SALT LAKE CITY – More than 150 years after a small Eurasian tree named tamarisk or saltcedar started taking over river banks throughout the U.S. Southwest, saltcedar leaf beetles were unleashed to defoliate the exotic invader.

Now, University of Utah scientists say their new study shows it is feasible to use satellite data to monitor the extent of the beetle’s attack on tamarisk, and whether use of the beetles may backfire with unintended environmental consequences.

“We don’t have any idea of the long-term impacts of using the beetles; their release may have unexpected repercussions,” says Philip Dennison, an assistant professor of geography and first author of the study scheduled for online publication later this month in the journal Remote Sensing of Environment.

“The impact of this defoliation is largely unknown,” says study co-author Kevin Hultine, a research assistant professor of biology at the University of Utah. “The net impact of controlling tamarisk could be positive or negative.”

“We would like on-the-ground scientists and managers to understand and think about the long-term impact – what are these riparian [riverbank] areas going to look like 15 years from now, and how can we can maintain ecosystems” as well as water flows for farms, cities and river recreation, Hultine says.

Dennison and Hultine conducted the study with Jim Ehleringer, a distinguished professor of biology at the University of Utah; physical scientist Pamela Nagler, of the U.S. Geological Survey in Tucson, Ariz.; and Edward Glenn, a University of Arizona environmental scientist.

A Shady Invader from Eurasia

Anyone who has rafted Southwestern rivers like the Green and Colorado knows about the shady thickets of tamarisk that line the riverbanks. The trees can grow up to 30 feet tall. There are about 10 species of tamarisk.

This 2007 infrared image from the ASTER instrument on NASA’s Terra satellite shows the effects of saltcedar leaf beetles that were released to defoliate tamarisk. An alfalfa field along the Colorado River remains vegetated and thus is bright red. But the wet “bottom” area along the Dolores River (lower right) appears much darker than in the 2006 image because the beetles have eaten tamarisk leaves. Remaining areas of bright red within the “bottom” area are due to willow and cottonwood trees. University of Utah researchers propose using satellites to monitor tamarisk defoliation by beetles in remote areas of the Southwest.

Credit: Phil Dennison, University of Utah, from NASA data.

The U.S. Animal and Plant Health Inspection Service (APHIS) says saltcedar or tamarisk is “a highly invasive, exotic weed” in the form of “a large shrub or small tree that was introduced to North America from Asia in the early 1800s. The plant has been used for windbreaks, ornamentals, and erosion control. By 1850, saltcedar had infested river systems and drainages in the Southwest, often displacing native vegetation.”

“By 1938, infestations were found from Florida to California and as far north as Idaho,” according to APHIS. “Saltcedar continues to spread rapidly and currently infests water drainages and areas throughout the United States.”

Tamarisk dominates riverbank habitats, limiting camping areas for river runners, reducing diversity and providing poor habitat for some species of wildlife. Tamarisk also raises the risk of fires that destroy cottonwoods and other native plants but not tamarisk, which re-sprouts from roots. And tamarisk forms a dense canopy, also helping wipe out competing plants. Finally, tamarisk has a bad rap as a water-sucking wastrel that dries springs, lowers water tables and reduces stream flows, even impairing boating.

Dennison and Hultine say recent research indicates tamarisk’s thirst is overstated.

“Some of the earliest research on tamarisk water use suggested tamarisk uses dramatically more water than other tree species,” Hultine says. “So a lot of estimates on water loss over entire river reaches are based on information that now has been discredited in the scientific literature.”

Hultine believes that unless aggressive programs to restore defoliated areas are implemented, tamarisk will be replaced by other invaders – Russian knapweed, Russian olive and pepperweed – that may use more water than tamarisk. Eradicating tamarisk with beetles also may reduce bird habitat, he adds.

Monitoring the Attack of the Tamarisk-Munching Beetles

The saltcedar leaf beetle, Diorhabda elongata, was brought to the U.S. from Kazakhstan. After an environmental assessment, APHIS approved them for tamarisk control.

Dennison says thousands of the beetles first were released in Utah during summer 2004, then again in summer 2005 and 2006 at locations along the Colorado River near Moab. Widespread defoliation of tamarisk in the area was noted during summer 2007.

Because long stretches of rivers in the Colorado River Basin are remote, Dennison and colleagues decided to test the feasibility of using satellite images to detect tamarisk leaf loss due to the spread of the saltcedar leaf beetles.

This 2006 infrared image of the confluence of the Colorado and Dolores rivers in Utah was taken by the ASTER instrument on NASA’s Terra satellite. The Colorado flows from north to south and the Dolores enters the image from the east. Vegetation appears bright red, including an alfalfa field along the Colorado and a wet “bottom” area along the Dolores that has extensive tamarisk, an invasive tree from Eurasia.

Credit: Phil Dennison, University of Utah, from NASA data.

They mapped 56 accessible areas already defoliated by tamarisk, and studied if the defoliation could be detected using two instruments on Terra, one of the National Aeronautics and Space Administration’s Earth-observing satellites.

Both instruments make images using red and near-infrared light. Plant pigments absorb red from sunlight and reflect near-infrared. In near-infrared images, tamarisk-covered areas appear red. Defoliated areas appear brown or black because there are no leaves to absorb red light and reflect near-infrared light. The two instruments are:

• ASTER, the Advanced Spaceborne Thermal Emission and Reflection Radiometer, obtains relatively high-resolution images, with each pixel covering an area about 50 feet long by 50 feet wide. It can detect big changes like tamarisk defoliation on an even smaller scale. It only obtains one to three images of a given area every summer.
• MODIS, the Moderate Resolution Imaging Spectroradiometer, which can detect less detail – a pixel measures about 820 feet by 820 feet. But it can see where large swaths of tamarisk have been defoliated, Dennison says. MODIS makes daily images.

Dennison says the infrequent, higher-resolution ASTER images allow researchers to map defoliated areas, while the frequent, lower-resolution MODIS images help them detect changes in vegetation over time.

The area studied included four sites along the Colorado River northeast of Moab, and a fifth site along the tributary Dolores River at the Entrada Field Station operated by the University of Utah for education and research. The five sites covered 589 acres, and within them, researchers mapped 56 polygon-shaped areas totaling 57 acres where tamarisk had been defoliated by the beetles.

ASTER measured what is known as NVDI – the normalized difference vegetation index, which is the difference between red light absorbed by plants and near-infrared light reflected by them. The index is high when plants are present, low when they are absent.

Those satellite measurements showed minor changes in vegetation at the test sites from 2005 to 2006, but a large change between 2006 and 2007 – indicating extensive defoliation of tamarisk, even though the defoliated plants regrow within about six weeks.

The satellite’s MODIS instrument used another vegetation index that also revealed widespread tamarisk defoliation at the five sites in July 2007.

While some tamarisk has died in Nevada where the beetles first were established, “we don’t understand whether repeated defoliation eventually will kill most of the trees, or will they reach some point where they’ll just have less leaf area over the entire year,” Hultine says.

The researchers also used the satellite to estimate “evapotranspiration” – the evaporation of water from soil and the transpiration or use of water by plants – to learn more about how defoliation of tamarisk affects water use. For comparison, Hultine measured sap flow through trees, which reflects how much water is used by the trees.

Satellite estimates of tamarisk water use declined modestly as the plants were defoliated, Dennison says. The findings also were consistent with earlier research indicating tamarisk is less of a water hog than previously thought.

Dennison says he and his colleagues did the study to test the feasibility of using satellites to monitor tamarisk defoliation on an ongoing basis. That, he says, could be done by federal agencies such as the Bureau of Land Management, Bureau of Reclamation and U.S. Geological Survey.

Source: University of Utah

NASA’s Cassini spacecraft has found within Saturn’s G ring an embedded moonlet that appears as a faint, moving pinprick of light. Scientists believe it is a main source of the G ring and its single ring arc.

Cassini imaging scientists analyzing images acquired over the course of about 600 days found the tiny moonlet, half a kilometer (about a third of a mile) across, embedded within a partial ring, or ring arc, previously found by Cassini in Saturn’s tenuous G ring.

The finding is being announced today in an International Astronomical Union circular. Images can be found at http://saturn.jpl.nasa.gov. A larger version of Saturn’s new moon image can be viewed here.

“Before Cassini, the G ring was the only dusty ring that was not clearly associated with a known moon, which made it odd,” said Matthew Hedman, a Cassini imaging team associate at Cornell University in Ithaca, N.Y. “The discovery of this moonlet, together with other Cassini data, should help us make sense of this previously mysterious ring.”

Saturn’s rings were named in the order they were discovered. Working outward they are: D, C, B, A, F, G and E. The G ring is one of the outer diffuse rings. Within the faint G ring there is a relatively bright and narrow, 250-kilometer-wide (150-miles) arc of ring material, which extends 150,000 kilometers (90,000 miles), or one-sixth of the way around the ring’s circumference. The moonlet moves within this ring arc. Previous Cassini plasma and dust measurements indicated that this partial ring may be produced from relatively large, icy particles embedded within the arc, such as this moonlet.

Scientists imaged the moonlet on Aug. 15, 2008, and then they confirmed its presence by finding it in two earlier images. They have since seen the moonlet on multiple occasions, most recently on Feb. 20, 2009. The moonlet is too small to be resolved by Cassini’s cameras, so its size cannot be measured directly. However, Cassini scientists estimated the moonlet’s size by comparing its brightness to another small Saturnian moon, Pallene.

Hedman and his collaborators also have found that the moonlet’s orbit is being disturbed by the larger, nearby moon Mimas, which is responsible for keeping the ring arc together.

This brings the number of Saturnian ring arcs with embedded moonlets found by Cassini to three. The new moonlet may not be alone in the G ring arc. Previous measurements with other Cassini instruments implied the existence of a population of particles, possibly ranging in size from 1 to 100 meters (about three to several hundred feet) across. “Meteoroid impacts into, and collisions among, these bodies and the moonlet could liberate dust to form the arc,” said Hedman.

Carl Murray, a Cassini imaging team member and professor at Queen Mary, University of London, said, “The moon’s discovery and the disturbance of its trajectory by the neighboring moon Mimas highlight the close association between moons and rings that we see throughout the Saturn system. Hopefully, we will learn in the future more about how such arcs form and interact with their parent bodies.”

Early next year, Cassini’s camera will take a closer look at the arc and the moonlet. The Cassini Equinox mission, an extension of the original four-year mission, is expected to continue until fall of 2010.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA’s Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

Source: NASA.

Credit: Rice University

The Martian volcano Olympus Mons is about three times the height of Mount Everest, but it’s the small details that Rice University professors Patrick McGovern and Julia Morgan are looking at in thinking about whether the Red Planet ever had – or still supports – life.

Using a computer modeling system to figure out how Olympus Mons came to be, McGovern and Morgan reached the surprising conclusion that pockets of ancient water may still be trapped under the mountain. Their research is published in February’s issue of the journal Geology.

The scientists explained that their finding is more implication than revelation. “What we were analyzing was the structure of Olympus Mons, why it’s shaped the way it is,” said McGovern, an adjunct assistant professor of Earth science and staff scientist at the NASA-affiliated Lunar and Planetary Institute. “What we found has implications for life – but implications are what go at the end of a paper.”

Co-author Morgan is an associate professor of Earth science.

In modeling the formation of Olympus Mons with an algorithm known as particle dynamics simulation, McGovern and Morgan determined that only the presence of ancient clay sediments could account for the volcano’s asymmetric shape. The presence of sediment indicates water was or is involved.

Olympus Mons is tall, standing almost 15 miles high, and slopes gently from the foothills to the caldera, a distance of more than 150 miles. That shallow slope is a clue to what lies beneath, said the researchers. They suspect if they were able to stand on the northwest side of Olympus Mons and start digging, they’d eventually find clay sediment deposited there billions of years ago, before the mountain was even a molehill.

The Martian volcano Olympus Mons is about three times the height of Mount Everest, but it’s the small details that Rice University professors Patrick McGovern and Julia Morgan are looking at in thinking about whether the Red Planet ever had — or still supports — life.

Credit: Rice University

The European Space Agency’s Mars Express spacecraft has in recent years found abundant evidence of clay on Mars. This supports a previous theory that where Olympus Mons now stands, a layer of sediment once rested that may have been hundreds of meters thick.

Morgan and McGovern show in their computer models that volcanic material was able to spread to Olympus-sized proportions because of the clay’s friction-reducing effect, a phenomenon also seen at volcanoes in Hawaii.

What may be trapped underneath is of great interest, said the researchers. Fluids embedded in an impermeable, pressurized layer of clay sediment would allow the kind of slipping motion that would account for Olympus Mons’ spread-out northeast flank – and they may still be there.

Thanks to NASA’s Phoenix lander, which scratched through the surface to find ice underneath the red dust last year, scientists now know there’s water on Mars. So Morgan and McGovern feel it’s reasonable to suspect water may be trapped in pores in the sediment underneath the mountain.

“This deep reservoir, warmed by geothermal gradients and magmatic heat and protected from adverse surface conditions, would be a favored environment for the development and maintenance of thermophilic organisms,” they wrote. This brings to mind the primal life forms found deep in Earth’s oceans, thriving near geothermal vents.

Finding a source of heat will be a challenge, they admitted. “We’d love to have the answer to that question,” said McGovern, noting evidence of methane on Mars is considered by some to be another marker for life. “Spacecraft up there have the capability to detect a thermal anomaly, like a magma flow or a volcano, and they haven’t.

“What we need is ‘ground truth’ – something reporting from the surface saying, ‘Hey, there’s a Marsquake,’ or ‘Hey, there’s unusual emissions of gas.’ Ultimately, we’d like to see a series of seismic stations so we can see what’s moving around the planet.”

Source: Rice University

Credit: NASA, ESA and R. Sharples (University of Durham, U.K.)

About 100 million light-years away, in the constellation of Piscis Austrinus (the Southern Fish), three galaxies are playing a game of gravitational give-and-take that might ultimately lead to their merger into one enormous entity. A new image from the Advanced Camera for Surveys on the NASA/ESA Hubble Space Telescope allows astronomers to view the movement of gases from galaxy to galaxy, revealing the intricate interplay among them.

The three pictured galaxies — NGC 7173 (middle left), NCG 7174 (middle right) and NGC 7176 (lower right) — are part of the Hickson Compact Group 90, named after astronomer Paul Hickson, who first catalogued these small clusters of galaxies in the 1980s. NGC 7173 and NGC 7176 appear to be smooth, normal elliptical galaxies without much gas and dust. In stark contrast, NGC 7174 is a mangled spiral galaxy, barely clinging to independent existence as it is ripped apart by its close neighbours. The strong tidal interaction surging through the galaxies has dragged a significant number of stars away from their home galaxies. These stars are now spread out, forming a tenuous luminous component in the galaxy group.

Ultimately, astronomers believe that the stars in NGC 7174 will be redistributed into a giant ‘island universe’, tens to hundreds of times as massive as our own Milky Way.

Source: ESA/Hubble Information Centre

Credit: ESO/L. Calçada

“With lots of methane in the atmosphere, it becomes clear why Pluto’s atmosphere is so warm,” says Emmanuel Lellouch, lead author of the paper reporting the results.

Pluto, which is about a fifth the size of Earth, is composed primarily of rock and ice. As it is about 40 times further from the Sun than the Earth on average, it is a very cold world with a surface temperature of about minus 220 degrees Celsius!

It has been known since the 1980s that Pluto also has a tenuous atmosphere [1], which consists of a thin envelope of mostly nitrogen, with traces of methane and probably carbon monoxide. As Pluto moves away from the Sun, during its 248 year-long orbit, its atmosphere gradually freezes and falls to the ground. In periods when it is closer to the Sun — as it is now — the temperature of Pluto’s solid surface increases, causing the ice to sublimate into gas.

Until recently, only the upper parts of the atmosphere of Pluto could be studied. By observing stellar occultations (ESO 21/02), a phenomenon that occurs when a Solar System body blocks the light from a background star, astronomers were able to demonstrate that Pluto’s upper atmosphere was some 50 degrees warmer than the surface, or minus 170 degrees Celsius. These observations couldn’t shed any light on the atmospheric temperature and pressure near Pluto’s surface. But unique, new observations made with the CRyogenic InfraRed Echelle Spectrograph (CRIRES), attached to ESO’s Very Large Telescope, have now revealed that the atmosphere as a whole, not just the upper atmosphere, has a mean temperature of minus 180 degrees Celsius, and so it is indeed “much hotter” than the surface.

In contrast to the Earth’s atmosphere [2], most, if not all, of Pluto’s atmosphere is thus undergoing a temperature inversion: the temperature is higher, the higher in the atmosphere you look. The change is about 3 to 15 degrees per kilometre. On Earth, under normal circumstances, the temperature decreases through the atmosphere by about 6 degrees per kilometre.

“It is fascinating to think that with CRIRES we are able to precisely measure traces of a gas in an atmosphere 100 000 times more tenuous than the Earth’s, on an object five times smaller than our planet and located at the edge of the Solar System,” says co-author Hans-Ulrich Käufl. “The combination of CRIRES and the VLT is almost like having an advanced atmospheric research satellite orbiting Pluto.”

The reason why Pluto’s surface is so cold is linked to the existence of Pluto’s atmosphere, and is due to the sublimation of the surface ice; much like sweat cools the body as it evaporates from the surface of the skin, this sublimation has a cooling effect on the surface of Pluto. In this respect, Pluto shares some properties with comets, whose coma and tails arise from sublimating ice as they approach the Sun.

The CRIRES observations also indicate that methane is the second most common gas in Pluto’s atmosphere, representing half a percent of the molecules. “We were able to show that these quantities of methane play a crucial role in the heating processes in the atmosphere and can explain the elevated atmospheric temperature,” says Lellouch.

Two different models can explain the properties of Pluto’s atmosphere. In the first, the astronomers assume that Pluto’s surface is covered with a thin layer of methane, which will inhibit the sublimation of the nitrogen frost. The second scenario invokes the existence of pure methane patches on the surface.

“Discriminating between the two will require further study of Pluto as it moves away from the Sun,” says Lellouch. “And of course, NASA’s New Horizons space probe will also provide us with more clues when it reaches the dwarf planet in 2015.”

Source: ESO

The anthropology world is all abuzz with a discovery in Africa that’s knocking scientists off their feet.

It’s the finding of 1.5 million-year-old fossilized human footprints in Kenya at Rutgers University’s Koobi Fora Field School.

Researchers say the ancient footprints show that some of the earliest humans walked just like we do today and also had anatomically modern feet.

The area around the human footprints was also littered with a range of animal prints, all discovered within two 1.5 million-year-old sedimentary layers near Ileret in northern Kenya.

Three footprint trails were found in the upper sediment layer. Two of them had two prints each, while the other had seven prints and numerous isolated prints. Perfectly preserved 15 feet below were one trail of two prints and a single isolated smaller print, possibly that of a child.

The discovery is detailed in this month’s issue of the journal Science.

What makes these footprints decidely human? Researchers say the big toe is parallel to the other toes, whereas in apes, it is separated for better grasping in the trees. What’s more, the footprints show a human-like arch and short toes, typically associated with walking upright. Other clues found to be within the range of modern humans were the size, spacing and depth of the impressions which provided estimates of weight, stride and gait.

The authors say the size of the footprints and their modern anatomical characteristics point to the hominid Homo ergaster, the name by which early Homo erectus is more generally known. This was the first hominid to have had the same body proportions (longer legs and shorter arms) as modern Homo sapiens. Other H. ergaster or H. erectus remains have been found in Tanzania, Ethiopia, Kenya and South Africa, at dates consistent with the Ileret footprints.

Credit: NASA/Swift/Univ. of Leicester/Bodewits et al.

GREENBELT, Md. – While waiting for high-energy outbursts and cosmic explosions, NASA’s Swift Gamma-ray Explorer satellite is monitoring Comet Lulin as it closes on Earth. For the first time, astronomers are seeing simultaneous ultraviolet and X-ray images of a comet.

“We won’t be able to send a space probe to Comet Lulin, but Swift is giving us some of the information we would get from just such a mission,” said Jenny Carter, at the University of Leicester, U.K., who is leading the study.

“The comet is releasing a great amount of gas, which makes it an ideal target for X-ray observations,” said Andrew Read, also at Leicester.

A comet is a clump of frozen gases mixed with dust. These “dirty snowballs” cast off gas and dust whenever they venture near the sun. Comet Lulin, which is formally known as C/2007 N3, was discovered last year by astronomers at Taiwan’s Lulin Observatory. The comet is now faintly visible from a dark site. Lulin will pass closest to Earth — 38 million miles, or about 160 times farther than the moon — late on the evening of Feb. 23 for North America.

On Jan. 28, Swift trained its Ultraviolet/Optical Telescope (UVOT) and X-Ray Telescope (XRT) on Comet Lulin. “The comet is quite active,” said team member Dennis Bodewits, a NASA Postdoctoral Fellow at the Goddard Space Flight Center in Greenbelt, Md. “The UVOT data show that Lulin was shedding nearly 800 gallons of water each second.” That’s enough to fill an Olympic-size swimming pool in less than 15 minutes.

Swift can’t see water directly. But ultraviolet light from the sun quickly breaks apart water molecules into hydrogen atoms and hydroxyl (OH) molecules. Swift’s UVOT detects the hydroxyl molecules, and its images of Lulin reveal a hydroxyl cloud spanning nearly 250,000 miles, or slightly greater than the distance between Earth and the moon.

The UVOT includes a prism-like device called a grism, which separates incoming light by wavelength. The grism’s range includes wavelengths in which the hydroxyl molecule is most active. “This gives us a unique view into the types and quantities of gas a comet produces, which gives us clues about the origin of comets and the solar system,” Bodewits explains. Swift is currently the only space observatory covering this wavelength range.

In the Swift images, the comet’s tail extends off to the right. Solar radiation pushes icy grains away from the comet. As the grains gradually evaporate, they create a thin hydroxyl tail.

Farther from the comet, even the hydroxyl molecule succumbs to solar ultraviolet radiation. It breaks into its constituent oxygen and hydrogen atoms. “The solar wind — a fast-moving stream of particles from the sun — interacts with the comet’s broader cloud of atoms. This causes the solar wind to light up with X rays, and that’s what Swift’s XRT sees,” said Stefan Immler, also at Goddard.

This interaction, called charge exchange, results in X-rays from most comets when they pass within about three times Earth’s distance from the sun. Because Lulin is so active, its atomic cloud is especially dense. As a result, the X-ray-emitting region extends far sunward of the comet.

“We are looking forward to future observations of Comet Lulin, when we hope to get better X-ray data to help us determine its makeup,” noted Carter. “They will allow us to build up a more complete 3-D picture of the comet during its flight through the solar system.”

Source: NASA/Goddard Space Flight Center

At a meeting in Washington last week, National Aeronautics and Space Administration and European Space Agency officials decided to continue pursuing studies of a mission to Jupiter and its four largest moons, and to plan for another potential mission to visit Saturn’s largest moon Titan and Enceladus.

Both of these proposed missions are grand endeavors that set the stage for future planetary science research. These outer planet flagship missions could eventually answer questions about how our solar system formed and whether life exists elsewhere in the universe.

The missions, called the Europa Jupiter System Mission and the Titan Saturn System Mission, are the result of NASA and ESA merging their separate mission concepts. NASA originally studied four mission concepts during 2007, which were narrowed down to two proposals in 2008. One finalist was a Europa Orbiter to explore that icy moon of Jupiter and its subsurface water ocean. The other was a Titan Orbiter to visit the Saturn moon. Independently, in 2007, ESA also initiated a competition to select its flagship mission for the Cosmic Vision 2015-2025 slot of the ESA scientific programme. Two finalists, called Laplace and Tandem, were selected by ESA for further study. Laplace was a set of spacecraft to orbit Jupiter and eventually orbit and land on Europa. Tandem was a set of spacecraft intended to orbit Titan and explore its surface, after also exploring the surface of Saturn’s moon Enceladus.

NASA and ESA engineers and scientists carefully studied both potential missions in preparation for last week’s meeting. Based on these and other studies as well as stringent independent assessment reviews, NASA and ESA agreed that the Europa Jupiter System Mission, called Laplace in Europe, was the most technically feasible to do first. However, ESA’s Solar System Working Group concluded the scientific merits of this mission and a Titan Saturn System Mission could not be separated. The group recommended, and NASA agreed, that both missions should move forward for further study and implementation.

“The decision means a win, win situation for all parties involved,” said Ed Weiler, associate administrator for NASA’s Science Mission Directorate in Washington. “Although the Jupiter system mission has been chosen to proceed to an earlier flight opportunity, a Saturn system mission clearly remains a high priority for the science community.”

Both agencies will need to undertake several more steps and detailed studies before officially moving forward.

“This joint endeavour is a wonderful new exploration challenge and will be a landmark of 21st Century planetary science,” said David Southwood, ESA Director of Science and Robotic Exploration. “What I am especially sure of is that the cooperation across the Atlantic that we have had so far and we see in the future, between America and Europe, NASA and ESA, and in our respective science communities is absolutely right. Let’s get to work.”

New Exploration Challenges at Jupiter and Saturn

The Europa Jupiter System Mission would use two robotic orbiters to conduct unprecedentedly detailed studies of the giant gaseous planet Jupiter and its moons Io, Europa, Ganymede and Callisto. NASA would build one orbiter, initially named Jupiter Europa. ESA would build the other orbiter, initially named Jupiter Ganymede. The probes would launch in 2020 on two separate launch vehicles from different launch sites. The orbiters would reach the Jupiter system in 2026 and spend at least three years conducting research.

Europa has a surface of ice, and scientists theorize it has an ocean of water beneath that could provide a home for living things. Ganymede, the largest moon in the solar system, is the only moon known to have its own internally generated magnetic field and is suspected to have a deep undersurface water ocean. Scientists long have sought to understand the causes of the magnetic field. Callisto’s surface is extremely heavily cratered and ancient, providing a clear indication of a record of events from the early history of the Solar System. Finally, Io is the most volcanically active body in the solar system.

The orbiters would spend nearly a year orbiting Europa and Ganymede. NASA’s probe would investigate whether Europa might harbor life, and ESA’s spacecraft would orbit Ganymede to conduct investigations of the surface and interior of this satellite, to better understand the formation and evolution of the Jovian system.

The Titan Saturn System Mission would consist of a NASA orbiter and an ESA lander and research balloon. The complex mission faces several technical challenges requiring significant study and technology development. NASA will continue studying and developing those technologies. Future work also will provide important input into the next Planetary Science Decadal Survey by the National Research Council of the U.S. National Academy of Sciences, which will serve as a roadmap for new NASA planetary missions to begin after 2013. On the European side, the interested community of scientists will have to re-submit the Titan mission at the next opportunity for mission proposals in the Cosmic Vision programme in the years to come.

NASA’s Jet Propulsion Laboratory in Pasadena, California, will manage NASA’s contributions to the projects for NASA’s Science Mission Directorate in Washington. ESA’s Directorate of Science and Robotic Exploration will manage the European contribution to the Jupiter mission.

Source: NASA

MOFFETT FIELD, Calif. — NASA’s Lunar Crater Observation and Sensing Satellite, known as LCROSS, is enroute from Northrop Grumman’s facility in Redondo Beach, Calif., to NASA’s Kennedy Space Center in Florida in preparation for a spring launch.

The satellite’s primary mission is to search for water ice on the moon in a permanently shadowed crater near one of the lunar poles. LCROSS is a low-cost, accelerated-development, companion mission to NASA’s Lunar Reconnaissance Orbiter, or LRO. At Kennedy, the two spacecraft will be integrated with an Atlas V launch vehicle and tested for final flight worthiness. LCROSS and LRO are the first missions in NASA’s plan to return humans to the moon and begin establishing a lunar outpost by 2020.

After launch, the LCROSS spacecraft and the Atlas V’s Centaur upper stage rocket will fly by the moon and enter into an elongated orbit to position the satellite for impact. On final approach, the spacecraft and Centaur will separate. The Centaur will strike the chosen lunar crater, creating a debris plume that will rise above the surface. Four minutes later, LCROSS will fly through the debris plume, collecting and relaying data back to Earth before striking the moon’s surface and creating a second debris plume. Scientists will use data from the debris clouds to determine the presence or absence of water ice.

“The LCROSS project has had to work within very challenging cost-cap and schedule-cap constraints,” said Dan Andrews, LCROSS project manager at NASA’s Ames Research Center in Moffett Field, Calif. “The shipping of our spacecraft is a testament to our balanced approach and the great people working on this project.”

To remain within budget and a short schedule of 26 months, the LCROSS project team developed a simple yet innovative spacecraft that uses existing NASA systems, commercial-off-the-shelf components modified to survive the harsh conditions of space, and the spacecraft design and development expertise of integration partner Northrop Grumman Space Technologies.

“LCROSS delivers a high science value per dollar,” said Steve Hixson, vice president for advanced concepts at Northrop Grumman Aerospace Systems in Redondo Beach. “With its versatile, fast and cost efficient architecture, the LCROSS spacecraft serves as a pathfinder for future low-cost Earth and space science missions.”

Ames manages the LCROSS mission and will conduct mission and science operations. Northrop Grumman designed, built, integrated and tested the spacecraft. The LCROSS and LRO missions are components of the Lunar Precursor Robotic Program at NASA’s Marshall Space Flight Center in Huntsville, Ala. The program manages pathfinding robotic missions to the moon for the Exploration Systems Mission Directorate at NASA Headquarters in Washington.

Source: NASA.

“This is one of the first images made using near-infrared interferometry,” says lead author Jean-Baptiste Le Bouquin. Interferometry is a technique that combines the light from several telescopes, resulting in a vision as sharp as that of a giant telescope with a diameter equal to the largest separation between the telescopes used. Achieving this requires the VLTI system components to be positioned to an accuracy of a fraction of a micrometre over about 100 metres and maintained so throughout the observations — a formidable technical challenge.

When doing interferometry, astronomers must often content themselves with fringes, the characteristic pattern of dark and bright lines produced when two beams of light combine, from which they can model the physical properties of the object studied. But, if an object is observed on several runs with different combinations and configurations of telescopes, it is possible to put these results together to reconstruct an image of the object. This is what has now been done with ESO’s VLTI, using the 1.8-metre Auxiliary Telescopes.

“We were able to construct an amazing image, and reveal the onion-like structure of the atmosphere of a giant star at a late stage of its life for the first time,” says Antoine Mérand, member of the team. “Numerical models and indirect data have allowed us to imagine the appearance of the star before, but it is quite astounding that we can now see it, and in colour.”

Although it is only 15 by 15 pixel across, the reconstructed image shows an extreme close-up of a star 100 times larger than the Sun, a diameter corresponding roughly to the distance between the Earth and the Sun. This star is, in turn, surrounded by a sphere of molecular gas, which is about three times as large again.

T Leporis, in the constellation of Lepus (the Hare), is located 500 light-years away. It belongs to the family of Mira stars, well known to amateur astronomers. These are giant variable stars that have almost extinguished their nuclear fuel and are losing mass. They are nearing the end of their lives as stars, and will soon die, becoming white dwarfs. The Sun will become a Mira star in a few billion years, engulfing the Earth in the dust and gas expelled in its final throes.

Mira stars are among the biggest factories of molecules and dust in the Universe, and T Leporis is no exception. It pulsates with a period of 380 days and loses the equivalent of the Earth’s mass every year. Since the molecules and dust are formed in the layers of atmosphere surrounding the central star, astronomers would like to be able to see these layers. But this is no easy task, given that the stars themselves are so far away — despite their huge intrinsic size, their apparent radius on the sky can be just half a millionth that of the Sun.

“T Leporis looks so small from the Earth that only an interferometric facility, such as the VLTI at Paranal, can take an image of it. VLTI can resolve stars 15 times smaller than those resolved by the Hubble Space Telescope,” says Le Bouquin.

To create this image with the VLTI astronomers had to observe the star for several consecutive nights, using all the four movable 1.8-metre VLT Auxiliary Telescopes (ATs). The ATs were combined in different groups of three, and were also moved to different positions, creating more new interferometric configurations, so that astronomers could emulate a virtual telescope approximately 100 metres across and build up an image.

“Obtaining images like these was one of the main motivations for building the Very Large Telescope Interferometer. We have now truly entered the era of stellar imaging,” says Mérand.

A perfect illustration of this is another VLTI image showing the double star system Theta1 Orionis C in the Orion Nebula Trapezium. This image, which was the first ever constructed from VLTI data, separates clearly the two young, massive stars from this system. The observations themselves have a spatial resolution of about 2 milli-arcseconds. From these, and several other observations, the team of astronomers, led by Stefan Kraus and Gerd Weigelt from the Max-Planck Institute in Bonn, could derive the properties of the orbit of this binary system, including the total mass of the two stars (47 solar masses) and their distance from us (1350 light-years).
Source: ESO