Thursday, July 29, 2010

Martian Dust Devil Whirls into Opportunity's View

In its six-and-a-half years on Mars, NASA's Mars Exploration Rover Opportunity had never seen a dust devil before this month, despite some systematic searches in past years and the fact that its twin rover, Spirit, has seen dozens of dust devils at its location halfway around the planet.

A tall column of swirling dust appears in a routine image that Opportunity took with its panoramic camera on July 15. The rover took the image in the drive direction, east-southeastward, right after a drive of about 70 meters (230 feet). The image was taken for use in planning the next drive.

"This is the first dust devil seen by Opportunity," said Mark Lemmon of Texas A&M University, College Station, a member of the rover science team.

Spirit's area, inside Gusev Crater, is rougher in ground texture, and dustier, than the area where Opportunity is working in the Meridiani Planum region. Those factors at Gusev allow vortices of wind to form more readily and raise more dust, compared to conditions at Meridiani, Lemmon explained. Orbiters have photographed tracks left by dust devils near Opportunity, but the tracks are scarcer there than near Spirit. Swirling winds at Meridiani may be more common than visible signs of them, if the winds occur where there is no loose dust to disturb.

This is the first dust devil that NASA's Mars Exploration Rover Opportunity has observed in the rover's six-and-a-half years on Mars. Image credit: NASA/JPL-Caltech/Cornell University/Texas A&M

Just one day before Opportunity captured the dust devil image, wind cleaned some of the dust off the rover's solar array, increasing electricity output from the array by more than 10 percent.

"That might have just been a coincidence, but there could be a connection," Lemmon said. The team is resuming systematic checks for afternoon dust devils with Opportunity's navigation camera, for the first time in about three years.

Opportunity and Spirit arrived on Mars in January 2004 for missions designed to last for three months. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Exploration Rover Project for the NASA Science Mission Directorate, Washington. For more information about the project and images from the rovers, visit .

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Bright Lights, Green City

Two extremely bright stars illuminate a greenish mist in this and other images from the new "GLIMPSE360" survey from NASA's Spitzer Space Telescope. This fog is comprised of hydrogen and carbon compounds called polycyclic aromatic hydrocarbons (PAHs), which are found right here on Earth in sooty vehicle exhaust and on charred grills. In space, PAHs form in the dark clouds that give rise to stars. These molecules provide astronomers a way to visualize the peripheries of gas clouds and study their structures in great detail. They are not actually "green;" but are color coded in these images to let scientists see their glow in infrared.

Strange streaks – likely dust grains that lined up with magnetic fields – distort the star in the top left. The fairly close, well-studied star GL 490 gleams in the middle right. The new observations have revealed several small, blobby outflows of gas from nearby forming stars, which indicate their youth. Such outflows are a great way to target really young, massive stars in their very earliest, hard-to-catch stages.

This image is a combination of data from Spitzer and the Two-Micron All-Sky Survey (2MASS). The Spitzer data was taken after Spitzer's liquid coolant ran dry in May 2009, marking the beginning of its "warm" mission. Light from Spitzer's remaining infrared channels at 3.6 and 4.5 microns has been represented in green and red, respectively. 2MASS observations at 2.2 microns are blue.

Image credit: NASA/JPL-Caltech/2MASS/SSI/University of Wisconsin

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Wednesday, July 28, 2010

Beastly Stars and a Bubble

A star-forming region called BG2107+49 shines from the considerable distance of more than 30,000 light-years away in the upper left of this image from NASA's Spitzer Space Telescope. With Spitzer's resolution and sensitivity, however, astronomers can "zoom in" on the action of star birth unfolding there, where behemoth stars ten to twenty times the mass of our sun are taking shape. To the right looms an expanding bubble of star formation likely triggered by powerful stellar winds blown from an earlier generation of stars that arose in the ring's center. The smattering of little red dots in the area and elsewhere are young forming stars still cocooned in gas and dust.

This image is a combination of data from Spitzer and the Two Micron All Sky Survey (2MASS). The Spitzer data was taken after Spitzer's liquid coolant ran dry in May 2009, marking the beginning of its "warm" mission. Light from Spitzer's remaining infrared channels at 3.6 and 4.5 microns has been represented in green and red, respectively. 2MASS observations at 2.2 microns are blue.

Image credit: NASA/JPL-Caltech/2MASS/SSI/University of Wisconsin

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GRAIL Spacecraft Takes Shape

Engineers have conducted a fuel tank check of one of NASA's GRAIL mission spacecraft (Gravity Recovery and Interior Laboratory), scheduled for launch in 2011. Confirming the size and fit of manufactured components is one of the steps required prior to welding the spacecraft's fuel tanks into the propulsion system's feed lines.

The image was taken on June 29, 2010, during the propulsion subsystem assembly and integration effort in the Space Support Building clean room at Lockheed Martin Space Systems in Denver.

Engineers conduct checks on one of NASA's GRAIL spacecraft in the Space Support Building at Lockheed Martin Space Systems in Denver. Image credit: NASA/JPL/LockheedMartin

The GRAIL mission will fly twin spacecraft (spacecraft "A" and "B") in tandem orbits around the moon for several months to measure its gravity field in unprecedented detail. The mission will also answer longstanding questions about Earth's moon, and provide scientists a better understanding of how Earth and other rocky planets in the solar system formed.

For more information about GRAIL, please visit: .

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Tuesday, July 27, 2010

Cutting Into Arctic Sea Ice

"Over by the fish, below the soccer field," said ice scientist Bonnie Light, pointing at the Arctic sea ice from the bridge of the U.S. Coast Guard Cutter Healy earlier this month during NASA's ICESCAPE oceanographic mission.

Light, of University of Washington, and other ice scientists crowd around the windows on the bridge of the Healy describing shapes created by the melt ponds on the surface of the Arctic sea ice. They point out everything from unicorns to Volkswagons. But the imaginative morning ritual is serious business; the ice teams are discussing where on the ice to work and planning the logistics of the day’s field work.

Since 1979, satellites have tracked changes to Arctic sea ice extent, showing dramatic declines. On average the ice is losing about 13 percent of its summer coverage each decade and the record low was set in 2007. The decline raises two key questions: Why are these changes happening and what do they mean for Arctic ecosystems, particularly the ocean-dwelling plants -- phytoplankton -- that play an integral role in Earth's carbon cycle?

Chris Polashenski of Dartmouth College (left) and Benny Hopson from the Barrow (Alaska) Arctic Science Consortium bore a hole through sea ice in the Chukchi Sea on July 4. Credit: NASA/Kathryn Hansen

Exploring those questions since last month is the ICESCAPE mission onboard the Healy, which is studying the physics, chemistry and biology of the ocean and sea ice within a changing Arctic. On 12 days scattered throughout the five-week mission, the Healy "parked" amid an ice floe and teams of ice scientists stepped foot on the floating ice for a close up look.

After agreeing on a plan from the bridge, ice scientists on July 9, 2010, readied for work at ice station 10 in the Chukchi Sea. The ship's crane lowered sleds of scientific equipment over the side of the ship and then scientists descended down a steep ramp to the ice where they dispersed and set up equipment.

Coast Guard crew and scientists checked the ice for safety, and then guided a deafening drill through the ice and into the ocean. Researchers deployed instruments above, through and below the drill holes -- scattered strategically across the study site -- to characterize how much light is reflected, absorbed and transmitted by the ice.

The ICESCAPE mission is looking at how Arctic ecology is changing with the changes in ice cover. The Earth is undergoing a grand experiment and scientists want to understand those changes because some of those changes may affect our future.

Surprisingly, polar oceans are rich with life and play a major role in drawing down carbon from the atmosphere. But how will that capability change in an ice-free Arctic? How will the creatures in the sea themselves change? Understanding the connections between the ice and the phytoplankton -- the lower rungs on the food chain -- are key to understanding these changes.

Teams of scientists set up equipment on sea ice near the U.S. Coast Guard icebreaker Healy in the Chukchi Sea on July 4.Credit: NASA/Kathryn Hansen

"From a couple of optical measurements, a lot of thickness measurements, and some melt pond measurements, we can do some calculations and get a 2D map of how much light gets through at different wavelengths, and how much of that light is what's called 'photosynthetically available radiation,' which is the stuff the little algae really like," said Don Perovich of the Cold Regions Research and Engineering Laboratory.

To characterize the ice and its optical properties, researchers begin work on top of the ice. Here, pools of water, or "melt ponds," litter the surface, absorbing more sunlight -- both accelerating melt and passing more of that light along to the ocean below.

Chris Polashenski of Dartmouth College waded onto thin ice supporting a pond, drilled a hole, and measured the ice thickness. Just 30 centimeters of ice separated Polashenski from 150 feet of ocean. In contrast, surrounding ice measured in at an average thickness of 80 centimeters.

ICESCAPE scientists draw on the ship's bridge windows on July 9 as they plan a day of work on sea ice in the Arctic's Chukchi Sea. Credit: NASA/Kathryn Hansen

"The thickness distribution is one of the key parameters of sea ice," Perovich said. "In particular for this experiment it strongly governs how much light gets through into the ocean."

So how much light makes it through these ice thicknesses? To find out, Light worked with her team to collect optical measurements tracking the transmission of light above, inside, and just below the ice at the borehole sites.

Still other groups looked deeper, at both the life forms in the water column below the ice and the light that is sustains them. To gather these snapshots, Karen Frey of Clark University and colleagues dropped an optical sensor down 30 meters, while simultaneously collecting samples of water with Chief Scientist Kevin Arrigo’s group from Stanford University.

Back in the ship's onboard lab, Frey and Arrigo's groups looked at the life contained in the samples, while Sam Laney of Woods Hole Oceanographic Institution fed them under an microscope that automatically collects images of the tiny life forms.

Researchers are finding strong connections between the properties of the ice and the communities of microbes beneath them. For example, ponds were found to transmit between three and 10 times more light than bare ice.

"Algae are affected by what's above them," said Laney, who noted that algae communities photographed under melt pond ice were different compared to those that turned up under white ice.

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WISE Peers Into the Stellar Darkness

New stars are forming inside this giant cloud of dust and gas as seen in infrared light by NASA's Wide-field Infrared Survey Explorer, or WISE. Sprawling across the constellation Vela is a complex of dark, dense clouds of dust and gas, difficult to detect with telescopes that see only visible light. The complex is called the Vela Molecular Cloud Ridge. This ridge may form part of the edge of the Orion spiral arm spur in our Milky Way galaxy. Astronomers mapping out the region in radio light in the late 1980s found four distinct regions of the densest gas and named them clouds A, B, C and D. This image takes in the first of those clouds, Vela A.

Vela A is about 3,300 light-years away. This image of Vela A covers a region on the sky over 4.5 full moons wide and over 3 full moons tall, spanning about 130 light-years in space. The core of the cloud is being excavated by the radiation and winds from hot, young stars. The energy from the new stars is absorbed by the surrounding dust. This hides them from view in visible light, but the heated dust glows in infrared light (seen here in green and red). Sprinkled around Vela A are a few groups of sources that appear very red in this image, and have no known counterparts in visible-light images of the region. It's possible that these may be Young Stellar Objects, which are stars in their very infancy enveloped in dust. The infrared light seen from these baby stars does not come directly from the stars, but rather from the dust around them, which glows as the nascent stars heat it.

All four infrared detectors aboard WISE were used to make this mosaic. Color is representational: blue and cyan represent infrared light at wavelengths of 3.4 and 4.6 microns, which is dominated by light from stars. Green and red represent light at 12 and 22 microns, which is mostly light from warm dust.

Image Credit: NASA/JPL-Caltech/UCLA

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Sunday, July 25, 2010

Mars Curiosity Takes First Baby Steps

Like proud parents savoring their baby's very first steps, mission team members gathered in a gallery above a clean room at NASA's Jet Propulsion Laboratory to watch the Mars Curiosity rover roll for the first time.

Engineers and technicians wore "bunny suits" while guiding Curiosity through its first steps, or more precisely, its first roll on the clean room floor. The rover moved forward and backward about 1 meter (3.3 feet).

Mars Curiosity team members gather in the gallery above the clean room at NASA's Jet Propulsion Laboratory to watch the rover roll for the first time. Image credit: NASA/JPL-Caltech

Mars Science Laboratory (aka Curiosity) is scheduled to launch in fall 2011 and land on the Red Planet in August 2012. Curiosity is the largest rover ever sent to Mars. It will carry 10 instruments that will help search an intriguing region of the Red Planet for two things:
  1. Environments where life might have existed
  2. The capacity of those environments to preserve evidence of past life

Learn more about Curiosity at

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NASA Spacecraft Camera Yields Most Accurate Mars Map Ever

PASADENA, Calif. -- A camera aboard NASA's Mars Odyssey spacecraft has helped develop the most accurate global Martian map ever. Researchers and the public can access the map via several websites and explore and survey the entire surface of the Red Planet.

The map was constructed using nearly 21,000 images from the Thermal Emission Imaging System, or THEMIS, a multi-band infrared camera on Odyssey. Researchers at Arizona State University's Mars Space Flight Facility in Tempe, in collaboration with NASA's Jet Propulsion Laboratory in Pasadena, Calif., have been compiling the map since THEMIS observations began eight years ago.

The pictures have been smoothed, matched, blended and cartographically controlled to make a giant mosaic. Users can pan around images and zoom into them. At full zoom, the smallest surface details are 100 meters (330 feet) wide. While portions of Mars have been mapped at higher resolution, this map provides the most accurate view so far of the entire planet.

The new map is available at: .

Advanced users with large bandwidth, powerful computers and software capable of handling images in the gigabyte range can download the full-resolution map in sections at: .

Valles Marineris, the "Grand Canyon of Mars," sprawls wide enough to reach from Los Angeles to nearly New York City, if it were located on Earth. The red outline box shows the location of a second, full-resolution image. Credit: NASA/JPL/Arizona State University

"We've tied the images to the cartographic control grid provided by the U.S. Geological Survey, which also modeled the THEMIS camera's optics," said Philip Christensen, principal investigator for THEMIS and director of the Mars Space Flight Facility. "This approach lets us remove all instrument distortion, so features on the ground are correctly located to within a few pixels and provide the best global map of Mars to date."

Working with THEMIS images from the new map, the public can contribute to Mars exploration by aligning the images to within a pixel's accuracy at NASA's "Be a Martian" website, which was developed in cooperation with Microsoft Corp. Users can visit the site at: .

"The Mars Odyssey THEMIS team has assembled a spectacular product that will be the base map for Mars researchers for many years to come," said Jeffrey Plaut, Odyssey project scientist at JPL. "The map lays the framework for global studies of properties such as the mineral composition and physical nature of the surface materials."

Other sites build upon the base map. At Mars Image Explorer, which includes images from every Mars orbital mission since the mid-1970s, users can search for images using a map of Mars at: .

"The broad purpose underlying all these sites is to make Mars exploration easy and engaging for everyone," Christensen said. "We are trying to create a user-friendly interface between the public and NASA's Planetary Data System, which does a terrific job of collecting, validating and archiving data."

This image shows a 90-mile-wide portion of the giant Valles Marineris canyon system. Landslide debris and gullies in the canyon walls on Mars can be seen at 100 meters (330 feet) per pixel. Credit: NASA/JPL/Arizona State University

Mars Odyssey was launched in April 2001 and reached the Red Planet in October 2001. Science operations began in February 2002. The mission is managed by JPL for NASA's Science Mission Directorate in Washington. Lockheed Martin Space Systems in Denver is the prime contractor for the project and built the spacecraft. NASA's Planetary Data System, sponsored by the Science Mission Directorate, archives and distributes scientific data from the agency's planetary missions, astronomical observations, and laboratory measurements.

For more information about NASA's Odyssey spacecraft, visit: .

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

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Friday, July 23, 2010

Close-Up View of Curiosity's 'Head'

This image shows a close-up of the Curiosity rover's "head." At the top is a white box structure with a large red circle (the rover's laser called ChemCam) to the right. Beneath the box are two cameras, which will provide views of the Martian surface. They are covered with protective silvery material.

Image credit: NASA/JPL-Caltech

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Clean Technology in 'Hot Water'

What if work performed in space could improve the treatment of household and nuclear waste on Earth? That's what investigators are hoping to do with the results of a fluid physics study in progress on the International Space Station.

The experiment, called DECLIC-HTI, is studying supercritical water that could lead to spin-offs in the field of clean technologies for treating waste here on Earth.

A supercritical fluid is any substance at a temperature and pressure above its critical point -- the point at which the fluid is one homogeneous phase and exhibits properties of both liquids and gases. In this form, the substance can flow through solids like a gas and dissolve materials like a liquid. Water and carbon dioxide are the most commonly used supercritical fluids. Using extremely high temperatures, supercritical water can completely break down waste into benign forms.

DECLIC, or DEvice for the study of Critical LIquids and Crystallization, is a miniaturized, automatic thermo-optical laboratory that studies transparent fluids by finely tuning the temperature of a sample and sending images and video to the ground. The HTI, or high temperature insert, can measure fluid temperatures up to 400 degrees Celsius.

The optical fluid cell for the study of water properties inside DECLIC-HTI. Image credit: CNES

For the experiment, astronauts plug an insert, containing the water sample cell, into the DECLIC payload. The sample is precisely heated and observed in real time by investigators on the ground.

"These phenomena will be of interest to understand the behavior of supercritical fluids in space, but also to improve industrial processes on the ground," said Gabriel Pont, DECLIC mission manager with the CNES, or Centre National d'Etudes Spatiales, in Toulouse, France.

"A typical example is burning completely organic or industrial waste in supercritical water at a much lower temperature than in conventional systems, thus saving energy and being cleaner. Microgravity will provide the ideal environment to understand how to do that."

Pure water above the critical point observed in wide field transmission during ground tests of DECLIC-HTI. Image credit: CNES

The supercritical water temperature is very sensitive to gravity and has never been measured in microgravity conditions. "We expect HTI to give us the best measurement of this temperature ever found," added Pont.

The experiment began in October 2009 when the High Temperature Insert commissioning was performed. Since then, four experimental sequences have been performed, leading to more than 80 running days. "We are very excited about what we've seen thus far, and cannot wait to see the potential benefits of our work on Earth," added Pont.

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Thursday, July 22, 2010

NASA Telescope Finds Elusive Buckyballs in Space

PASADENA, Calif. -- Astronomers using NASA's Spitzer Space Telescope have discovered carbon molecules, known as "buckyballs," in space for the first time. Buckyballs are soccer-ball-shaped molecules that were first observed in a laboratory 25 years ago.

They are named for their resemblance to architect Buckminster Fuller's geodesic domes, which have interlocking circles on the surface of a partial sphere. Buckyballs were thought to float around in space, but had escaped detection until now.

"We found what are now the largest molecules known to exist in space," said astronomer Jan Cami of the University of Western Ontario, Canada, and the SETI Institute in Mountain View, Calif. "We are particularly excited because they have unique properties that make them important players for all sorts of physical and chemical processes going on in space." Cami has authored a paper about the discovery that will appear online Thursday in the journal Science.

Buckyballs are made of 60 carbon atoms arranged in three-dimensional, spherical structures. Their alternating patterns of hexagons and pentagons match a typical black-and-white soccer ball. The research team also found the more elongated relative of buckyballs, known as C70, for the first time in space. These molecules consist of 70 carbon atoms and are shaped more like an oval rugby ball. Both types of molecules belong to a class known officially as buckminsterfullerenes, or fullerenes.

The Cami team unexpectedly found the carbon balls in a planetary nebula named Tc 1. Planetary nebulas are the remains of stars, like the sun, that shed their outer layers of gas and dust as they age. A compact, hot star, or white dwarf, at the center of the nebula illuminates and heats these clouds of material that has been shed.

The buckyballs were found in these clouds, perhaps reflecting a short stage in the star's life, when it sloughs off a puff of material rich in carbon. The astronomers used Spitzer's spectroscopy instrument to analyze infrared light from the planetary nebula and see the spectral signatures of the buckyballs. These molecules are approximately room temperature -- the ideal temperature to give off distinct patterns of infrared light that Spitzer can detect. According to Cami, Spitzer looked at the right place at the right time. A century from now, the buckyballs might be too cool to be detected.

The data from Spitzer were compared with data from laboratory measurements of the same molecules and showed a perfect match.

NASA's Spitzer Space Telescope has at last found buckyballs in space, as illustrated by this artist's conception showing the carbon balls coming out from the type of object where they were discovered. Image credit: NASA/JPL-Caltech

"We did not plan for this discovery," Cami said. "But when we saw these whopping spectral signatures, we knew immediately that we were looking at one of the most sought-after molecules."

In 1970, Japanese professor Eiji Osawa predicted the existence of buckyballs, but they were not observed until lab experiments in 1985. Researchers simulated conditions in the atmospheres of aging, carbon-rich giant stars, in which chains of carbon had been detected. Surprisingly, these experiments resulted in the formation of large quantities of buckminsterfullerenes. The molecules have since been found on Earth in candle soot, layers of rock and meteorites.

The study of fullerenes and their relatives has grown into a busy field of research because of the molecules' unique strength and exceptional chemical and physical properties. Among the potential applications are armor, drug delivery and superconducting technologies.

These data from NASA's Spitzer Space Telescope show the signatures of buckyballs in space. Image credit: NASA/JPL-Caltech/University of Western Ontario

Sir Harry Kroto, who shared the 1996 Nobel Prize in chemistry with Bob Curl and Rick Smalley for the discovery of buckyballs, said, "This most exciting breakthrough provides convincing evidence that the buckyball has, as I long suspected, existed since time immemorial in the dark recesses of our galaxy."

Previous searches for buckyballs in space, in particular around carbon-rich stars, proved unsuccessful. A promising case for their presence in the tenuous clouds between the stars was presented 15 years ago, using observations at optical wavelengths. That finding is awaiting confirmation from laboratory data. More recently, another Spitzer team reported evidence for buckyballs in a different type of object, but the spectral signatures they observed were partly contaminated by other chemical substances.

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Hyperfast Star Was Booted From Milky Way

A hundred million years ago, a triple-star system was traveling through the bustling center of our Milky Way galaxy when it made a life-changing misstep. The trio wandered too close to the galaxy's giant black hole, which captured one of the stars and hurled the other two out of the Milky Way. Adding to the stellar game of musical chairs, the two outbound stars merged to form a super- hot, blue star.

This story may seem like science fiction, but astronomers using NASA's Hubble Space Telescope say it is the most likely scenario for a so-called hypervelocity star, known as HE 0437-5439, one of the fastest ever detected. It is blazing across space at a speed of 1.6 million miles (2.5 million kilometers) an hour, three times faster than our Sun's orbital velocity in the Milky Way. Hubble observations confirm that the stellar speedster hails from the Milky Way's core, settling some confusion over where it originally called home.

Most of the roughly 16 known hypervelocity stars, all discovered since 2005, are thought to be exiles from the heart of our galaxy. But this Hubble result is the first direct observation linking a high-flying star to a galactic center origin.

"Using Hubble, we can for the first time trace back to where the star comes from by measuring the star's direction of motion on the sky. Its motion points directly from the Milky Way center," says astronomer Warren Brown of the Harvard- Smithsonian Center for Astrophysics in Cambridge, Mass., a member of the Hubble team that observed the star. "These exiled stars are rare in the Milky Way's population of 100 billion stars. For every 100 million stars in the galaxy lurks one hypervelocity star."

This illustration shows one possible mechanism for how the star HE 0437-5439 acquired enough energy to be ejected from our Milky Way galaxy. In this scenario, a triple-star system, consisting of a close binary system and another outer member bound to the group, is orbiting near the galaxy's monster black hole. One star is captured by the black hole and the tightly bound pair gets ejected from the galaxy. As the duo speeds through the galaxy, one member evolves more quickly and consumes the other. The resulting rejuvenated star, massive and very blue, is called a blue straggler. Credit: NASA, ESA, and A. Feild (STScI)

The movements of these unbound stars could reveal the shape of the dark matter distribution surrounding our galaxy. "Studying these stars could provide more clues about the nature of some of the universe's unseen mass, and it could help astronomers better understand how galaxies form," says team leader Oleg Gnedin of the University of Michigan in Ann Arbor. "Dark matter's gravitational pull is measured by the shape of the hyperfast stars' trajectories out of the Milky Way."

The stellar outcast is already cruising in the Milky Way's distant outskirts, high above the galaxy's disk, about 200,000 light-years from the center. By comparison, the diameter of the Milky Way's disk is approximately 100,000 light- years. Using Hubble to measure the runaway star's direction of motion and determine the Milky Way's core as its starting point, Brown and Gnedin's team calculated how fast the star had to have been ejected to reach its current location.

"The star is traveling at an absurd velocity, twice as much as the star needs to escape the galaxy's gravitational field," explains Brown, a hypervelocity star hunter who found the first unbound star in 2005. "There is no star that travels that quickly under normal circumstances-something exotic has to happen."

The hot, blue star HE 0437-5439 has been tossed out of the center of our Milky Way galaxy with enough speed to escape the galaxy's gravitational clutches. The stellar outcast is rocketing through the Milky Way's distant outskirts at 1.6 million miles an hour, high above the galaxy's disk, about 200,000 light-years from the center. The star is destined to roam intergalactic space. Credit: NASA, ESA, and G. Bacon (STScI)

There's another twist to this story. Based on the speed and position of HE 0437- 5439, the star would have to be 100 million years old to have journeyed from the Milky Way's core. Yet its mass - nine times that of our Sun - and blue color mean that it should have burned out after only 20 million years - far shorter than the transit time it took to get to its current location.

The most likely explanation for the star's blue color and extreme speed is that it was part of a triple-star system that was involved in a gravitational billiard-ball game with the galaxy's monster black hole. This concept for imparting an escape velocity on stars was first proposed in 1988. The theory predicted that the Milky Way's black hole should eject a star about once every 100,000 years.

Brown suggests that the triple-star system contained a pair of closely orbiting stars and a third outer member also gravitationally tied to the group. The black hole pulled the outer star away from the tight binary system. The doomed star's momentum was transferred to the stellar twosome, boosting the duo to escape velocity from the galaxy. As the pair rocketed away, they went on with normal stellar evolution. The more massive companion evolved more quickly, puffing up to become a red giant. It enveloped its partner, and the two stars spiraled together, merging into one superstar - a blue straggler.

"While the blue straggler story may seem odd, you do see them in the Milky Way, and most stars are in multiple systems," Brown says.

Compass/Scale Image of Hypervelocity Star HE 0437-5439 Credit: NASA, ESA, and Z. Levay (STScI)

This vagabond star has puzzled astronomers since its discovery in 2005 by the Hamburg/European Southern Observatory sky survey. Astronomers had proposed two possibilities to solve the age problem. The star either dipped into the Fountain of Youth by becoming a blue straggler, or it was flung out of the Large Magellanic Cloud, a neighboring galaxy.

In 2008 a team of astronomers thought they had solved the mystery. They found a match between the exiled star's chemical makeup and the characteristics of stars in the Large Magellanic Cloud. The rogue star's position also is close to the neighboring galaxy, only 65,000 light-years away. The new Hubble result settles the debate over the star's birthplace.

Astronomers used the sharp vision of Hubble's Advanced Camera for Surveys to make two separate observations of the wayward star 3 1/2 years apart. Team member Jay Anderson of the Space Telescope Science Institute in Baltimore, Md., developed a technique to measure the star's position relative to each of 11 distant background galaxies, which form a reference frame.

Anderson then compared the star's position in images taken in 2006 with those taken in 2009 to calculate how far the star moved against the background galaxies. The star appeared to move, but only by 0.04 of a pixel (picture element) against the sky background. "Hubble excels with this type of measurement," Anderson says. "This observation would be challenging to do from the ground."

Location of Hypervelocity Star HE 0437-5439 Credit: NASA, ESA, and Z. Levay (STScI)

The team is trying to determine the homes of four other unbound stars, all located on the fringes of the Milky Way.

"We are targeting massive 'B' stars, like HE 0437-5439," says Brown, who has discovered 14 of the 16 known hypervelocity stars. "These stars shouldn't live long enough to reach the distant outskirts of the Milky Way, so we shouldn't expect to find them there. The density of stars in the outer region is much less than in the core, so we have a better chance to find these unusual objects."

The results were published online in The Astrophysical Journal Letters on July 20, 2010. Brown is the paper's lead author.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA's Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI) conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc. in Washington, D.C.

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Wednesday, July 21, 2010

NASA Moves Forward on Commercial Partnership for Rocket Engine Testing

Engineers at NASA's John C. Stennis Space Center recently installed an Aerojet AJ26 rocket engine for qualification testing as part of a partnership that highlights the space agency's commitment to work with commercial companies to provide space transportation.

Stennis has partnered with Orbital Sciences Corporation to test the AJ26 engines that will power the first stage of the company's Taurus® II space launch vehicle. Orbital is working in partnership with NASA under the agency's Commercial Orbital Transportation Services (COTS) joint research and development project. The company is under contract with NASA through the Commercial Resupply Services program to provide eight cargo missions to the International Space Station through 2015.

An Aerojet AJ26 rocket engine is prepared to be installed in the E-1 Test Stand at Stennis Space Center. Image credit: NASA

Stennis operators have been modifying their E-1 test facility since April 2009 to test the AJ26 engines for Orbital. Work has included construction of a 27-foot-deep flame deflector trench.

The latest step in the project involved delivery and installation of an AJ26 engine for testing. In upcoming days, operators will perform a series of "chilldown" test, which involves running sub-cooled rocket propellants through the engine, just as will occur during an actual "hotfire" ignition test.

The chilldown tests are used to verify proper temperature conditioning of the engine systems and elapse time required to properly chill the engine, and to measure the quantity of liquid oxygen required to perform the operation.

Once the installed engine passes the chilldown and other qualification tests, it will be removed from the Stennis E-1 test facility. The first actual flight engine then will be delivered and installed for hotfire testing.

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Arctic Voyage Illuminating Ocean Optics

During NASA's ICESCAPE voyage to the Arctic, scientists have been looking at the phytoplankton in the Arctic's Chukchi Sea -- how many, how big and at what depths they are found. But there are other ways of looking at these small life forms.

"We measure phytoplankton in terms of their pigments and light absorption properties," said Stan Hooker of NASA's Ocean Biology and Biogeochemistry Calibration and Validation Office at Goddard Space Flight Center, Greenbelt, Md. Hooker, Joaquin Chaves and Aimee Neeley, also of NASA, measure the color of the water. Anything in the water, plankton or not, can influence that color.

The Arctic survey boat is lowered by crane for science excursions away from the main ship, which can mix water and cast a shadow. On July 2, NASA's Stan Hooker and Joaquin Chaves board the boat with Coast Guard crew to make first-of-a-kind measurements near the edge of Arctic sea ice. Credit: NASA/Kathryn Hansen

On July 2, a crane maneuvered a small boat halfway down the side of the U.S. Coast Guard Cutter Healy – the platform for the five-week ICESCAPE mission, NASA's first dedicated oceanographic field campaign, which is studying the physics, chemistry and biology of the ocean and sea ice within a changing Arctic.

Hooker, Chaves and Coast Guard crew boarded the small boat and readied for an expedition away from the stirred water and shadow of the 420-foot Healy. Lowered to the ocean surface, Hooker's team powered away, entering uncharted waters.

Maneuvering over smooth water and around chunks of sea ice, the small boat slowed to a stop near the edge of an ice floe.

Sensors on the Hydroscat 6 instrument measured optical properties of the Chukchi Sea at various depths. Some sensors emit light and measure how much is scattered back, while others measure the abundance of chlorophyll and dissolved organic matter. Credit: NASA/Kathryn Hansen

"This is new for us because we usually haven't been able to work this close to the ice before," Hooker said. "Satellites can't measure near the ice, so we do this to help specify the next generation of equipment, and to contribute to the science objectives."

First over the side was a small red instrument that the crew dropped on a line into the ocean and then reeled by hand, as if wrangling a fish. Sensors on the instrument measured the wavelengths of sunlight at different depths - both what's coming into the ocean and what's reflected back out which is similar to what is "seen" by satellites.

Next the crew lowered a second, larger package of instruments into the depths of the ocean. One pair of sensors emits light and measures how much is scattered back. Another pair measures the fluorescence of chlorophyll and colored dissolved organic matter, an important distinction as both appear green to satellites.

Last, the crew collected water samples to be returned to the Healy for analysis in the lab.

Crew from the Healy worked on the Arctic survey boat on July 2 reeling in an instrument from the Chukchi Sea that measures sunlight and how it interacts with the water. The measurements are similar to those made by ocean-observing satellites. Credit: NASA/Kathryn Hansen

"We can measure the changes in the color to find out what's happening with the ecology," said Greg Mitchell, a research biologist at Scripps Institution of Oceanography in San Diego, who analyzes the water samples. "We can relate color back to how much chlorophyll is in the ocean, how much algae biomass there is, and processes such as the rate of photosynthesis."

Similar, more frequent measurements are made from the Healy, which marked its one-hundredth ocean station of the mission on July 8. The small boat deploys less often -- almost daily -- but reaches more targeted regions.

"We do the measurements at sea in order to relate what's going on in the ocean with the optics," Mitchell said. "Then we apply those relationships to the optical data from the ocean color satellites and we can make estimates of processes and distributions globally."

Onboard the Healy to help scientists figure out where to sample is Bob Pickart, a physical oceanographer from Woods Hole Oceanographic Institution. Pickart can decipher water type and circulation to guide where to make measurements.

A great unknown, for example, is a picture of what's feeding the evolution of a "hotspot" in Barrow Canyon. Right now, winter water -- rich with nutrients -- has been carried across the shallow shelf where the Healy is surveying.

"This is a really interesting, important time of year," Pickart said. "As the ice recedes, productivity is starting and things are getting cranked up."

Chief scientist Kevin Arrigo (right) and physical oceanographer Bob Pickart analyze a map of the Chukchi and Beaufort seas on July 2, planning a route for the science mission. Pickart points to Barrow Canyon, the site of an ecological hotspot. Credit: NASA/Kathryn Hansen

But for how long will these hotspots thrive? While this is dictated by light and nutrients, the circulation near Barrow and Herald canyons -- two fissures that channel water off the shelf -- plays a vitally important role as well.

On July 12, after a night of cutting through sea ice, ICESCAPE scientists caught a glimpse of the hotspot. As an instrument lowered from the Healy descended through the water, real-time fluorescence information showed low levels of chlorophyll.

Scientists on the Healy will analyze the hotspot data and water samples, but whether a plankton bloom has come and gone, the region remains a hotspot for ground-dwelling communities, according to Karen Frey of Clark University. Feeding off plankton that sink to the seafloor, species here are diverse and large. A single sample retrieved from the ocean floor turned up a large crab, sponges and a sea star.

Meanwhile, samples returned from the near-ice survey July 2 on the small boat are turning up mixed results – sometimes indicating the presence of phytoplankton communities and sometimes not, according to Atsushi Matsuoka, of Laboratoire d'Oceanographie de Villefranche. To find out why, his group will look at trends after returning home from ICESCAPE.

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Tuesday, July 20, 2010

Robot Goes to Work While Crew Prepares for Spacewalks

Robotics and spacewalk preparations took center stage Tuesday aboard the International Space Station as the Expedition 24 crew orbited above the Earth.

Dextre, an agile, two-armed extension for the station’s Canadarm2 robotic arm, continues its debut task to replace a failed Remote Power Control Module (RPCM) from a truss segment on the station’s port side. On Tuesday flight controllers in Houston began conducting a “dress rehearsal” of the actual replacement as they commanded Dextre to partially remove and reinstall an RPCM on the P1 truss. After Dextre successfully completes the test, Mission Control plans to swap the failed RPCM with a spare from the P3 truss Wednesday.

Meanwhile the Expedition 24 crew continued its own preparations to venture outside the station for an upcoming pair of spacewalks.

Image above: The Soyuz TMA-19 spacecraft (partially out of frame in the foreground), docked to the Rassvet Mini-Research Module 1, and the ISS Progress 37 resupply vehicle, docked to the Pirs Docking Compartment, are featured in this image. Credit: NASA

Cosmonauts Fyodor Yurchikhin and Mikhail Kornienko, both flight engineers, prepared the cooling loops of the Russian Orlan spacesuits they will wear during a six-hour spacewalk set to begin the evening of July 26. The pair will install Kurs automated rendezvous equipment on the exterior of the recently delivered Rassvet module to facilitate future dockings with Russian spacecraft.

Flight Engineers Doug Wheelock and Tracy Caldwell Dyson continued preparations for their Aug. 5 spacewalk as they each conducted a session of onboard training for Simplified Aid for EVA Rescue, or SAFER. Should a spacewalker become untethered during a spacewalk and begin floating away, the small nitrogen-jet thrusters of SAFER could help the astronaut get back to the station.

Shannon Walker, also a station flight engineer, assisted with the American spacewalk preparations as she inspected safety and waist tethers for structural integrity and reviewed spacewalk procedures.

The Expedition 24 crew also tackled a number of science investigations Tuesday. Commander Alexander Skvortsov spent part of his day working with a Russian experiment known as Russalka, which involves using a camera equipped with an ultraviolet filter to collect measurements of methane and carbon dioxide in the Earth’s atmosphere.

Wheelock prepared the Solution Crystallization Observation Facility for a Japanese study of facet-like crystallization. The results of this experiment may provide valuable data on creating high quality materials for industrial use such as superconducting magnets.

The Americans also continued maintenance work on the Oxygen Generation System, flushing the components that allow liquid to flow through the system so that oxygen can be extracted from recycled water to provide air for the crew to breathe.

Later, Walker assisted Wheelock with the latest session of Kids In Micro-Gravity!, an experiment that gives students a hands-on opportunity to design a demonstration that can be performed both in the classroom and aboard the station. Tuesday’s activity, a look at whether blowing across the tops of bottles filled with different amounts of water will create the same tones in space as on Earth, was developed by fifth grade students at Vaughan Elementary in Powder Springs, Ga.

Researchers can learn more about opportunities to develop and fly science experiments on the International Space Station (ISS) at the NASA ISS Research Academy Aug. 3-5 in League City, Texas.

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Test Image by Mars Descent Imager

The Mars Descent Imager for NASA's Mars Science Laboratory took this image inside the Malin Space Science Systems clean room in San Diego, Calif., during calibration testing of the camera in June 2008. It shows the instrument's deputy principal investigator, Ken Edgett, holding a six-foot metal ruler that was used as a depth-of-field test target. The camera is focused at 7 meters (23 feet) so that everything between about 2 meters (7 feet) and infinity is in focus.

This image shows a slightly out-of-focus rock (a rounded cobble of Icelandic basalt with tiny crystals and vesicles) at a distance of about 70 centimeters (2.3 feet), equivalent to the distance the camera will be from the ground after the rover has landed.

Image credit: NASA/JPL-Caltech/Malin Space Science Systems

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Mars Descent Imager for Curiosity

This Mars Descent Imager (MARDI) camera will fly on the Curiosity rover of NASA's Mars Science Laboratory mission.

The downward-looking camera will take about four frames per second at nearly 1,600 by 1,200 pixels per frame for about the final two minutes before Curiosity touches down on Mars in August 2012. Malin Space Science Systems, San Diego, Calif., supplied MARDI and two other camera instruments for the mission. A pocketknife provides scale for the image.

Image credit: NASA/JPL-Caltech/Malin Space Science Systems

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Monday, July 19, 2010

See Beautiful Ontario Lacus: Cassini's Guided Tour

Ontario Lacus, the largest lake in the southern hemisphere of Saturn's moon Titan, turns out to be a perfect exotic vacation spot, provided you can handle the frosty, subzero temperatures and enjoy soaking in liquid hydrocarbon.

Several recent papers by scientists working with NASA's Cassini spacecraft describe evidence of beaches for sunbathing in Titan's low light, sheltered bays for mooring boats, and pretty deltas for wading out in the shallows. They also describe seasonal changes in the lake's size and depth, giving vacationers an opportunity to visit over and over without seeing the same lake twice. (Travel agents, of course, will have to help you figure out how to breathe in an atmosphere devoid of oxygen.)

Using data that give us the most detailed picture yet of a lake on another world, scientists and animators have collaborated on a new video tour of Ontario Lacus based on radar data from Cassini's Titan flybys on June 22, 2009, July 8, 2009, and Jan. 12, 2010. A Web video explaining how scientists look to Earth's Death Valley to understand places like Titan's Ontario Lacus is available at:

"With such frigid temperatures and meager sunlight, you wouldn't think Titan has a lot in common with our own Earth," said Steve Wall, deputy team lead for the Cassini radar team, based at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "But Titan continues to surprise us with activity and seasonal processes that look marvelously, eerily familiar."

Cassini arrived at Saturn in 2004 when the southern hemisphere of the planet and its moons were experiencing summer. The seasons have started to change toward autumn, with winter solstice darkening the southern hemisphere of Titan in 2017. A year on Titan is the equivalent of about 29 Earth years.

This image of Ontario Lacus, the largest lake on the southern hemisphere of Saturn's moon Titan, was obtained by NASA's Cassini spacecraft on Jan. 12, 2010. Image Credit: NASA/JPL-Caltech

Titan is the only other world in our solar system known to have standing bodies of liquid on its surface. Because surface temperatures at the poles average a chilly 90 Kelvin (about minus 300 degrees Fahrenheit), the liquid is a combination of methane, ethane and propane, rather than water. Ontario Lacus has a surface area of about 15,000 square kilometers (6,000 square miles), slightly smaller than its terrestrial namesake Lake Ontario.

Cassini first obtained an image of Ontario Lacus with its imaging camera in 2004. A paper submitted to the journal Icarus by Alex Hayes, a Cassini radar team associate at the California Institute of Technology in Pasadena, and colleagues finds that the lake's shoreline has receded by about 10 kilometers (6 miles). This has resulted in a liquid level reduction of about 1 meter (3 feet) per year over a four–year period.

The shoreline appears to be receding because of liquid methane evaporating from the lake, with a total amount of evaporation that would significantly exceed the yearly methane gas output of all the cows on Earth, Hayes said. Some of the liquid could also seep into porous ground material. Hayes said the changes in the lake are likely occurring as part of Titan's seasonal methane cycle, and would be expected to reverse during southern winter.

This seasonal filling and receding is similar to what occurs at the shallow lakebed known as Racetrack Playa in Death Valley National Park, Hayes said. In fact, from the air, the topography and shape of Racetrack Playa and Ontario Lacus are quite similar, although Ontario Lacus is about 60 times larger.

"We are very excited about these results, because we did not expect Cassini to be able to detect changes of this magnitude in Titan's lakes," Hayes said. "It is only through the continued monitoring of seasonal variation during Cassini's extended mission that these discoveries have been made possible."

Other parts of the Ontario Lacus' shoreline, as described in the paper published in Geophysical Research Letters in March 2010 by Wall, Hayes and other colleagues, show flooded valleys and coasts, further proof that the lake level has changed.

The delta revealed by Cassini radar data on the western shore of Ontario Lacus is also the first well-developed delta observed on Titan, Wall said. He explained that the shape of the land there shows liquid flowing down from a higher plain switching channels on its way into the lake, forming at least two lobes.

Examples of this kind of channel switching and wave-modified deltas can be found on Earth at the southern end of Lake Albert between Uganda and the Democratic Republic of Congo in Africa, and the remains of an ancient lake known as Megachad in the African country Chad, Wall said.

The radar data also show a smooth beach on the northwestern shore of Ontario Lacus. Smooth lines parallel to the current shoreline could be formed by low waves over time, which were likely driven by winds sweeping in from the west or southwest. The pattern at Ontario Lacus resembles what might be seen on the southeastern side of Lake Michigan, where waves sculpt the shoreline in a similar fashion.

"Cassini continues to take our breath away as it fills in the details on the surfaces of these far-off moons," said Linda Spilker, Cassini project scientist based at JPL. "It's exhilarating to ride along as it takes us on the ultimate cold-weather adventure."

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. JPL manages the Cassini-Huygens mission for NASA's Science Mission Directorate. The Cassini orbiter was designed, developed and assembled at JPL. The radar instrument was built by JPL and the Italian Space Agency, working with team members from the United States and several European countries.

More Cassini information is available, at,

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Giant Antenna Propped up and Ready for Joint Replacement

Workers at NASA's Deep Space Network complex in Goldstone, Calif., have been making precise, laser-assisted measurements to ensure a flat surface for pouring new grout as part of a major renovation on the 70-meter-wide (230-foot-wide) "Mars antenna." While officially dubbed Deep Space Station 14, the antenna picked up the Mars name from its first task: tracking NASA's Mariner 4 spacecraft, which had been lost by smaller antennas after its historic flyby of Mars.

This work represents the first time network engineers have redesigned and replaced the hydrostatic bearing assembly, which enables the antenna to rotate horizontally. To accomplish this, they lifted the entire rotating structure of the giant antenna for the first time.

The hydrostatic bearing assembly puts the weight of the antenna on three pads, which glide on a film of oil around a large steel ring. The ring measures about 24 meters (79 feet) in diameter and must be flat to work efficiently. After 44 years of near-constant use, the Mars antenna needed a kind of joint replacement, since the bearing assembly had become uneven.

As the sun sets on July 8, 2010, workers prepare to pour new epoxy grout for thehydrostatic bearing assembly of the giant "Mars antenna" at NASA's Deep Space Network communications site in Goldstone, Calif. Image credit: NASA/JPL-Caltech

Engineers and managers at NASA's Jet Propulsion Laboratory in Pasadena, Calif., which manages the Deep Space Network for NASA, drew up plans for new runner segments, new sole plates below the runner segments, and an epoxy grout that is more impervious to oil. The thicker segments deform less when the antenna's pads pass over them, and allow for more tightly sealed joints.

Tim Sink, an engineer at NASA's Jet Propulsion Laboratory in Pasadena, Calif., checks the evenness of sole plates installed on the giant "Mars antenna" at the DSN site. Image credit: NASA/JPL-Caltech

Since beginning work in March, engineers and technicians have carefully lifted several million pounds of delicate scientific instruments about five millimeters (0.2 inches) and transferred the weight of the antenna to temporary supporting legs. They have removed the old steel runner and cement-based grout. They have also installed sole plates, which cover the grout and anchor the new runner. Over the past week, JPL engineers checked to make sure the sole plates were level, and workers poured the new epoxy grout underneath to hold them in place. Mixing and pouring the new grout occurred at night to ensure the work was completed within the tight temperature tolerances required to handle this material.

Over the next few weeks, the new, thicker steel runner segments will be installed. Work is on track to return the antenna to service on Nov. 1, 2010.

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Sunday, July 18, 2010

NASA Finds Super-Hot Planet with Unique Comet-Like Tail

Astronomers using NASA's Hubble Space Telescope have confirmed the existence of a baked object that could be called a "cometary planet." The gas giant planet, named HD 209458b, is orbiting so close to its star that its heated atmosphere is escaping into space.

Observations taken with Hubble's Cosmic Origins Spectrograph (COS) suggest powerful stellar winds are sweeping the cast-off atmospheric material behind the scorched planet and shaping it into a comet-like tail.

"Since 2003 scientists have theorized the lost mass is being pushed back into a tail, and they have even calculated what it looks like," said astronomer Jeffrey Linsky of the University of Colorado in Boulder, leader of the COS study. "We think we have the best observational evidence to support that theory. We have measured gas coming off the planet at specific speeds, some coming toward Earth. The most likely interpretation is that we have measured the velocity of material in a tail."

The planet, located 153 light-years from Earth, weighs slightly less than Jupiter but orbits 100 times closer to its star than the Jovian giant. The roasted planet zips around its star in a short 3.5 days. In contrast, our solar system's fastest planet, Mercury, orbits the Sun in 88 days. The extrasolar planet is one of the most intensely scrutinized, because it is the first of the few known alien worlds that can be seen passing in front of, or transiting, its star. Linsky and his team used COS to analyze the planet's atmosphere during transiting events. During a transit, astronomers study the structure and chemical makeup of a planet's atmosphere by sampling the starlight that passes through it. The dip in starlight because of the planet's passage, excluding the atmosphere, is very small, only about 1.5 percent. When the atmosphere is added, the dip jumps to 8 percent, indicating a bloated atmosphere.

Illustration Credit: NASA, ESA, and G. Bacon (STScI)

COS detected the heavy elements carbon and silicon in the planet's super-hot, 2,000-degree-Fahrenheit atmosphere. This detection revealed the parent star is heating the entire atmosphere, dredging up the heavier elements and allowing them to escape the planet.

The COS data also showed the material leaving the planet was not all traveling at the same speed. "We found gas escaping at high velocities, with a large amount of this gas flowing toward us at 22,000 miles per hour," Linsky said. "This large gas flow is likely gas swept up by the stellar wind to form the comet-like tail trailing the planet."

Hubble's newest spectrograph has the ability to probe a planet's chemistry at ultraviolet wavelengths not accessible to ground-based telescopes. COS is proving to be an important instrument for probing the atmospheres of "hot Jupiters" like HD 209458b.

Another Hubble instrument, the Space Telescope Imaging Spectrograph (STIS), observed the planet in 2003. The STIS data showed an active, evaporating atmosphere, and a comet-tail-like structure was suggested as a possibility. But STIS wasn't able to obtain the spectroscopic detail necessary to show a tail, or an Earthward-moving component of the gas, during transits. The tail was detected for the first time because of the unique combination of very high ultraviolet sensitivity and good spectral resolution provided by COS.

Although this extreme planet is being roasted by its star, it won't be destroyed anytime soon. "It will take about a trillion years for the planet to evaporate," Linsky said.

The results appeared in the July 10 issue of The Astrophysical Journal.

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency. NASA’s Goddard Space Flight Center manages the telescope. The Space Telescope Science Institute (STScI) conducts Hubble science operations. STScI is operated for NASA by the Association of Universities for Research in Astronomy, Inc. in Washington, D.C.

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Final Tank Arrives at Kennedy

At NASA's Kennedy Space Center in Florida, workers inspect External Tank-138, newly offloaded from the Pegasus barge docked in the turn basin near the Vehicle Assembly Building.

The external fuel tank arrived in Florida on July 13, from NASA's Michoud Assembly Facility near New Orleans. It is the last newly manufactured tank and is designated to fly on space shuttle Endeavour's STS-134 mission to the International Space Station.

Image credit: NASA/Jack Pfaller
July 14, 2010

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Monday, July 05, 2010

Saturn System Moves Oxygen From Enceladus to Titan

Complex interactions between Saturn and its satellites have led scientists using NASA's Cassini spacecraft to a comprehensive model that could explain how oxygen may end up on the surface of Saturn's icy moon Titan. The presence of these oxygen atoms could potentially provide the basis for pre-biological chemistry.

The interactions are captured in two papers, one led by John Cooper and another led by Edward Sittler, published in the journal Planetary and Space Science in late 2009. Cooper and Sittler are Cassini plasma spectrometer team scientists at NASA's Goddard Space Flight Center in Greenbelt, Md.

"Titan and Enceladus, another icy moon of Saturn, are chemically connected by the flow of material through the Saturn system," Cooper said.

In one paper, Cooper and colleagues provide an explanation for forces that could generate the Enceladus geysers that spew water vapor into space. In the other, published in the same issue, Sittler and colleagues describe a unique new process in which oxygen that circulates in the upper atmosphere of Titan can be carried all the way to the surface without further chemical contamination by being encased in carbon cages called fullerenes.

The work draws upon previous work by Sittler and others that model the dynamics of how particles, including water molecules, travel from Enceladus to Titan. At Enceladus the flow process begins with what they call the "Old Faithful" model, after the Old Faithful geyser in Yellowstone National Park. In this model, gas pressure slowly builds up inside Enceladus, then gets released occasionally in geyser-like eruptions.

Unlike terrestrial geysers, or even geyser-like forces on Jupiter's moon Io, the model proposed by Cooper shows that charged particle radiation raining down from Saturn’s magnetosphere can create the forces from below the surface that are required to eject gaseous jets.

Energetic particles raining down from Saturn's magnetosphere – at Enceladus, mostly electrons from Saturn's radiation belts -- can break up molecules within the surface. This process is called radiolysis. Like a process called photolysis, in which sunlight can break apart molecules in the atmosphere, energetic radiation from charged particles that hit an icy surface, like that of Enceladus, can cause damage to molecules within the ice. These damaged molecules can get buried deeper and deeper under the surface by the perpetual churning forces that can repave the icy surface. Meteorites constantly crashing into the surface and splashing out material might also be burying the molecules.

This annotated image collage features Saturn and the moons Titan, Enceladus, Dione, Rhea and Helene, which are being studied by the Cassini mission. Image credit: NASA/JPL/Space Science Institute

When chemically altered icy grains come into contact beneath the surface with icy contaminants such as ammonia, methane and other hydrocarbons, they can produce volatile gases that can explode outward. Such gases can create plumes of the size seen by Cassini. Cooper and colleagues call such icy volatile mechanics "cryovolcanism."

What's unique about the "Old Faithful" model is that it "is a model for cryovolcanism that is based on not only liquid water, but also requires the production of gases by the radiolytic chemistry observed at Enceladus," said Sittler.

The plumes that emanate from Enceladus' south polar region consist of water, ammonia and other compounds. Scientists have known since the 1980s that Saturn's magnetosphere is inexplicably filled with neutral particles. In the intervening decades, particularly since the discovery of plumes jetting out from the south pole of Enceladus, work has shown how some of the water molecules that escape from Enceladus get split up into neutral and charged particles and are transported throughout Saturn's magnetosphere.

Sittler's new model indicates that as these broken water molecules enter Titan's atmosphere, they may be captured by fullerenes—hollow, soccer-ball shaped shells made of carbon atoms. Although the heavy molecules Cassini has detected in the upper atmosphere of Titan may be other molecules, Sittler suggests they are likely fullerenes.

In Sittler's model, the fullerenes then condense into larger clusters that can attach to polycyclic aromatic hydrocarbons—chemical compounds also found on Earth in oil, coal and tar deposits, and as the byproducts of burning fossil fuels. The fullerene clusters form even larger aerosols that travel down to Titan's surface.

This process protects the trapped oxygen from Titan's atmosphere, which is saturated with hydrogen atoms and compounds that are capable of breaking down other molecules. Otherwise, the oxygen would combine with methane in Titan's atmosphere and form carbon monoxide or carbon dioxide. Until now, scientists have not been able to explain how oxygen fits into the picture of the dynamics and chemistry of Saturn and its moons.

As the oxygen-rich aerosols fall to Titan's surface, they are further bombarded by products of galactic cosmic ray interactions with Titan's atmosphere. Cosmic rays bombarding the oxygen-stuffed fullerenes could produce more complex organic materials, such as amino acids, in the carbon-rich and oxygen-loaded fullerenes. Amino acids are considered important for pre-biological chemistry.

Scientists have been able to couple the new models that describe the generation of plumes at Enceladus and oxygen ion capture in fullerenes near the top of Titan's atmosphere to existing theories of the transport of oxygen across the magnetosphere. Taken together, Sittler and Cooper suggest a chemical pathway that allows the oxygen to be introduced to Titan's surface chemistry.

"Cooper and Sittler's work helps us understand more about the potential for chemical interactions among Saturn's moons," said Linda Spilker, Cassini project scientist at NASA's Jet Propulsion Laboratory in Pasadena, Calif.

"The Saturn system is indeed a dynamic place, with the Enceladus plumes creating the E ring and loading the magnetosphere with water which interacts with Titan and the other moons," Spilker said.

The Cassini mission is a joint effort of NASA, the European Space Agency, and the Italian space agency Agenzia Spaziale Italiana. The mission is managed for NASA by the Jet Propulsion Laboratory, a division of the California Institute of Technology. Partners include the U.S. Air Force, Department of Energy, and academic and industrial participants from 19 countries.

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