Friday, October 29, 2010

NASA Work Helps Better Predict World's Smoggiest Days

World's Smoggiest Days
PASADENA, Calif. – A research team led by NASA's Jet Propulsion Laboratory and the California Institute of Technology (Caltech), both in Pasadena, Calif., has fully characterized a key chemical reaction that affects the formation of pollutants in smoggy air in the world's urban areas. When applied to Los Angeles, the laboratory results suggest that, on the most polluted days and in the most polluted parts of L.A., current models are underestimating ozone levels by 5 to 10 percent.

The results—published this week in the journal Science—are likely to have "a small but significant impact on the predictions of computer models used to assess air quality, regulate emissions and estimate the health impact of air pollution," said Mitchio Okumura, professor of chemical physics at Caltech and one of the principal investigators on the research.

"This work demonstrates how important accurate laboratory measurements are to our understanding of the atmosphere," said JPL senior research scientist Stanley P. Sander, who led the JPL team's effort. "This is the first time this crucial chemical reaction has been studied by two teams using complementary methods that allow its details to be understood."

The key reaction in question in this research is between nitrogen dioxide and the hydroxyl radical. In the presence of sunlight, these two compounds, along with volatile organic compounds, play important roles in the chemical reactions that form ozone, which at ground-level is an air pollutant harmful to plants and animals, including humans.

Until about the last decade, scientists thought these two compounds only combined to form nitric acid, a fairly stable molecule with a long atmospheric life that slows ozone formation. Chemists suspected a second reaction might also occur, creating peroxynitrous acid, a less stable compound that falls apart quickly once created, releasing the hydroxyl radical and nitrogen dioxide to resume ozone creation. But until now they weren't sure how quickly these reactions occur and how much nitric acid they create relative to peroxynitrous acid. The JPL team measured this rate using a high-accuracy, JPL-built, advanced chemical reactor. The Caltech team then determined the ratio of the rates of the two separate processes.

Theoretical calculations by chemistry professor Anne McCoy at Ohio State University, Columbus, contributed to understanding of the not-well-studied peroxynitrous acid molecule.

"This work was the synthesis of two very different and difficult experiments," added lead author and former Caltech graduate student Andrew Mollner with Aerospace Corporation, El Segundo, Calif. "While neither experiment in isolation provided definitive results, by combining the two data sets, the parameters needed for air quality models could be precisely determined."

In the end, the researchers found the loss of hydroxyl radical and nitrogen dioxide is slower than previously thought—although the reactions are fast, fewer of the radicals are ending up as nitric acid than had been supposed, and more of them are ending up as peroxynitrous acid. "This means less of the hydroxyl radical and nitrogen dioxide go away, leading to proportionately more ozone, mostly in polluted areas," Okumura said.

Just how much more? To try to get a handle on how their results might affect predictions of ozone levels, they turned to Robert Harley, professor of environmental engineering at the University of California, Berkeley, and William Carter, a research chemist at the University of California, Riverside—both experts in atmospheric modeling—to look at the ratio's impact on predictions of ozone concentrations in various parts of Los Angeles in the summer of 2010.

The result: "In the most polluted areas of L.A.," said Okumura, "they calculated up to 10 percent more ozone production when they used the new rate for nitric acid formation."

Okumura said this strong effect would only occur during the most polluted times of the year, not all year long. Still, he said, considering the significant health hazards ozone can have—recent research has reported that a 10 part-per-billion increase in ozone concentration may lead to a four percent increase in deaths from respiratory causes—any increase in expected ozone levels will be important to people who regulate emissions and evaluate health risks. The precision of these results reduces the uncertainty in the models—an important step in the ongoing effort to improve the accuracy of models used by policymakers.

Okumura believes this work will cause other scientists to reevaluate recommendations made to modelers on the best parameters to use. For the team, however, the next step is to start looking at a wider range of atmospheric conditions where this reaction may also be important.

Sander agrees. "The present work focused on atmospheric conditions related to urban smog—i.e., relatively warm temperatures and high atmospheric pressure," he said. "But the hydroxyl radical/nitrogen dioxide reaction is important at many other altitudes. Future work by the two groups will focus on the parts of the atmosphere affected by long-range transport of pollution by high-altitude winds [in Earth's middle and upper troposphere] and where ozone depletion from human-produced substances is important [the stratosphere]."

The research was supported by grants from NASA, the California Air Resources Board, and the National Science Foundation, along with NASA and Department of Defense fellowships.

JPL is managed for NASA by the California Institute of Technology in Pasadena.

Thursday, October 28, 2010

Explore Energy with NASA during Earth Science Week

Earth Science Week
We all know how it feels to be low on energy after a long day. Or how it feels to be full of energy after a good night’s rest or a good meal. Energy is just as important to Earth’s everyday life as it is to ours.

“Exploring Energy” is the theme of this year’s Earth Science Week, Oct. 10-16. The American Geological Institute hosts Earth Science Week annually in cooperation with various sponsors to engage people in Earth science and encourage stewardship of Earth.

NASA develops, deploys and manages an array of satellites that monitor and measure energy as it flows into, through and out of the Earth system. During Earth Science Week, a series of short videos will be posted to NASA’s Earth Science Week website at Aimed at educators, the videos will present activities for different grade levels that highlight how NASA explores Earth’s energy, such as the energy that fuels hurricanes.

In addition, NASA has contributed to the following materials included in an educator kit designed to help teachers engage students in Earth science before, during and after this special week:

* NASA Climate and Energy Education Resources – A two-sided color information sheet lists NASA websites and other resources for Earth science news, data and imagery, and education activities and programs.
* Web Ranger Bookmark – An oversized color bookmark contains information about WebRangers, a National Park Service program through which kids can explore national parks, monuments and historic sites. The WebRangers website includes a series of activities on climate change and its potential impact on families, neighborhoods and national parks. This series and the bookmark were developed by the National Park Service, NASA and the U.S. Fish and Wildlife Service.
* Tour of the Electromagnetic Spectrum DVD – A NASA video uses 3-D animations to explain the electromagnetic spectrum and shows examples of how people interact with it on a daily basis. The video is also available online at , and a companion educators guide can be downloaded at [link to be made available in next couple weeks].
* Earth's Energy Budget Lithograph – A two-sided lithograph features a full-page color diagram illustrating the various kinds and amounts of energy that enter and leave the Earth system.
* The GLOBE Earth System Science Poster Learning Activities – An activities guide examines connections among environmental phenomena at the local, regional and global scales. The activities help students understand that the environment is a result of the interplay among many processes that take place on varying scales of time and space.
* Solar Cell Energy Nationwide Learning Activity – A MY NASA DATA lesson for grades 7-12 is featured as the March learning activity in the Earth Science Week 2010-2011 Earth Science Activity Calendar. The activity text provides background information about the sun’s energy, what happens to it upon entering Earth’s atmosphere, and the factors impacting the amount of energy produced by solar panels. Students use NASA data to determine areas of the country that are most likely to produce solar energy.

Wednesday, October 27, 2010

Wind Shear Accident Was Catalyst for Technology

Wind Shear Accident Was Catalyst for Technology
On that day 25 years ago the public affairs specialist was a young U.S. Air Force airman heading home on leave to North Carolina, flying out of Dallas Fort Worth International Airport.

"I was looking out my window, sitting at the end of the runway aboard the second airplane lined up to take off," said Creech. "I had a window seat and was looking out the window when I noticed some really, really black thunder clouds at our end of the runway. Then I saw orange, extremely bright orange, light. My brain didn't register what I was seeing."

What Creech saw was Delta Flight 191 as it crashed on landing.

"It was like a slow motion thing. There was the initial fireball, but then as the airplane rolled over, breaking apart and slowing down, the fire caught up with it and enveloped it," added Creech. "It all came to a halt directly even with my window, across the other side of the runway in the grass. As soon as the movement stopped, the rain hit. It was like a wall of rain and the fire quickly became a smoke ball, black and white smoke mixed."

"I remember our pilot coming over the intercom and saying something to the effect -- ladies and gentlemen, there has been a tragedy and I'm sorry, but we can't return to the terminal and let anyone deplane," said Creech. "Of course that was the last thing any of us wanted to hear, because anybody who saw that wasn't wanting to stay on their plane and go flying. I know I didn't."

Tail-mounted camera on NASA's 737 captures approach to thunderstorm in Colo., 1992
Click to enlarge

This photo was taken from a tail-mounted camera on board NASA’s Boeing 737 as it approached a thunderstorm during microburst wind shear research in Colorado in 1992. Credit: NASA
One hundred and thirty four people of the 163 on board the Delta Lockheed L-1011 and one person on the ground died that day, in part because of a powerful thunderstorm microburst-induced wind shear, a rare but potentially deadly downdraft.

Dave Hinton, now the deputy director of the Aeronautics Research Directorate at NASA's Langley Research Center, also remembers that accident vividly. He and a team of researchers studied it for years as part of their efforts to help develop predictive wind shear radar, a technology that is now standard on all airliners.

"That [Dallas] microburst has been modeled extensively," said Hinton. "It was very strong as microbursts go -- at the top of the range and a mile and a half to two miles in diameter. That would be easily detectable with the technologies that are out there today."

The Dallas accident, one of three fatal wind shear events in the 70s and 80s, was the catalyst for the invention of those technologies. Within months a government/industry/academia partnership started attacking the problem of wind shear from all sides.

"It was a tremendously productive cooperation between multiple agencies and companies," said Hinton. "We advanced the state of the art from basic knowledge of a meteorological phenomena to developing well-defined system requirements for on-board sensors and crew procedures."

Hinton was part of the NASA team that took to the skies in search of some of those answers. The team flew on a Langley-based Boeing 737 aircraft, equipped with airborne Doppler radar and forward-looking infrared sensors, and went looking for storms near Denver, Colo., and Orlando, Fla. Crews on the ground, from MIT Lincoln Labs and the National Center for Atmospheric Research (NCAR), staffed ground-based radars to help them find events quickly.

"We flew over a two-year period and penetrated on the order of some 70 microbursts, starting with very weak ones and working up to stronger ones," added Hinton. "We validated the models for the sensors, proving that they do in fact work as we intended."

NASA worked very closely with the Federal Aviation Administration and companies interested in building systems during the seven-year wind shear research program.

"They followed the technology development and as a result provided the credibility and basis for certification," said Hinton. "That meant that within two to three years of our wrapping up the project there were certified systems available. " Those airborne systems, better ground-based radar and improved pilot training have now virtually eliminated U.S. airliner wind shear accidents.

Tuesday, October 26, 2010

Chandra: What Lies Beneath? Magnetar Enigma Deepens


CAMBRIDGE, Mass. -- Observations with NASA’s Chandra, Swift and Rossi X-ray observatories, Fermi Gamma-ray Space Telescope and ESA’s XMM-Newton have revealed that a slowly rotating neutron star with an ordinary surface magnetic field is giving off bursts of X-rays and gamma rays. This discovery may indicate the presence of an internal magnetic field much more intense than the surface magnetic field, with implications for how the most powerful magnets in the cosmos evolve.

The neutron star, SGR 0418+5729, was discovered on June 5, 2009, when the Fermi Gamma-ray Space Telescope detected bursts of gamma-rays from this object. Follow-up observations four days later with the Rossi X-Ray Timing Explorer (RXTE) showed that, in addition to sporadic X-ray bursts, the neutron star exhibits persistent X-ray emission with regular pulsations that indicate that the star has a rotational period of 9.1 seconds. RXTE was able to monitor this activity for about 100 days. This behavior is similar to a class of neutron stars called magnetars, which have strong to extreme magnetic fields 20 to 1000 times above the average of the galactic radio pulsars.

As neutron stars rotate, the radiation of low frequency electromagnetic waves -- or winds of high-energy particles -- carry energy away from the star, causing the rotation rate of the star to gradually decrease. Careful monitoring of SGR 0418 was possible because Chandra and XMM-Newton were able to measure its pulsation period even though it faded by a factor of 10 after the initial detection. What sets SGR 0418 apart from other magnetars is that careful monitoring over a span of 490 days has revealed no detectable decrease in its rotation rate.

The lack of rotational slowing implies that the radiation of low frequency waves must be weak, and hence the surface magnetic field must be much weaker than normal. But this raises another question: Where does the energy come from to power bursts and the persistent X-ray emission from the source?

The generally accepted answer for magnetars is that the energy to power the X-ray and gamma-ray emission comes from an internal magnetic field that has been twisted and amplified in the turbulent interior of the neutron star. Theoretical studies indicate that if the internal field becomes about ten or more times stronger than the surface field, the decay or untwisting of the field can lead to the production of steady and bursting X-ray emission through the heating of the neutron star crust or the acceleration of particles.

A crucial question is how large an imbalance can be maintained between the surface and interior fields. SGR 0418 represents an important test case. The observations already imply an imbalance of between 50 and 100. If further observations by Chandra push the surface magnetic field limit lower, then theorists may have to dig deeper for an explanation of this enigmatic object.

This discovery is the result of an international teamwork from CSIC-IEEC, INAF, University of Padua, MSSL-UCL, CEA-Saclay, Sabanci University and NASA’s Marshall Space Flight Center in Huntsville, Ala. These results appear in the Oct. 14 issue of Science Express, which provides electronic publication of selected science papers in advance of print.

The Marshall Center manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra's science and flight operations from Cambridge, Mass.

Monday, October 25, 2010

NASA Simulates the Sun's Power on Earth to Test Hardware Intended for Space

NASA's Marshall Space Flight Center
In the hostile environment of space, satellites could get burned by the ultra-hot sun in front of them and chilled by the frigid cold conditions of space behind them.

Researchers at NASA's Marshall Space Flight Center in Huntsville, Ala., are using their Solar Thermal Test Facility to simulate some of the harshest conditions space has to offer to learn what these extreme temperatures can do to flight hardware close to the sun. They're currently testing Strofio, a unique NASA instrument that will fly aboard an upcoming European Space Agency mission, in this facility to test the thermal balance before the instrument is on its way to Mercury.

The facility looks like it belongs in a galaxy far, far away. A two-story tall curved mirror -- actually is made of 144 separate mirror segments, each hexagonally shaped and about 18 inches in diameter -- forms the backbone of the facility.

NASA's Marshall Space Flight Center

About 50 yards away, sitting in a field, lies another mirror tilted at a slight angle. This secondary mirror reflects the sun towards the primary mirror, which captures the energy and then focuses inside a small vacuum chamber mounted in front of the mirror’s focal point.

The giant wall of mirrors works by capturing the light from the sun and redirecting that energy to whatever happens to be sitting in the vacuum chamber. That superheats the instrument, allowing scientists to know how their hardware will behave as it nears the sun. Of course they can't use all 144 mirror segments at once -- that would beam 5000 watts worth of energy onto whatever happens to be inside the vacuum chamber. For the Strofio tests, engineers will only need to partially uncover about 26 mirror segments. They'll reach temperatures hot enough to test their instrument, but not so high that they melt away their hard work.

But that's only half the equation. Thanks to the Southwest Research Institute, the NASA facility has installed a liquid nitrogen shroud on the inside of the vacuum chamber that will flow super-cold liquid nitrogen. That will allow engineers to chill the vacuum chamber to the freezing cold temperatures, just like those in deep space.

In the front, the mirrors expose the instrument to the hotness of the sun. In the back, the nitrogen exposes it to the coldness of a vacuum. Together they accurately mimic the conditions of space, allowing scientists to test how their instrument will perform on its actual mission.

"It really gives you a good opportunity to understand how your instrument will perform in the conditions of deep space," says Dr. Jimmy Lee, mission manager for Strofio. "We're trying to understand on Earth how our tool will perform thousands of miles away in radically different conditions. That’s critical for a mission like ours."

These tests prove vital for equipment like Stofio that are destined to travel close to the sun. Strofio will fly in polar orbit around Mercury where it will determine the chemical composition of Mercury's surface using a technique called mass spectroscopy, providing a powerful new data to study the planet's geological history. It will launch with the ESA's Mercury Planetary Orbiter mission in 2014.

When Strofio reaches its orbit around mercury, the sun will expose it to temperatures over 120 degrees Celsius or 248 Fahrenheit. That's a stretch even for the relatively resilient NASA computers which historically only operate at around 24 degrees Celsius or 75 Fahrenheit. Engineers will have to continuously test Strofio to handle the tough Mercury conditions.

Friday, October 22, 2010

NASA TV Program Wins Emmy

NASA TV Program Wins Emmy
When Tom Shortridge was growing up in small Laurel, Del., with a population of 3,600, he knew he wanted to work in television. He graduated from a technical high school with a concentration in media broadcasting. There Shortridge helped produce daily school newscasts and a weekly news show that aired on local cable. He went on to major in communications in college with a minor in film and video

But the 25-year-old never guessed some day he would be part of a team that would win a regional Emmy award for a NASA TV educational program geared towards high schools students and hosted by Vince Whitfield. "NASA Launchpad" took home a statuette in the Informational/Instructional category for its episode, "Bernoulli's Principle," at the 52nd Capital Regional Emmy Awards held in Washington, June 5.

"I didn't think we even had a chance to get a nomination for the Emmy, let alone win it," said Shortridge. "I guess I'd had dreams of winning a regional Emmy, but I figured if it happened, it would be years away."

Even more amazing than the Emmy he says is the fact that he produces the show for NASA's Langley Research Center, through his employer the National Institute of Aerospace (NIA) in Hampton, Va. "If you told me when I was in high school that I'd win an Emmy working for NASA, I'd be more surprised by the NASA part," said Shortridge. "I was never that into science or engineering."

He credits the team of educators-in-residence at NIA for helping him and co-producer Scott Bednar make award-winning five to seven minute programs that apply science, technology, engineering and mathematics concepts learned in the classroom, to real world challenges.

"They're able to identify the science content to meet educational standards, which allows me to focus on the video production end of things and making sure the content is presented in a way that people like me, non-science-heads, can not only understand it, but be excited by it," said Shortridge.

Co-producers Bednar and Shortridge also work on other NASA "eClips" informational and educational projects, both web-based and broadcast on NASA TV.

Bednar also majored in electronic media and film with a concentration in TV production. "In college I had to make a decision which path to follow, science or media and working with NASA and NIA has allowed me to merge my passion for both," he said.

Like Shortridge, Bednar is at the beginning of his career. "I just turned 25 last week. The Emmy win will definitely help stave off my quarter-life crisis," said the New York Long Island native. "The Emmy nod, let alone win, was completely unexpected at this point in my career. To be honest, winning an Emmy was never even on my radar."

Also like his co-producer Bednar says the award is really a team award. "We work with such an amazing group of people that credit is truly deserved across the board," he said.

Thursday, October 21, 2010

NASA Invites Students to Study the Sun During Solar Week

Solar Week
Want to build a pinhole camera to look at an eclipse? Or learn more about how gigantic telescopes examine the sun? The place to go on the Web is from October 18-22. Twice a year, Solar Week provides a weeklong series of web-based educational activities for classrooms about our magnetic variable star, the sun, and its interactions with Earth and the solar system.

Each day of Solar Week offers a different set of lessons and games for students ranging from the upper elementary to high school level. The site covers everything from solar radiation to pursuing careers in science. For example, on Monday, after learning details about how the sun is a star just like the other ones in the sky, students can play a game to determine just where the sun lies in the Milky Way. Or on Thursday, they measure how fast a coronal mass ejection races from the sun.

Helping to answer the students’ questions on an online bulletin board will be three scientists from NASA’s Goddard Space Flight Center in Greenbelt, Md. who have been involved almost since the project began in 2000. Throughout the week, Heliophysics researchers Terry Kucera, Dawn Myers, and Holly Gilbert will be among some twenty scientists who will share their excitement about the dynamic star at the center of our solar system. “I think it’s great that the kids get direct interaction with the scientists,” says solar physicist Kucera, who is involved with the Solar and Heliospheric Observatory and the Solar Terrestrial Relations Observatory.

Currently run by UC Berkeley, Solar Week was originated by David Alexander in 2000 in coordination with his public outreach work for the Yohkoh solar observatory. He began Solar Week as a means of reaching out to girls and encouraging them in the sciences – incorporating many female solar scientists as role models. The site incorporates only women scientists, but welcomes students of both sexes. The former Sun-Earth Connection Education Forum at UC Berkeley took over Solar Week in 2003 where it is now managed by Karin Hauck and funded through spring of 2011 by NASA’s Sun-Earth Day. Berkeley has continued the tradition of incorporating student interaction with leading scientists at the forefront of Sun-Earth research. “The part of the website I enjoy most is the interactive message board because it’s dynamic,” says Hauck. “You never know what’s going to pop up. Students can be very creative with their questions, and I always learning something new from the scientists’ answers.”

Since one of the goals of Solar Week is to encourage girls to pursue STEM (science, technology, engineering, and math) careers, the Goddard scientists often have to answer questions about their jobs specifically, such as how often they travel or whether their jobs are impacted by the current economy –- and, of course, hobbies like Gilbert’s tournament pool-playing and Myers’s work as a dance teacher come up as well.

“I’m always so grateful,” says Hauck, “that these incredibly busy scientists are willing, year after year, to take time out of their very busy schedules to answer the students’ questions.”

Solar Week is ideal for students studying the solar system, the stars, or astronomy in general. It's also for kids wondering what it's like being a scientist, and pondering possible career choices. For those who miss this week, the activities remain online all year around, but the scientists won’t be available again to answer questions online until next March

Wednesday, October 20, 2010

The Moon Puts on Camo

The Moon Puts on Camo
A new geologic map of the moon's Schrödinger basin paints an instant, camouflage-colored portrait of what a mash-up the moon's surface is after eons of violent events. The geologic record at Schrödinger is still relatively fresh because the basin is only about 3.8 billion years old; this makes it the moon's second-youngest large basin (it's roughly 320 kilometers, or 200 miles, in diameter).

Schrödinger is located near the moon's south pole, a region where pockets of permanent ice are thought to exist. The map will help researchers understand lunar geologic history and identify suitable landing sites for future exploration. Scott Mest, a research scientist with the Planetary Science Institute working at NASA's Goddard Space Flight Center in Greenbelt, Md., and his colleagues created this geologic map -- the most detailed one to date -- by combining topographic data from the Lunar Orbiter Laser Altimeter, a Goddard instrument aboard the 2009 Lunar Reconnaissance Orbiter, with images and spectral data from the earlier Clementine and Lunar Prospector missions

Schrödinger is an example of an intriguing type of basin called a peak-ring. Like the basin rim (brown outer ring), the smaller and more fragmented peak ring (brown inner ring) is a mountainous region of crust that rose up after a huge object, probably measuring 35-40 kilometers, or about 21-25 miles, smacked into the moon here. These areas of raised crust are the oldest rocks in the basin and just about the only material that wasn't melted by the heat from the object's impact. The melted material was spewed in all directions and formed the plains. Patches of plains material can have slightly different textures and albedo (indicated by dark green and kelly green), probably because they cooled at different times. Fractures (black lines) formed in the basin floor as the material cooled

Schrödinger Basin is one of the few areas near the moon's south pole with evidence of recent volcanic activity. This includes lava flows from volcanic activity on the surface (beige areas) as well as explosive eruptions from a vent inside the red area; this vent has brought up dark material that mantles the plains (red area, which is newer than the beige regions). Older volcanic material is spread over a wider range (gray and lime green). More recent cratering by smaller objects has scattered material (yellow areas) near the top of the basin. Next to that (very light green beside yellow) is a region with a knobby texture that suggests loose material that could have come from cratering outside the basin or from a landslide on the basin's rim.

Tuesday, October 19, 2010

NASA Mission to Asteroid Gets Help From Hubble

Hubble Space Telescope
PASADENA, Calif. – NASA's Hubble Space Telescope has captured images of the large asteroid Vesta that will help refine plans for the Dawn spacecraft's rendezvous with Vesta in July 2011.

Scientists have constructed a video from the images that will help improve pointing instructions for Dawn as it is placed in a polar orbit around Vesta. Analyses of Hubble images revealed a pole orientation, or tilt, of approximately four degrees more to the asteroid's east than scientists previously thought.

This means the change of seasons between the southern and northern hemispheres of Vesta may take place about a month later than previously expected while Dawn is orbiting the asteroid. The result is a change in the pattern of sunlight expected to illuminate the asteroid. Dawn needs solar illumination for imaging and some mapping activities.

"While Vesta is the brightest asteroid in the sky, its small size makes it difficult to image from Earth," said Jian-Yang Li, a scientist participating in the Dawn mission from the University of Maryland in College Park. "The new Hubble images give Dawn scientists a better sense of how Vesta is spinning, because our new views are 90 degrees different from our previous images. It's like having a street-level view and adding a view from an airplane overhead."

The recent images were obtained by Hubble's Wide Field Camera 3 in February. The images complemented previous ones of Vesta taken from ground-based telescopes and Hubble's Wide Field and Planetary Camera 2 between 1983 and 2007. Li and his colleagues looked at 216 new images -- and a total of 446 Hubble images overall -- to clarify how Vesta was spinning. The journal Icarus recently published the report online.

"The new results give us food for thought as we make our way toward Vesta," said Christopher Russell, Dawn's principal investigator at the University of California, Los Angeles. "Because our goal is to take pictures of the entire surface and measure the elevation of features over most of the surface to an accuracy of about 33 feet, or the height of a three-story building, we need to pay close attention to the solar illumination. It looks as if Vesta is going to have a late northern spring next year, or at least later than we planned."

Launched in September 2007, Dawn will leave Vesta to encounter the dwarf planet Ceres in 2015. Vesta and Ceres are the most massive objects in the main asteroid belt between Mars and Jupiter. Scientists study these celestial bodies as examples of the building blocks of terrestrial planets like Earth. Dawn is approximately 216 million kilometers (134 million miles) away from Vesta. Next summer, the spacecraft will make its own measurements of Vesta's rotating surface and allow mission managers to pin down its axis of spin.

"Vesta was discovered just over 200 years ago, and we are excited now to be on the threshold of exploring it from orbit," said Bob Mase, Dawn's project manager at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We planned this mission to accommodate our imprecise knowledge of Vesta. Ours is a journey of discovery and, with our ability to adapt, we are looking forward to collecting excellent science data at our target."

The Dawn mission is managed by JPL, a division of the California Institute of Technology in Pasadena, for NASA's Science Mission Directorate at the agency's headquarters in Washington. Orbital Sciences Corporation of Dulles, Va., designed and built the spacecraft. Several international space organizations are part of the mission team.

Monday, October 18, 2010

Cassini Catches Saturn Moons in Paintball Fight

Saturn's moon Rhea
PASADENA, Calif. – Scientists using data from NASA's Cassini spacecraft have learned that distinctive, colorful bands and splotches embellish the surfaces of Saturn's inner, mid-size moons. The reddish and bluish hues on the icy surfaces of Mimas, Enceladus, Tethys, Dione and Rhea appear to be the aftermath of bombardments large and small.

A paper based on the findings was recently published online in the journal Icarus. In it, scientists describe prominent global patterns that trace the trade routes for material exchange between the moons themselves, an outer ring of Saturn known as the E ring and the planet's magnetic environment. The finding may explain the mysterious Pac-Man thermal pattern on Mimas, found earlier this year by Cassini scientists, said lead author Paul Schenk, who was funded by a Cassini data analysis program grant and is based at the Lunar and Planetary Institute in Houston.

"The beauty of it all is how the satellites behave as a family, recording similar processes and events on their surfaces, each in its own unique way," Schenk said. "I don't think anyone expected that electrons would leave such obvious fingerprints on planetary surfaces, but we see it on several moons, including Mimas, which was once thought to be rather bland."

Schenk and colleagues processed raw images obtained by Cassini's imaging cameras from 2004 to 2009 to produce new, high-resolution global color maps of these five moons. The new maps used camera frames shot through visible-light, ultraviolet and infrared filters which were processed to enhance our views of these moons beyond what could be seen by the human eye.

The new images are available at and

"The richness of the Cassini data set – visible images, infrared images, ultraviolet images, measurements of the radiation belts – is such that we can finally 'paint a picture' as to how the satellites themselves are 'painted,'" said William B. McKinnon, one of six co-authors on the paper. McKinnon is based at Washington University in St. Louis and was also funded by the Cassini data analysis program.

Icy material sprayed by Enceladus, which makes up the misty E ring, appears to leave a brighter, blue signature. The pattern of bluish material on Enceladus, for example, indicates that the moon is covered by the fallback of its own "breath."

Enceladean spray also appears to splatter the parts of Tethys, Dione and Rhea that run into the spray head-on in their orbits around Saturn. But scientists are still puzzling over why the Enceladean frost on the leading hemisphere of these moons bears a coral-colored, rather than bluish, tint.

On Tethys, Dione and Rhea, darker, rust-colored, reddish hues paint the entire trailing hemisphere, or the side that faces backward in the orbit around Saturn. The reddish hues are thought to be caused by tiny particle strikes from circulating plasma, a gas-like state of matter so hot that atoms split into an ion and an electron, in Saturn's magnetic environment. Tiny, iron-rich "nanoparticles" may also be involved, based on earlier analyses by the Cassini visual and infrared mapping spectrometer team.

Mimas is also touched by the tint of Enceladean spray, but it appears on the trailing side of Mimas. This probably occurs because it orbits inside the path of Enceladus, or closer to Saturn, than Tethys, Dione and Rhea.

In addition, Mimas and Tethys sport a dark, bluish band. The bands match patterns one might expect if the surface were being irradiated by high-energy electrons that drift in a direction opposite to the flow of plasma in the magnetic bubble around Saturn. Scientists are still figuring out exactly what is happening, but the electrons appear to be zapping the Mimas surface in a way that matches the Pac-Man thermal pattern detected by Cassini's composite infrared spectrometer, Schenk said.

Schenk and colleagues also found a unique chain of bluish splotches along the equator of Rhea that re-open the question of whether Rhea ever had a ring around it. The splotches do not seem related to Enceladus, but rather appear where fresh, bluish ice has been exposed on older crater rims. Though Cassini imaging scientists recently reported that they did not see evidence in Cassini images of a ring around Rhea, the authors of this paper suggest the crash of orbiting material, perhaps a ring, to the surface of Rhea in the not-too-distant past could explain the bluish splotches.

"Analyzing the image color ratios is a great way to really enhance the otherwise subtle color variations and make apparent some of the processes at play in the Saturn system," said Amanda Hendrix, Cassini deputy project scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "The Cassini images highlight the importance and potential effects of so-called 'space weathering' that occurs throughout the solar system – on any surface that isn't protected by a thick atmosphere or magnetic field."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo

Friday, October 15, 2010

Cluster Helps Disentangle Turbulence in the Solar Wind

Disentangle Turbulence in the Solar Wind
From Earth, the Sun looks like a calm, placid body that does little more than shine brightly while marching across the sky. Images from a bit closer, of course, show it’s an unruly ball of hot gas that can expel long plumes out into space – but even this isn’t the whole story. Surrounding the Sun is a roiling wind of electrons and protons that shows constant turbulence at every size scale: long streaming jets, smaller whirling eddies, and even microscopic movements as charged particles circle in miniature orbits. Through it all, great magnetic waves and electric currents move through, stirring up the particles even more.

This solar wind is some million degrees Celsius, can move as fast as 750 kilometers (466 statute miles) per second, and – so far – defies a complete description by any one theory. It’s hotter than expected, for one, and no one has yet agreed which of several theories offers the best explanation.

Now, the ESA/NASA Cluster mission – four identical spacecraft that fly in a tight formation to provide 3-dimensional snapshots of structures around Earth – has provided new information about how the protons in the solar wind are heated.

“We had a perfect window of 50 minutes,” says NASA scientist Melvyn Goldstein, chief of the Geospace Physics Laboratory at NASA’s Goddard Space Flight Center in Greenbelt, Md. and co-author of the new paper that appeared in Physical Review Letters on September 24. “It was a time when the four Cluster spacecraft were so close together they could watch movements in the solar wind at a scale small enough that it was possible to observe the heating of protons through turbulence directly for the first time."

Scientists know that large turbulence tends to “cascade” down into smaller turbulence -- imagine the sharply defined whitecaps on top of long ocean waves. In ocean waves, the energy from such cascades naturally adds a small amount of heat from friction as the particles shift past each other, thus heating the water slightly. But the fast, charged particles – known as “plasma” -- around the sun don’t experience that kind of friction, yet they heat up in a similar way.

“Unlike the usual fluids of everyday life,” says Fouad Sahraoui, lead author of a new paper on the solar wind and a scientist at the CNRS-Ecole Polytechnique-UPMC in France, “plasmas possess electric and magnetic fields generated by the motions of proton and electrons. This changes much of the intuitive images that we get from observing conventional fluids.”

Somehow the magnetic and electric fields in the plasma must contribute to heating the particles. Decades of research on the solar wind have been able to infer the length and effects of the magnetic waves, but direct observation was not possible before the Cluster mission watched large waves from afar. These start long as long wavelength fluctuations, but lose energy – while getting shorter – over time. Loss of energy in the waves transfer energy to the solar wind particles, heating them up, but the exact method of energy transfer, and the exact nature of the waves doing the heating, has not been completely established.

In addition to trying to find the mechanism that heats the solar wind, there’s another mystery: The magnetic waves transfer heat to the particles at different rates depending on their wavelength. The largest waves lose energy at a continuous rate until they make it down to about 100-kilometer wavelength. They then lose energy even more quickly before they hit around 2-kilometer wavelength and return to more or less the previous rate. To tackle these puzzles, scientists used data from Cluster when it was in the solar wind in a position where it could not be influenced by Earth’s magnetosphere.

For this latest paper, the four Cluster spacecraft provided 50 minutes of data at a time when conditions were just right -- the spacecraft were in a homogeneous area of the solar wind, they were close together, and they formed a perfect tetrahedral shape -- such that the instruments could measure electromagnetic waves in three dimensions at the small scales that affect protons.

The measurements showed that the cascade of turbulence occurs through the action of a special kind of traveling waves – named Alfvén waves after Nobel laureate Hannes Alfvén, who discovered them in 1941.

The surprising thing about the waves that Cluster observed is that they pointed perpendicular to the magnetic field. This is in contrast to previous work from the Helios spacecraft, which in the 1970’s examined magnetic waves closer to the sun. That work found magnetic waves running parallel to the magnetic field, which can send particles moving in tight circular orbits – a process known as cyclotron resonance -- thus giving them a kick in both energy and temperature. The perpendicular waves found here, on the other hand, create electric fields that efficiently transfer energy to particles by, essentially, pushing them to move faster.

Indeed, earlier Cluster work suggested that this process – known as Landau damping – helped heat electrons. But, since much of the change in temperature with distance from the sun is due to changes in the proton temperature, it was crucial to understand how they obtained their energy. Since hot electrons do not heat protons very well at all, this couldn’t be the mechanism.

That Landau damping is what adds energy to both protons and electrons – at least near Earth – also helps explain the odd rate change in wave fluctuations as well. When the wavelengths are about 100 kilometers or a bit shorter, the electric fields of these perpendicular waves heat protons very efficiently. So, at these lengths, the waves transfer energy quickly to the surrounding protons -- offering an explanation why the magnetic waves suddenly begin to lose energy at a faster rate. Waves that are about two kilometers, however, do not interact efficiently with protons because the electric fields oscillate too fast to push them. Instead these shorter waves begin to push and heat electrons efficiently and quickly deplete all the energy in the waves.

“We can see that not all the energy is dissipated by protons,” Sahraoui said. “The remaining energy in the wave continues its journey toward smaller scales, wavelengths of about two kilometers long. At that point, electrons in turn get heated.”

Future NASA missions such as the Magnetospheric Multiscale mission, scheduled for launch in 2014, will be able to probe the movements of the solar wind at even smaller scales.

Cluster recently surpassed a decade of passing in and out of our planet's magnetic field, returning invaluable data to scientists worldwide. Besides studying the solar wind, Cluster’s other observations include studying the composition of the earth’s aurora and its magnetosphere.

Thursday, October 14, 2010

NASA Loosens GRIP On Atlantic Hurricane Season

Atlantic Hurricane Season
NASA wrapped up one of its largest hurricane research efforts ever last week after nearly two months of flights that broke new ground in the study of tropical cyclones and delivered data that scientists will now be able to analyze for years to come.

While the 2010 hurricane season has been a rather quiet one for coastal dwellers, the churning meteorology of the Atlantic Ocean and Caribbean Sea seemed to cooperate well with the science goals of Genesis and Rapid Intensification Processes (GRIP) experiment. Those goals were designed to answer some of the most fundamental yet still unanswered questions of hurricane science: What ultimately causes hurricanes to form? Why do some tropical depressions become strong hurricanes, while others dissipate? What causes the rapid strengthening often seen in hurricanes?

Mission scientists wanted to capture data on hurricanes as they formed and intensified. Ideally, the NASA planes – the DC-8, WB-57 and Global Hawk – would also fly over systems that were weakening, or that were expected to form into hurricanes yet did not. When the flights had ended, all those goals had been met.

“It was successful beyond my reasonable expectations. It requires cooperation with the weather, and good luck with the aircraft,” said mission scientist Ed Zipser, of the University of Utah. “It's not so much a logistical challenge as it is a toss of the dice by Mother Nature during our time available. But it takes a good airplane, a skillful crew and good luck with the equipment.”

Flying to Hurricanes

Hurricanes Earl and Karl each became important objects of observation for scientists during GRIP. The DC-8 flew to Earl four times, criss-crossing the storm as it intensified to a category 4 hurricane and then weakened. On the final Earl flight, as the storm was breaking down and losing strength, the Global Hawk made its debut hurricane flight and passed over Earl’s eye in concert with the DC-8, providing valuable comparison measurements for the instruments on-board both aircraft. The WB-57 also flew Earl as well as Karl.

At the outset, scientists hoped that several aspects of GRIP would help gather important data as well as complete a couple of technical accomplishments. First, collaboration with the Air Force, NOAA and the National Science Foundation would allow scientists to observe a single storm system with as many as six aircraft. Second, GRIP featured the debut of NASA’s Global Hawk drone in a hurricane research capacity. The unmanned plane’s 24-hour flight range gave scientists the ability to directly observe a hurricane as it changed over time and distance in a way that conventional planes and satellites have not done before.

Both of these aspects of GRIP were used to great effect during the two major hurricanes observed during the campaign, Earl and Karl. “We’re all very pleased we were able to get the Global Hawk over a hurricane,” said mission scientist Gerry Heymsfield, of NASA’s Goddard Space Flight Center, Greenbelt, Md. “There was a question about that. That’s a major accomplishment both on the science side and the capability side. It really paves the way for future research.”

As the campaign went on, Global Hawk pilots, based remotely at Dryden Flight Research Center, near Palmdale, Calif., grew more comfortable with the drone’s capability at 60,000 feet and over a hurricane. On Sept. 16 and 17, the Global Hawk made a 25-hour flight that included 20 passes over the eye of Karl as it was emerging into a hurricane – precisely the type of formation and storm development that scientists hoped to capture during GRIP.

Wednesday, October 13, 2010

'A-Train' Satellites Search for 770 Million Tons of Dust in the Air

NASA's Terra satellite
Using data from several research satellites, scientists will spend the next three years trying to understand the climate impacts of about 770 million tons of dust carried into the atmosphere every year from the Sahara Desert.

Terra satellite's MODIS image of dust off the west coast of Africa
Click to enlarge

"The people who build climate models make some assumptions about dust and its impact on the climate," said Dr. Sundar Christopher, a professor of atmospheric science at The University of Alabama in Huntsville.

Christopher will use a $500,000 grant from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) mission, developed and managed by NASA's Langley Research Center in Hampton, Va.

CALIPSO is an Earth observing satellite that provides new insight into the role that clouds and atmospheric aerosols play in air quality, weather and climate. Christopher will use both CALIPSO and Aqua satellite data in his research.

Aqua was the first member launched of a group of satellites termed the Afternoon Constellation, or A-Train, a group of satellites that travel in line, one behind the other, along the same track, as they orbit Earth. Combining the information from several instruments gives a more complete answer to many questions about Earth's atmosphere than would be possible from any single satellite observation taken by itself.

Tuesday, October 12, 2010

NASA Assets Provide Orbital View to Study Phoenix Heat Waves

Phoenix Heat Waves
Where you live may say a lot about your socioeconomic status. It also may suggest how vulnerable you are to long periods of excessively hot weather.

Researchers at NASA’s Johnson Space Center, Arizona State University and the University of California at Riverside are studying the relationship between temperature variations and socioeconomic variables across metropolitan Phoenix. They have found that the urban poor are the most vulnerable to extreme heat.

Those in higher incomes tend to live in areas that are cooler due to the increased amount of vegetation, such as lush lawns and canopy trees, that surrounds homes or on higher-elevation hillslopes above the hotter Salt River valley floor. The urban poor tend to live in the urban core of metro Phoenix where the heat island effect is intense. These neighborhoods are located near industrial areas, commercial centers, and transportation corridors. There are few amenities, such as parks, and the landscaping has little or no grass or trees.

Propelled by a $1.4 million grant from the National Science Foundation as part of its Dynamics of Coupled Natural and Human Systems Program, the research team is compiling a history of the development of the metro Phoenix urban heat island. Urban heat islands result when existing soil and grass is replaced with materials such as asphalt and concrete that absorb heat during the day and reradiate it at night, thus causing increased temperatures especially during nighttime.

Sharon Harlan, a sociologist in the School of Human Evolution and Social Change at ASU, has pulled together the interdisciplinary team, which is comprised of social and natural scientists, public health experts, and educators.

Harlan is excited about the potential for this pioneering research.

“The problem of heat-related deaths and illnesses is very serious,” said Harlan. “Each year, heat fatalities in the U.S. occur in greater numbers than mortality from any other type of weather disaster. Global climate changes and rapidly growing cities are likely to compound and intensify the adverse health effects of heat islands around the world. Our research is integrating data with sophisticated modeling tools to analyze urban systems while keeping health equity considerations and the well-being of vulnerable populations at the center of attention. We want our research to be used to promote better decision-making about climate adaptation in cities.”

The primary objective of the research is to study high heat wave events—unexpected long-duration heat waves. Many cities including Chicago, Phoenix and Paris have encountered these events over the past several years.

Data from numerous sources, including remotely sensed imagery from NASA, are being used to create an historical record of how temperatures and vegetation patterns changed across metro Phoenix from the early 1970s to 2000. William Stefanov, senior geoscientist with Jacobs Technology in JSC’s Astromaterials Research and Exploration Science Directorate, is providing the orbital view of the metropolitan area.

The remotely sensed information is collected from satellites or airplanes and includes vegetation, temperature and land cover. Together it provides a map of the urban and suburban surface at a moment in time. In addition, researchers will use the data to do what is called change detection analysis. Images from one year or one season can be compared with those from another. The changes, such as those in vegetation, can be highlighted.

“We’re using a series of Landsat data for historical vegetation and surface temperature, high-resolution airborne imagery to get detailed maps of the land cover in our study neighborhoods and the Advanced Spaceborne Thermal Emission and Reflection Radiometer, or ASTER, a Japanese sensor on board the NASA Terra satellite, for current surface temperature data,” said Stefanov.

An airborne data flight over Phoenix by the NASA MODIS/ASTER Simulator, or MASTER, sensor is planned for next year to coincide with a ground data collection campaign. Among other biophysical information, high-resolution measurements of ground surface temperature will be obtained from the MASTER data throughout the metropolitan area to compare with and validate other airborne and satellite data sets used in the project.

According to several global climate change models, the southwestern United States is predicted to experience higher temperatures and more droughts over the coming century. If that happens, Phoenix is expected to experience more heat wave events.

The remotely sensed data are fed into high-resolution urban climate models to build predictive simulations of what will happen to the Phoenix metropolitan area if predicted climate change occurs there. Maps of “riskscapes” produced by this project will show where people in Phoenix are most vulnerable to high heat events.

“This project has theoretical aspects, but it also has an applied focus,” said Stefanov. “We are trying to develop tools that city planners and emergency responders can use. Urban planners also can use this data so that they can help plan the city’s growth and perhaps replace materials that absorb heat with those that are more reflective.”

“A lot of urban development is taking place around the world in arid or semiarid climates,” said Stefanov. “By studying Phoenix, researchers can better understand what these developing cities may face and how their environments may change as populations expand.”

Monday, October 11, 2010

WISE Spies a Comet with its Powerful Infrared Eye

WISE Spies a Comet
NASA's Wide-field Infrared Survey Explorer, or WISE, has discovered its first comet, one of many the mission is expected to find among millions of other objects during its ongoing survey of the whole sky in infrared light.

Officially named "P/2010 B2 (WISE)," but known simply as WISE, the comet is a dusty mass of ice more than 2 kilometers (1.2 miles) in diameter. It probably formed around the same time as our solar system, about 4.5 billion years ago. Comet WISE started out in the cold, dark reaches of our solar system, but after a long history of getting knocked around by the gravitational forces of Jupiter, it settled into an orbit much closer to the sun. Right now, the comet is heading away from the sun and is about 175 million kilometers (109 million miles) from Earth.

"Comets are ancient reservoirs of water. They are one of the few places besides Earth in the inner solar system where water is known to exist," said Amy Mainzer of NASA's Jet Propulsion Laboratory in Pasadena, Calif. Mainzer is the principal investigator of NEOWISE, a project to find and catalog new asteroids and comets spotted by WISE (the acronym combines WISE with NEO, the shorthand for near-Earth object).

"With WISE, we have a powerful tool to find new comets and learn more about the population as a whole. Water is necessary for life as we know it, and comets can tell us more about how much there is in our solar system."

The WISE telescope, which launched into a polar orbit around Earth on Dec. 14, 2009, is expected to discover anywhere from a few to dozens of new comets, in addition to hundreds of thousands of asteroids. Comets are harder to find than asteroids because they are much more rare in the inner solar system. Whereas asteroids tour around in the "main belt" between the orbits of Mars and Jupiter, large numbers of comets orbit farther away, in the icy outer reaches of our solar system.

Both asteroids and comets can fall into orbits that bring them close to Earth's path around the sun. Most of these "near-Earth objects" are asteroids but some are comets. WISE is expected to find new near-Earth comets, and this will give us a better idea of how threatening they might be to Earth.

"It is very unlikely that a comet will hit Earth," said James Bauer, a scientist at JPL working on the WISE project, "But, in the rare chance that one did, it could be dangerous. The new discoveries from WISE will give us more precise statistics about the probability of such an event, and how powerful an impact it might yield."

The space telescope spotted the comet during its routine scan of the sky on January 22. Sophisticated software plucked the comet out from the stream of images pouring down from space by looking for objects that move quickly relative to background stars. The comet discovery was followed up by a combination of professional and amateur astronomers using telescopes across the United States.

A teacher also teamed up with an observer to measure comet WISE using a home-built telescope next to a cornfield in Illinois. Their research is part of the International Astronomical Search Collaboration, an education program that helps teachers and students observe comets and asteroids (more information is online at ).

All the data are catalogued at the Minor Planet Center, in Cambridge, Mass., the worldwide clearinghouse for all observations and orbits of minor planets and comets.

Comet WISE takes 4.7 years to circle the sun, with its farthest point being about 4 astronomical units away, and its closest point being 1.6 astronomical units (near the orbit of Mars). An astronomical unit is the distance between Earth and the sun. Heat from the sun causes gas and dust to blow off the comet, resulting in a dusty coma, or shell, and a tail.

Though this particular body is actively shedding dust, WISE is also expected to find dark, dead comets. Once a comet has taken many trips around the sun, its icy components erode away, leaving only a dark, rocky core. Not much is known about these objects because they are hard to see in visible light. WISE's infrared sight should be able to pick up the feeble glow of some of these dark comets, answering questions about precisely how and where they form.

"Dead comets can be darker than coal," said Mainzer. "But in infrared light, they will pop into view. One question we want to answer with WISE is how many dead comets make up the near-Earth object population."

The mission will spend the next eight months mapping the sky one-and-a-half times. A first batch of data will be available to the public in the spring of 2011, and the final catalog a year later. Selected images and findings will be released throughout the mission.

JPL manages the Wide-field Infrared Survey Explorer for NASA's Science Mission Directorate, Washington. The principal investigator, Edward Wright, is at UCLA. The mission was competitively selected under NASA's Explorers Program managed by the Goddard Space Flight Center, Greenbelt, Md. The science instrument was built by the Space Dynamics Laboratory, Logan, Utah, and the spacecraft was built by Ball Aerospace & Technologies Corp., Boulder, Colo. Science operations and data processing take place at the Infrared Processing and Analysis Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA. The ground-based observations are partly supported by the National Science Foundation. The Minor Planet Center is funded by NASA.

Wednesday, October 6, 2010

IBEX Finds Surprising Changes at Solar Boundary

Interstellar Boundary ExplorerWhen NASA launched the Interstellar Boundary Explorer (IBEX) on October 19, 2008, space physicists held their collective breath for never-before-seen views of a collision zone far beyond the planets, roughly 10 billion miles away. That’s where the solar wind, an outward rush of charged particles and magnetic fields continuously spewed by the Sun, runs into the flow of particles and fields that permeates interstellar space in our neighborhood of the Milky Way galaxy.

No spacecraft had ever imaged the collision zone, which occurs in a region known as the heliosheath, because it emits no light. But the two detectors on IBEX are designed to “see” what the human eye cannot. The interaction of the solar wind and interstellar medium creates energetic neutral atoms of hydrogen, called ENAs, that zip away from the heliosheath in all directions. Some of these atoms pass near Earth, where IBEX records their arrival direction and energy. As the spacecraft slowly spins, the detectors gradually build up pictures of the ENAs as they arrive from all over the sky.

Mission scientists got their first surprise six months after launch, once the spacecraft had scanned enough overlapping strips of sky to create a complete 360° map. Instead of recording a relatively even distribution all the way around, as expected, IBEX found that the counts of ENAs — and thus the strength of the interaction in the heliosheath — varied dramatically from place to place. The detectors even discovered a long, enhanced “ribbon,” accentuated by an especially intense hotspot or “knot,” arcing across the sky. (IBEX Explores Galactic Frontier, Releases First-Ever All-Sky Map)

Now scientists have finished assembling a second complete sweep around the sky, and IBEX has again delivered an unexpected result: the map has changed significantly. Overall, the intensity of ENAs has dropped 10% to 15%, and the hotspot has diminished and spread out along the ribbon. Details of these findings appear in the September 27th issue of Journal of Geophysical Research (Space Physics).

“We thought we might detect small changes occurring gradually throughout the Sun’s 11-year-long activity cycle, but not over just 6 months,” notes David McComas (Southwest Research Institute), principal investigator for the IBEX mission and the paper’s lead author. “These observations show that the interaction of the Sun with the interstellar medium is far more dynamic and variable than anyone envisioned.”

In the past, space physicists had little notion of what to expect along the boundary where the Sun’s own magnetic bubble, the heliosphere, meets interstellar space. Even though the solar wind travels outward at roughly a million miles per hour, it still takes about a year to reach the heliosphere’s edge. Also, the encounter zone within the heliosheath is believed to be several billion miles thick (roughly Pluto’s distance from the Sun). Finally, the ENAs take another six months to many years to complete the return trip back to Earth, depending on their direction and energy.

With ENAs starting out from such a wide range of distances and traveling back toward Earth at different speeds, IBEX mission scientists had expected that any highs and lows in intensity arising within the heliosheath would be hopelessly smeared out in the spacecraft’s all-sky maps. So they’re elated by the variations and changes seen so far by IBEX. These early results hint that the solar wind and the interstellar flow might be interacting in a thinner layer than many researchers had imagined possible.

McComas says the dropoff in intensity between the two all-sky maps perhaps makes sense, because the Sun is only now emerging from an unusually long period of very low activity and a correspondingly weak solar wind. The fewer the solar-wind particles that reached the heliosheath in recent years, the fewer the ENAs that got created. “We didn’t plan it this way,” says McComas, “but it’s an almost perfect situation, in that we’re seeing the interaction in its simplest state — before trying to interpret what turns out to be a much more complicated interaction than anticipated.”

Tuesday, October 5, 2010

NASA Study Sees Earth's Water Cycle Pulse Quickening

Earth's Water Cycle Pulse QuickeningFreshwater is flowing into Earth's ocean in greater amounts every year, thanks to more frequent and extreme storms related to global warming, according to a first-of-its-kind study by a team of NASA and university researchers.

The team, led by Tajdarul Syed of the Indian School of Mines, Dhanbad, India, and formerly with the University of California, Irvine, used NASA and other world-scale satellite observations to track total water volume flowing from the continents into the ocean each month. They found 18 percent more water fed into the world's ocean from rivers and melting polar ice sheets in 2006 than in 1994. The average annual rise was 1.5 percent.

"That might not sound like much – 1.5 percent a year – but after a few decades, it's huge," said Jay Famiglietti, UC Irvine Earth system science professor and principal investigator on the study, published this week in the Proceedings of the National Academy of Sciences. He noted that while freshwater is essential to humans and ecosystems, the rain is falling in all the wrong places, for all the wrong reasons.

"In general, more water is good," Famiglietti said. "But here's the problem: Not everybody is getting more rainfall, and those who are may not need it. What we're seeing is exactly what the Intergovernmental Panel on Climate Change predicted – that precipitation is increasing in the tropics and the Arctic Circle with heavier, more punishing storms. Meanwhile, hundreds of millions of people live in semiarid regions, and those are drying up."

Famiglietti said the evaporation and precipitation cycle taught in grade school is accelerating dangerously because of higher temperatures fueled by greenhouse gases. Hotter weather above the ocean causes freshwater to evaporate faster, which leads to thicker clouds unleashing more powerful storms over land. The resulting rainfall then travels via rivers to the sea in ever-larger amounts, and the cycle begins again.

"Many scientists and models have suggested that if the water cycle is intensifying because of climate change, then we should be seeing increasing river flow. Unfortunately, there is no global discharge measurement network, so we have not been able to tell," wrote Famiglietti and Syed.

Satellite records of sea-level rise, precipitation and evaporation were used to create a unique 13-year record – the longest and first of its kind. The trends the researchers found were all the same: increased evaporation from the ocean that led to increased precipitation on land and more flow back into the ocean.

Among the NASA data used in the ongoing study are measurements from the NASA/European Topex/Poseidon and Jason-1 satellite altimeters and the NASA/German Aerospace Center Gravity Recovery and Climate Experiment (GRACE) satellites. The study is funded by NASA and Earth system science fellowships.

"As we turn up the thermostat on planet Earth, it's not just higher temperatures we have to think about," said co-author Josh Willis of NASA's Jet Propulsion Laboratory, Pasadena, Calif. "Long-term changes in rainfall will be a part of climate change too. What we've shown here is that we now have the tools to see global climate change as it occurs – not just the warming, but changes in the hydrological cycle as well."

The researchers cautioned that although they had analyzed more than a decade of data, it was still a relatively short time frame. Natural ups and downs that appear in climate data make detecting long-term trends challenging. Further study is needed, they said, and is underway.

Other authors of the study include Don Chambers of the University of South Florida, Tampa, Fla.; and Kyle Hilburn of Remote Sensing Systems, Santa Rosa, Calif.

Monday, October 4, 2010

NASA Ames Scientists Train the Next Generation of Earth Explorers

NASA Ames Scientists
South of the San Francisco Bay is a 100-year tidal floodplain near NASA Ames Research Center, Moffett Field, Calif. Because of the potential for flooding, Ames purchased a segment of the mud flats for flood storm management, and has used the area for field experiments to teach and train gifted science students about the practical benefits of studying the tidal salt marsh and its wildlife.

For the last eight years, NASA Ames Earth Science Division has been participating in a student internship program called DEVELOP. Funding comes through the Applied Sciences Program in the Earth Science Division in the Science Mission Directorate at NASA Head Quarters. It is a training and development program that provides an opportunity for talented science students to learn and use sophisticated NASA technology, while mentored by science advisors from NASA and partner agencies. At the completion of the program, students share their research results with local communities, demonstrating how NASA science measurements and predictions can be used to address local policy issues.

“Every summer is full of surprises. Our students usually work on some aspect of the South Bay Salt Ponds Restoration Project,” said Jay Skiles, a research scientist and program science mentor at NASA Ames. “This year, one of our student teams studied the sedimentation now taking place in the salt ponds after some of the levees were purposely breached. The DEVELOP program is a great way for students to learn science skills and meet professionals in the field.”

During the past two centuries, the San Francisco Bay has lost an estimated 85 percent of its historic wetlands to fill or alteration. This dramatic decline in the wetlands has caused a severe impact to tidal marsh habitats and the fish and wildlife. In addition, the changed environment has increased the risk of local floods, according to South Bay Salt Ponds Restoration Project literature.

To help restore the wetlands, one of the first defenses was to build levees that separate the ponds from the tides. It was expected that once the levees breach, the sediment from the ponds would evolve into tidal marsh. In addition, by phasing the restoration of tidal marsh over many years, the need for large volumes of sediment also would be reduced.

NASA scientists regularly mentor and teach students about the scientific method, using inquiry and data collecting as a means of assessment and resolution. At Ames, scientists have taken a proactive role monitoring and studying fluvial (stream) and coastal flood sources. In this case, they helped a team of students, ranging from high school to university graduates, model the sediment deposits to predict marsh habitat development.

“I heard about the internship program while I was attending San Francisco State University,” said Michelle Newcomer, a master’s student at SFSU and a DEVELOP team member. “I applied because it sounded really exciting. I wanted to apply my geographic information system (GIS) and remote sensing skills to a real-world project.”

The five-member team called themselves the Salt Pond Restoration Sedimentation Team. They identified four project objectives: (1) track sediment transport pathways to determine the source of sediment in the South Bay; (2) calibrate satellite imagery with the collected suspended sediment concentration measurements, using Landsat 5 imagery, and data and imagery from NASA satellite instruments Moderate Resolution Imaging Spectroradiometer (MODIS), and Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER); (3) create a GIS model to predict sediment deposition and (4) assess the applicability of remote sensing for predicting sediment deposition during restoration.

“We focused on two salt ponds in the Alviso complex, one of which was referred to as Pond A21. Coyote Creek is the waterway that connects the pond to the Bay. We also were interested in Pond A6 because it is the next pond to be breached; we wanted to use our model to forecast marsh accumulation in A6,” said Newcomer.

To predict marsh accumulation, students used the marsh sedimentation model, called MarSed, which was implemented in a geographic information systems platform. The conceptual model has different variables that effect marsh accumulation, including the concentration of suspended sediments, how quickly sediment settles, and time of flooding. Field work was necessary to get the suspended sedimentation measurements.

Field work consisted of going out into the San Francisco Bay on pontoon boats, provided by NASA’s Disaster Assistance and Rescue Team (DART) facility. While on the boats, students collected water samples at the bay’s surface, and recorded their exact location using a Global Positioning System (GPS) device.

Once samples were collected, students began processing them at the U.S. Geological Survey laboratory in Menlo Park, Calif.

The team concluded that (1) the delta and Coyote Creek are primary sources of suspended sediment to the Alviso ponds, (2) suspended sediment concentrations could successfully be detected using remote sensing, (3) sediment deposition for Pond A21 was successfully predicted using remote sensing and GIS techniques, and (4) Pond A6 is predicted to reach equilibrium conditions stable enough for vegetation colonization after 60 months of tidal inundation.

The team reported that restoration managers can use these products as a tool for determining the locations of pond breaches, as well as understanding the time frame of future marsh development.

“We knew that we wanted our calibrated model to do well. At the end of the project, we were all very happy, and felt accomplished that we had actually got it to work,” said Newcomer.