Learning Can Be a 'Drag'

When Ajay Ramesh and Prithvi Aiyaswamy, two seventh graders from Chaboya Middle School, San Jose, Calif., visited the Fluid Mechanics Laboratory at NASA Ames Research Center they found that the principles of fluid mechanics are not such a 'drag' after all. The two youngsters both showed up for their experiment with a half dozen toy cars they found at home. "Our project is to find the best design shape that has the least amount of drag," said Aiyaswamy. "As we began the experiment, we realized that cars with a sloping shape perform better." The orange liquid behind the car illustrates the wake, which can be used to determine drag for the car. The green lines across illustrate the air moving across the car.

The boys were fortunate to request their visit when the Fluid Mechanics Laboratory was uniquely set up to accommodate their request. Kurtis Long, test engineer at the Fluid Mechanics Lab received permission for the boys to visit and donated his lunch hour to help the boys perform their test.

The boys placed the cars in a pool of water. Dye was added to the water and photos were taken of the dye flowing around the toy cars. "Air and water have the same flow characteristics, but by using water we can slow down time and see the flow more clearly," explained Long. With these photos, the boys could measure the drag of each car. The orange liquid behind the car illustrates the wake, which can be used to determine the car's drag. The green lines across illustrate air moving across the car.

Preparing Discovery for Flight

A specialized transporter brought the payload canister to Launch Pad 39A in preparation for the STS-131 mission. The canister, which is the same dimensions as the shuttle's cargo bay, held the Leonardo supply module during the move from processing to the shuttle. Leonardo will be packed inside space shuttle Discovery for launch. In this image, the payload canister holding the Leonardo supply module is hoisted to the clean room at Launch pad 39A.

Mars' Concepcion Crater

NASA's Mars Exploration Rover Opportunity took this image in preparation for the first autonomous selection of an observation target by a spacecraft on Mars.

Opportunity used its navigation camera to take this image after a drive during the 2,172nd Martian day, or sol, of its mission on Mars (March 4, 2010). Using newly developed and uploaded software named Autonomous Exploration for Gathering Increased Science, or AEGIS, the rover analyzed the image to identify the feature that best matched criteria given for selecting a target. The top target that Opportunity selected with AEGIS is shown by the yellow marker. AEGIS was directed to look for rocks that were larger and darker in color. The rover then used the software to take more detailed observations of the selected target using its panoramic camera.

The more-than-50 rocks in this image are near a young crater called 'Concepcion' and might have been thrown outward by the impact that excavated the crater.

Earth’s Real Movers and Shakers Star in Tectonic Model

When it comes to 3-D puzzles, Rubik's cube pales in comparison with the latest creation from JPL Geophysicist Donald Argus and colleagues Chuck DeMets of the University of Wisconsin-Madison and Richard Gordon of Rice University, Houston. The trio has just put the finishing touches on a 20-year effort to precisely describe the relative movements of the 25 interlocking tectonic plates that account for about 97 percent of Earth's surface.

Earth's tectonic plates are in constant motion, sliding past one another as they float atop our planet's molten interior. Their collisions and shifts can create mountain ranges or cause earthquakes, like the ones that struck Haiti and Chile this year.

A new model uses measurements from mid-ocean ridges (yellow and green) to precisely describe the movements of interlocking tectonic plates that make up about 97 percent of Earth's surface. Image credit: D. Sandwell/Scripps Institute of Oceanography and W. H. F. Smith/NOAA

The model, called MORVEL, for "Mid-Ocean Ridge Velocities," significantly improves the resolution and precision of the researchers' previous model of tectonic plate velocities published in 1990. It can be used to predict how each tectonic plate moves in relation to other plates, and allows scientists to predict future plate movements and identify places where movements have changed over time, areas that are useful for studying the underlying forces that control plate movements.

For more information on MORVEL, see the Rice news release at: http://www.news.wisc.edu/releases/15916 .

For more information visit http://www.nasa.gov/topics/earth/features/tectonic20100322.html

New Coming Attractions Trailer Shows an Exciting Webb Telescope Mission

Picture yourself in a movie theater waiting for the main attraction to begin and the scent of popcorn wafts through the air. The screen lights up with coming attractions and you see a "movie trailer" that you think is really cool. That's what the latest promotional video for NASA's James Webb Space Telescope is like, but instead of a coming Hollywood blockbuster, it is about the future of space astronomy.

This new 90 second video produced at NASA hurls the viewer through space and asks if you can imagine seeing 13 billion years back in time, see the first stars, galaxies evolve and solar systems form. That's what the Webb telescope is going to show us after it launches in four years.

The movie trailer also shows some of the technological highlights included in the Webb space telescope, and creates excitement for the mission.

The James Webb Space Telescope is the next-generation premier space observatory, exploring deep space phenomena from distant galaxies to nearby planets and stars. The telescope will give scientists clues about the formation of the universe and the evolution of our own solar system, from the first light after the Big Bang to the formation of star systems capable of supporting life on planets like Earth.

The video was created by Michael McClare, Senior Producer in the multi-media group at NASA's Goddard Space Flight Center, Greenbelt, Md. McClare said,"It struck me that the perfect way to highlight the Webb Telescope’s mission is with a movie trailer-like production. The challenge is creating something that grabs the viewer right away. Then, in the next 90-seconds explain the mission's science goals, tease its revolutionary technology and hopefully, elicit interjections like, 'Cool!' and 'Wow!' for this incredible endeavor. It’s only the first of series of media features planned. I’m excited to be part of this extraordinary mission and some of that excitement found its way into the movie trailer."

The 1.7-minute Webb movie trailer is available in many formats. Credit: NASA/Goddard/Mike McClare

It took a super-computer to create the science parts of the movie trailer and a collaborative "movie-making" effort. Those visuals were based on theoretical super-computer models and NASA worked with the National Center for Supercomputing Applications to create them.

People do not need to run to the theater to see the movie trailer they just need to get on the Internet. The video is available in various formats, High Resolution DVCPro HD, High Resolution Photo JPG, QuickTime format (720 H.264), MPEG-4 (1280x720 29.97) and h264. Mov format. All of these will be available at NASA's Scientific Visualization Studio Web site: http://svs.gsfc.nasa.gov/, or at the James Webb Space Telescope mission Web Site: http://www.jwst.nasa.gov.

This "movie trailer" has a lot of production behind it, in terms of designing and building the telescope. In fact, this effort is multinational because the Webb telescope is a joint project of NASA, the European Space Agency and the Canadian Space Agency.

The movie trailer had its debut at the American Astronautical Society's Robert H. Goddard Memorial Symposium, in Greenbelt on March 11 and will air for all time on the Internet for all to enjoy. The Webb telescope's "major motion picture" begins when it launches in 2014!

The movie trailer is available in various formats at:
› svs.gsfc.nasa.gov/goto?10565

For more information about the Webb Telescope, visit:
› www.jwst.nasa.gov

For more information visit http://www.nasa.gov/topics/universe/features/webb-movie-trailer.html

NASA Mars Rover Getting Smarter as it Gets Older

PASADENA, Calif. -- NASA's Mars Exploration Rover Opportunity, now in its seventh year on Mars, has a new capability to make its own choices about whether to make additional observations of rocks that it spots on arrival at a new location.

Software uploaded this winter is the latest example of NASA taking advantage of the twin Mars rovers' unanticipated longevity for real Martian test drives of advances made in robotic autonomy for future missions.

Now, Opportunity's computer can examine images that the rover takes with its wide-angle navigation camera after a drive, and recognize rocks that meet specified criteria, such as rounded shape or light color. It can then center its narrower-angle panoramic camera on the chosen target and take multiple images through color filters.

"It's a way to get some bonus science," said Tara Estlin of NASA's Jet Propulsion Laboratory, Pasadena, Calif. She is a rover driver, a senior member of JPL's Artificial Intelligence Group and leader of development for this new software system.

Images taken through three of the filters in Opportunity's new software are combined into this approximately true-color view of the rock, which is about the size of a football. Image credit: NASA/JPL-Caltech/Cornell University

The new system is called Autonomous Exploration for Gathering Increased Science, or AEGIS. Without it, follow-up observations depend on first transmitting the post-drive navigation camera images to Earth for ground operators to check for targets of interest to examine on a later day. Because of time and data-volume constraints, the rover team may opt to drive the rover again before potential targets are identified or before examining targets that aren't highest priority.

The first images taken by a Mars rover choosing its own target show a rock about the size of a football, tan in color and layered in texture. It appears to be one of the rocks tossed outward onto the surface when an impact dug a nearby crater. Opportunity pointed its panoramic camera at this unnamed rock after analyzing a wider-angle photo taken by the rover's navigation camera at the end of a drive on March 4. Opportunity decided that this particular rock, out of more than 50 in the navigation camera photo, best met the criteria that researchers had set for a target of interest: large and dark.

This false color view results from the first observation of a target selected autonomously by a spacecraft on Mars. Image Credit: NASA/JPL-Caltech/Cornell University

"It found exactly the target we would want it to find," Estlin said. "This checkout went just as we had planned, thanks to many people's work, but it's still amazing to see Opportunity performing a new autonomous activity after more than six years on Mars."

Opportunity can use the new software at stopping points along a single day's drive or at the end of the day's drive. This enables it to identify and examine targets of interest that might otherwise be missed.

"We spent years developing this capability on research rovers in the Mars Yard here at JPL," said Estlin. "Six years ago, we never expected that we would get a chance to use it on Opportunity."

The developers anticipate that the software will be useful for narrower field-of-view instruments on future rovers.

NASA's Mars Exploration Rover Opportunity took this image in preparation for the first autonomous selection of an observation target by a spacecraft on Mars. Image Credit: NASA/JPL-Caltech

Other upgrades to software on Opportunity and its twin, Spirit, since the rovers' first year on Mars have improved other capabilities. These include choosing a route around obstacles and calculating how far to reach out a rover's arm to touch a rock. In 2007, both rovers gained the know-how to examine sets of sky images to determine which ones show clouds or dust devils, and then to transmit only the selected images. The newest software upload takes that a step further, enabling Opportunity to make decisions about acquiring new observations.

The AEGIS software lets scientists change the criteria it used for choosing potential targets. In some environments, rocks that are dark and angular could be higher-priority targets than rocks that are light and rounded, for example.

This new software system has been developed with assistance from NASA's Mars Exploration Rover Project and with funding from the New Millennium Program, the Mars Technology Program, the JPL Interplanetary Network Development Program, and the Intelligent Systems Program. The New Millennium Program tests advanced technology in space flight. JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover Project for the NASA Science Mission Directorate, Washington.

More information about the Mars rovers is online at: http://www.nasa.gov/rovers. More information about AEGIS is at: http://scienceandtechnology.jpl.nasa.gov/newsandevents/newsdetails/?NewsID=677.

For more information visit http://www.nasa.gov/mission_pages/mer/news/mer20100323.html

NASA Ames 'Tops Out' First Building in Thirty Years

"Beam me up!" was the message signed on the final beam hoisted into place on the iron skeleton of NASA’s new building, called Sustainability Base, Friday, March 12, 2010.

Although not yet completed, Sustainability Base has begun ushering in a new era of innovation, good will and renewed American tradition. Under construction at NASA’s Ames Research Center, Moffett Field, Calif., the building advances the standard for what it means to be “green.” Sustainability Base is expected to achieve a platinum rating under the Leadership in Energy and Environmental Design (LEED) standards for environmentally sustainable. The building, however, goes beyond LEED to serve as a showcase of NASA and partner ingenuity, incorporating technologies designed for space exploration and applied to improve life here on our home planet. Sustainability Base will be a window to the future on Earth.

The final beam was placed as the building, called Sustainability Base, reached its height and completed its skeletal structure. Photo Credit: NASA

"It will be one of the greenest and highest performance building in the federal government," said Steve Zornetzer, associate administrator of NASA Ames. "Today is a good day to celebrate. It's a good day to stop, reflect and show appreciation for work that was well done."

Together, NASA and Swinerton Builders workers and management signed the final beam as part of a celebration, called the "Topping Out." No one really knows how or when it originated, but the tradition places an evergreen tree, a flag or both on the last beam as it is lifted into place, it signifies the structure has reached its height and the skeleton is completed.

"As a company, we are proud to be part of a green effort that is so successful," said Dan Beyer, vice president of Swinerton Builders., San Francisco, Calif. "The tree signifies new growth as the building construction comes to fruition and is used over time; the flag represents who we are as Americans."

"It will be one of the greenest and highest performance buildings in the federal government," said Steve Zornetzer, associate administrator of NASA Ames. "Today is a good day to celebrate. It's a good day to stop, reflect and show appreciation for work that was well done." Photo Credit: NASA

Over the years, the Topping Out custom remains important to ironworkers in the steel construction industry. For some, the evergreen symbolizes the successful completion of construction without loss of life, for others, it’s a good luck charm for the occupants. Similarly, the flag also has multiple meanings: the construction of a federal building, patriotism, or the American dream. Whatever the interpretation, it welcomes the future while providing a link with the past.

"We need buildings like this to bring back America," said John W. Elwood, vice president of Swinerton, Builders, Santa Clara, Calif. "The flag represents our full support for our country and our American troops. The evergreen tree is our good luck charm."

For more information visit http://www.nasa.gov/topics/nasalife/features/sustainability_base.html

X-15 Pilot Robert White Dies

On July 17, 1962, Major Robert White flew the X-15 to an altitude of 314,750 feet, or 59 miles, becoming the first "winged astronaut." He was the first to fly at Mach 4, Mach 5 and Mach 6; he was the first to fly a winged vehicle into space. After a career of 'firsts' White died on March 17, 2010.

White was one of the initial pilots selected for the X-15 program, representing the Air Force in the joint program with NASA, the Navy, and North American Aviation. Between April 13, 1960, and Dec. 14, 1962, he made 16 flights in the rocket-powered aircraft.

His July 17, 1962, flight to an altitude of 314,750 feet set a world record. This was 59.6 miles, significantly higher than the 50 miles the Air Force accepted as the beginning of space, qualifying White for astronaut wings. The X-15 rocket-powered aircraft were built by North American Aviation and developed to provide in-flight information and data on aerodynamics, structures, flight controls and the physiological aspects of high-speed, high-altitude flight.

X-15 with test pilot Major Robert M. White. Credit: NASA.

A follow-on program used the aircraft as testbeds to carry various scientific experiments beyond the Earth's atmosphere on a repeated basis. Information gained from the highly successful X-15 program contributed to the development of the Mercury, Gemini and Apollo manned spaceflight programs, and also the space shuttle program. The X-15s made a total of 199 flights and the first aircraft X-15-1, serial number 56-6670, is now located at the National Air and Space Museum in Washington, D.C.

According to an article by Al Hallonquist, White's achievements as an X-15 pilot "allowed him to become the fifth American to attain astronaut wings and only the second Air Force pilot to do this."

White retired from the Air Force as a Major General.

For more information visit http://www.nasa.gov/topics/aeronautics/features/robert-white.html

Cassini Shows Saturnian Roller Derby, Strange Weather

From our vantage point on Earth, Saturn may look like a peaceful orb with rings worthy of a carefully raked Zen garden, but NASA's Cassini spacecraft has been shadowing the gas giant long enough to see that the rings are a rough and tumble roller derby. It has also revealed that the planet itself roils with strange weather and shifting patterns of charged particles. Two review papers to be published in the March 19 issue of the journal Science synthesize Cassini's findings since arriving at Saturn in 2004.

"This rambunctious system gives us a new feel for how an early solar system might have behaved," said Linda Spilker, a planetary scientist and the new Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "This kind of deep, rich data can only be collected by an orbiting spacecraft, and we look forward to the next seven years around Saturn bringing even more surprises."

In the paper describing the elegant mess of activity in the rings, lead author Jeff Cuzzi, Cassini's interdisciplinary scientist for rings and dust who is based at NASA Ames Research Center, Moffett Field, Calif., describes how Cassini has shown us that collisions are routine and chunks of ice leave trails of debris in their wakes. Spacecraft data have also revealed how small moons play tug-of-war with ring material and how bits of rubble that would otherwise join together to become moons are ultimately ripped apart by the gravitational pull that Saturn exerts.

During equinox, the period when sunlight hits the rings exactly edge-on, Cassini witnessed rings that are normally flat - about tens of meters (yards) thick - being flipped up as high as the Rocky Mountains.

The spacecraft has also shown that the rings are composed mostly of water ice, with a mysterious reddish contaminant that could be rust or small organic molecules similar to those found in red vegetables on Earth.

"It has been amazing to see the rings come to life before our very eyes, changing even as we watch, being colorful and taking on a tangible, 3-D nature," Cuzzi said. "The rings were still a nearly unstructured object in even the best telescopes when I was a grad student, but Cassini has brought us an intimate familiarity with them."

This natural color view from the Cassini spacecraft highlights the myriad gradations in the transparency of Saturn's inner rings. Image credit: NASA/JPL/Space Science Institute

Cuzzi said Cassini scientists were surprised to find such fine-scale structure nearly everywhere in the rings, forcing them to be very careful about generalizing their findings across the entire ring disk. The discovery that the rings are clumpy has also called into question some of the previous estimates for the mass of the rings because there might be clusters of material hidden inside of the clumps that have not yet been measured.

In the review paper on Saturn's atmosphere, ionosphere and magnetosphere, lead author Tamas Gombosi, Cassini's interdisciplinary scientist for magnetosphere and plasma science who is based at the University of Michigan in Ann Arbor, describes how Cassini helped scientists understand a south polar vortex that has a diameter 20 to 40 times that of a terrestrial hurricane, and the bizarrely stable hexagon-shaped jet stream at the planet's north pole. Cassini scientists have also calculated a variation in Saturn's wind speeds at different altitudes and latitudes that is 10 times greater than the wind speed variation on Earth.

According to Gombosi's paper, Cassini has also shown us that the small moon Enceladus, not the sun or Saturn's largest moon Titan, is the biggest contributor of charged particles to Saturn's magnetic environment. The charged particles from Enceladus, a moon that features a plume of water vapor and other gases spraying from its south polar region, also contribute to the auroras around the poles of the planet.

"We learned from Cassini that the Saturnian magnetosphere is swimming in water," Gombosi said. "This is unique in the solar system and makes Saturn's plasma environment particularly fascinating."

Of course, Cassini's intense investigation has opened up a host of new mysteries. For example, Cassini has shown us images of occasional cannon-ball-like objects that rocket across one of the outer rings known as the F ring, without many clues about where they came from or why they quickly disappear.

Learning more about a kind of radio emission known as "kilometric radiation" at Saturn has unsettled debates about the planet's rotation rate rather than settled them. While the regular periods of kilometric radiation have given scientists a sense of the rotation rate at Jupiter, Saturn has clocked different periods for the radiation during NASA's Voyager flybys in 1980 and 1981 and the nearly six years of Cassini's investigations. The modulations vary by about 30 seconds to a minute, but they shouldn't be varying at all. The inconsistency may be related to a source in the magnetic bubble around the planet rather than the core of the gas giant, but scientists are still debating.

"Cassini has answered questions we were not even smart enough to ask when the mission was planned and raised a lot of new ones," Cuzzi said. "We are hot on the trail, though."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the project for NASA's Science Mission Directorate in Washington. The Cassini orbiter was designed, developed and assembled at JPL.

More Cassini information is available at http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.

For more information visit http://www.nasa.gov/mission_pages/cassini/whycassini/cassini20100318.html

ISS Photography: 100 Million Words

If a picture is worth a thousand words, then the Expedition 22 crew aboard the International Space Station is about to complete the generation of 100 million words worth of information.

That’s because Commander Jeff Williams and Flight Engineers Max Suraev, Oleg Kotov, T.J. Creamer, and Soichi Noguchi are expected to snap a total of 100,000 images by the end of their mission in Earth orbit.

Expedition 22 Commander Jeffrey Williams works with test samples in the Human Research Facility 2 Refrigerated Centrifuge as a part of the Nutritional Status Assessment experiment in the International Space Station's Columbus laboratory. Credit: NASA

Williams is setting a record that surpasses his own previous record of 83,856 images taken during Expedition 13 in 2006.

“This week we broke my old Exp. 13 record for number of Earth photos,” Williams “tweeted” from the station. “Later, after landing and recovery, I will post some of best.”

Among those digital still images is this spectacular nighttime image taken of Houston, Texas, the home of Mission Control and astronaut training, and the hub of the International Space Station Program that unites five space agencies and 15 countries in peaceful exploration and scientific research.

Williams and Suraev will end their five-and-a-half-month stay on the station Thursday, when they undock their Soyuz spacecraft and head for a landing in Kazakhstan. They were part of both the Expedition 21 and 22 crews. Kotov, Creamer and Noguchi will stay on orbit, snapping more photos, for two more months before returning home after being part of both the Expedition 22 and 23 crews.

All told, space station crews so far have amassed a total of almost 639,000 images. Those images include photos that document life and work aboard the space station, and photos that document the condition of the home planet from its unique perspective 220 miles above Earth. Their efforts are part of a larger collection that began with Earth observations photos during the Gemini Program of the 1960s. Many of the images are used in scientific research about the Earth, its climate, its resources and the effects humans are having on both.

The Houston metropolitan area at night is featured in this image photographed by an Expedition 22 crew member on the International Space Station. Credit: NASA

The recent STS-130 space shuttle mission delivered a new observation deck known as the cupola that offers the largest window ever flown on a spacecraft, and the upcoming STS-131 shuttle mission to the station will deliver the Window Observational Research Facility (WORF), which will provide a new facility dedicated to multi- and hyper-spectral remote sensing and high resolution Earth observation photography to enhance the use of the best optical-quality window ever flown in space, in the U.S. Destiny Laboratory.

For more information about Earth observations photography, visit the Gateway to Astronaut Photography of the Earth at:

http://eol.jsc.nasa.gov

For more information about WORF, visit:

http://www.nasa.gov/mission_pages/station/science/experiments/WORF.html

For more information about the International Space Station, visit:

http://www.nasa.gov/station

For more information visit http://www.nasa.gov/mission_pages/station/expeditions/expedition22/iss_photography.html

NASA's Spitzer Unearths Primitive Black Holes

Astronomers have come across what appear to be two of the earliest and most primitive supermassive black holes known. The discovery, based largely on observations from NASA's Spitzer Space Telescope, will provide a better understanding of the roots of our universe, and how the very first black holes, galaxies and stars came to be.

"We have found what are likely first-generation quasars, born in a dust-free medium and at the earliest stages of evolution," said Linhua Jiang of the University of Arizona, Tucson. Jiang is the lead author of a paper announcing the findings in the March 18 issue of Nature.

This artist's conception illustrates one of the most primitive supermassive black holes known (central black dot) at the core of a young, star-rich galaxy. Image credit: NASA/JPL-Caltech

Black holes are beastly distortions of space and time. The most massive and active ones lurk at the cores of galaxies, and are usually surrounded by doughnut-shaped structures of dust and gas that feed and sustain the growing black holes. These hungry, supermassive black holes are called quasars.

As grimy and unkempt as our present-day universe is today, scientists believe the very early universe didn't have any dust -- which tells them that the most primitive quasars should also be dust-free. But nobody had seen such immaculate quasars -- until now. Spitzer has identified two -- the smallest on record -- about 13 billion light-years away from Earth.

The quasars, called J0005-0006 and J0303-0019, were first unveiled in visible light using data from the Sloan Digital Sky Survey. That discovery team, which included Jiang, was led by Xiaohui Fan, a coauthor of the recent paper at the University of Arizona. NASA's Chandra X-ray Observatory had also observed X-rays from one of the objects. X-rays, ultraviolet and optical light stream out from quasars as the gas surrounding them is swallowed.

"Quasars emit an enormous amount of light, making them detectable literally at the edge of the observable universe," said Fan.

When Jiang and his colleagues set out to observe J0005-0006 and J0303-0019 with Spitzer between 2006 and 2009, their targets didn't stand out much from the usual quasar bunch. Spitzer measured infrared light from the objects along with 19 others, all belonging to a class of the most distant quasars known. Each quasar is anchored by a supermassive black hole weighing more than 100 million suns.

Of the 21 quasars, J0005-0006 and J0303-0019 lacked characteristic signatures of hot dust, the Spitzer data showed. Spitzer's infrared sight makes the space telescope ideally suited to detect the warm glow of dust that has been heated by feeding black holes.

"We think these early black holes are forming around the time when the dust was first forming in the universe, less than one billion years after the Big Bang," said Fan. "The primordial universe did not contain any molecules that could coagulate to form dust. The elements necessary for this process were produced and pumped into the universe later by stars."

These two data plots from NASA's Spitzer Space Telescope show a primitive supermassive black hole (top) compared to a typical one. Image credit: NASA/JPL-Caltech

The astronomers also observed that the amount of hot dust in a quasar goes up with the mass of its black hole. As a black hole grows, dust has more time to materialize around it. The black holes at the cores of J0005-0006 and J0303-0019 have the smallest measured masses known in the early universe, indicating they are particularly young, and at a stage when dust has not yet formed around them.

Other authors include W.N. Brandt of Pennsylvania State University, University Park; Chris L. Carilli of the National Radio Astronomy Observatory, Socorro, N.M.; Eiichi Egami of the University of Arizona; Dean C. Hines of the Space Science Institute, Boulder, Colo.; Jaron D. Kurk of the Max Planck Institute for Extraterrestrial Physics, Germany; Gordon T. Richards of Drexel University, Philadephia, Pa.; Yue Shen of the Harvard Smithsonian Center for Astrophysics, Cambridge, Mass.; Michael A. Strauss of Princeton, N.J.; Marianne Vestergaard of the University of Arizona and Niels Bohr Institute in Denmark; and Fabian Walter of the Max Planck Institute for Astronomy, Germany. Fan and Kurk were based in part at the Max Planck Institute for Astronomy when this research was conducted.

The Spitzer observations were made before the telescope ran out of its liquid coolant in May 2009, beginning its "warm" mission.

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate in Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology in Pasadena. Caltech manages JPL for NASA. For more information about Spitzer, visit http://www.spitzer.caltech.edu/spitzer and http://www.nasa.gov/spitzer .

For more information visit http://www.nasa.gov/mission_pages/spitzer/news/spitzer20100317.html

Planck Mission Images Galactic Web of Cold Dust

Tendrils of the coldest stuff in our galaxy can be seen in a new, large image from Planck, a mission surveying the whole sky to learn more about the birth of our universe.

Planck, a European Space Agency-led mission with important participation from NASA, launched into space in May 2009 from Kourou, French Guiana. The space telescope has almost finished its first of at least four separate scans of the entire sky, a voluminous task that will be completed in early 2012.

The new image, available online at http://www.nasa.gov/mission_pages/planck/pia12964.html highlights a swath of our Milky Way galaxy occupying about one-thirteenth of the entire sky. It shows the bright band of our galaxy's spiral disk amidst swirling clouds where gas and dust mix together and, sometimes, ignite to form new stars. The data were taken in the so-called far-infrared portion of the light spectrum, using two of nine different frequencies available on Planck.

"We've got huge amounts of data streaming down from space," said Ulf Israelsson, the NASA project manager for the mission at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "The intricate process of sorting through all of it has begun."

Planck images a galactic web of cold dust. Image credit: ESA and the HFI Consortium, IRAS

The mission's primary objective is to map the cosmic microwave background -- relic radiation left over from the Big Bang that created our universe about 13.7 billion years ago. Planck's state-of-the-art technology will provide the most detailed information yet about the size, mass, age, geometry, composition and fate of the universe.

In addition to cosmological questions like these, the mission will address such astronomy topics as star formation and galactic structure. Its observations will be used in synergy with data from other missions, such as the Herschel Space Observatory, another ESA mission with important NASA participation, and NASA's Spitzer Space Telescope.

"Planck is the first big cosmology mission that will also have a large impact on our understanding of our galaxy, the Milky Way," said Charles Lawrence, the mission's NASA project scientist at JPL. "We can see the cold dust and gas that permeate our galaxy on very large scales, while other missions like Herschel can zoom in to see the detail."

Filamentary structures in our Milky Way galaxy are apparent at large scales and small scales. Image credit: ESA and the HFI Consortium

Planck is scheduled to release a first batch of astronomy data, called the Early Release Compact Source Catalog, in Jan. 2011. Cosmology results on the first two years' worth of data are expected to be released in Dec. 2012.

Planck is a European Space Agency mission, with significant participation from NASA. NASA's Planck Project Office is based at JPL. JPL contributed mission-enabling technology for both of Planck's science instruments. European, Canadian, U.S. and NASA Planck scientists will work together to analyze the Planck data. More information is online at http://www.nasa.gov/planck and http://www.esa.int/planck .

For more information visit http://www.nasa.gov/mission_pages/planck/planck20100317.html

Surprise Shrimp Under Antarctic Ice

At a depth of 600 feet beneath the West Antarctic ice sheet, a small shrimp-like creature managed to brighten up an otherwise gray polar day in late November 2009. This critter is a three-inch long Lyssianasid amphipod found beneath the Ross Ice Shelf, about 12.5 miles away from open water. NASA scientists were using a borehole camera to look back up towards the ice surface when they spotted this pinkish-orange creature swimming beneath the ice. Credit: NASA

For more information visit http://www.nasa.gov/topics/earth/features/antarctic-shrimp.html

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Soviet Union Lunar Sample Return Missions

The Soviet Union successfully executed three robotic sample return missions as part of the Cold War competition with the United States. The first mission, Luna 16, returned a small sample (101 grams) from Mare Fecunditatis in September of 1970, a time between the US Apollo 12 and 14 manned landings. A year and half later (February 1972) Luna 20 returned 55 grams of soil from the Apollonius highlands region.

On Feb. 21, 1972, Luna 20 soft landed in the rugged highlands between Mare Fecunditatis and Mare Crisium. The next day a sample return capsule blasted off carrying 55 grams of lunar soil. The Luna 20 descent stage still sits silently on the Moon, clearly visible in LROC NAC image M119482862RE. Credit: NASA/Goddard/Arizona State University

Luna 16 and 20 were very similar in design and sampling method. A drill at the end of the sampling arm collected soil from a few tens of cm below the surface. The arm then placed the sample into the return capsule on top of the vehicle. The distinctive shadow seen in the LROC image of Luna 20 is most likely that of the sampling arm. The Luna 20 sample contained minerals similar to those sampled by the US Apollo 16 astronauts two months later from the Cayley plains (8°58"S, 15°30"E).

Luna 16 robotic sample return spacecraft. Image courtesy National Space Science Data Center.

Enlargement of Luna 20 descent stage. Note the shadow of the sampling arm. Credit: NASA/Goddard/Arizona State University

In October of 1974 Luna 23 set down on Mare Crisium, however technical difficulties prevented it from successfully acquiring a sample. Undeterred, the Soviets tried again in August of 1976, this time with much better luck. Luna 24 was designed to auger over 2 meters into the lunar soil thus collecting a better section and a larger sample, 170 grams. The positions of Luna 23 and 24 were not well constrained and are reported as within several hundred meters of each other. From the new NAC images we can accurately measure the distance between the two landers to be about 2400 meters. However the absolute position of the landers is only know to about 500 meters accuracy. As the LRO mission ephemeris improves, the Luna absolute positions should be known to better than 100 meters. Scroll around in a mosaic of two NAC high Sun images (M111185087L,R) and find Luna 23 and Luna 24. Look for a few very bright pixels near Luna 24; they may be small pieces of material blown off the descent stage as the ascent staged blasted off towards Earth.

Luna 24 sitting on the edge of a 60 meter diameter crater, NAC image M119449091RE. Credit: NASA/Goddard/Arizona State University

The successful Soviet Luna sample return missions returned small, but important, samples from three locations on the Moon. In this new era of lunar exploration several countries plan to soft land on the Moon in the near future, the first soft-landed spacecraft since Luna 24. India and Russia plan to launch a lander and rover called Chandrayaan 2 in 2013. The Chinese Chang'e lunar exploration program also plans a soft landing in 2013.

For more information visit http://www.nasa.gov/mission_pages/LRO/multimedia/lroimages/lroc-20100316-luna.html

See Spot on Jupiter. See Spot Glow.

New thermal images from powerful ground-based telescopes show swirls of warmer air and cooler regions never seen before within Jupiter's Great Red Spot, enabling scientists to make the first detailed interior weather map of the giant storm system.

The observations reveal that the reddest color of the Great Red Spot corresponds to a warm core within the otherwise cold storm system, and images show dark lanes at the edge of the storm where gases are descending into the deeper regions of the planet. These types of data, detailed in a paper appearing in the journal Icarus, give scientists a sense of the circulation patterns within the solar system's best-known storm system.

"This is our first detailed look inside the biggest storm of the solar system," said Glenn Orton, a senior research scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif., who was one of the authors of the paper. "We once thought the Great Red Spot was a plain old oval without much structure, but these new results show that it is, in fact, extremely complicated."

New thermal images from powerful ground-based telescopes show swirls of warmer air and cooler regions never seen before within Jupiter's Great Red Spot. Image credit: NASA/JPL/ESO and NASA/ESA/GSFC

Sky gazers have been observing the Great Red Spot in one form or another for hundreds of years, with continuous observations of its current shape dating back to the 19th century. The spot, which is a cold region averaging about 110 Kelvin (minus 260 degrees Fahrenheit) is so wide about three Earths could fit inside its boundaries.

The thermal images obtained by giant 8-meter (26-foot) telescopes used for this study -- the European Southern Observatory's Very Large Telescope in Chile, the Gemini Observatory telescope in Chile and the National Astronomical Observatory of Japan's Subaru telescope in Hawaii -- have provided an unprecedented level of resolution and extended the coverage provided by NASA's Galileo spacecraft in the late 1990s. Together with observations of the deep cloud structure by the 3-meter (10-foot) NASA Infrared Telescope Facility in Hawaii, the level of thermal detail observed from these giant observatories is comparable to visible-light images from NASA's Hubble Space Telescope for the first time.

One of the most intriguing findings shows the most intense orange-red central part of the spot is about 3 to 4 Kelvin (5 to 7 degrees Fahrenheit) warmer than the environment around it, said Leigh Fletcher, the lead author of the paper, who completed much of the research as a postdoctoral fellow at JPL and is currently a fellow at the University of Oxford in England. This temperature differential might not seem like a lot, but it is enough to allow the storm circulation, usually counter-clockwise, to shift to a weak clockwise circulation in the very middle of the storm. Not only that, but on other parts of Jupiter, the temperature change is enough to alter wind velocities and affect cloud patterns in the belts and zones.

"This is the first time we can say that there's an intimate link between environmental conditions -- temperature, winds, pressure and composition - and the actual color of the Great Red Spot," Fletcher said. "Although we can speculate, we still don't know for sure which chemicals or processes are causing that deep red color, but we do know now that it is related to changes in the environmental conditions right in the heart of the storm."

Unlocking the secrets of Jupiter's giant storm systems will be one of the targets for infrared spacecraft observations from future missions including NASA's Juno mission.

For more information visit http://www.nasa.gov/topics/solarsystem/features/jupiter20100316.html

Digital Elevation Models of the Moon

Robotic exploration missions provide NASA vast amounts of data to prepare for future human exploration missions and learn more about the universe.

Objective: The U.S. Geological Survey (USGS) is working with NASA to make lunar maps. Digital elevation models (DEMs) will be used to map terrain, locate lunar resources and assess prospective landing sites.

Description: The USGS constructed this DEM of a 50x80 km area of the Aristarchus Plateau, including the “Cobra Head.” Using Apollo Panoramic Camera images, the elevation of each lunar feature is calculated to an accuracy of 0.75 to 1.2 m.

Timeframe: The new Lunar Mapping and Modeling Project (LMMP) Web site, available in late fall 2010, will build integrated data sets from the Lunar Reconnaissance Orbiter (LRO), and other lunar missions over the next two years. The USGS generated maps will be available on that Web site.

Application: An integrated, easy-to-use Web site allows easy access to current lunar data and can be used by any scientist, student or lunar explorer.

For more information visit http://www.nasa.gov/exploration/multimedia/highlights/2010-09B.html

Version 1.2 of the NASA App is Now Available!

The first official NASA App invites you to discover a wealth of NASA information right on your iPhone or iPod Touch. The NASA App collects, customizes and delivers an extensive selection of dynamically updated information, images and videos from various online NASA sources in a convenient mobile package. It is available free of charge on the App Store from Apple directly on iPhone and/or iPod Touch or within iTunes.

What's new in version 1.2:

• Facebook® Connect for easy sharing of images, videos, tweets and mission information
• Integrated Twitter™ client for posting, retweeting, replying to, and direct messaging
• NASAImages.org collection - With over 125,000 new images to browse and search
• "Center" button for the orbital tracking feature
• Advanced search option
• Offline caching system

Version 1.1 changes:

• Visible sighting opportunities listed for the International Space Station (ISS) and Space Shuttle, by home location and through search for location
• Richer Mission details and more content
• Enhancements to Videos and Updates panels
• High-resolution image option (configured in device settings)
• Status updates on upcoming launches
• Prevent sleep mode setting for tracking launches (configured in device settings)

The Application Features These Screens:







For more information about the NASA's App for iPhone or iPod touch, visit:

http://www.nasa.gov/nasaapp

For more information visit http://www.nasa.gov/topics/nasalife/features/iphone-V-1-2.html

NACA Credo

The NACA’s credo: “It shall be the duty of the advisory committee for aeronautics to supervise and direct the scientific study of the problems of flight with a view to their practical solution.

Image credit: NACA

For more information visit http://www.nasa.gov/centers/ames/news/features/2010/image_sign.html

The Lunar Far Side as Seen by the Lunar Orbiter Laser Altimeter

Topography data from the Lunar Orbiter Laser Altimeter (LOLA) aboard the Lunar Reconnaissance Orbiter reveal a violent impact history on the far side of the Moon. Scientists are using LOLA data to identify and map the distribution of impact craters and basins on the lunar surface, which in turn reveals information about the age of the lunar crust and early bombardment of the Solar System.

Credit: NASA/Goddard Space Flight Center

For more information visit http://www.nasa.gov/mission_pages/LRO/multimedia/lroimages/lola-20100312-farside.html

Solar 'Conveyor Belt' Runs at Record-High Speeds

Solar physicist David Hathaway of NASA's Marshall Space flight Center in Huntsville, AL and graduate student Lisa Rightmire of the University of Memphis in Tennessee have been monitoring the sun using the Solar and Heliospheric Observatory (SOHO). They observe a massive circulating current of fire (hot plasma) within the sun operating at a faster pace as reported in the March 12th issue of Science.

Diagram of the distribution of the sun's magnetic field over three 11-year solar cycles. Yellow represents magnetic field directed out of the sun. Blue represents magnetic field into the sun. Sunspots themselves produce the "Butterfly" pattern at low latitudes. The sun's meridional flow from the equator to the poles in each hemisphere carries magnetic remains of the sunspots to the poles. This produces the streaks seen at higher latitudes and reverses the magnetic polarity of the sun's poles every 11 years. Image credit: NASA/MSFC/David Hathaway

The current of fire is a conveyor belt-like system called the Meridional Flow which rises to the surface at the sun's equator and spreads out toward the poles where it sinks back into the sun. "Normally it reaches peak speeds of about 20 mph," says Hathaway. "However, in 2004 the speed increased to nearly 30 mph and has remained that fast since."

Video showing the association of magnetic field with sunspots and coronal loops.

The faster pace is a revelation because it occurred during the deepest solar minimum in almost 100 years and indications that the next solar cycle will be a weak one. This contradicts some theories that say a fast pace results in increased sunspot production. But it agrees with others that say a fast pace results in decreased sunspot production.

The faster rate of currents on the sun and the expected weaker solar cycle have affects for those of us here on Earth. One affect is the temperature increase of the Earth could slow down, there would be fewer auroras, and to the extent that we depend on satellites, GPS, and cell phones there should be less disruption in service.

For more information about the sun's meridional flow:
"Solar 'Current of Fire' Speeds Up" (Science@NASA article)
"Variations in the Sun's Meridional Flow Over a Solar Cycle" (Science magazine article)

For more information visit http://www.nasa.gov/topics/solarsystem/features/solar_plasma.html

Crisium's Region of Interest

The region of interest located in Mare Crisium is a compelling Exploration site for many reasons. First, this site was visited by several Soviet landers - Luna 23 and Luna 24 both touched down in Crisium. Luna 24 succeeded in returning a 170 gram sample in 1976. Though the amount was small, it provided a wealth of information and an interesting mystery. The Luna 24 basalt has a titanium dioxide content of about 1%, placing it among the lowest abundances of any lunar basalt sampled. The titanium content of basalts on the Moon varies widely, from almost none up to nearly 15%; a much wider range than typically seen on Earth. Because samples were only returned from a few limited locations on the Moon, we use remote sensing data to fill in the gaps of our knowledge (read this PSRD article for more details!). Basalts that are rich in titanium absorb more light in ultraviolet and visible wavelengths than those with less titanium, and many people have used this relationship to estimate titanium contents for mare basalts across the Moon. However, in the case of Mare Crisium, the remote sensing estimates put the titanium abundance at two to four times higher than what is seen in the Luna 24 samples. Plus, the way the light is reflected from the samples (the reflectance spectrum) looks different from what spacecraft observe for Mare Crisium. Other landing sites for which we have samples and that we have observed with spacecraft do not show this difference. So what is happening in Mare Crisium, and why should we care?

Boulders on a wrinkle ridge in Mare Crisium may help us understand the geology of this Constellation region of interest. The scene is 460 meters across; image number M119469420LE. Credit: NASA/Goddard/Arizona State University/The Ohio State University

Scientists love a good mystery, but it's also important because titanium is both a valuable resource that could be utilized when people return to the Moon, and titanium abundances can tell us about the lunar interior. Basalts formed by partially melting the lunar mantle billions of years ago, and the wide range in titanium contents can tell us about the wide range of compositions and processes in the lunar mantle. Most of the high titanium basalts appear to be concentrated on the lunar nearside. But why? A straightforward interpretation of the lunar magma ocean theory, where the Moon was partially or completely molten just after its formation, suggests that titanium should be globally distributed, but that's clearly not the case. Human exploration of this region will produce valuable sampling and fieldwork to address this question.

The geology of this site is also compelling. The Constellation site is located near the rim of the Crisium impact basin (see image below), and samples and field work would give insight into the processes that occurred during the formation of the basin, as well as the age of the basin. Was this impact basin part of the so-called lunar cataclysm? This site also contains beautiful wrinkle ridges, sites of compressive stresses that resulted in faulting and wrinkling of the mare basalt surface. In the image below, you can even see a wrinkle-ridge ring, where a buried crater localized the stresses.

A WAC monochrome image centered on the Crisium Constellation region of interest. The highlands area in the south is the rim of the Crisium impact basin and wrinkle ridges and a wrinkle-ridge ring can be seen in the mare to the north. Arrow shows the location of the NAC frame above. Scene is 62 km across; image number M117107778ME Credit: NASA/GSFC/Arizona State University

In the WAC monochrome image above, the arrow indicates the location of the NAC frame at the beginning of this post, which shows a portion of a wrinkle ridge. A fascinating feature of this ridge when seen in high resolution is that its face is littered with boulders. Perhaps these boulders are generated by breakup of the of the mare basalt, and they're visible now because of the faulting and folding that caused this ridge. (Judge for yourself in the full-resolution NAC frame here.) Lunar scientists (but not engineers!) love boulders because they usually come from below the surficial regolith layer, and can indicate buried rock units of different compositions. Some have suggested that perhaps Luna 24 sampled a basalt unit that was buried by a subsequent lava flow of a different composition, and only exposed on the surface where impact craters excavated the material from depth. This scenario would explain why spacecraft don't see the sampled material widespread on the surface. Visiting the Crisium region of interest could help scientists unravel this interesting puzzle.

For more information visit http://www.nasa.gov/mission_pages/LRO/multimedia/lroimages/lroc-2010310-crisium.html

Three FASTSAT Instruments Pass Tests

The outer layers of Earth's atmosphere hold many secrets yet to be uncovered and three scientific instruments will fly soon on the FASTSAT-HSV01 satellite and seek to uncover them to benefit us here on Earth. Known as MINI-ME, PISA and TTI, these instruments recently passed a series of important final tests to prove their readiness for spaceflight.

These instruments were conceived and built at NASA's Goddard Space Flight Center in Greenbelt, Md., and were integrated to the satellite and tested at NASA's Marshall Spaceflight Center, Huntsville, Ala.

MINI-ME, acronym for Miniature Imager for Neutral Ionospheric atoms and Magnetospheric Electrons, is a low energy neutral atom imager which will detect neutral atoms formed in the plasma population of the Earth's outer atmosphere to improve global space weather prediction. Low energy neutral atom imaging is a technique first pioneered at Goddard which allows scientists to observe remotely various trapped charged particle populations around Earth that we would normally only be able to observe in-situ through direct instrument contact with the particles.

Michael Collier, Principal Investigator for the MINI-ME instrument at NASA Goddard said, "The satellite has gone through vibration, thermal, and Electromagnetic Interference (EMI) tests and everything looks great. The MINI-ME instrument is performing as expected."

PISA is an acronym for the Plasma Impedance Spectrum Analyzer, which will test a new measurement technique for the thermal electron populations in the ionosphere, and their density structuring, which can interfere with or scatter radio signals used for communication and navigation. PISA will tell scientists on Earth when and where the ionosphere becomes structured or turbulent. That will give us better predictions of how space weather will affect GPS signals.

The MINI-ME instrument. Credit: NASA

Doug Rowland, PISA's Principal Investigator at NASA Goddard said, "PISA has completed the same tests that the Mini-ME endured and has just passed powered Electromagnetic Interference Test. PISA is on track for spacecraft to be packed up and delivered to the launch site." The EMI, vibration and thermal testing are critical tests for all instruments and satellites before they're loaded aboard a rocket and put into orbit.

The Thermospheric Temperature Imager, or TTI, will provide the first global-scale measurements of thermospheric temperature profiles in the 56-168 mile (90-270 km) region of the Earth's atmosphere. The temperature profile sets the scale height of the thermosphere which determines the density at orbital altitudes and therefore the aerodynamic drag experienced by military spacecraft.

John Sigwarth, TTI's Principal Investigator at NASA Goddard, said "The TTI survived the satellite launch vibration levels, being blasted with radio waves, and the TTI had a great thermal vacuum test. We were able to characterize the operation of the instrument in space-like environments and the TTI is ready for launch. We are eagerly anticipating obtaining great data from orbit."

Electromagnetic Interference or EMI testing is done to ensure that powerful ground-based communications and radar systems do not cause interference on the satellite or instrument systems.

Vibration testing is an important part of the testing process, because when the rocket carrying the satellite lifts off and travels through Earth's atmosphere it experiences intense vibrations. Successful vibration testing assures scientists and engineers that their instrument will remain intact and fully functional after launch.

The PISA instrument. Credit: NASA/Doug Rowland

Thermal testing is also critical, because of the extreme temperatures in space. Scientists need to be sure that the instruments will maintain function at extreme temperatures, from the extreme heat the rocket carrying the satellite will experience during launch and when it travels through Earth's atmosphere into the cold void of space.

"With the completion of the last phase of environmental testing of the integrated FASTSAT-HSV01 spacecraft, our team is focused on readying the satellite and its six science and technology instruments, for its near term shipment to Kodiak, Alaska, and for an on time launch no earlier than May 28, 2010," said FASTSAT Project Manager Mark Boudreaux at NASA Marshall.

"FASTSAT-HSV" means "Fast, Affordable, Science and Technology Satellite, Huntsville" The development, integration, test and operations of the three instruments is a collaborative effort between NASA Goddard, NASA Marshall, and the U.S. Naval Academy, Annapolis, Md.

FASTSAT-HSV01 will be flying a total of six instruments approved by the U.S. Department of Defense (DoD) Space Experiments Review Board multi-spacecraft/payload mission named STP-S26, which is executed by the DoD Space Test Program (STP) at the Space Development and Test Wing (SDTW), Kirtland Air Force Base, N.M. which is a unit of the Air Force Space and Missile Systems Center. The mission was designated S26 to correspond to the 26th small launch vehicle mission in STP's more than 40 year history of flying DoD space experiments. The mission will launch four satellites and three cubesats into low earth orbit.

The satellite was created at NASA Marshall with the Von Braun Center for Science and Innovation, in partnership with Dynetics, a corporate partner.

For more information visit http://www.nasa.gov/centers/goddard/news/features/2010/fastsat-instruments.html

Cassini Data Show Ice and Rock Mixture Inside Titan

PASADENA, Calif. -- By precisely tracking NASA's Cassini spacecraft on its low swoops over Saturn's moon Titan, scientists have determined the distribution of materials in the moon's interior. The subtle gravitational tugs they measured suggest the interior has been too cold and sluggish to split completely into separate layers of ice and rock.

The finding, to be published in the March 12 issue of the journal Science, shows how Titan evolved in a different fashion from inner planets such as Earth, or icy moons such as Jupiter's Ganymede, whose interiors have split into distinctive layers.

"These results are fundamental to understanding the history of moons of the outer solar system," said Cassini Project Scientist Bob Pappalardo, commenting on his colleagues' research. Pappalardo is with NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We can now better understand Titan's place among the range of icy satellites in our solar system."

Scientists have known that Titan, Saturn's largest moon, is about half ice and half rock, but they needed the gravity data to figure out how the materials were distributed. It turns out Titan's interior is a sorbet of ice studded with rocks that probably never heated up beyond a relatively lukewarm temperature. Only in the outermost 500 kilometers (300 miles) is Titan's ice devoid of any rock, while ice and rock are mixed to various extents at greater depth.

This artist's illustration shows the likely interior structure of Saturn's moon Titan deduced from gravity field data collected by NASA's Cassini spacecraft. Image credit: NASA/JPL

"To avoid separating the ice and the rock, you must avoid heating the ice too much," said David J. Stevenson, one of the paper's co-authors and a professor of planetary science at the California Institute of Technology in Pasadena. "This means that Titan was built rather slowly for a moon, in perhaps around a million years or so, back soon after the formation of the solar system."

This incomplete separation of ice and rock makes Titan less like Jupiter's moon Ganymede, where ice and rock have fully separated, and perhaps more like another Jovian moon, Callisto, which is believed to have a mixed ice and rock interior. Though the moons are all about the same size, they clearly have diverse histories.

The Cassini measurements help construct a gravity map, which may help explain why Titan has a stunted topography, since interior ice must be warm enough to flow slowly in response to the weight of heavy geologic structures, such as mountains.

Creating the gravity map required tracking minute changes in Cassini's speed along a line of sight from Earth to the spacecraft as it flew four close flybys of Titan between February 2006 and July 2008. The spacecraft took paths between about 1,300 to 1,900 kilometers (800 to 1,200 miles) above Titan.

"The ripples of Titan's gravity gently push and pull Cassini along its orbit as it passes by the moon and all these changes were accurately recorded by the ground antennas of the Deep Space Network within 5 thousandths of a millimeter per second [0.2 thousandths of an inch per second] even as the spacecraft was over a billion kilometers [more than 600 million miles] away," said Luciano Iess, a Cassini radio science team member at Sapienza University of Rome in Italy, and the paper's lead author. "It was a tricky experiment."

The results don't speak to whether Titan has an ocean beneath the surface, but scientists say this hypothesis is very plausible and they intend to keep investigating. Detecting tides induced by Saturn, a goal of the radio science team, would provide the clearest evidence for such a hidden water layer.

A Cassini interdisciplinary investigator, Jonathan Lunine, said of his colleagues' findings, "Additional flybys may tell us whether the crust is thick or thin today." Lunine is with the University of Rome, Tor Vergata, Italy, and the University of Arizona, Tucson. "With that information we may have a better understanding of how methane, the ephemeral working fluid of Titan's rivers, lakes and clouds, has been resupplied over geologic time. Like the history of water on Earth, this is fundamental to a deep picture of the nature of Titan through time."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of Caltech, manages the project for NASA's Science Mission Directorate in Washington. The Cassini orbiter was designed, developed and assembled at JPL. Cassini's radio science subsystem has been jointly developed by NASA and the Italian Space Agency (ASI).

More Cassini information is available, at http://www.nasa.gov/cassini and http://saturn.jpl.nasa.gov.

For more information visit http://www.nasa.gov/mission_pages/cassini/whycassini/cassini20100311.html

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