NASA Funds High School Student Robotics Program

NASA is providing up to $20 million over the next five years to support a national program to inspire student interest in science, technology and mathematics with a focus on robotic technology.

The funding is part of a cooperative agreement with the Foundation for Inspiration and Recognition of Science and Technology (FIRST), a nonprofit organization in Manchester, N.H. FIRST provides students the opportunity to engage with government, industry and university experts, including those at NASA's Jet Propulsion Laboratory, Pasadena, Calif., for hands-on, realistic exposure to engineering and technical professions.

"This is the largest NASA-funded student program geared toward robotics activities," said NASA Administrator Charles Bolden. "For the next five years, approximately 25,000 students across the country will not only learn from our nation's best and brightest, but also compete and have fun at the same time."

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NASA Study Finds Earth's Lakes are Warming

In the first comprehensive global survey of temperature trends in major lakes, NASA researchers determined Earth's largest lakes have warmed during the past 25 years in response to climate change.

Researchers Philipp Schneider and Simon Hook of NASA's Jet Propulsion Laboratory in Pasadena, Calif., used satellite data to measure the surface temperatures of 167 large lakes worldwide.

They reported an average warming rate of 0.45 degrees Celsius (0.81 degrees Fahrenheit) per decade, with some lakes warming as much as 1 degree Celsius (1.8 degrees Fahrenheit) per decade. The warming trend was global, and the greatest increases were in the mid- to high-latitudes of the Northern Hemisphere.

"Our analysis provides a new, independent data source for assessing the impact of climate change over land around the world," said Schneider, lead author of the study published this week in the journal Geophysical Research Letters. "The results have implications for lake ecosystems, which can be adversely affected by even small water temperature changes."

Small changes in water temperature can result in algal blooms that can make a lake toxic to fish or result in the introduction of non-native species that change the lake's natural ecosystem.

Scientists have long used air temperature measurements taken near Earth's surface to compute warming trends. More recently, scientists have supplemented these measurements with thermal infrared satellite data that can be used to provide a comprehensive, accurate view of how surface temperatures are changing worldwide.

The NASA researchers used thermal infrared imagery from National Oceanic and Atmospheric Administration and European Space Agency satellites. They focused on summer temperatures (July to September in the Northern Hemisphere and January to March in the Southern Hemisphere) because of the difficulty in collecting data in seasons when lakes are ice-covered and/or often hidden by clouds. Only nighttime data were used in the study.

The bodies studied were selected from a global database of lakes and wetlands based on size (typically at least 500 square kilometers – 193 square miles – or larger) or other unique characteristics of scientific merit. The selected lakes also had to have large surface areas located away from shorelines, so land influences did not interfere with the measurements. Satellite lake data were collected from the point farthest from any shoreline.

The largest and most consistent area of warming was northern Europe. The warming trend was slightly weaker in southeastern Europe, around the Black and Caspian seas and Kazakhstan. The trends increased slightly farther east in Siberia, Mongolia and northern China.

In North America, trends were slightly higher in the southwest United States than in the Great Lakes region. Warming was weaker in the tropics and in the mid-latitudes of the Southern Hemisphere. The results were consistent with the expected changes associated with global warming.

The satellite temperature trends largely agreed with trends measured by nine buoys in the Great Lakes, Earth's largest group of freshwater lakes in terms of total surface area and volume.

The lake temperature trends were also in agreement with independent surface air temperature data from NASA's Goddard Institute for Space Studies in New York. In certain regions, such as the Great Lakes and northern Europe, water bodies appear to be warming more quickly than surrounding air temperature.

For more information about NASA and agency programs, visit: http://www.nasa.gov .

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Spitzer Sees Shrouded Burst of Stars

Astronomers using NASA's Spitzer Space Telescope have found a stunning burst of star formation that beams out as much infrared light as an entire galaxy. The collision of two spiral galaxies has triggered this explosion, which is cloaked by dust that renders its stars nearly invisible in other wavelengths of light.

The starburst newly revealed by Spitzer stands as the most luminous ever seen taking place away from the centers, or nuclei, of merging parent galaxies. It blazes ten times brighter than the nearby Universe's previous most famous "off-nuclear starburst" that gleams in another galactic smashup known as the Antennae Galaxy.

The new findings show that galaxy mergers can pack a real star-making wallop far from the respective galactic centers, where star-forming dust and gases typically pool.

"This discovery proves that merging galaxies can generate powerful starbursts outside of the centers of the parent galaxies," says Hanae Inami, first author of a paper detailing the results in the July issue of The Astronomical Journal. Inami is a graduate student at The Graduate University for Advanced Studies in Japan and the Spitzer Science Center at the California Institute of Technology. She adds: "The infrared light emission of the starburst dominates its host galaxy and rivals that of the most luminous galaxies we see that are relatively close to our home, the Milky Way."

"No matter how you slice it, this starburst is one of the most luminous objects in the local Universe," agrees Lee Armus, second author of the paper and a senior research astronomer also at the Spitzer Science Center.
A dazzling galactic dust-up

Inami, Armus and their colleagues spotted the buried starburst with Spitzer in the interacting galaxies known as II Zw 096. This galactic train wreck - located around 500 million light years away in the constellation Delphinus (the Dolphin) - will continue to unfold for a few hundred million years. Gravitational forces have already dissolved the once-pinwheel shape of one of II Zw 096's pair of merging galaxies.

The ultra-bright starburst region spans 700 light-years or so - just a tiny portion of II Zw 096, which streams across some 50,000 to 60,000 light-years - yet it blasts out 80 percent of the infrared light from this galactic tumult. Based on Spitzer data, researchers estimate the starburst is cranking out stars at the breakneck pace of around 100 solar masses, or masses of our Sun, per year.

The prodigious energy output of this starburst in a decentralized location as revealed in the infrared has surprised the Spitzer researchers. The new observations go to show how the notion of a cosmic object's nature can change tremendously when viewed at different wavelengths of light. In this way, the shapes and dynamics of distant, harder-to-study galactic mergers could turn out to be a good deal more complex than current observations over a narrow range of wavelengths imply.

"Most of the far-infrared emission in II Zw 096, and hence most of the power, is coming from a region that is not associated with the centers of the merging galaxies," Inami explains. "This suggests that the appearances and interactions of distant, early galaxies during epochs when mergers were much more common than today in the Universe might be more complicated than we think."
A fleeting, perhaps prophetic vista?

In galaxy mergers, individual stars rarely slam into one another because of the vast distances separating them; even in the comparatively crowded central hubs of spiral galaxies, trillions of kilometers still often yawn between the stars.

But giant, diffuse clouds of gas and dust in galaxies do crash together - passing through each other somewhat like ocean waves - and in turn spur the gravitational collapse of dense pockets of matter into new stars. These young, hot stars shine intensely in the energetic ultraviolet part of the spectrum. In the case of II Zw 096, however, a thick shroud of gas and dust still surrounds this stellar brood. The blanket of material absorbs the stars' light and re-radiates it in the lower-energy, infrared wavelengths that gleam clear through the dust to Spitzer's camera.

Astronomers were lucky to capture this transient phase in the evolution of the starburst and of the daughter galaxy that will eventually coalesce out of the collision. "Spitzer has allowed us to see the fireworks before all the gas and dust has cleared away, giving us a preview of the exciting new galaxy being built under the blanket," Inami says.

Merging galaxies such as II Zw 096 also offer a sneak peek at the fate of our Milky Way in some 4.5 billion years when it is expected to plow into its nearest large galactic neighbor, the Andromeda Galaxy. Off-nuclear starbursts such as that in II Zw 096 and the Antennae Galaxy could occur in the vicinity of our Solar System, perhaps, which is located about two-thirds of the way out from the Milky Way's glowing, bulging center.

"This kind of dramatic thing happening in II Zw 096 could happen to the Milky Way and Andromeda when they meet in the far future," says Inami.

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NASA Mars Rover Images Honor Apollo 12

NASA's Mars Exploration Rover Opportunity has visited and photographed two craters informally named for the spacecraft that carried men to the moon 41 years ago this week.

Opportunity drove past "Yankee Clipper" crater on Nov. 4 and reached "Intrepid crater" on Nov. 9. For NASA's Apollo 12, the second mission to put humans onto the moon, the command and service module was called Yankee Clipper, piloted by Dick Gordon, and the lunar module was named Intrepid, piloted by Alan Bean and commanded by the late Pete Conrad. The Intrepid landed on the moon with Bean and Conrad on Nov. 19, 1969, while Yankee Clipper orbited overhead. Their landing came a mere four months after Apollo 11's first lunar landing.

This week, Bean wrote to the Mars Exploration Rover team: "I just talked with Dick Gordon about the wonderful honor you have bestowed upon our Apollo 12 spacecraft. Forty-one years ago today, we were approaching the moon in Yankee Clipper with Intrepid in tow. We were excited to have the opportunity to perform some important exploration of a place in the universe other than planet Earth where humans had not gone before. We were anxious to give it our best effort. You and your team have that same opportunity. Give it your best effort."

Rover science team member James Rice, of NASA's Goddard Space Flight Center, Greenbelt, Md., suggested using the Apollo 12 names. He was applying the rover team's convention of using names of historic ships of exploration for the informal names of craters that Opportunity sees in the Meridian Planum region of Mars.

"The Apollo missions were so inspiring when I was young, I remember all the dates. When we were approaching these craters, I realized we were getting close to the Nov. 19 anniversary for Apollo 12," Rice said. He sent Bean and Gordon photographs that Opportunity took of the two craters.

The images are available online at http://photojournal.jpl.nasa.gov/catalog/PIA13593 and http://photojournal.jpl.nasa.gov/catalog/PIA13596. Intrepid crater is about 20 meters (66 feet) in diameter. Yankee Clipper crater is about half that width.

After a two-day stop to photograph the rocks exposed at Intrepid, Opportunity continued on a long-term trek toward Endeavour crater, a highly eroded crater about 1,000 times wider than Intrepid. Endeavour's name comes from the ship of James Cook's first Pacific voyage.

During a drive of 116.9 meters (383.5 feet) on Nov. 14, Opportunity's "odometer" passed 25 kilometers (15.53 miles). That is more than 40 times the driving-distance goal set for Opportunity to accomplish during its original three-month prime mission in 2004.

Mars Exploration Project Manager John Callas, of NASA's Jet Propulsion Laboratory, Pasadena, Calif., said, "Importantly, it's not how far the rovers have gone but how much exploration and science discovery they have accomplished on behalf of all humankind."

At the beginning of Opportunity's mission, the rover landed inside "Eagle crater," about the same size as Intrepid crater. The team's name for that landing-site crater paid tribute to the lunar module of Apollo 11, the first human landing on the moon. Opportunity spent two months inside Eagle crater, where it found multiple lines of evidence for a wet environment in the area's ancient past.

The rover team is checking regularly for Opportunity's twin, Spirit, in case the increasing daily solar energy available at Spirit's location enables the rover to reawaken and resume communication. No signal from Spirit has been received since March 22. Spring began last week in the southern hemisphere of Mars.

JPL, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rovers for the NASA Science Mission Directorate, Washington. For more information about the rovers, visit: http://www.nasa.gov/rovers.

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Camera on Curiosity's Arm will Magnify Clues in Rocks

NASA's next Mars rover, Curiosity, will wield an arm-mounted magnifying camera similar to one on the Mars Rover Opportunity, which promptly demonstrated its importance for reading environmental history from rocks at its landing site in 2004.

Within a few weeks after the landing, that camera at the end of Opportunity's arm revealed details of small spheres embedded in the rocks, hollows where crystals had dissolved, and fine layering shaped like smiles. These details all provided information about the site's wet past.

The camera installed on the end of Curiosity's arm this month is the Mars Hand Lens Imager, or MAHLI. Its work will include the same type of close-up inspections accomplished by the comparable camera on Opportunity, but MAHLI has significantly greater capabilities: full-color photography, adjustable focus, lights, and even video. Also, it sits on a longer arm, one that can hold MAHLI up higher than the cameras on the rover's mast. MAHLI will use those capabilities as one of 10 science instruments to study the area of Mars where NASA's Mars Science Laboratory mission lands Curiosity in August 2012.

The Mars Hand Lens Imager takes its name from the magnifying tool that every field geologist carries. Ken Edgett of Malin Space Science Systems, San Diego, is the principal investigator for the instrument. He said, "When you’re out in the field and you want to get a quick idea what minerals are in a rock, you pick up the rock in one hand and hold your hand lens in the other hand. You look through the lens at the colors, the crystals, the cleavage planes: features that help you diagnose what minerals you see.

"If it's a sedimentary rock, such as the sandstone you see at Arches National Park in Utah, or shale -- which is basically petrified mud -- like in the Painted Desert in Arizona, you use the hand lens not just to see what minerals are in it but also the sizes and shapes of the grains in the rock. You also look at the fine-scale layering in the rock to get an idea of the sequence of events. Sedimentary rocks record past events and environments."

While other instruments on Curiosity will provide more information about what minerals are in rocks, the Mars Hand Lens Imager will play an important role in reading the environmental history recorded in sedimentary rocks. The mission's science team will use the instruments to assess whether the selected landing area has had environmental conditions favorable for life and for preserving evidence about whether life existed.

The team currently assembling and testing Curiosity and other parts of the Mars Science Laboratory spacecraft at NASA's Jet Propulsion Laboratory, Pasadena, Calif., is continuing tests of MAHLI this month, now that the camera is mounted beside other tools on the robotic arm. The spacecraft will launch from Florida between Nov. 25 and Dec. 18, 2011.

Edgett led the preparation in early 2004 of a proposal to include MAHLI in the Mars Science Laboratory's payload. During those same months, the camera on Opportunity's arm -- that mission's Microscopic Imager -- was demonstrating the potential value of a successor, and generating ideas for improvements. Opportunity's Microscopic Imager has a fixed focus. To get targets in focus, it always needs to be placed the same distance from the target, recording a view of an area 3 centimeters (1.2 inches) across. To view a larger area, the camera takes multiple images, sometimes more than a dozen, each requiring a repositioning of Opportunity's arm.

"When I was writing the proposal, the Microscopic Imager took about 40 images for a mosaic of one rock," Edgett said. "That's where the idea came from to make the focus adjustable. With adjustable focus, the science team has more flexibility for trade-offs among the rover's resources, such as power, time, data storage and data downlink. For example, the camera could take one or two images from farther away to cover a larger area, then go in and sample selected parts in higher resolution from closer up."

MAHLI can focus on targets as close as about 21 millimeters (0.8 inch) and as distant as the horizon or farther. JPL's Ashwin Vasavada, deputy project scientist for the Mars Science Laboratory, said, "MAHLI is really a fully functional camera that happens to be on the end of the arm. The close-up capability is its specialty, but it will also be able to take images or videos from many viewpoints inaccessible to the cameras on the mast, such as up high, down low, under the rover and on the rover deck. Think of it like a hand-held camera with a macro lens, one that you could use for taking pictures of the Grand Canyon, of yourself, or of a bumblebee on a flower."

Edgett is looking forward to what the camera will reveal in rock textures. "Just like larger rocks in a river, grains of sand carried in a stream get rounded from bouncing around and colliding with each other," he said. "If you look at a sandstone with a hand lens and see rounded grains, that tells you they came from a distance. If they are more angular, they didn't come as far before they were deposited in the sediment that became the rock. Where an impact excavated a crater, particles of the material ejected from the crater would be very angular.

"When you're talking about ancient rocks as clues for assessing habitability," he continued, "you're talking about the environments the sediments were deposited in -- whether a lake, a desert, an ice field. Also, what cemented the particles together to become rocks, and what changes have affected the rock after the sediments were deposited? All these things are relevant to whether an environment was favorable for life and also whether it was favorable for preserving the record of that life. Earth is a planet teeming with life, but most rocks have not preserved ancient organisms; Mars will be even more challenging than Earth in this sense."

Edgett says he is eager to see an additional image from this camera besides the details of rock textures. With the arm extended upwards, the camera can look down at the rover for a dramatic self-portrait on Mars. But as for the most important image the Mars Hand Lens Imager will take: "That will be something that surprises us, something we're not expecting."

Mars Science Laboratory is managed by NASA’s Jet Propulsion Laboratory, Pasadena, Calif. JPL also manages the Mars Exploration Rovers Spirit and Opportunity. JPL is a division of the California Institute of Technology in Pasadena.

More information about NASA's Mars Science Laboratory is at: http://www.nasa.gov/msl .

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Shedding 'Bent' Light on Dark Matter

Astronomers using NASA's Hubble Space Telescope took advantage of a giant cosmic magnifying glass to create one of the sharpest and most detailed maps of dark matter in the universe. Dark matter is an invisible and unknown substance that makes up the bulk of the universe's mass. Astronomer Dan Coe led the research while working at NASA's Jet Propulsion Laboratory in Pasadena, Calif.; he is currently with the Space Telescope Science Institute in Baltimore, Md.

The astronomers used Hubble to chart the invisible matter in the massive galaxy cluster Abell 1689, located 2.2 billion light-years away. The cluster's gravity, the majority of which comes from dark matter, acts like a cosmic magnifying glass, bending and amplifying the light from distant galaxies behind it. This effect, called gravitational lensing, produces multiple, warped, and greatly magnified images of those galaxies, like the view in a funhouse mirror. By studying the distorted images, astronomers estimated the amount of dark matter within the cluster.

The new dark matter observations may yield new insights into the role of dark energy in the universe's early formative years. A mysterious property of space, dark energy fights against the gravitational pull of dark matter. The new results suggest that galaxy clusters may have formed earlier than expected, before the push of dark energy inhibited their growth. Dark energy pushes galaxies apart from one another by stretching the space between them, suppressing the formation of giant structures called galaxy clusters. One way astronomers can probe this primeval tug-of-war is by mapping the distribution of dark matter in clusters.

Read the full story at http://hubblesite.org/newscenter/archive/releases/2010/37/full/ .

The California Institute of Technology in Pasadena manages JPL for NASA.

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NASA Study Shows Role of Melt in Arctic Sea Ice Loss

A NASA analysis of satellite data has quantified, for the first time, the amount of older and thicker "multiyear" sea ice lost from the Arctic Ocean due to melting.

Since the start of the satellite record in 1979, scientists have observed the continued disappearance of older "multiyear" sea ice that survives more than one summer melt season. Some scientists suspected that this loss was due entirely to wind pushing the ice out of the Arctic Basin -- a process that scientists refer to as "export." In this study, Ron Kwok and Glenn Cunningham at NASA's Jet Propulsion Laboratory in Pasadena, Calif., used a suite of satellite data to clarify the relative role of export versus melt within the Arctic Ocean.

Kwok and Cunningham show that between 1993 and 2009, a significant amount of multiyear ice -- 1,400 cubic kilometers (336 cubic miles) -- was lost due to melt, not export.

"The paper shows that there is indeed melt of old ice within the Arctic basin and the melt area has been increasing over the past several years," Kwok said. "The story is always more complicated -- there is melt as well as export -- but this is another step in calculating the mass and area balance of the Arctic ice cover."

The results have implications for understanding how Arctic sea ice gets redistributed, where melt occurs in the Arctic Ocean, and how the ocean, ice and atmosphere interact as a system to affect Earth's climate. The study was published in October 2010 in Geophysical Research Letters.

Scientists track the annual cycle of Arctic sea ice coverage as it melts through the summer to reach a minimum extent each September, before refreezing through fall and winter. Much of that ice is seasonal, meaning that it forms and melts within the year.

But multiyear ice that survives more than one season has also been declining, as noted in previous work by Joey Comiso of NASA's Goddard Space Flight Center in Greenbelt, Md., who shows a loss of about 10 percent per decade since the beginning of the satellite record in 1979. Scientists want to know where this loss is occurring.

"The decline of the multiyear ice cover of the last several decades has not been quantitatively explained," Kwok said.

To investigate the loss of multiyear ice, Kwok and Cunningham looked at a 17-year span of data from 1993 to 2009 from a range of polar-observing satellites and instruments, including NASA's Quick Scatterometer (QuikScat); the Ice, Cloud and land Elevation Satellite (ICESat); the Advanced Microwave Scanning Radiometer (AMSR); and the European Space Agency's European Remote Sensing (ERS)-1 and -2 satellites. Some instruments track ice coverage, while others track motion and concentration.

The team collected satellite images and tracked pixels of multiyear ice from April 1, prior to the onset of seasonal melt, and into the summer. Pixels that deviated away from images of the ice edge were considered lost to melt.

The team compared summertime melt of multiyear ice in the Beaufort Sea with estimates of ice lost from the Arctic basin through the Fram Strait -- a major passage through which ice can exit the Arctic Ocean. The comparison revealed how much multiyear ice was lost to export and how much was lost to melt.

They found that over the 17-year period, an area of 947,000 square kilometers (365,639 square miles), or about 32 percent of the decline in multiyear sea ice area, was lost in the Beaufort Sea due to melt.

A similar calculation using thickness estimates from NASA's ICESat from 2004 to 2009 show a volume loss of 1,400 cubic kilometers (336 cubic miles), or about 20 percent of the total loss by volume.

How and where multiyear ice is lost has impacts on the Arctic system. For example, more loss by melt means more freshwater remains in local Arctic waters rather than being transported southward.

"These results also show that thick multiyear sea ice is not immune to melt in the Pacific sector of the Arctic Ocean in today's climate," Kwok said.

The additional freshwater from melt in the Pacific sector, which encompasses the area of study, could contribute to the freshening of the Beaufort Gyre and potentially influence circulation, but the degree of that influence remains uncertain.

Not all of the multiyear ice loss is accounted for, however. Ice loss through Fram Strait and from melt from 2005 to 2008 accounts for just 52 percent of total ice loss. The team suggests that melt in other Arctic regions and outflow through other passages besides Fram Strait could account for the difference.

Since its launch in 1999, QuikScat, developed and managed by JPL, has advanced Earth science research and helped improve environmental predictions using measurements of global radar backscatter from Earth's ocean, land and ice surfaces. QuikScat data help scientists better understand and predict the processes that drive our climate, such as ocean circulation and the global water cycle. In addition to its numerous weather forecasting and climate research applications, QuikScat data also help monitor changes in Arctic sea ice and icebergs, as well as snow and soil moisture changes on land. For more on QuikScat, visit: http://winds.jpl.nasa.gov/index.cfm.

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Cassini Sees Saturn on a Cosmic Dimmer Switch

Like a cosmic lightbulb on a dimmer switch, Saturn emitted gradually less energy each year from 2005 to 2009, according to observations by NASA's Cassini spacecraft. But unlike an ordinary bulb, Saturn's southern hemisphere consistently emitted more energy than its northern one. On top of that, energy levels changed with the seasons and differed from the last time a spacecraft visited Saturn in the early 1980s.

These never-before-seen trends came from a detailed analysis of long-term data from the composite infrared spectrometer (CIRS), an instrument built by NASA's Goddard Space Flight Center in Greenbelt, Md., as well as a comparison with earlier data from NASA's Voyager spacecraft. When combined with information about the energy coming to Saturn from the sun, the results could help scientists understand the nature of Saturn's internal heat source.

"The fact that Saturn actually emits more than twice the energy it absorbs from the sun has been a puzzle for many decades now," said Kevin Baines, a Cassini team scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif., and a co-author on a new paper about Saturn's energy output. "What generates that extra energy? This paper represents the first step in that analysis."

The research, reported this week in the Journal of Geophysical Research-Planets, was led by Liming Li of Cornell University in Ithaca, N.Y. (now at the University of Houston).

"The Cassini CIRS data are very valuable because they give us a nearly complete picture of Saturn," Li said. "This is the only single data set that provides so much information about this planet, and it's the first time that anybody has been able to study the power emitted by one of the giant planets in such detail."

The planets in our solar system lose energy in the form of heat radiation in wavelengths that are invisible to the human eye. The CIRS instrument picks up wavelengths in the thermal infrared region, far enough beyond red light where the wavelengths correspond to heat emission.

"In planetary science, we tend to think of planets as losing power evenly in all directions and at a steady rate," Li said. "Now we know Saturn is not doing that." (Power is the amount of energy emitted per unit of time.)

Instead, Saturn's flow of outgoing energy was lopsided, with its southern hemisphere giving off about one-sixth more energy than the northern one, Li explains. This effect matched Saturn's seasons: during those five Earth-years, it was summer in the southern hemisphere and winter in the northern one.

(A season on Saturn lasts about seven Earth-years.) Like Earth, Saturn has these seasons because the planet is tilted on its axis, so one hemisphere receives more energy from the sun and experiences summer, while the other receives less energy and is shrouded in winter. Saturn's equinox, when the sun was directly over the equator, occurred in August 2009.

In the study, Saturn's seasons looked Earth-like in another way: in each hemisphere, its effective temperature, which characterizes its thermal emission to space, started to warm up or cool down as a change of season approached.

The effective temperature provides a simple way to track the response of Saturn's atmosphere to the seasonal changes, which is complicated because Saturn's weather is variable and the atmosphere tends to retain heat. Cassini's observations revealed that the effective temperature in the northern hemisphere gradually dropped from 2005 to 2008 and started to warm up again by 2009. In the southern hemisphere, the effective temperature cooled from 2005 to 2009.

The emitted energy for each hemisphere rose and fell along with the effective temperature. Even so, during this five-year period, the planet as a whole seemed to be slowly cooling down and emitting less energy.

To find out if similar changes were happening one Saturn-year ago, the researchers looked at data collected by the Voyager spacecraft in 1980 and 1981 and did not see the imbalance between the southern and northern hemispheres. Instead, the two regions were much more consistent with each other.

Why wouldn't Voyager have seen the same summer-versus-winter difference between the two hemispheres? One explanation is that cloud patterns at depth could have fluctuated, blocking and scattering infrared light differently.

"It's reasonable to think that the changes in Saturn's emitted power are related to cloud cover," says Amy Simon-Miller, who heads the Planetary Systems Laboratory at Goddard and is a co-author on the paper. "As the amount of cloud cover changes, the amount of radiation escaping into space also changes. This might vary during a single season and from one Saturn-year to another. But to fully understand what is happening on Saturn, we will need the other half of the picture: the amount of power being absorbed by the planet."

Scientists will be doing that as a next step by comparing the instrument's findings to data obtained by Cassini's imaging cameras and infrared mapping spectrometer instrument. The spectrometer, in particular, measures the amount of sunlight reflected by Saturn. Because scientists know the total amount of solar energy delivered to Saturn, they can derive the amount of sunlight absorbed by the planet and discern how much heat the planet itself is emitting. These calculations help scientists tackle what the actual source of that warming might be and whether it changes.

Better understanding Saturn's internal heat flow "will significantly deepen our understanding of the weather, internal structure and evolution of Saturn and the other giant planets," Li said.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency, and the Italian Space Agency. NASA's Jet Propulsion Laboratory, Pasadena, Calif., 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 composite infrared spectrometer team is based at NASA Goddard, where the instrument was built.

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

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Cassini Sees Saturn on a Cosmic Dimmer Switch

Like a cosmic lightbulb on a dimmer switch, Saturn emitted gradually less energy each year from 2005 to 2009, according to observations by NASA's Cassini spacecraft.

But unlike an ordinary bulb, Saturn's southern hemisphere consistently emitted more energy than its northern one. On top of that, energy levels changed with the seasons and differed from the last time a spacecraft visited Saturn in the early 1980s.

These never-before-seen trends came from a detailed analysis of long-term data from the composite infrared spectrometer (CIRS), an instrument built by NASA's Goddard Space Flight Center in Greenbelt, Md., as well as a comparison with earlier data from NASA's Voyager spacecraft. When combined with information about the energy coming to Saturn from the sun, the results could help scientists understand the nature of Saturn's internal heat source.

"The fact that Saturn actually emits more than twice the energy it absorbs from the sun has been a puzzle for many decades now," said Kevin Baines, a Cassini team scientist at NASA's Jet Propulsion Laboratory, Pasadena, Calif., and a co-author on a new paper about Saturn's energy output. "What generates that extra energy? This paper represents the first step in that analysis."

The research, reported this week in the Journal of Geophysical Research-Planets, was led by Liming Li of Cornell University in Ithaca, N.Y. (now at the University of Houston).

"The Cassini CIRS data are very valuable because they give us a nearly complete picture of Saturn," Li said. "This is the only single data set that provides so much information about this planet, and it's the first time that anybody has been able to study the power emitted by one of the giant planets in such detail."

The planets in our solar system lose energy in the form of heat radiation in wavelengths that are invisible to the human eye. The CIRS instrument picks up wavelengths in the thermal infrared region, far enough beyond red light where the wavelengths correspond to heat emission.

"In planetary science, we tend to think of planets as losing power evenly in all directions and at a steady rate," Li said. "Now we know Saturn is not doing that." (Power is the amount of energy emitted per unit of time.)

Instead, Saturn's flow of outgoing energy was lopsided, with its southern hemisphere giving off about one-sixth more energy than the northern one, Li explains. This effect matched Saturn's seasons: during those five Earth-years, it was summer in the southern hemisphere and winter in the northern one.

(A season on Saturn lasts about seven Earth-years.) Like Earth, Saturn has these seasons because the planet is tilted on its axis, so one hemisphere receives more energy from the sun and experiences summer, while the other receives less energy and is shrouded in winter. Saturn's equinox, when the sun was directly over the equator, occurred in August 2009.

In the study, Saturn's seasons looked Earth-like in another way: in each hemisphere, its effective temperature, which characterizes its thermal emission to space, started to warm up or cool down as a change of season approached. The effective temperature provides a simple way to track the response of Saturn's atmosphere to the seasonal changes, which is complicated because Saturn's weather is variable and the atmosphere tends to retain heat.

Cassini's observations revealed that the effective temperature in the northern hemisphere gradually dropped from 2005 to 2008 and started to warm up again by 2009. In the southern hemisphere, the effective temperature cooled from 2005 to 2009.

The emitted energy for each hemisphere rose and fell along with the effective temperature. Even so, during this five-year period, the planet as a whole seemed to be slowly cooling down and emitting less energy.

To find out if similar changes were happening one Saturn-year ago, the researchers looked at data collected by the Voyager spacecraft in 1980 and 1981 and did not see the imbalance between the southern and northern hemispheres. Instead, the two regions were much more consistent with each other.

Why wouldn't Voyager have seen the same summer-versus-winter difference between the two hemispheres? One explanation is that cloud patterns at depth could have fluctuated, blocking and scattering infrared light differently.

"It's reasonable to think that the changes in Saturn's emitted power are related to cloud cover," says Amy Simon-Miller, who heads the Planetary Systems Laboratory at Goddard and is a co-author on the paper. "As the amount of cloud cover changes, the amount of radiation escaping into space also changes. This might vary during a single season and from one Saturn-year to another. But to fully understand what is happening on Saturn, we will need the other half of the picture: the amount of power being absorbed by the planet."

Scientists will be doing that as a next step by comparing the instrument's findings to data obtained by Cassini's imaging cameras and infrared mapping spectrometer instrument. The spectrometer, in particular, measures the amount of sunlight reflected by Saturn.

Because scientists know the total amount of solar energy delivered to Saturn, they can derive the amount of sunlight absorbed by the planet and discern how much heat the planet itself is emitting. These calculations help scientists tackle what the actual source of that warming might be and whether it changes.

Better understanding Saturn's internal heat flow "will significantly deepen our understanding of the weather, internal structure and evolution of Saturn and the other giant planets," Li said.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency, and the Italian Space Agency. NASA's Jet Propulsion Laboratory, Pasadena, Calif., 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 composite infrared spectrometer team is based at NASA Goddard, where the instrument was built.

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

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Cool Star is a Gem of a Find

NASA's Wide-field Infrared Survey Explorer, or WISE, has eyed its first cool brown dwarf: a tiny, ultra-cold star floating all alone in space.

WISE is scanning the whole sky in infrared light, picking up the glow of not just brown dwarfs but also asteroids, stars and galaxies. It has sent millions of images down to Earth, in which infrared light of different wavelengths is color-coded in the images.

"The brown dwarfs jump out at you like big, fat, green emeralds," said Amy Mainzer, the deputy project scientist of WISE at NASA's Jet Propulsion Laboratory in Pasadena, Calif. Mainzer, who makes jewelry in her spare time, explained that the brown dwarfs appear like green gems in WISE images because the methane in their atmospheres absorbs the infrared light that has been coded blue, and because they are too faint to give off the infrared light that is color-coded red. The only color left is green.

Like Jupiter, brown dwarfs are made up of gas -- a lot of it in the form of methane, hydrogen sulfide, and ammonia. These gases would be deadly to humans at the concentrations found around brown dwarfs. And they wouldn't exactly smell pretty.

"If you could bottle up a gallon of this object's atmosphere and bring it back to Earth, smelling it wouldn't kill you, but it would stink pretty badly -- like rotten eggs with a hint of ammonia," said Mainzer.

Mainzer and other members of the WISE team are already accumulating a quarry of brown dwarf candidates similar to this one. Brown dwarfs have masses somewhere between those of a star and a planet. They start out like stars as collapsing balls of gas, but they lack the mass to fuse atoms together at their core and shine with starlight.

As time goes on, these lightweights cool off, until they can only be seen in infrared light. There could be many such objects lurking in the neighborhood of our sun, but astronomers know of only a handful so far. WISE is expected to find hundreds, including the coolest and closest of all.

To scientists, brown dwarfs represent the perfect laboratories for studying planet-like atmospheres.

"They're a great test of our understanding of atmospheric physics of planets, since they don't have solid surfaces, and there's no big, bright sun to get in the way," said co-author Michael Cushing, a postdoctoral fellow at JPL.

WISE's new brown dwarf is named WISEPC J045853.90+643451.9 for its location in the sky. It is estimated to be 18 to 30 light-years away and is one of the coolest brown dwarfs known, with a temperature of about 600 Kelvin, or 620 degrees Fahrenheit. That's downright chilly as far as stars go.

The fact that this brown dwarf jumped out of the data so easily and so quickly -- it was spotted 57 days into the survey mission -- indicates that WISE will discover many, many more. The discovery was confirmed by follow-up observations at the University of Virginia's Fan Mountain telescope, the Large Binocular Telescope in southeastern Arizona, and NASA's Infrared Telescope Facility on Mauna Kea, Hawaii. The results are in press at the Astrophysical Journal.

Read more about how NASA's Spitzer Space Telescope and WISE are hunting down the coldest brown dwarfs.

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. More information is online at http://www.nasa.gov/wise and http://wise.astro.ucla.edu.

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Cool Star is a Gem of a Find

NASA's Wide-field Infrared Survey Explorer, or WISE, has eyed its first cool brown dwarf: a tiny, ultra-cold star floating all alone in space.

WISE is scanning the whole sky in infrared light, picking up the glow of not just brown dwarfs but also asteroids, stars and galaxies. It has sent millions of images down to Earth, in which infrared light of different wavelengths is color-coded in the images.

"The brown dwarfs jump out at you like big, fat, green emeralds," said Amy Mainzer, the deputy project scientist of WISE at NASA's Jet Propulsion Laboratory in Pasadena, Calif. Mainzer, who makes jewelry in her spare time, explained that the brown dwarfs appear like green gems in WISE images because the methane in their atmospheres absorbs the infrared light that has been coded blue, and because they are too faint to give off the infrared light that is color-coded red. The only color left is green.

Like Jupiter, brown dwarfs are made up of gas -- a lot of it in the form of methane, hydrogen sulfide, and ammonia. These gases would be deadly to humans at the concentrations found around brown dwarfs. And they wouldn't exactly smell pretty.

"If you could bottle up a gallon of this object's atmosphere and bring it back to Earth, smelling it wouldn't kill you, but it would stink pretty badly -- like rotten eggs with a hint of ammonia," said Mainzer.

Mainzer and other members of the WISE team are already accumulating a quarry of brown dwarf candidates similar to this one. Brown dwarfs have masses somewhere between those of a star and a planet. They start out like stars as collapsing balls of gas, but they lack the mass to fuse atoms together at their core and shine with starlight. As time goes on, these lightweights cool off, until they can only be seen in infrared light. There could be many such objects lurking in the neighborhood of our sun, but astronomers know of only a handful so far. WISE is expected to find hundreds, including the coolest and closest of all.

To scientists, brown dwarfs represent the perfect laboratories for studying planet-like atmospheres.

"They're a great test of our understanding of atmospheric physics of planets, since they don't have solid surfaces, and there's no big, bright sun to get in the way," said co-author Michael Cushing, a postdoctoral fellow at JPL.

WISE's new brown dwarf is named WISEPC J045853.90+643451.9 for its location in the sky. It is estimated to be 18 to 30 light-years away and is one of the coolest brown dwarfs known, with a temperature of about 600 Kelvin, or 620 degrees Fahrenheit. That's downright chilly as far as stars go. The fact that this brown dwarf jumped out of the data so easily and so quickly -- it was spotted 57 days into the survey mission -- indicates that WISE will discover many, many more. The discovery was confirmed by follow-up observations at the University of Virginia's Fan Mountain telescope, the Large Binocular Telescope in southeastern Arizona, and NASA's Infrared Telescope Facility on Mauna Kea, Hawaii. The results are in press at the Astrophysical Journal.

Read more about how NASA's Spitzer Space Telescope and WISE are hunting down the coldest brown dwarfs.

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. More information is online at http://www.nasa.gov/wise and http://wise.astro.ucla.edu.

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Flight of the Comet

This video clip was compiled from images taken by NASA's EPOXI mission spacecraft during its flyby of comet Hartley 2 on Nov. 4, 2010. During the encounter, the spacecraft and comet whisked past each other at a speed of 12.3 kilometers per second (27,560 miles per hour). The spacecraft came within about 700 kilometers (435 miles) of the comet's nucleus at the time of closest approach.

"While future generations should have the opportunity to truly explore comets, this flyby gives us an excellent preview of what they will get to enjoy," said EPOXI principal investigator Michael A'Hearn of the University of Maryland, College Park. "Hartley 2 exceeded all our expectations in not only scientific value but in its stark majestic beauty."

The video clip of the flyby is comprised of 40 frames taken from the spacecraft's Medium-Resolution Instrument during the encounter. The first image was taken at about 37 minutes before the time of closest approach at a distance of about 27,350 kilometers (17,000 miles). The last image was taken 30 minutes after closest approach at a distance of 22,200 kilometers (13,800 miles). The spacecraft was able to image nearly 50 percent of the comet's illuminated surface in detail.

The EPOXI mission's flyby of comet Hartley 2 was only the fifth time in history that a comet nucleus has been imaged, and the first time in history that two comets have been imaged with the same instruments and same spatial resolution.

EPOXI is an extended mission that utilizes the already "in flight" Deep Impact spacecraft to explore distinct celestial targets of opportunity. The name EPOXI itself is a combination of the names for the two extended mission components: the extrasolar planet observations, called Extrasolar Planet Observations and Characterization (EPOCh), and the flyby of comet Hartley 2, called the Deep Impact Extended Investigation (DIXI). The spacecraft will continue to be referred to as "Deep Impact."

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the EPOXI mission for NASA's Science Mission Directorate, Washington. The University of Maryland, College Park, is home to the mission's principal investigator, Michael A'Hearn. Drake Deming of NASA's Goddard Space Flight Center, Greenbelt, Md., is the science lead for the mission's extrasolar planet observations. The spacecraft was built for NASA by Ball Aerospace & Technologies Corp., Boulder, Colo.

For more information about EPOXI visit http://epoxi.umd.edu/.

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NASA Spacecraft on Final Approach Toward Comet

The EPOXI mission spacecraft has refined its path toward a Nov. 4 flyby of comet Hartley 2, successfully performing its final maneuver today at 8 a.m. PDT (11 a.m. EDT). The spacecraft burned its engines for 6.8 seconds, changing the spacecraft's velocity by 1.4 meters per second (3 miles per hour).

"I've worked the Stardust flyby of comet Wild 2 and the Deep Impact encounter with comet Tempel 1, and I have never seen a comet flit around the sky like this one," said mission navigator Shyam Bhaskaran of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We needed to make this burn to re-locate the spacecraft for the 700-kilometer [about 435 miles] flyby distance."

Part of the reason Hartley 2 is hard to pin down is because the small comet is very active.

"Hartley 2 is one-seventh the size of comet Tempel 1, but it releases almost the same amount of material into the space environment," said EPOXI Principal Investigator Mike A'Hearn of the University of Maryland. "These jets can act as thrusters and actually make small changes to the comet's orbit around the sun."

On Thursday, Nov. 4, the spacecraft will fly past the comet, with closest approach expected about 7 a.m. PDT [10 a.m. EDT]. This flyby will mark the fifth time in history that a spacecraft has been close enough to image the heart of the comet, more commonly known as the nucleus.

EPOXI is an extended mission that uses the already "in-flight" Deep Impact spacecraft to explore distinct celestial targets of opportunity. The name EPOXI itself is a combination of the names for the two extended mission components: the extrasolar planet observations, called Extrasolar Planet Observations and Characterization (EPOCh), and the flyby of comet Hartley 2, called the Deep Impact Extended Investigation (DIXI). The spacecraft will continue to be referred to as "Deep Impact."

JPL, a division of the California Institute of Technology in Pasadena, manages the EPOXI mission for NASA's Science Mission Directorate, Washington. The University of Maryland, College Park, is home to the mission's principal investigator, Michael A'Hearn. Drake Deming of NASA's Goddard Space Flight Center, Greenbelt, Md., is the science lead for the mission's extrasolar planet observations. The spacecraft was built for NASA by Ball Aerospace & Technologies Corp., Boulder, Colo.

For more information about EPOXI, visit: http://www.nasa.gov/epoxi and http://epoxi.umd.edu/.

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Major Surgery Complete for Deep Space Network Antenna

The seven-month upgrade to the historic "Mars antenna" at NASA's Deep Space Network site in Goldstone, Calif. has been completed. After a month of intensive testing, similar to the rehabilitation stage after surgery, the antenna is now ready to help maintain communication with spacecraft during the next decade of space exploration.

The month of October was used as a testing period to make sure the antenna was in working order and fully functional, as scheduled, for Nov. 1. A team of workers completed an intense series of tasks to reach its first milestone - upgrading the 70-meter-wide (230-foot-wide) antenna in time to communicate with the EPOXI mission spacecraft during its planned flyby of comet Hartley 2 on Nov. 4.

The first official demonstration space track was on Sept. 28, when the antenna communicated with NASA's EPOXI mission spacecraft.

"We've been testing the antenna since Sept. 28, and we've had no problems in tracking the spacecraft," said Peter Hames of NASA's Jet Propulsion Laboratory, Pasadena, Calif., who is responsible for maintaining the network's antennas. "We are ready to resume service as scheduled." JPL manages the Deep Space Network for NASA.

During the upgrade process, workers raised a portion of the antenna that weighs 3.2 million kilograms (7 million pounds) up from the base by 5 millimeters (0.2 inches) while they performed a precise, delicate repair. They replaced a portion of the hydrostatic bearing (enabling the antenna to rotate horizontally) and the four elevation bearings (enabling the antenna to track up and down from the horizon).

Unlike the sterile confines of an operating room, this surgery took place in the middle of California's Mojave Desert, a hot oasis baked by the unforgiving desert heat. The team members were able to cheat the heat by completing a number of the 375 tasks during early morning and night shifts. The tasks required the team to analyze, load, lift, install, test, analyze again and inspect.

The Deep Space Network consists of three deep-space communication facilities positioned approximately 120 degrees of longitude apart. In addition to the Mojave Desert location at Goldstone, the other locations are outside of Madrid, Spain, and Canberra, Australia. Each 70-meter (230-foot) antenna is capable of tracking a spacecraft traveling more than 16 billion kilometers (10 billion miles) from Earth. The antennas are strategically situated at each location in semi-mountainous basins to reduce radio frequency interference. This careful placement helps make the Deep Space Network the largest and most sensitive science telecommunications system in the world.

In March 1966, the antenna, officially known as Deep Space Station 14, earned its nickname as the Mars antenna by receiving the first signal from NASA's Mariner 4 mission to Mars. The historic dish is now responsible for tracking an entire fleet of missions, including the rovers Spirit and Opportunity currently on the surface of Mars, the Cassini orbiter at Saturn, the twin Voyager spacecraft in the outer reaches of our solar system, and the Spitzer Space Telescope, which observes stars, galaxies and other celestial objects.

"We are nearing the completion of a very challenging engineering effort that will extend the life of one of the DSN's workhorses, making it more available and reliable in returning critical science data through at least 2025," said Wayne Sible, the network's deputy project manager at JPL.

The antenna upgrade was a collaborative effort between JPL, Diani Building Corp., Santa Maria, Calif., and ITT Corp., White Plains, N.Y. Their shared goal was to emerge from the "operating room" with a healthy patient.

"The 70-meter antenna gets under your skin, everyone involved in this project was so passionate about it, from the grout workers to the machine shops to the guys on the antenna, everybody was giving it their absolute all," said Hames.

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NASA Survey Suggests Earth-Sized Planets are Common

Nearly one in four stars similar to the sun may host planets as small as Earth, according to a new study funded by NASA and the University of California.

The study is the most extensive and sensitive planetary census of its kind. Astronomers used the W.M. Keck Observatory in Hawaii for five years to search 166 sun-like stars near our solar system for planets of various sizes, ranging from three to 1,000 times the mass of Earth. All of the planets in the study orbit close to their stars. The results show more small planets than large ones, indicating small planets are more prevalent in our Milky Way galaxy.

"We studied planets of many masses -- like counting boulders, rocks and pebbles in a canyon -- and found more rocks than boulders, and more pebbles than rocks. Our ground-based technology can't see the grains of sand, the Earth-size planets, but we can estimate their numbers," said Andrew Howard of the University of California, Berkeley, lead author of the new study. "Earth-size planets in our galaxy are like grains of sand sprinkled on a beach -- they are everywhere."

The study appears in the Oct. 29 issue of the journal Science.

The research provides a tantalizing clue that potentially habitable planets could also be common. These hypothesized Earth-size worlds would orbit farther away from their stars, where conditions could be favorable for life. NASA's Kepler spacecraft is also surveying sun-like stars for planets and is expected to find the first true Earth-like planets in the next few years.

Howard and his planet-hunting team, which includes principal investigator Geoff Marcy, also of the University of California, Berkeley, looked for planets within 80-light-years of Earth, using the radial velocity, or "wobble," technique.

They measured the numbers of planets falling into five groups, ranging from 1,000 times the mass of Earth, or about three times the mass of Jupiter, down to three times the mass of Earth. The search was confined to planets orbiting close to their stars -- within 0.25 astronomical units, or a quarter of the distance between our sun and Earth.

A distinct trend jumped out of the data: smaller planets outnumber larger ones. Only 1.6 percent of stars were found to host giant planets orbiting close in. That includes the three highest-mass planet groups in the study, or planets comparable to Saturn and Jupiter. About 6.5 percent of stars were found to have intermediate-mass planets, with 10 to 30 times the mass of Earth -- planets the size of Neptune and Uranus. And 11.8 percent had the so-called "super-Earths," weighing in at only three to 10 times the mass of Earth.

"During planet formation, small bodies similar to asteroids and comets stick together, eventually growing to Earth-size and beyond. Not all of the planets grow large enough to become giant planets like Saturn and Jupiter," Howard said. "It's natural for lots of these building blocks, the small planets, to be left over in this process."

The astronomers extrapolated from these survey data to estimate that 23 percent of sun-like stars in our galaxy host even smaller planets, the Earth-sized ones, orbiting in the hot zone close to a star. "This is the statistical fruit of years of planet-hunting work," said Marcy. "The data tell us that our galaxy, with its roughly 200 billion stars, has at least 46 billion Earth-size planets, and that's not counting Earth-size planets that orbit farther away from their stars in the habitable zone."

The findings challenge a key prediction of some theories of planet formation. Models predict a planet "desert" in the hot-zone region close to stars, or a drop in the numbers of planets with masses less than 30 times that of Earth. This desert was thought to arise because most planets form in the cool, outer region of solar systems, and only the giant planets were thought to migrate in significant numbers into the hot inner region. The new study finds a surplus of close-in, small planets where theories had predicted a scarcity.

"We are at the cusp of understanding the frequency of Earth-sized planets among planetary systems in the solar neighborhood," said Mario R. Perez, Keck program scientist at NASA Headquarters in Washington. "This work is part of a key NASA science program and will stimulate new theories to explain the significance and impact of these findings."

NASA's Exoplanet Science Institute at the California Institute of Technology, Pasadena, Calif., manages time allocation on the Keck telescope for NASA. NASA's Jet Propulsion Laboratory, also in Pasadena, manages NASA's Exoplanet Exploration program office. More information about exoplanets and NASA's planet-finding program is at http://planetquest.jpl.nasa.gov .

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