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Unfurling October 19, 2008

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Solar Prominence Eruption
Credit:

NASA

Description:

The STEREO (Ahead) spacecraft observed this visually stunning prominence eruption on Sept. 29, 2008, in the 304 angstrom wavelength of extreme UV light. Prominences are relatively cool clouds of gas suspended above the sun and controlled by magnetic forces.

The prominence rose and cascaded to the right over several hours, appearing something like a flag unfurling, as it broke apart and headed into space. The prominence is composed of ionized Helium that is about 60,000 degrees Kelvin

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Layering in Uzer Crater Wall October 18, 2008

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Layering in Uzer Crater Wall

Credit:

NASA/JPL/University of Arizona

Description:

This image shows a portion of Uzer Crater, located in Sinus Meridiani near the equator in the northern hemisphere of Mars.

Light-toned layered rocks are visible on the wall of Uzer Crater. Differences in color highlight variations in the layered units. Wind erosion, in particular, has modified the layers since exposure creating rounded depressions. These layers are interpreted to be an outcrop of sedimentary rocks that formed by sediments once deposited in this area. The origin of the sediments composing the layers is unknown but may have included fluvial processes and wind blown particles such as dust or volcanic ash.

Over time, the sediments were solidified into rock and eventually exposed when an impact formed Uzer Crater. Northern Sinus Meridiani has many similar outcrops of light-toned sedimentary material that are observed over a large region.

On Mars, as on Earth, sedimentary rocks preserve a record of past environments. HiRISE color images reveal details in the layers that will help scientists learn more about their origin.

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Internal Waves in the Atlantic Ocean October 17, 2008

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Internal Waves in the Atlantic Ocean' width=

Credit:

Jeff Schmaltz, MODIS Land Rapid Response Team, NASA GSFC

Description:

This image, captured by the MODIS on the Terra satellite on October 2, 2008, shows an interesting phenomena called “internal waves”. These particular waves are northeast of Brazil, out in the deep waters of the Atlantic Ocean. They are highlighted by sunglint.

Internal waves are waves that occur underwater at the boundary between layers of water with different densities. Like all major bodies of water, the Atlantic Ocean is composed of layers of water with different densities: the topmost is the least dense, while each successively deeper layer is denser. Internal waves are usually caused by the lower layer being forced against a shallow obstacle, such as a ridge, by tidal action. The ridge causes a disturbance, which creates a wave in the water layer, similar to the way that the wind can cause waves on the water’s surface. Unlike normal surface waves, internal waves can stretch for tens of kilometers in length and move throughout the ocean for several days.

Internal waves alter sea surface currents, changing the overall “sea surface roughness.” Where these currents converge, the sea surface is more turbulent, and therefore brighter because it catches more of the Sun´s reflection. Where the currents diverge, the surface is smoother and darker, creating zones called “slicks.”

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Antares DLR-H2 approaching Stuttgart Airport October 17, 2008

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Antares DLR-H2 approaching Stuttgart Airport
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The Antares DLR-H2 flying test bed, jointly developed by the DLR Institute of Technical Thermodynamics (DLR-Institut für Technische Thermodynamik) and Lange Aviation GmbH, will complete its maiden flight before the end of the year. This artist’s impression shows the aircraft approaching Stuttgart Airport.

Credit:

DLR/Flughafen Stuttgart.

Anatomy of a Busted Comet October 16, 2008

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image
Credit:

NASA/JPL-Caltech/B. Reach (Spitzer Science Center)

Description:

NASA’s Spitzer Space Telescope captured the picture on the left of comet Holmes in March 2008, five months after the comet suddenly erupted and brightened a millionfold overnight. The contrast of the picture has been enhanced on the right to show the anatomy of the comet.

Every six years, comet 17P/Holmes speeds away from Jupiter and heads inward toward the sun, traveling the same route typically without incident. However, twice in the last 116 years, in November 1892 and October 2007, comet Holmes mysteriously exploded as it approached the asteroid belt. Astronomers still do not know the cause of these eruptions.

Spitzer’s infrared picture at left reveals fine dust particles that make up the outer shell, or coma, of the comet. The nucleus of the comet is within the bright whitish spot in the center, while the yellow area shows solid particles that were blown from the comet in the explosion. The comet is headed away from the sun, which lies beyond the right-hand side of the picture.

The contrast-enhanced picture on the right shows the comet’s outer shell, and strange filaments, or streamers, of dust. The streamers and shell are a yet another mystery surrounding comet Holmes. Scientists had initially suspected that the streamers were small dust particles ejected from fragments of the nucleus, or from hyerpactive jets on the nucleus, during the October 2007 explosion. If so, both the streamers and the shell should have shifted their orientation as the comet followed its orbit around the sun. Radiation pressure from the sun should have swept the material back and away from it. But pictures of comet Holmes taken by Spitzer over time show the streamers and shell in the same configuration, and not pointing away from the sun. The observations have left astronomers stumped.

The horizontal line seen in the contrast-enhanced picture is a trail of debris that travels along with the comet in its orbit.

The Spitzer picture was taken with the spacecraft’s multiband imaging photometer at an infrared wavelength of 24 microns.

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NASA’s Fermi Telescope Discovers First Gamma-Ray-Only Pulsar October 16, 2008

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https://i1.wp.com/www.nasa.gov/images/content/283508main_fermigrop_labeled_HI.jpg
Credit:

NASA/S. Pineault, DRAO, Lynn Cominsky, David Harris, J.D. Harrington, 

Description:

About three times a second, a 10,000-year-old stellar corpse sweeps a beam of gamma-rays toward Earth. Discovered by NASA’s Fermi Gamma-ray Space Telescope, the object, called a pulsar, is the first one known that only “blinks” in gamma rays.

“This is the first example of a new class of pulsars that will give us fundamental insights into how these collapsed stars work,” said Stanford University’s Peter Michelson, principal investigator for Fermi’s Large Area Telescope in Palo Alto, Calif.

The gamma-ray-only pulsar lies within a supernova remnant known as CTA 1, which is located about 4,600 light-years away in the constellation Cepheus. Its lighthouse-like beam sweeps Earth’s way every 316.86 milliseconds. The pulsar, which formed about 10,000 years ago, emits 1,000 times the energy of our sun.

A pulsar is a rapidly spinning neutron star, the crushed core left behind when a massive sun explodes. Astronomers have cataloged nearly 1,800 pulsars. Although most were found through their pulses at radio wavelengths, some of these objects also beam energy in other forms, including visible light and X-rays. However, the source in CTA 1 only pulses at gamma-ray energies.

“We think the region that emits the pulsed gamma rays is broader than that responsible for pulses of lower-energy radiation,” explained team member Alice Harding at NASA’s Goddard Space Flight Center in Greenbelt, Md. “The radio beam probably never swings toward Earth, so we never see it. But the wider gamma-ray beam does sweep our way.”

Scientists think CTA 1 is only the first of a large population of similar objects.

“The Large Area Telescope provides us with a unique probe of the galaxy’s pulsar population, revealing objects we would not otherwise even know exist,” says Fermi project scientist Steve Ritz, also at Goddard.

The pulsar in CTA 1 is not located at the center of the remnant’s expanding gaseous shell. Supernova explosions can be asymmetrical, often imparting a “kick” that sends the neutron star careening through space. Based on the remnant’s age and the pulsar’s distance from its center, astronomers believe the neutron star is moving at about a million miles per hour — a typical speed.

Fermi’s Large Area Telescope scans the entire sky every three hours and detects photons with energies ranging from 20 million to more than 300 billion times the energy of visible light. The instrument sees about one gamma ray every minute from CTA 1, enough for scientists to piece together the neutron star’s pulsing behavior, its rotation period, and the rate at which it is slowing down.

A pulsar’s beams arise because neutron stars possess intense magnetic fields and rotate rapidly. Charged particles stream outward from the star’s magnetic poles at nearly the speed of light to create the gamma-ray beams Fermi sees. Because the beams are powered by the neutron star’s rotation, they gradually slow the pulsar’s spin. In the case of CTA 1, the rotation period is increasing by about one second every 87,000 years.

“This observation shows the power of the Large Area Telescope,” Michelson said. “It is so sensitive that we can now discover new types of objects just by observing their gamma-ray emissions.”

NASA’s Fermi Gamma-ray Space Telescope is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, along with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden, and the U.S.

A paper about the new pulsar appears in the Oct. 16 edition of Science Express. For images and animations associated with this release, visit: http://www.nasa.gov/fermi

Crater on North Polar Layered Deposits October 16, 2008

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Crater on North Polar Layered Deposits

Credit:

NASA/JPL/University of Arizona

Description:

The north polar layered deposits, and the bright ice cap that covers them, are very young (by geologic standards) features. To try and figure out the age of an area, or how quickly it’s being resurfaced, planetary scientists count up the number of craters at different sizes. An older surface has more time to accumulate more craters whereas a younger surface, or one that has a lot of geologic activity that destroys craters, doesn’t have many impact craters.

These polar deposits have a very low crater count so it is possible that the ice cap (bright white in this image) might only by about 10,000 years old and the surface of the layered deposits (orange-brown in this image) may be only a few million years old. This sounds like a long time but is very short compared to other surfaces on Mars.

HiRISE is enabling a more detailed study of these polar craters and the target of this observation is visible in the center of the image. This crater proved to be a surprise in a few ways. Its shape is non-circular which is quite unusual for an impact crater. One possibility is that flow of the ice beneath the surrounding terrain has deformed the crater; however, ice-flow rates are thought to be very low on Mars today.

The crater also contains a patch of bright ice despite being surrounded by terrain that has mostly lost its ice cover. This seems typical for these polar craters and it may be that ice within these craters is protected from ablation by shading from the crater walls.

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Warped F Ring October 16, 2008

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Prometheus and the F ring
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Full-Res: PIA10489

Description:

The gravity of Prometheus alters the orbits of the fine, icy particles in Saturn’s F ring, creating dazzling structures like those seen here.Each of these diagonal features, called “streamer-channels” by ring scientists, represents a single close approach of Prometheus (86 kilometers, or 53 miles across) to the inner edge of the ring.

This observation was optimized to show faint details in the F ring, leaving Prometheus (86 kilometers, or 53 miles across, at bottom) overexposed.

The view looks toward the unilluminated side of the rings from about 15 degrees above the ringplane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Aug. 30, 2008. The view was obtained at a distance of approximately 1.2 million kilometers (751,000 miles) from Saturn. Image scale is 7 kilometers (4 miles) per pixel.

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, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colo.

For more information about the Cassini-Huygens mission visasit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Credit:

NASA/JPL/Space Science Institute

Saltating Gypsum into Dark Polar Dunes October 16, 2008

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Saltating Gypsum into Dark Polar Dunes

Credit:

NASA/JPL/University of Arizona

Description:

Gypsum is a common water-based mineral found in evaporative beds (ancient lakes or seas) on Earth. Gypsum rarely occurs in sand dunes on Earth as it is water-soluble (dissolves in water). However, gypsum can be trapped in basins that have no water outlets or receive very light precipitation and form beautiful dunes. The White Sands National Monument in the Tularosa Basin, New Mexico, is the largest gypsum dune field in the world. OMEGA, an instrument onboard the European Space Agency’s (ESA) Mars Express has detected gypsum deposits in the Martian north polar erg.

Where did the gypsum come from? Scientists propose that gypsum deposits formed as a result of melting or retreating ice sheets in a polar evaporate basal unit. In this image, gypsum may originate from the bright bedrock and may mix with saltating dark sand. However, the true source of the gypsum is still debated among planetary scientists.

The mafic (basaltic) dark dunes are predominately transverse with transitioning linear and barchanoid dunes with the wind coming from changing west-northwest and west-southwest directions. These dunes have several active processes occurring within them; grain avalanching is present at the crest of dunes and fading dark slope streaks are visible on the slipface.

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Massive Young Stars Trigger Stellar Birth October 15, 2008

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RCW 108
Credit:

X-ray: NASA/CXC/CfA/S.Wolk et al; IR: NASA/JPL-Caltech

Description:

RCW 108 is a region where stars are actively forming within the Milky Way galaxy about 4,000 light years from Earth. This is a complicated region that contains young star clusters, including one that is deeply embedded in a cloud of molecular hydrogen. By using data from different telescopes, astronomers determined that star birth in this region is being triggered by the effect of nearby, massive young stars.

This image is a composite of X-ray data from Chandra (blue) and infrared emission detected by Spitzer (red and orange). More than 400 X-ray sources were identified in Chandra’s observations of RCW 108. About 90% of these X-ray sources are thought to be part of the cluster and not stars that lie in the field-of-view either behind or in front of it. Many of the stars in RCW 108 are experiencing the violent flaring seen in other young star-forming regions such as the Orion Nebula. Gas and dust blocks much of the X-rays from the juvenile stars located in the center of the image, explaining the relative dearth of Chandra sources in this part of the image.

The Spitzer data show the location of the embedded star cluster, which appears as the bright knot of red and orange just to the left of the center of the image. Some stars from a larger cluster, known as NGC 6193, are also visible on the left side of the image. Astronomers think that the dense clouds within RCW 108 are in the process of being destroyed by intense radiation emanating from hot and massive stars in NGC 6193.

Taken together, the Chandra and Spitzer data indicate that there are more massive star candidates than expected in several areas of this image. This suggests that pockets within RCW 108 underwent localized episodes of star formation. Scientists predict that this type of star formation is triggered by the effects of radiation from bright, massive stars such as those in NGC 6193. This radiation may cause the interior of gas clouds in RCW 108 to be compressed, leading to gravitational collapse and the formation of new stars.

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