vendredi 9 décembre 2011

Cassini to Make a Double Play

NASA - Cassini Mission to Saturn patch.

Dec. 9, 2011

Image above: A quartet of Saturn's moons, from tiny to huge, surround and are embedded within the planet's rings in this Cassini composition. Image credit: NASA/JPL-Caltech/Space Science Institute.

In an action-packed day and a half, NASA's Cassini spacecraft will be making its closest swoop over the surface of Saturn's moon Dione and scrutinizing the atmosphere of Titan, Saturn's largest moon.

The closest approach to Dione, about 61 miles (99 kilometers) above the surface, will take place at about 1:39 a.m. PST (4:39 a.m. EST) on Dec. 12. One of the questions Cassini scientists will be asking during this flyby is whether Dione's surface shows any signs of activity. Understanding Dione's internal structure will help address that question, so Cassini's radio science instrument will learn how highly structured the moon's interior is by measuring variations in the moon's gravitational tug on the spacecraft. The composite infrared spectrometer instrument will also look for heat emissions along fractures on the moon's surface.

Cassini will also be probing whether Dione, like another Saturnian moon, Rhea, has a tenuous atmosphere. Scientists expect a Dionean atmosphere – if there is one – to be much more ethereal than even Rhea's. Research published in journal Geophysical Research Letters and led by Sven Simon, a Cassini magnetometer team member at the University of Cologne, Germany, found magnetic field disturbances around Dione, hinting at a tenuous atmosphere. But scientists hope to get stronger confirmation by "tasting" the space around the moon with Cassini's ion and neutral mass spectrometer.

On Cassini's journey out from Dione toward Titan, the imaging science subsystem will turn back to look at Dione's distinctive, wispy fractures and a ridge called Janiculum Dorsa.

Cassini will approach within about 2,200 milles (3,600 kilometers) of the Titan surface, at about 12:11 p.m. PST (3:11 PM EST) on Dec. 13. At Titan, the composite infrared spectrometer will be making measurements to understand how the seasonal transition from spring to summer affects wind patterns in the atmosphere near Titan's north pole. It will also search for mist.

Cassini spacecraft

The visual and infrared mapping spectrometer and imaging science subsystem will be observing the same equatorial deserts where the imaging science subsystem saw sudden and dramatic surface changes last year, when Titan was experiencing early northern spring. One possibly theory is that rainstorms caused these changes. As Cassini recedes from Titan, the imaging cameras will also continue to observe the moon for another day to monitor any new weather systems. The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington.

More Cassini information is available at and

Image, Text, Credit: NASA / JPL / Jia-Rui Cook.


LRO Observes Final Lunar Eclipse of the Year

NASA - Lunar Reconnaissance Orbiter (LRO) patch.

Dec. 9, 2011

Orbiting 31 miles above the lunar surface, NASA's Lunar Reconnaissance Orbiter (LRO) spacecraft will get a "front-row seat" to the total lunar eclipse on Dec. 10, 2011.

LRO's Diviner instrument will record how quickly targeted areas on the moon's day side cool off during the eclipse. The degree of cooling is dependent on factors such as how rocky the surface is, how densely packed the soil is, and its mineral composition. By studying the lunar surface during the eclipse, scientists can learn even more about our nearest celestial neighbor.

Video above: During the December 2011 lunar eclipse, scientists will be able to get a unique view of the moon. While the sun is blocked by the Earth, LRO's Diviner instrument will take the temperature on the lunar surface. Since different rock sizes cool at different rates, scientists will be able to infer the size and density of rocks on the moon. (Video Credit: Christopher Smith, NASA's Goddard Space Flight Center).

From beginning to end, the eclipse will last from 11:33 UT (6:33 a.m. EST, 3:33 a.m. PST) to 17:30 UT (12:30 p.m. EST, 9:30 a.m. PST). Totality, the time when Earth's shadow completely covers the moon, will last 51 minutes. All of the United States will see some portion of the eclipse. The West Coast will have a more complete view of this particular eclipse.

The West Coast will see totality as the moon sets and the sun rises. For West Coast viewers, the eclipse begins at 3:33 a.m. PST. The peak, when the moon is a deep red, occurs at 6:30 a.m. PST.

For East Coast residents, the only stage of the eclipse that will be visible is the earliest portion when the moon begins to enter Earth's shadow. This dimming is very slight and may be difficult to see.

Video above: When the moon passes through the Earth's shadow, it causes the moon to look very unusual for a short period of time. This event is called a lunar eclipse, and it occurs roughly twice a year. Learn more about how lunar eclipses work in this video! Credit goes to TheWusa from for the illustrations that this video’s light scattering animations are based on. (Video Credit: Christopher Smith, NASA's Goddard Space Flight Center).

A lunar eclipse occurs when Earth is directly between the sun and the moon, blocking the sun's rays and casting a shadow on the moon. As the moon moves deeper and deeper into Earth's shadow, the moon changes color before your very eyes, turning from gray to an orange or deep shade of red.

This 2003 image shows the ruddy appearance typical of the moon during a lunar eclipse. Credit: Fred Espenak.

The moon takes on this new color because sunlight is still able to pass through Earth's atmosphere and cast a glow on the moon. Our atmosphere filters out most of the blue colored light, leaving the red and orange hues that we see during a lunar eclipse. If there are additional dust particles in the atmosphere, the moon will appear to be a darker shade of red.

Unlike solar eclipses, lunar eclipses are perfectly safe to view without any special glasses or equipment. All you need is your own two eyes. Our next opportunity to view a total lunar eclipse from the U.S. is April 15, 2014, so mark your calendars!

For more information on lunar eclipses, visit or

Image (mentioned), Videos (mentioned), Text, Credit: NASA's Goddard Space Flight Center / Nancy Jones.


Antarctic expedition checks CryoSat down-under

ESA - Cryosat 2 Mission logo.

9 December 2011

Next week marks 100 years since Roald Amundsen reached the South Pole. As a team of scientists brave the Antarctic to validate data from ESA’s CryoSat mission, it’s hard to imagine what these first intrepid explorers would have thought of today’s advances in polar science.

The remote and vast expanse of the Antarctic is arguably the most hostile environment on Earth – infamously claiming the lives of Captain Robert Scott and his party all those years ago in their fated race to the South Pole.

Skidoo and corner reflector

While the polar regions are challenging, to say the least, for human survival, they are also very sensitive to climate change. In turn, polar ice plays a crucial role in regulating climate and sea level.

With the effects of climate change becoming more apparent, the CryoSat mission is gathering data on changes in the thickness of ice, both on land and floating in the oceans. 

This information is needed to understand exactly how Earth’s ice is responding to climate change and to help predict what will happen if trends continue.


To ensure CryoSat’s data are as accurate as possible, ESA organises numerous research campaigns in the Arctic and Antarctic.

These campaigns involve taking measurements from the air and on the ice to compare with the data from CryoSat orbiting above.

A team of Australian and German scientists from the University of Tasmania, the Australian Antarctic Division and the Alfred Wegner Institute has just finished the first leg a remarkable measurement campaign.

Polar-6 research aircraft

The campaign is being carried out in East Antarctica around Law Dome and Totten Glacier. Law Dome is relatively stable but features steep surface slopes and Totten Glacier is changing rapidly – so both offer ideal locations for validating CryoSat.

CryoSat carries a new generation of altimeter called SIRAL. It is designed to measure very precisely the elevation of polar ice – even around the edges of ice sheets, which are difficult to observe from space because of their steep slopes.

Instruments inside the Polar-6

The campaign involves taking measurements from a Polar-6 aircraft. It carries the ASIRAS radar, which mimics CryoSat’s SIRAL. Ground-truth measurements are also collected for comparison.

Christopher Watson from the University of Tasmania said, “Travelling on skidoo, the team gathered ground measurement over about 250 km transects.

“The skidoos drag GPS to map the height of the ice, which are later compared to the aircraft and satellite measurements.”

“The experiment examines the influence that physical properties of the top snow and ice layer have on the radar signal that CryoSat emits and receives,” explained Veit Helm from the Alfred Wegner Institute.

Sampling snow and ice

“Depending on factors such as snow particle size, the extent to which it has compacted and how it is layered, the radar signal can penetrate deeper or less deep and so is reflected differently.

“If we ignore these factors in the data, it may result in misinterpretations and less accurate maps of the changing Antarctic surface.”

Malcolm Davidson, ESA’s CryoSat Validation Manager, said, “The first attempt in East Antarctica had to be abandoned owing to terrible weather conditions.


“This makes the success of this year’s activity highly-value and very welcome – both for ESA and for the scientists carrying out this challenging field work.

“It also provides a welcome opportunity to bring together the Alfred Wegener Institute, the University of Tasmania and the Australian Antarctic Division, whose work will help ensure we have the best-possible data to understand changing polar ice from space.”

Related links:

University of Tasmania:

Australian Antarctic Division:

Alfred Wegener Institute:

Access CryoSat data:

In depth:



Images, Video, Text, Credits: ESA /AOES Medialab / FIELAX–J. Käßbohrer / AWI–V. Helm / AAD–D. Blight / AWI–V. Helm.

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jeudi 8 décembre 2011

NASA Mars Rover Finds Mineral Vein Deposited by Water

NASA- Mars Exploration Rover "Opportunity" (MER-B).

Dec. 8, 2011

This color view of a mineral vein called "Homestake" comes from the panoramic camera (Pancam) on NASA's Mars Exploration Rover Opportunity. Image credit: NASA/JPL-Caltech/Cornell/ASU.

NASA's Mars Exploration Rover Opportunity has found bright veins of a mineral, apparently gypsum, deposited by water. Analysis of the vein will help improve understanding of the history of wet environments on Mars.

"This tells a slam-dunk story that water flowed through underground fractures in the rock," said Steve Squyres of Cornell University, principal investigator for Opportunity. "This stuff is a fairly pure chemical deposit that formed in place right where we see it. That can't be said for other gypsum seen on Mars or for other water-related minerals Opportunity has found. It's not uncommon on Earth, but on Mars, it's the kind of thing that makes geologists jump out of their chairs."

This close-up view of a mineral vein called "Homestake" comes from the microscopic imager on NASA's Mars Exploration Rover Opportunity. Image credit: NASA / JPL-Caltech / Cornell / USGS.

The latest findings by Opportunity were presented Wednesday at the American Geophysical Union's conference in San Francisco.

The vein examined most closely by Opportunity is about the width of a human thumb (0.4 to 0.8 inch), 16 to 20 inches long, and protrudes slightly higher than the bedrock on either side of it. Observations by the durable rover reveal this vein and others like it within an apron surrounding a segment of the rim of Endeavour Crater. None like it were seen in the 20 miles (33 kilometers) of crater-pocked plains that Opportunity explored for 90 months before it reached Endeavour, nor in the higher ground of the rim.

This view from the front hazard-avoidance camera on NASA's Mars Exploration Rover Opportunity shows the rover's arm's shadow falling near a bright mineral vein informally named "Homestake." Image credit: NASA / JPL-Caltech.

Last month, researchers used the Microscopic Imager and Alpha Particle X-ray Spectrometer on the rover's arm and multiple filters of the Panoramic Camera on the rover's mast to examine the vein, which is informally named "Homestake." The spectrometer identified plentiful calcium and sulfur, in a ratio pointing to relatively pure calcium sulfate.

Calcium sulfate can exist in many forms, varying by how much water is bound into the minerals' crystalline structure. The multi-filter data from the camera suggest gypsum, a hydrated calcium sulfate. On Earth, gypsum is used for making drywall and plaster of Paris.

Where Are The Rovers Now? Opportunity's Traverse Map, Sol 2781. Image Credit: NASA / JPL / Cornell / University of Arizona.

Observations from orbit have detected gypsum on Mars previously. A dune field of windblown gypsum on far northern Mars resembles the glistening gypsum dunes in White Sands National Monument in New Mexico.

"It is a mystery where the gypsum sand on northern Mars comes from," said Opportunity science-team member Benton Clark of the Space Science Institute in Boulder, Colo. "At Homestake, we see the mineral right where it formed. It will be important to see if there are deposits like this in other areas of Mars."

The Homestake deposit, whether gypsum or another form of calcium sulfate, likely formed from water dissolving calcium out of volcanic rocks. The minerals combined with sulfur either leached from the rocks or introduced as volcanic gas, and was deposited as calcium sulfate into an underground fracture that later became exposed at the surface.

The total distance driven on Mars by NASA's Mars Exploration Rover, 21.35 miles by early December 2011, is approaching the record total for off-Earth driving, held by the robotic Lunokhod 2 rover operated on Earth's moon by the Soviet Union in 1973. Image credit: NASA / JPL-Caltech.

Throughout Opportunity's long traverse across Mars' Meridiani plain, the rover has driven over bedrock composed of magnesium, iron and calcium sulfate minerals that also indicate a wet environment billions of years ago. The highly concentrated calcium sulfate at Homestake could have been produced in conditions more neutral than the harshly acidic conditions indicated by the other sulfate deposits observed by Opportunity.

"It could have formed in a different type of water environment, one more hospitable for a larger variety of living organisms," Clark said.

Homestake and similar-looking veins appear in a zone where the sulfate-rich sedimentary bedrock of the plains meets older, volcanic bedrock exposed at the rim of Endeavour. That location may offer a clue about their origin.

"We want to understand why these veins are in the apron but not out on the plains," said the mission's deputy principal investigator, Ray Arvidson, of Washington University in St. Louis. "The answer may be that rising groundwater coming from the ancient crust moved through material adjacent to Cape York and deposited gypsum, because this material would be relatively insoluble compared with either magnesium or iron sulfates."

Artist concept of Mars Exploration Rover (credit: NASA / JPL)

Opportunity and its rover twin, Spirit, completed their three-month prime missions on Mars in April 2004. Both rovers continued for years of extended missions and made important discoveries about wet environments on ancient Mars that may have been favorable for supporting microbial life. Spirit stopped communicating in 2010. Opportunity continues exploring, currently heading to a sun-facing slope on the northern end of the Endeavour rim fragment called "Cape York" to keep its solar panels at a favorable angle during the mission's fifth Martian winter.

NASA launched the next-generation Mars rover, the car-sized Curiosity, on Nov. 26. It is slated for arrival at the planet's Gale Crater in August 2012. 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 in Washington. For more information about the rovers, visit and . You can follow the project on Twitter at and on Facebook at

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 in Washington.

for see all images:

Images (mentioned), Text, Credit: NASA / JPL / Cornell / University of Arizona / Steve Cole / Guy Webster / Alan Buis.


mercredi 7 décembre 2011

SMOS maps Europe’s dry autumn soils

ESA - SMOS Mission logo.

7 December 2011

 Soil moisture, November 2010 and 2011

Dry soil resulting from Europe’s exceptionally warm and dry autumn is being monitored by ESA’s SMOS water mission. The images here show the stark comparison between soil moisture in November 2010 and November 2011.

Like the most of the year, this autumn has been particularly dry. In the Netherlands, for example, just 9 mm of rain fell in November, compared to the average of 82 mm. According to the Royal Netherlands Meteorological Institute KNMI, November was the driest since records began in 1906.

Prolonged dry weather in Germany is not only disrupting shipping in the Rhine and Elbe rivers, but has also recently sparked a forest fire in Bavaria.

The UK Environment Agency says that even if England experiences average rainfall over winter and spring, parts of the country are unlikely to see a full recovery from drought conditions in 2012.

Sensing soil moisture

The lack of rain across Europe is reflected in the readings from ESA’s Soil Moisture and Ocean Salinity (SMOS) mission.

Orbiting above, SMOS records the amount of moisture held in the surface layer of soil.

With its novel instrument and imaging technique, SMOS can measure the moisture in soil within an accuracy of 4% – about the same as detecting a teaspoonful of water mixed into a handful of dry soil.

Data from SMOS show the difference in soil moisture between this November and November 2010 right across Europe. The difference is especially pronounced in Germany, Austria and further east.

While these maps offer an interesting snapshot, the information is important for a better understanding of the water cycle and, in particular, the exchange processes between Earth’s surface and the atmosphere.

Soil moisture is a variable in the weather and climate system and these data are used by hydrologists, soil scientists, meteorologists and ecologists.

In addition, since the amount of water in soil dictates plant growth and crop yield, the information is useful for agricultural applications and managing water resources.

Related links:


Access SMOS data:

In depth SMOS:

Credits: ESA / CESBIO / F. Cabot / Y. Kerr / AOES Medialab.


Vampire Star Reveals its Secrets

ESO - European Southern Observatory logo.

7 December 2011

 The unusual double star SS Leporis

Astronomers have obtained the best images ever of a star that has lost most of its material to a vampire companion. By combining the light captured by four telescopes at ESO’s Paranal Observatory they created a virtual telescope 130 metres across with vision 50 times sharper than the NASA/ESA Hubble Space Telescope. Surprisingly, the new results show that the transfer of mass from one star to the other in this double system is gentler than expected.

“We can now combine light from four VLT telescopes and create super-sharp images much more quickly than before,” says Nicolas Blind (IPAG, Grenoble, France), who is the lead author on the paper presenting the results, “The images are so sharp that we can not only watch the stars orbiting around each other, but also measure the size of the larger of the two stars.”

A unusual double star in the constellation of Lepus

The astronomers observed [1] the unusual system SS Leporis in the constellation of Lepus (The Hare), which contains two stars that circle around each other in 260 days. The stars are separated by only a little more than the distance between the Sun and the Earth, while the largest and coolest of the two stars extends to one quarter of this distance — corresponding roughly to the orbit of Mercury. Because of this closeness, the hot companion has already cannibalised about half of the mass of the larger star.

“We knew that this double star was unusual, and that material was flowing from one star to the other,” says co-author Henri Boffin, from ESO. “What we found, however, is that the way in which the mass transfer most likely took place is completely different from previous models of the process. The ‘bite’ of the vampire star is very gentle but highly effective.”

Wide field view of the unusual double star SS Leporis

The new observations are sharp enough to show that the giant star is smaller than previously thought, making it much more difficult to explain how the red giant lost matter to its companion. The astronomers now think that, rather than streaming from one star to the other, the matter must be expelled from the giant star as a stellar wind and captured by the hotter companion.

Zooming in on the unusual double star SS Leporis

“These observations have demonstrated the new snapshot imaging capability of the Very Large Telescope Interferometer. They pave the way for many further fascinating studies of interacting double stars,” concludes co-author Jean-Philippe Berger.

The vampire double star SS Leporis

The vampire double star SS Leporis (unannotated)


[1] The images were created from observations made with the Very Large Telescope Interferometer (VLTI) at ESOʼs Paranal Observatory using the four 1.8-metre Auxiliary Telescopes to feed light into a new instrument called PIONIER (see ann11021:

PIONIER, developed at LAOG/IPAG in Grenoble, France, is a visiting instrument at the Paranal Observatory. PIONIER is funded by Université Joseph Fourier, IPAG, INSU-CNRS (ASHRA-PNPS-PNP) ANR 2G-VLTI and ANR Exozodi. IPAG is part of the Grenoble Observatory (OSUG).

The VLTI engineers had to control the distance traversed by the light from the widely separated telescopes with an accuracy of about one hundredth of the thickness of a strand of human hair. Once the light reached PIONIER, it was then channelled into the heart of the instrument: a remarkable optical circuit, smaller than a credit card, that finally brought the light waves from the different telescopes together in a very precise way so that they could interfere. The resulting resolving power of the telescope array has the sharpness not of the individual 1.8-metre Auxiliary Telescopes, but that of a much bigger “virtual telescope” about 130 metres across, limited only by how far apart the telescopes can be positioned.

The resolution of the NASA/ESA Hubble Space Telescope is approximately 50 milliarcseconds whereas the resolution attainable with the VLTI is about one milliarcsecond — corresponding to the apparent size of an astronaut on the surface of the Moon, seen from Earth.

More information:

This research was presented in a paper, “An incisive look at the symbiotic star SS Leporis — Milli-arcsecond imaging with PIONIER/VLTI”, by N. Blind et al. in press in the journal Astronomy & Astrophysics.

The team is composed of Nicolas Blind (UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble, France [IPAG]), Henri Boffin (ESO, Chile), Jean-Philippe Berger (ESO, Chile), Jean-Baptiste Le Bouquin (IPAG, France), Antoine Mérand (ESO, Chile), Bernard Lazareff (IPAG, France), and Gérard Zins (IPAG, France).

ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 40-metre-class European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.


    Research paper in Astronomy & Astrophysics:

Images, Text, Credits: ESO / PIONIER / IPAG / IAU and Sky & Telescope / Digitized Sky Survey 2 / Nicolas Blind (IPAG) / Jean-Baptiste Le Bouquin  (IPAG) / Henri Boffin (ESO) / Jean-Philippe Berger (ESO) / Acknowledgment: Davide De Martin / Videos: ESO / Digitized Sky Survey 2 / Nick Risinger / ( / PIONIER / IPAG. Music: John Dyson (from the album Moonwind).


mardi 6 décembre 2011

New NASA Dawn Visuals Show Vesta's 'Color Palette'

NASA - Dawn Mission patch.

Dec. 6, 2011

Vesta appears in a splendid rainbow-colored palette in new images obtained by NASA's Dawn spacecraft. The colors, assigned by scientists to show different rock or mineral types, reveal Vesta to be a world of many varied, well-separated layers and ingredients. Vesta is unique among asteroids visited by spacecraft to date in having such wide variation, supporting the notion that it is transitional between the terrestrial planets -- like Earth, Mercury, Mars and Venus -- and its asteroid siblings.

This image using color data obtained by the framing camera aboard NASA's Dawn spacecraft shows Vesta's southern hemisphere in color, centered on the Rheasilvia formation. Image credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA.

In images from Dawn's framing camera, the colors reveal differences in the rock composition associated with material ejected by impacts and geologic processes, such as slumping, that have modified the asteroid's surface. Images from the visible and infrared mapping spectrometer reveal that the surface materials contain the iron-bearing mineral pyroxene and are a mixture of rapidly cooled surface rocks and a deeper layer that cooled more slowly. The relative amounts of the different materials mimic the topographic variations derived from stereo camera images, indicating a layered structure that has been excavated by impacts. The rugged surface of Vesta is prone to slumping of debris on steep slopes.

Dawn scientists presented the new images at the American Geophysical Union meeting in San Francisco on Monday, Dec. 5. The panelists included Vishnu Reddy, framing camera team associate, Max Planck Institute for Solar System Research, Katlenburg-Lindau, Germany; Eleonora Ammannito, visible and infrared spectrometer team associate, Italian Space Agency, Rome; and David Williams, Dawn participating scientist, Arizona State University, Tucson.

"Vesta's iron core makes it special and more like terrestrial planets than a garden-variety asteroid," said Carol Raymond, Dawn's deputy principal investigator at NASA's Jet Propulsion Laboratory, Pasadena, Calif. "The distinct compositional variation and layering that we see at Vesta appear to derive from internal melting of the body shortly after formation, which separated Vesta into crust, mantle and core." The presentation also included a new movie, created by David O'Brien of the Planetary Science Institute, Tucson, Ariz., that takes viewers on a spin around a hill on Vesta that appears to be made of a distinctly darker material than the rest of the crust.

Dark Hill on Asteroid Vesta

This video includes images from NASA's Dawn framing camera instrument. The hill is about 26 miles (42.5 kilometers) long by about 17 miles (28 kilometers wide), and appears to be sculpted by impact craters. Image credit: NASA / JPL-Caltech / UCLA / MPS / DLR / IDA / PSI.

Dawn launched in September 2007 and arrived at Vesta on July 15, 2011. Following a year at Vesta, the spacecraft will depart in July 2012 for the dwarf planet Ceres, where it will arrive in 2015.

Dawn's mission to Vesta and Ceres is managed by JPL for NASA's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena. Dawn is a project of the directorate's Discovery Program, managed by NASA's Marshall Space Flight Center in Huntsville, Ala. UCLA is responsible for overall Dawn mission science. Orbital Sciences Corp. in Dulles, Va., designed and built the spacecraft. The German Aerospace Center, the Max Planck Institute for Solar System Research, the Italian Space Agency and the Italian National Astrophysical Institute are international partners on the mission team.

More information about the Dawn mission is online at: and .
To follow the mission on Twitter, visit: .

Image (mentioned), Video (mentioned), Text, Credit: Jet Propulsion Laboratory / Priscilla Vega.

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lundi 5 décembre 2011

NASA's Kepler Mission Confirms Its First Planet in Habitable Zone of Sun-like Star

NASA - KEPLER Mission logo labeled.

Dec. 5, 2011

NASA's Kepler mission has confirmed its first planet in the "habitable zone," the region where liquid water could exist on a planet’s surface. Kepler also has discovered more than 1,000 new planet candidates, nearly doubling its previously known count. Ten of these candidates are near-Earth-size and orbit in the habitable zone of their host star. Candidates require follow-up observations to verify they are actual planets.

The newly confirmed planet, Kepler-22b, is the smallest yet found to orbit in the middle of the habitable zone of a star similar to our sun. The planet is about 2.4 times the radius of Earth. Scientists don't yet know if Kepler-22b has a predominantly rocky, gaseous or liquid composition, but its discovery is a step closer to finding Earth-like planets.

This artist's conception illustrates Kepler-22b, a planet known to comfortably circle in the habitable zone of a sun-like star. Image credit: NASA / Ames / JPL-Caltech.

Previous research hinted at the existence of near-Earth-size planets in habitable zones, but clear confirmation proved elusive. Two other small planets orbiting stars smaller and cooler than our sun recently were confirmed on the very edges of the habitable zone, with orbits more closely resembling those of Venus and Mars.

"This is a major milestone on the road to finding Earth's twin," said Douglas Hudgins, Kepler program scientist at NASA Headquarters in Washington. "Kepler's results continue to demonstrate the importance of NASA's science missions, which aim to answer some of the biggest questions about our place in the universe."

Kepler discovers planets and planet candidates by measuring dips in the brightness of more than 150,000 stars to search for planets that cross in front, or "transit," the stars. Kepler requires at least three transits to verify a signal as a planet.

"Fortune smiled upon us with the detection of this planet," said William Borucki, Kepler principal investigator at NASA Ames Research Center at Moffett Field, Calif., who led the team that discovered Kepler-22b. "The first transit was captured just three days after we declared the spacecraft operationally ready. We witnessed the defining third transit over the 2010 holiday season."

The Kepler science team uses ground-based telescopes and the Spitzer Space Telescope to review observations on planet candidates the spacecraft finds. The star field that Kepler observes in the constellations Cygnus and Lyra can only be seen from ground-based observatories in spring through early fall. The data from these other observations help determine which candidates can be validated as planets.

Kepler-22b is located 600 light-years away. While the planet is larger than Earth, its orbit of 290 days around a sun-like star resembles that of our world. The planet's host star belongs to the same class as our sun, called G-type, although it is slightly smaller and cooler.

Of the 54 habitable zone planet candidates reported in February 2011, Kepler-22b is the first to be confirmed. This milestone will be published in The Astrophysical Journal.

The Kepler team is hosting its inaugural science conference at Ames Dec. 5-9, announcing 1,094 new planet candidate discoveries. Since the last catalog was released in February, the number of planet candidates identified by Kepler has increased by 89 percent and now totals 2,326. Of these, 207 are approximately Earth-size, 680 are super Earth-size, 1,181 are Neptune-size, 203 are Jupiter-size and 55 are larger than Jupiter.

The findings, based on observations conducted May 2009 to September 2010, show a dramatic increase in the numbers of smaller-size planet candidates.

Kepler observed many large planets in small orbits early in its mission, which were reflected in the February data release. Having had more time to observe three transits of planets with longer orbital periods, the new data suggest that planets one to four times the size of Earth may be abundant in the galaxy.

The number of Earth-size and super Earth-size candidates has increased by more than 200 and 140 percent since February, respectively.

This diagram compares our own solar system to Kepler-22, a star system containing the first "habitable zone" planet discovered by NASA's Kepler mission. Image credit: NASA / Ames / JPL-Caltech.

There are 48 planet candidates in their star's habitable zone. While this is a decrease from the 54 reported in February, the Kepler team has applied a stricter definition of what constitutes a habitable zone in the new catalog, to account for the warming effect of atmospheres, which would move the zone away from the star, out to longer orbital periods.

"The tremendous growth in the number of Earth-size candidates tells us that we're honing in on the planets Kepler was designed to detect: those that are not only Earth-size, but also are potentially habitable," said Natalie Batalha, Kepler deputy science team lead at San Jose State University in San Jose, Calif. "The more data we collect, the keener our eye for finding the smallest planets out at longer orbital periods."

NASA's Ames Research Center manages Kepler's ground system development, mission operations and science data analysis. NASA's Jet Propulsion Laboratory in Pasadena, Calif., managed Kepler mission development.

Ball Aerospace and Technologies Corp. in Boulder, Colo., developed the Kepler flight system and supports mission operations with the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

The Space Telescope Science Institute in Baltimore archives, hosts and distributes the Kepler science data. Kepler is NASA's 10th Discovery Mission and is funded by NASA's Science Mission Directorate at the agency's headquarters.

Related links:

- NASA’s Kepler Mission:
- Kepler Science Conference News Briefing Press Kit:
- NASA’s Ames Research Center:

Images (mentioned), Text, Credit: NASA Ames Research Center / Michele Johnson.


NASA's Voyager Hits New Region at Solar System Edge

NASA - VOYAGER Mission patch.

Dec. 5, 2011

An this artist's concept, NASA's Voyager 1 spacecraft has entered a new region between our solar system and interstellar space, which scientists are calling the stagnation region. Image credit: NASA/JPL-Caltech.

NASA's Voyager 1 spacecraft has entered a new region between our solar system and interstellar space. Data obtained from Voyager over the last year reveal this new region to be a kind of cosmic purgatory. In it, the wind of charged particles streaming out from our sun has calmed, our solar system's magnetic field has piled up, and higher-energy particles from inside our solar system appear to be leaking out into interstellar space.

"Voyager tells us now that we're in a stagnation region in the outermost layer of the bubble around our solar system," said Ed Stone, Voyager project scientist at the California Institute of Technology in Pasadena. "Voyager is showing that what is outside is pushing back. We shouldn't have long to wait to find out what the space between stars is really like."

Although Voyager 1 is about 11 billion miles (18 billion kilometers) from the sun, it is not yet in interstellar space. In the latest data, the direction of the magnetic field lines has not changed, indicating Voyager is still within the heliosphere, the bubble of charged particles the sun blows around itself. The data do not reveal exactly when Voyager 1 will make it past the edge of the solar atmosphere into interstellar space, but suggest it will be in a few months to a few years.

The latest findings, described today at the American Geophysical Union's fall meeting in San Francisco, come from Voyager's Low Energy Charged Particle instrument, Cosmic Ray Subsystem and Magnetometer.

Scientists previously reported the outward speed of the solar wind had diminished to zero in April 2010, marking the start of the new region. Mission managers rolled the spacecraft several times this spring and summer to help scientists discern whether the solar wind was blowing strongly in another direction. It was not. Voyager 1 is plying the celestial seas in a region similar to Earth's doldrums, where there is very little wind.

During this past year, Voyager's magnetometer also detected a doubling in the intensity of the magnetic field in the stagnation region. Like cars piling up at a clogged freeway off-ramp, the increased intensity of the magnetic field shows that inward pressure from interstellar space is compacting it.

Voyager probe

Voyager has been measuring energetic particles that originate from inside and outside our solar system. Until mid-2010, the intensity of particles originating from inside our solar system had been holding steady. But during the past year, the intensity of these energetic particles has been declining, as though they are leaking out into interstellar space. The particles are now half as abundant as they were during the previous five years.

At the same time, Voyager has detected a 100-fold increase in the intensity of high-energy electrons from elsewhere in the galaxy diffusing into our solar system from outside, which is another indication of the approaching boundary.

"We've been using the flow of energetic charged particles at Voyager 1 as a kind of wind sock to estimate the solar wind velocity," said Rob Decker, a Voyager Low-Energy Charged Particle Instrument co-investigator at the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. "We've found that the wind speeds are low in this region and gust erratically. For the first time, the wind even blows back at us. We are evidently traveling in completely new territory. Scientists had suggested previously that there might be a stagnation layer, but we weren't sure it existed until now."

Launched in 1977, Voyager 1 and 2 are in good health. Voyager 2 is 9 billion miles (15 billion kilometers) away from the sun.

The Voyager spacecraft were built by NASA's Jet Propulsion Laboratory in Pasadena, Calif., which continues to operate both. JPL is a division of the California Institute of Technology. The Voyager missions are a part of the NASA Heliophysics System Observatory, sponsored by the Heliophysics Division of the Science Mission Directorate in Washington. For more information about the Voyager spacecraft, visit:

For more information about NASA media events at the American Geophysical Union meeting, visit:

Images, Text,  Credit: NASA / JPL-Caltech.


VLT Finds Fastest Rotating Star

ESO - European Southern Observatory logo.

5 December 2011

 VFTS 102: the fastest rotating star

ESO's Very Large Telescope has picked up the fastest rotating star found so far. This massive bright young star lies in our neighbouring galaxy, the Large Magellanic Cloud, about 160 000 light-years from Earth. Astronomers think that it may have had a violent past and has been ejected from a double star system by its exploding companion.

An international team of astronomers has been using ESO’s Very Large Telescope at the Paranal Observatory in Chile, to make a survey of the heaviest and brightest stars in the Tarantula Nebula (eso1117), in the Large Magellanic Cloud. Among the many brilliant stars in this stellar nursery the team has spotted one, called VFTS 102 [1], that is rotating at more than two million kilometres per hour — more than three hundred times faster than the Sun [2] and very close to the point at which it would be torn apart due to centrifugal forces. VFTS 102 is the fastest rotating star known to date [3].

Artist’s impression of the fastest rotating star

The astronomers also found that the star, which is around 25 times the mass of the Sun and about one hundred thousand times brighter, was moving through space at a significantly different speed from its neighbours [4].

“The remarkable rotation speed and the unusual motion compared to the surrounding stars led us to wonder if this star had had an unusual early life. We were suspicious.” explains Philip Dufton (Queen’s University Belfast, Northern Ireland, UK), lead author of the paper presenting the results.

VFTS 102: the fastest rotating massive star (unannotated)

This difference in speed could imply that VFTS 102 is a runaway star — a star that has been ejected from a double star system after its companion exploded as a supernova. This idea is supported by two further clues: a pulsar and an associated supernova remnant in its vicinity [5].

The team has developed a possible back story for this very unusual star. It could have started life as one component of a binary star system. If the two stars were close, gas from the companion could have streamed over and in the process the star would have spun faster and faster. This would explain one unusual fact —  why it is rotating so fast. After a short lifetime of about ten million years, the massive companion would have exploded as a supernova — which could explain the characteristic gas cloud known as a supernova remnant found nearby. The explosion would also have led to the ejection of the star and could explain the third anomaly — the difference between its speed and that of other stars in the region. As it collapsed, the massive companion would have turned into the pulsar that is observed today, and which completes the solution to the puzzle.

Wide-field view of the sky around VFTS 102: the fastest rotating massive star

Although the astronomers cannot yet be sure that this is exactly what happened, Dufton concludes “This is a compelling story because it explains each of the unusual features that we’ve seen. This star is certainly showing us unexpected sides of the short, but dramatic lives of the heaviest stars.”


[1] The name VFTS102 refers to the VLT-FLAMES Tarantula Survey made using the Fibre Large Array Multi Element Spectrograph (FLAMES) on ESO’s Very Large Telescope.

[2] An aircraft travelling at this speed would take about one minute to circle the Earth at the equator.

[3] Some stars end their lives as compact objects such as pulsars (see note [5]), which may spin much more rapidly than VFTS 102, but they are also very much smaller and denser and do not shine by thermonuclear reactions like normal stars.

[4] VFTS 102 is moving at roughly 228 kilometres per second, which is slower than other similar stars in the region by about 40 kilometres per second.

[5] Pulsars are the result of supernovae. The core of the star collapses to a very small size creating a neutron star which spins very rapidly and emits powerful jets of radiation. These jets create a regular “pulse” as seen from Earth as the star rotates around its axis. The associated supernova remnant is a characteristic cloud of gas blown away by the shock wave resulting from the collapse of the star into a neutron star.

More information:

This research was presented in a paper in the Astrophysical Journal Letters, “The VLT-FLAMES Tarantula Survey: The fastest rotating O-type star and shortest period LMC pulsar — remnants of a supernova disrupted binary?”, by Philip L. Dufton et al.

The team is composed of P.L. Dufton (Astrophysics Research Centre, Queen’s University Belfast (ARC/QUB), UK), P.R. Dunstall (ARC/QUB, UK), C.J. Evans (UK Astronomy Technology Centre, Royal Observatory Edinburgh (ROE), UK), I. Brott (University of Vienna, Department of Astronomy, Austria), M. Cantiello (Argelander Institut fur Astronomie der Universitat Bonn, Germany, Kavli Institute for Theoretical Physics, University of California, USA), A. de Koter (Astronomical Institute ‘Anton Pannekoek’, University of Amsterdam, The Netherlands), S.E. de Mink (Space Telescope Science Institute, USA), M. Fraser (ARC/QUB, UK), V. Henault-Brunet (Scottish Universities Physics Alliance (SUPA), Institute for Astronomy, University of Edinburgh, ROE, UK), I.D. Howarth (Department of Physics & Astronomy, University College London, UK), N. Langer (Argelander Institut fur Astronomie der Universitat Bonn, Germany), D.J. Lennon (ESA, Space Telescope Science Institute, USA), N. Markova (Institute of Astronomy with NAO, Bulgaria), H. Sana (Astronomical Institute ‘Anton Pannekoek’, University of Amsterdam, The Netherlands), W.D. Taylor (SUPA, Institute for Astronomy, University of Edinburgh, ROE, UK).

ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive astronomical observatory. It is supported by 15 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 40-metre-class European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.


    Reference paper: “The VLT-FLAMES Tarantula Survey I. Introduction and observational overview”:

    Published paper in ApJL:

    Photos of ESO’s Very Large Telescope:

Images, Text, Credits: ESO / M.-R. Cioni / VISTA Magellanic Cloud survey. Acknowledgment: Cambridge Astronomical Survey Unit / NASA / ESA and G. Bacon (STScI) / Queen's University of Belfast / Philip Dufton / ESO, La Silla, Paranal, E-ELT & Survey Telescopes / Richard Hook.

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Veteran Space Shuttle Commander Chris Ferguson to Leave NASA

NASA logo.

Dec. 5, 2011

Astronaut Chris Ferguson, the last commander of a space shuttle mission, has announced his plans to retire from NASA on Dec. 9. He will leave for a new job in the private sector.

"Chris has been a true leader at NASA," NASA Administrator Charles Bolden said, "not just as a commander of the space shuttle, but also as an exemplary civil servant, a distinguished Navy officer and a good friend. I am confident he will succeed in his next career as he brings his skill and talents to new endeavors."

NASA Astronaut Christopher J. Ferguson

Ferguson, a retired U.S. Navy captain, served as the commander for STS-135, the final flight of space shuttle Atlantis and the 135th and final mission of America's 30-year Space Shuttle Program.

Atlantis' flight was Ferguson's third trip to space. During the 13-day mission, he and his crew delivered approximately 10,000 pounds of supplies and spare parts to the International Space Station. Before his assignment to STS-135, Ferguson served as deputy chief of the Astronaut Office at NASA's Johnson Space Center in Houston.

"Chris has been a great friend, a tremendous professional and an invaluable asset to the NASA team and the astronaut office," said Peggy Whitson, chief of the Astronaut Office. "His exceptional leadership helped ensure a perfect final flight of the space shuttle, a fitting tribute to the thousands who made the program possible."

Ferguson first flew in space as the pilot of Atlantis on STS-115 in 2006, during which the P3/P4 truss segments were delivered to the station. He next flew as commander of Endeavour on STS-126 in 2008. During the mission, Ferguson and his crew delivered water recycling and habitation hardware to the station and exchanged station crew members. In total, Ferguson logged more than 40 days in space.

Ferguson joined the astronaut corps in 1998. After completing his initial training, he performed technical duties related to the shuttle's main engines, external tank, solid rocket boosters and flight software. He also served as a spacecraft communicator in mission control for four shuttle missions.

For Ferguson's complete biography, visit:

Image, Text, Credit: NASA.


dimanche 4 décembre 2011

Super Earth-size Planet Confirmed Around Bright F6 Subgiant Star

NASA - KEPLER Mission patch.

Dec. 4, 2011

A research team led by Steve Howell, NASA Ames Research Center, has announced the discovery of an exoplanet orbiting one of the brightest stars in the Kepler field of view.

Coined Kepler-21b, the planet is approximately 1.6 times the radius of Earth and nearly ten times the mass of Earth. Circling its host star every 2.8 days, Kepler-21b orbits at a distance of six million km – nearly ten times closer than Mercury orbits the sun. The surface temperature is calculated to be 2,960 Fahrenheit. While this temperature is nowhere near the habitable zone in which liquid water might be found, the planet’s size is approaching that of Earth.

Image above: The Kepler field as seen in the sky over Kitt Peak National Observatory. The approximate position of Kepler-21 is indicated by the circle. Credit: sky imaged using a diffraction grating to show spectra of brighter stars ( J. Glaspey); telescopes imaged separately and combined (P. Marenfeld).

Kepler light curve of HD 179070 showing the eclipse of Kepler-21b

The parent star, HD 179070, a little hotter and brighter than the sun, is 352 light years away. Somewhat similar to the sun, the parent star has a mass of 1.3 solar masses, is larger at 1.9 solar radii, and its age, based on stellar models, is 2.84 billion years- younger than the sun’s 4.6 billion years. Although Kepler-21b is pretty small and very far away, unable to be seen with the naked eye, the parent star can easily be seen with binoculars or a small telescope.

KEPLER Space Telescope (Credit: NASA)

This incredibly sensitive and difficult detection required the collaboration of over 65 astronomers with both space and multiple ground-based telescopes to confirm the newest member of the Kepler family.

To read the press release from the National Optical Astronomy Observatory visit:

To learn more about the discovery, please see the details table at:

Images (mentioned), Text, Credit: NASA / JPL / Jessica Culler.