300 meters and 2 kilometers in diameter. This project is a collaborative partnership between PSI and the National Center for Atmospheric Research (NCAR), Pierazzo emphasized. NCAR scientists will provide the computer code and support for the atmospheric modeling parts of the project.
Atmospheric chemistry models are now being coupled to atmospheric GCMs, Pierazzo noted. This makes it possible to interactively evaluate the effects of atmospheric perturbations, such as those associated with an impact event, on the overall physical and chemical state of the atmosphere.
Pierazzo, an expert in modeling impact events, will determine the amount of dust and/or water that would be ejected from impacts of various types and sizes and how high the ejecta would rise in the atmosphere. Then she will run an atmospheric model that accounts for this extra material and the changes in atmospheric dynamics and chemistry.
"We're trying to find out the threshold for significant effects on climate and how long those effects will last," she said.
Destruction of ozone, for instance, would allow more ultraviolet radiation to reach the ground, potentially affecting the DNA of every living organism. Dust could alter weather patterns, with devastating effects on food supplies. "Even slight changes in the atmospheric circulation might affect weather patterns and agriculture," she said.
"The Spaceguard Survey is getting close to its goal of finding ninety percent of the Near Earth Objects larger than one kilometer in diameter," Pierazzo said. "But there are many more smaller objects out there than larger ones, so we still have a large potential threat that we haven't resolved."
A smaller object between 500 meters and 1 kilometer in diameter might be spotted months in advance or maybe only days, depending on its trajectory, she said. Or it might be seen only at the last minute or not at all, if its trajectory is close to the sun.
While attempts have been made to model large impacts, such as the Chicxulub meteorite that may have killed off the dinosaurs, GCMs are so sensitive to current conditions that they may not be able to withstand the introduction of Chicxulub-sized perturbations, Pierazzo said.
"We want to start with smaller impactors and then move on to larger ones," she said. "Eventually the idea would be to try to model the effects of a Chicxulub-sized impact."
"This project is going to be a learning experience because we really don't know what to expect," Pierazzo added. "There might be climatic effects we haven't anticipated, or maybe we'll find impacts of this size are not a big deal as far as climate is concerned. We just don't know yet."
Other researchers working with Pierazzo on the project are: Rolando Garcia, Charles Bardeen, Doug Kinnison, and Daniel Marsh, of NCAR; Natalia Artemieva, of PSI; and H. Jay Melosh and Tamara Goldin, of the University of Arizona.
Congresswoman Giffords Emphasizes Importance of Space Research During PSI Visit
June 4, 2009 - Congresswoman Gabrielle Giffords toured the Planetary Science Institute's headquarters in Tucson on June 1 to learn more about the institute's research and outreach activities.
Giffords, who chairs the Subcommittee on Space and Aeronautics of the House Committee on Science and Technology, emphasized the importance of adequate funding for space research and praised PSI for providing high-tech jobs in her Arizona Congressional District.
Giffords also said America's space program is vital to the country because access to space near Earth has important national-security implications.
During a presentation given for Giffords, PSI Director Mark Sykes explained that understanding other planets helps us better understand Earth and has already led to a deeper understanding of the effect humans have on Earth's atmospheric processes. He also said that the long-term dominance of the United States in space will depend on whether it is the first to address the possibility of openly expanding human activity in space.
Sykes noted that PSI participates on the science and instrument teams of a number missions sponsored by NASA and other agencies. These include: Mercury MESSENGER, Dawn, Cassini, Mars Odyssey, Mars Reconnaissance Orbiter, Mars Exploration Rovers, Mars Express (European Space Agency), Hayabusa (Japanese Aerospace Exploration Agency), NEO Surveillance and Tracking (Canadian Space Agency) and Chandrayaan-1 (Indian Space Research Organization). He added that PSI has 123 currently funded NASA projects.
Congresswoman Gabrielle Giffords looks at one of the samples Planetary Science Institute scientists use to teach K-12 students about meteors and impact craters.
During a talk given for Congresswoman Gabrielle Giffords, Planetary Science Institute Director Mark Sykes describes PSI support provided to numerous NASA missions and missions sponsored by ESA, Japan, India and Canada.
Congresswoman Gabrielle Giffords talks with scientists and staff members during her visit to the Tucson-based Planetary Science Institute.
Congresswoman Gabrielle Giffords and PSI Associate Research Scientist Dan Berman use 3D glasses to view 3D images of Gale crater on Mars that were taken by NASA's High Resolution Imaging Science Experiment (HiRISE) camera. HiRISE is flying on the Mars Reconnaissance Orbiter (MRO) mission.
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.