samedi 16 mai 2015

Rosetta - Closeup: Hathor, from Seth












ESA - Rosetta Mission patch.

May 16, 2015

Today’s post delves back in time to October last year, when Rosetta was orbiting the comet at a distance of just 10 km.

Hathor and Seth – NavCam

Image above: Single frame, processed NAVCAM image of Comet 67P/C-G taken on 23 October from a distance of 9.8 km to the comet centre. Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0.

This single frame NAVCAM image was captured on 23 October, when the distance to the centre of the comet was 9.76 km. The average image scale is therefore about 83 cm/pixel and the image measures 850 m across (note that because of the viewing geometry, foreground regions are up to 2 km closer to the viewer, and therefore have an approximate scale of 67 cm/pixel). For reference, an image in a similar orientation was captured on 26 November.

The scene highlights the hauntingly beautiful backlit cliffs of Hathor, the summit just catching the sunlight at top left. The image has been lightly processed to better bring out the details of this region, and also reveals the diffuse glow of the comet’s activity. Indeed, subtly brighter patches can be traced against the darker background, in particular at the right of the frame at the transition from the foreground terrain to Hathor in the background.

If you were standing at the base of Hathor in the Hapi region – out of view in this image – these near-vertical cliffs would tower some 900m above you. As can be seen here, Hathor is characterised by sets of linear features that extend for much of the height of the cliff. In places, lineaments and terraces also cut across roughly perpendicular to them. As described by Thomas et al in an OSIRIS science paper earlier this year, Hathor may be an eroded surface and as such is showing us the internal structure of the comet’s head.

Comet 67P/Churyumov-Gerasimenko regional maps. Image Credit: ESA

In the foreground, contrasting terrains within the Seth region on the comet’s large lobe are observed. While the left-hand portion exhibits a smooth surface, the right-hand portion shows outcrops of more rugged terrain and numerous boulders. The exposed surfaces also display linear structures in various orientations.

The portion of Seth seen here is at an intersection of several regions: at the far right of the frame lies the boundary between Seth and Anubis, while just out of view beyond the bottom of the frame are Ash and Atum.

The original 1024 x 1024 pixel image is provided below:

(Click on the image for enlarge)

Image above: Single frame, processed NAVCAM image of Comet 67P/C-G taken on 23 October from a distance of 9.8 km to the comet centre. Credits: ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0.

Today's image is one of many that will be included in the NAVCAM data release scheduled for the end of this month. This will see the release of the entire collection of images taken from the 10 km orbit last year, along with images taken around the events of comet landing. You can browse all NAVCAM images released so far in the Archive Image Browser: http://imagearchives.esac.esa.int/

Related links:

OSIRIS science paper: http://www.sciencemag.org/content/347/6220/aaa0440.full

CometWatch 26 November: http://blogs.esa.int/rosetta/2014/11/28/cometwatch-26-november/

For more information about Rosetta mission, visit: http://www.esa.int/Our_Activities/Space_Science/Rosetta

Images (mentioned), Text, Credit: ESA.

Best regards, Orbiter.ch

Russia "loses" a Mexican satellite and Progress M-26M engine failed to start for ISS reboost
















ILS - Proton-M / Mexsat-1 Centenario launch poster.

May 16, 2015


Image above: The damage would have occurred shortly after takeoff of the rocket.

The Russian space agency said it had "lost" a Mexican satellite Saturday after the failed launch of the carrier rocket. This is a new blow for the Russian space program.

"The launch of the Proton-M rocket with a MEXSAT-1 satellite has caused an emergency. The causes are being identified, "said the Roskosmos space agency in a statement.

The launch took place at 8:47 Moscow time (05:47 UTC) from Baikonur, Kazakhstan.

video
Launch of MexSat-1 on Russian Proton-M Rocket

A source at the space agency said on Saturday the government news agency Ria Novosti that communications with the Proton rocket had been lost about a minute before the time that the Mexican satellite should have separated the third floor of the rocket. The satellite could not be detached from the launcher and will not work, the source said.

Mexsat-1 Centenario, lost today

The accident took place just hours after Roscosmos announced that the engines of spacecraft Progress M-26M docked to the International Space Station (ISS) failed to start on time (4:00 Moscow time, 3:00 in Switzerland) to correct its orbit.

Meeting

Fragments of the rocket, containing several tons of toxic fuel, fell back on the Chita region of Siberia, but most pieces have disintegrated in the atmosphere, explained the sources of the space industry.

The Proton-M rocket is the primary tool used by Russia to launch commercial satellites, but has experienced many problems. The launcher is used since Soviet times with some adjustments that have expanded its functions.

The head of Roscosmos, Igor Komarov, organized a meeting to review detailed reports on both accidents Saturday Tass reported.

Second test

A source from the space agency Ria Novosti said in a second test to start the Progress engines should be done on Monday unless the checks reveal no "serious problems."

Russian Progress-M docked at the station

Russia has in recent years a series of problems that have highlighted gaps in its space program, however, allows him to earn millions of dollars through the launch of Western and Asian commercial satellites.

ROSCOSMOS Press Releases: http://www.federalspace.ru/21490/ and http://www.federalspace.ru/21491/

For more information about International Launch Services (ILS), visit: http://www.ilslaunch.com/

Images, Video, Text, Credits: ATS/AFP/ROSCOSMOS/NASA/Orbiter.ch Aerospace.

Greetings, Orbiter.ch

vendredi 15 mai 2015

Hubble Spots the Layers of NGC 3923











NASA - Hubble Space Telescope patch.

May 15, 2015


The glowing object in this Hubble Space Telescope image is an elliptical galaxy called NGC 3923. It is located over 90 million light-years away in the constellation of Hydra.

NGC 3923 is an example of a shell galaxy where the stars in its halo are arranged in layers.

Finding concentric shells of stars enclosing a galaxy is quite common and is observed in many elliptical galaxies. In fact, every tenth elliptical galaxy exhibits this onion-like structure, which has never been observed in spiral galaxies. The shell-like structures are thought to develop as a consequence of galactic cannibalism, when a larger galaxy ingests a smaller companion. As the two centers approach, they initially oscillate about a common center, and this oscillation ripples outwards forming the shells of stars just as ripples on a pond spread when the surface is disturbed.

NGC 3923 has over twenty shells, with only a few of the outer ones visible in this image, and its shells are much more subtle than those of other shell galaxies. The shells of this galaxy are also interestingly symmetrical, while other shell galaxies are more skewed.

video
Hubble and the sunrise over Earth

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

For images and more information about Hubble, visit:http://www.nasa.gov/hubble and http://hubblesite.org/ and http://www.spacetelescope.org/

Image, Video, Text, Credits: ESA/Hubble & NASA/Ashley Morrow.

Cheers, Orbiter.ch

Station to Raise Orbit before June Expedition 43 Undocking












ISS - Expedition 43 Mission patch.

May 15, 2015

The six-member Expedition 43 crew ends its work week with a wide variety of science exploring life in space benefiting both crews in space and humans on Earth. Meanwhile, one space freighter is preparing to fire its thrusters to lift the station’s orbit as another is being packed and readied for splashdown.

One-Year crew members Scott Kelly and Mikhail Kornienko participated in the Fine Motor Skills experiment which monitors different phases of a crew member’s microgravity adaptation and recovery back on Earth. Commander Terry Virts took samples of air and surface microbes for the Microbial Observatory-1 study which will be analyzed by scientists on the ground.


Image above: Astronaut Terry Virts and Scott Kelly were inside the Quest airlock Friday morning talking to reporters from The Weather Channel and Time Magazine . Credit: NASA TV

Samantha Cristoforetti studied the physics of where fluids and gases meet in Japan’s Kibo lab module. Flight Engineer Gennady Padalka worked on video gear and tested magnetometers in the station’s Russian segment. Flight Engineer Anton Shkaplerov studied chemical reactions in the Earth’s atmosphere, checked Russian docking systems and photographed windows in the Pirs and Poisk modules.

The ISS Progress 58 resupply ship docked to the Zvezda service module will fire its engines Friday night. The orbital boost will place the International Space Station at the correct altitude for the undocking of Expedition 43 in early June. The SpaceX Dragon loaded with science and gear will be released from the grips of the Canadarm2 May 21 at 7:05 a.m. EDT for a splashdown in the Pacific Ocean a few hours later.

Astronauts at Work on the International Space Station

Image above: This week, the six-member Expedition 43 crew worked a variety of onboard maintenance tasks, ensuring crew safety and the upkeep of the International Space Station's hardware. In this image, NASA astronauts Scott Kelly (left) and Terry Virts (right) work on a Carbon Dioxide Removal Assembly (CDRA) inside the station's Japanese Experiment Module. The CDRA system works to remove carbon dioxide from the cabin air, allowing for an environmentally safe crew cabin. Image Credit: NASA.

Related links:

Fine Motor Skills experiment: http://www.nasa.gov/mission_pages/station/research/experiments/1767.html

Microbial Observatory-1 study: http://www.nasa.gov/mission_pages/station/research/experiments/1794.html

Chemical reactions in the Earth’s atmosphere study: http://www.nasa.gov/mission_pages/station/research/experiments/429.html

For more information about the International Space Station (ISS), visit: http://www.nasa.gov/mission_pages/station/main/index.html

Images (mentioned), Text, Credits: NASA.

Greetings, Orbiter.ch

OPALS Boosts Space-to-Ground Optical Communications Research












NASA - OPALS Mission patch.

May 15, 2015

Ever wonder why stars seem to twinkle? This effect is caused by variations in the density of our atmosphere that cause blurring in light coming from space. It's pretty for stargazing, but a challenge for space-to-ground communications.

A key technology called adaptive optics corrects such distortions. By combining adaptive optics with a laser communications technology aboard the International Space Station, NASA is working toward advances in space communications that could have major benefits for our data transmission needs here on Earth as well.


Image above: This artist's rendition shows OPALS operating from the International Space Station. Credit: NASA/JPL-Caltech.

NASA's Optical Payload for Lasercomm Science (OPALS) on the space station has been conducting cutting-edge research on data transmission since June 2014. OPALS beams packets of information using lasers, which allows for sending data at a faster rate compared with transmission by radio waves.

For the first time, in March, researchers from NASA's Jet Propulsion Laboratory, Pasadena, California, used OPALS to demonstrate that the laser signal from the space station can be focused into single-mode optical fibers on the ground. Single-mode optical fiber, with one-quarter the width of a human hair, is the standard in the telecommunications industry.

In more recent experiments, researchers demonstrated a communications link between OPALS and the ground using an adaptive optics system. Researchers were able to transmit samples of video through the corrected laser signal and decode it on the ground.

Getting information from space to Earth is essential for exploring the solar system and studying our own planet from the vantage point of space. There are also benefits to Earthlings: The bandwidth for streaming your favorite shows or playing online games could be increased with laser communications technology.

"This technology could be used in the future for fast Internet connections from space by connecting satellite downlink signals to ground-based fiber optic networks," said Malcolm Wright, an optical engineer at JPL, where the OPALS project office is based.

The March demonstration, which used the one-meter Optical Communication Telescope Laboratory at Table Mountain near Wrightwood, California, advances the science of spacecraft-to-ground high-rate data transfer. Data links of tens of gigabits per second could potentially be supported through this technology.

"This represents the first demonstration of continuous adaptive-optics correction of a low Earth-orbiting spacecraft-to-ground optical link reported in the open literature," Wright said. "It lays the path for future robust, high-rate optical communications between low Earth-orbit and the ground."

One of the primary challenges is that laser beams are very narrow, and the OPALS instrument on the space station must be able to very accurately point the laser beam to the receiving telescope on Earth as it travels across the sky. The narrow laser beams and the movement of the space station also mean that even small distortions in the atmosphere can make a big difference in data transmission.

International Space Station (ISS) profile view. Image Credit: NASA

The space station's fast motion relative to the ground presents an additional challenge, compared to the traditional use of adaptive optics for static astronomical imaging. The adaptive optics instrument, which was provided by Boeing, headquartered in Chicago, uses the laser signal itself, in combination with mirrors and a high-speed camera, to sense the atmospheric differences that distort a signal from space and correct them.

"We wanted to find out: As the beam travels through different parts of the atmosphere, can we correct for the disturbances fast enough to get a stable signal for a good communications link?" Wright said.

During the March demonstration, when the OPALS instrument directed its downlink signal toward the telescope, the adaptive optics system received the signal and corrected for the effects of atmospheric turbulence for the entire 134-second pass.

"The way we communicate with and build spacecraft in the future could be revolutionized through the insights we gain from OPALS," said Matt Abrahamson, OPALS mission manager at JPL.

OPALS is a partnership between NASA's Jet Propulsion Laboratory in Pasadena, California; the International Space Station Program based at Johnson Space Center in Houston; Kennedy Space Center in Florida; Marshall Space Flight Center in Huntsville, Alabama, and the Advanced Exploration Systems Division at NASA Headquarters in Washington.

Related links:

International Space Station (ISS): http://www.nasa.gov/mission_pages/station/main/index.html

NASA's Optical Payload for Lasercomm Science (OPALS): http://phaeton.jpl.nasa.gov/external/projects/optical.cfm

NASA's Jet Propulsion Laboratory (JPL): http://www.jpl.nasa.gov/

Laser communications technology: http://www.nasa.gov/mission_pages/station/research/news/opals_data_rates_soar

Images (mentioned), Text, Credits: NASA/JPL/Elizabeth Landau.

Greetings, Orbiter.ch

Hubble traces the migration of white dwarfs in cluster 47 Tucanae












ESA - Hubble Space Telescope logo.

15 May 2015

Globular cluster 47 Tucanae

Astronomers using the NASA/ESA Hubble Space Telescope have, for the first time, collected a census of young white dwarf stars beginning their migration from the crowded centre of an ancient star cluster to its less populated outskirts. The new results challenge our ideas about how and when a star loses its mass near the end of its life.

White dwarfs are the burned-out relics of ancient stars that rapidly shut down their nuclear furnaces, cooling down and losing mass at the end of their active lives. As these stellar carcasses age and shed mass, they are expelled from the densely packed centre of the globular cluster and migrate to wider orbits [1]. Whilst astronomers knew about this process, they had never seen it in action, until now.

Central regions of 47 Tucanae

Astronomers used Hubble to trace this stellar journey by studying 3000 white dwarfs in the globular star cluster 47 Tucanae, a dense swarm of hundreds of thousands of stars in the Milky Way.

“We’ve seen the final picture before: white dwarfs that have migrated and settled into more distant orbits outside the core, determined by their mass,” explained Jeremy Heyl of the University of British Columbia, Canada, first author on the science paper. “But in this study, which comprises about a quarter of all the young white dwarfs in the cluster, we’re actually catching the stars in the process of moving outward and distributing themselves appropriately according to mass.”

Using the ultraviolet capabilities of Hubble’s sharp-eyed Wide Field Camera 3 [2], the astronomers traced populations of white dwarfs with a range of ages. Using the colours of the stars, the astronomers can also estimate the age of each star [3]. One group of six-million-year-old stars has just begun its journey from the dense cluster centre. Another population is around 100 million years old and has already arrived at its new position, roughly 1.5 light-years from its starting point, and far from the cluster centre.

Central regions of 47 Tucanae seen in the ultraviolet

“Before becoming white dwarfs, the migrating stars were among the most massive in the cluster, roughly as massive as the Sun,” explained co-author Elisa Antolini of the Università degli Studi di Perugia, Italy. “We knew that as they lost mass we would see a migration to the outskirts; that wasn’t a surprise. But, what did surprise us was that the youngest white dwarfs were only just embarking on their journey. This could be evidence that the stars shed much of their mass at a later stage in their lives than we once thought, which is an exciting find.”

About 100 million years before stars evolve into white dwarfs, they swell up and become red giant stars. Many astronomers thought that stars lost most of their mass during this phase. However, if this were the case, the stars would already have been expelled from the centre of the cluster at the red giant stage.

video
Pan across 47 Tucanae

“Our observations with Hubble found white dwarfs that are just beginning their migration to wider orbits,” explains team member Harvey Richer, also from the University of British Columbia, Canada. “This reveals that the migration of the stars from the centre — and the loss in their mass that has caused it — begins later in the star’s life than once thought. These white dwarfs are losing a large amount of mass just before they become white dwarfs and not during the earlier red giant phase.”

The new results imply that the stars actually lose 40 to 50 percent of their bulk just 10 million years before completely burning out as white dwarfs.

Studies into the mass segregation of white dwarfs will continue, and the 47 Tucanae cluster is an ideal place to do them due to its proximity to us and the significant number of stars at the cluster’s core that can be resolved by Hubble’s crisp vision.

Notes:

[1] White dwarfs are forced out of the densely packed centre of the cluster by gravitational interactions with more massive stars.

[2] Although the white dwarfs have exhausted the hydrogen fuel that makes them shine as stars, their brilliant hot cores have been exposed which makes them very luminous in ultraviolet light. Only Hubble can detect these stars because ultraviolet light is blocked by Earth’s atmosphere and therefore does not reach ground-based telescopes.

[3] The astronomers estimated the white dwarfs’ ages by analysing their colours, which gives them the stars’ temperatures. The hottest and youngest white dwarfs shine fiercely in ultraviolet light.

Notes for editors:

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

The international team of astronomers in this study consists of Jeremy Heyl (University of British Columbia, Canada), Harvey B. Richer (University of British Columbia, Canada), Elisa Antolini (Universita degli Studi di Perugia, Italia), Ryan Goldsbury (University of British Columbia, Canada), Jason Kalirai (STScI and Johns Hopkins University, USA), Javiera Parada (University of British Columbia, Canada), Pier-Emmanuel Tremblay (STScI).

Links:

Images of Hubble: http://www.spacetelescope.org/images/archive/category/spacecraft/

NASA press release: http://hubblesite.org/news/2015/16

Link to science paper: http://www.spacetelescope.org/static/archives/releases/science_papers/heic1510a.pdf

Images, Text, Credit: NASA, ESA, H. Richer and J. Heyl (University of British Columbia), and J. Anderson and J. Kalirai (STScI)/Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration/Acknowledgment: J. Mack (STScI) and G. Piotto (University of Padova, Italy)/Video: ESA/Hubble/Music: Johan Back Monell (www.johanmonell.com).

Best regards, Orbiter.ch

jeudi 14 mai 2015

Kepler Observes Neptune Dance with Its Moons












NASA - Kepler Mission patch.

May 14, 2015

NASA's Kepler spacecraft, known for its planet-hunting prowess of other stars, is also studying solar system objects. In its new K2 mission, Neptune and two of its moons, Triton and Nereid, have been imaged. The movie illustrates 70 days of uninterrupted observation making this one of the longer continuous studies of an outer solar system object.

video
Kepler Observes Neptune Dance with Its Moons

Video above: Seventy days worth of solar system observations from NASA's Kepler spacecraft, taken during its reinvented "K2" mission, are highlighted in this sped-up movie. The planet Neptune appears on day 15, followed by its moon Triton, which looks small and faint. Keen-eyed observers can also spot Neptune's tiny moon Nereid at day 24. Neptune is not moving backward but appears to do so because of the changing position of the Kepler spacecraft as it orbits around the sun. Video Credits: NASA Ames/SETI Institute/J. Rowe.

The movie, based on 101,580 images taken from November 2014 through January 2015 during K2's Campaign 3, reveals the perpetual clockwork of our solar system. The 70-day timespan is compressed into 34 seconds with the number of days noted in the top right corner.

Neptune appears on day 15 but does not travel alone in the video. The small faint object closely orbiting is its large moon Triton, which circles Neptune every 5.8 days. Appearing from the left at day 24, keen-eyed observers can also spot the tiny moon Nereid in its slow 360-day orbit around the planet. A few fast-moving asteroids make cameo appearances in the movie, showing up as streaks across the K2 field of view. The red dots are a few of the stars K2 examines in its search for transiting planets outside of our solar system.

Neptune's atmosphere reflects sunlight creating a bright appearance. The reflected light floods a number of pixels of the spacecraft's on board camera, producing the bright spikes extending above and below the planet. The celestial bodies in the stitched-together images are colored red to represent the wavelength response of the spacecraft's camera. In reality, Neptune is deep blue in color and its moons and the speeding asteroids are light grey while the background stars appear white from a distance.

Relative orbit speeds explain the interesting motion of Neptune and its moons beginning at day 42. Inner planets like Earth orbit more quickly than outer planets like Neptune. In the movie, Neptune’s apparent motion relative to the stationary stars is mostly due to the circular 372-day orbit of the Kepler spacecraft around the sun. If you look at distant objects and move your head back and forth, you will notice that objects close to you will also appear to move back and forth, relative to objects far away. The same concept is producing the apparent motion of Neptune.

NASA’s Kepler spacecraft. Image Credit: NASA

While NASA’s Kepler spacecraft is known for its discoveries of planets around other stars, an international team of astronomers plans to use these data to track Neptune’s weather and probe the planet’s internal structure by studying subtle brightness fluctuations that can only be observed with K2.

NASA's Ames Research Center in Moffett Field, California, manages the Kepler and K2 missions for NASA’s Science Mission Directorate. NASA's Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corp. operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

For more information about Kepler mission, visit: http://www.nasa.gov/mission_pages/kepler/overview/index.html and http://www.nasa.gov/mission_pages/kepler/main/index.html

Image (mentioned), Video (mentioned), Text, Credits: NASA/Michele Johnson.

Cheers, Orbiter.ch

Asteroid to Pass 6 Million Miles from Earth Thursday











Asteroid & Comet Watch logo.

May 14, 2015


Graphic above: This graphic depicts the passage of asteroid 1999 FN53, which will come no closer than 26 times the distance from Earth to the moon on May 14, 2015. Image Credits: NASA/JPL-Caltech.

An asteroid, designated 1999 FN53, will safely pass more than 26 times the distance of Earth to the moon on May 14. To put it another way, at its closest point, the asteroid will get no closer than 6.3 million miles away (10 million kilometers). It will not get closer than that for well over 100 years. And even then, (119 years from now) it will be so far away it will not affect our planet in any way, shape or form. 1999 FN53 is approximately 3,000 feet (1 kilometer) across.

"This is a flyby in the loosest sense of the term," said Paul Chodas, manager of NASA's Near-Earth Object Program Office, at the Jet Propulsion Laboratory in Pasadena, California. "We can compute the motion of this asteroid for the next 3,000 years and it will never be a threat to Earth. This is a relatively unremarkable asteroid, and its distant flyby of Earth tomorrow is equally unremarkable."

Artist's view of asteroids passing near Earth

NASA detects, tracks and characterizes asteroids and comets using both ground- and space-based telescopes. Elements of the Near-Earth Object Program, often referred to as "Spaceguard," discover these objects, characterize a subset of them and identify their close approaches to determine if any could be potentially hazardous to our planet. NASA’s Near-Earth Object Program is part of the agency's asteroid initiative, which includes sending a robotic spacecraft to capture a boulder from the surface of a near-Earth asteroid and move it into a stable orbit around the moon for exploration by astronauts, all in support of advancing the nation's journey to Mars.

JPL manages the Near-Earth Object Program Office for NASA's Science Mission Directorate in Washington. JPL is a division of the California Institute of Technology in Pasadena.

More information about asteroids and near-Earth objects is at:
http://www.jpl.nasa.gov/asteroidwatch/

To get updates on passing space rocks, follow:
http://twitter.com/asteroidwatch

Image, Graphic (mentioned), Text, Credits: NASA/Dwayne Brown/JPL/DC Agle/Wikimedia.

Greetings, Orbiter.ch

Magnetar Near Supermassive Black Hole Delivers Surprises












NASA - Chandra X-ray Observatory patch.

May 14, 2015

In 2013, astronomers announced they had discovered a magnetar exceptionally close to the supermassive black hole at the center of the Milky Way using a suite of space-borne telescopes including NASA’s Chandra X-ray Observatory.


Image above: Magnetar Near Supermassive Black Hole SGR 1745-2900. Image Credit: NASA/CXC/INAF/F. Coti Zelati et al.

Magnetars are dense, collapsed stars (called “neutron stars”) that possess enormously powerful magnetic fields. At a distance that could be as small as 0.3 light years (or about 2 trillion miles) from the 4-million-solar mass black hole in the center of our Milky Way galaxy, the magnetar is by far the closest neutron star to a supermassive black hole ever discovered and is likely in its gravitational grip.

Since its discovery two years ago when it gave off a burst of X-rays, astronomers have been actively monitoring the magnetar, dubbed SGR 1745-2900, with Chandra and the European Space Agency’s XMM-Newton. The main image of the graphic shows the region around the Milky Way’s black hole in X-rays from Chandra (red, green, and blue are the low, medium, and high-energy X-rays respectively). The inset contains Chandra’s close-up look at the area right around the black hole, showing a combined image obtained between 2005 and 2008 (left) when the magnetar was not detected, during a quiescent period, and an observation in 2013 (right) when it was caught as a bright point source during the X-ray outburst that led to its discovery.

A new study uses long-term monitoring observations to reveal that the amount of X-rays  from SGR 1745-2900 is dropping more slowly than other previously observed magnetars, and its surface is hotter than expected.

The team first considered whether “starquakes” are able to explain this unusual behavior. When neutron stars, including magnetars, form, they can develop a tough crust on the outside of the condensed star. Occasionally, this outer crust will crack, similar to how the Earth’s surface can fracture during an earthquake. Although starquakes can explain the change in brightness and cooling seen in many magnetars, the authors found that this mechanism by itself was unable to explain the slow drop in X-ray brightness and the hot crustal temperature.. Fading in X-ray brightness and surface cooling occur too quickly in the starquake model.

The researchers suggest that bombardment of the surface of the magnetar by charged particles trapped in twisted bundles of magnetic fields above the surface may provide the additional heating of the magnetar’s surface, and account for the slow decline in X-rays. These twisted bundles of magnetic fields can be generated when the neutron star forms.

The researchers do not think that the magnetar’s unusual behavior is caused by its proximity to a supermassive black hole, as the distance is still too great for strong interactions via magnetic fields or gravity.

Artist' view of NASA's Chandra X-ray Observatory. Image Credits: NASA/CXC

Astronomers will continue to study SGR 1745-2900 to glean more clues about what is happening with this magnetar as it orbits our galaxy’s supermassive black hole.

These results appear in Monthly Notices of the Royal Astronomical Society in a paper led by the PhD student Francesco Coti Zelati (Universita’ dell’ Insubria, University of Amsterdam, INAF-OAB), within a large international collaboration.

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for the agency’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations.

Read More from NASA's Chandra X-ray Observatory: http://chandra.harvard.edu/photo/2015/sgr1745/

For more information about Chandra X-ray Observatory, visit: http://www.nasa.gov/mission_pages/chandra/main/index.html and http://chandra.harvard.edu/

Images (mentioned), Text, Credits: NASA/Marshall Space Flight Center/Janet Anderson/Chandra X-ray Center/Megan Watzke/Jennifer Harbaugh.

Greetings, Orbiter.ch

mercredi 13 mai 2015

The Dark Side of Star Clusters












ESO - European Southern Observatory logo.

13 May 2015

VLT discovers new kind of globular star cluster

The giant elliptical galaxy Centaurus A (NGC 5128) and its strange globular clusters

Observations with ESO’s Very Large Telescope in Chile have discovered a new class of “dark” globular star clusters around the giant galaxy Centaurus A. These mysterious objects look similar to normal clusters, but contain much more mass and may either harbour unexpected amounts of dark matter, or contain massive black holes — neither of which was expected nor is understood.

Globular star clusters are huge balls of thousands of stars that orbit most galaxies. They are among the oldest known stellar systems in the Universe and have survived through almost the entire span of galaxy growth and evolution.

The strange galaxy Centaurus A in the constellation of Centaurus

Matt Taylor, a PhD student at the Pontificia Universidad Catolica de Chile, Santiago, Chile, and holder of an ESO Studentship, is lead author of the new study. He sets the scene: “Globular clusters and their constituent stars are keys to understanding the formation and evolution of galaxies. For decades, astronomers thought that the stars that made up a given globular cluster all shared the same ages and chemical compositions — but we now know that they are stranger and more complicated creatures.”

The elliptical galaxy Centaurus A (also known as NGC 5128) is the closest giant galaxy to the Milky Way and is suspected to harbour as many as 2000 globular clusters. Many of these globulars are brighter and more massive than the 150 or so orbiting the Milky Way.

Wide-field view of the giant galaxy Centaurus A

Matt Taylor and his team have now made the most detailed studies so far of a sample of 125 globular star clusters around Centaurus A using the FLAMES instrument on ESO’s Very Large Telescope at the Paranal Observatory in northern Chile [1].

They used these observations to deduce the mass of the clusters [2] and compare this result with how brightly each of the clusters shines.

For most of the clusters in the new survey, the brighter ones had more mass in the way that was expected — if a cluster contains more stars it has greater total brightness and more total mass. But for some of the globulars something strange showed up: they were many times more massive than they looked. And even more strangely, the more massive these unusual clusters were, the greater the fraction of their material was dark. Something in these clusters was dark, hidden and massive. But what?

video

Video above: Panning across the giant elliptical galaxy Centaurus A (NGC 5128) and its strange globular clusters.

There were several possibilities. Perhaps the dark clusters contain black holes, or other dark stellar remnants in their cores? This may be a factor that explains some of the hidden mass, but the team concludes that it cannot be the whole story. What about dark matter? Globular clusters are normally considered to be almost devoid of this mysterious substance, but perhaps, for some unknown reason, some clusters have retained significant dark matter clumps in their cores. This would explain the observations but does not fit into conventional theory.

Co-author Thomas Puzia adds: “Our discovery of star clusters with unexpectedly high masses for the amount of stars they contain hints that there might be multiple families of globular clusters, with differing formation histories. Apparently some star clusters look like, walk like, and smell like run-of-the-mill globulars, but there may quite literally be more to them than meets the eye.”

These objects remain a mystery. The team is also engaged in a wider survey of other globular clusters in other galaxies and there are some intriguing hints that such dark clusters may also be found elsewhere.

Matt Taylor sums up the situation: “We have stumbled on a new and mysterious class of star cluster! This shows that we still have much to learn about all aspects of globular cluster formation. It’s an important result and we now need to find further examples of dark clusters around other galaxies.”

Notes:

[1] Up to now astronomers have studied star clusters to this detail only in the Local Group. The relatively small distances make direct measurements of their masses possible. Looking at NGC 5128, which is an isolated, massive elliptical galaxy just outside the Local Group about 12 million light-years away, they were able to estimate masses of globular clusters in a completely different environment by pushing VLT/FLAMES to its limits.

[2] The FLAMES observations provide information about the motions of the stars in the clusters. This orbital information depends on the strength of the gravitational field and can hence be used to deduce the mass of the cluster — astronomers call such estimates dynamical masses. The light gathering power of a 8.2-metre VLT Unit Telescope mirror and FLAMES’s ability to observe more than 100 clusters simultaneously was the key to collecting the data necessary for the study.

More information:

This research was presented in a paper entitled “Observational evidence for a dark side to NGC 5128’s globular cluster system”, by M. Taylor et al., to appear in the Astrophysical Journal.

The team is composed of Matthew A. Taylor (Pontificia Universidad Catolica de Chile, Santiago, Chile; ESO, Santiago, Chile), Thomas H. Puzia (Pontificia Universidad Catolica de Chile), Matias Gomez (Universidad Andres Bello, Santiago, Chile) and Kristin A. Woodley (University of California, Santa Cruz, California, USA).

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. 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 a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Links:

Science paper: http://www.eso.org/public/archives/releases/sciencepapers/eso1519/eso1519a.pdf

Images of the VLT: http://www.eso.org/public/images/archive/category/paranal/

ESO’s Very Large Telescope (VLT): http://www.eso.org/paranal/

Images, Text, Credits: ESO/Digitized Sky Survey. Acknowledgement: Davide de Martin/IAU and Sky & Telescope/ESA/Hubble, NASA. Digitized Sky Survey. Acknowledgement: Davide de Martin/Video: ESO/Digitized Sky Survey. Acknowledgement: Davide de Martin/Music: Johan B Monell (www.johanmonell.com).

Greetings, Orbiter.ch

Space fever










ESA - European Astronauts patch.

13 May 2015

ESA Astronaut André Kuipers

It started with a simple question that ended with a surprising answer and new technology that is being used in cutting-edge heart surgery and could save millions of euros in hospital bills.

Hanns-Christian Gunga, working at the Center for Space Medicine and Extreme Environments in Berlin, Germany, has spent a lifetime working on how humans adapt to extreme environments and he wanted to know: what happens to an astronaut’s body temperature in space?

Astronaut André Kuipers exercising

People on Earth lose much of their body heat through convection – air around you is replaced by cooler air as it heats on the skin of your warm body and rises. Turning on a fan on a hot day can speed up the process and cool you down quicker as the air passes over and whisks some of the body heat away.

On the International Space Station there is no convection because of weightlessness and astronauts have reported feeling hot since the earliest days of spaceflight. ESA astronaut André Kuipers recounts: “Especially during exercise I would feel hot, afterwards I would always float to a fan to cool down.”

Thermolab

To understand what is happening you would need to continuously monitor astronaut’s body temperatures in space for a long period of time. The Thermolab experiment was born, but first a practical problem needed to be overcome.

Depending on where and when you measure your temperature a thermometer will give a different reading. Your body temperature is lower in your feet and lowest between four and six in the morning. Researchers and doctors refer to core body temperature – the temperature in your chest – to compare readings.

ESA Astronaut Alexander Gerst, forehead thermometer

Measuring core body temperature is not straightforward because a thermometer must be placed as close to your heart for best results. Many types of thermometers exist, from the under-your-tongue to the stick-in-your-ear variety but unfortunately the most accurate way of reading a core temperature was to insert a thermometer into your rectum.

Aside from the discomfort, this method has many impracticalities: it is time-consuming and asking astronauts to stop their work to insert a thermometer was not considered an option.

Professor Gunga decided to use a new technique he had developed and tested on firefighters, measuring the difference in heat radiated from the forehead. A simple calculation then reveals core body temperature with great accuracy.

Thermolab equipment

Eleven astronauts strapped with these sensors recorded their temperature over two sessions after three months in space and just before returning to Earth.

The sensor works so well that it is used in extreme environments by firefighters and in Antarctica, as well as during the Mars500 study.

A thermometer that can be read from a distance and continuously records very accurate data has enormous potential. The sensor is already being used in open-heart surgery on children but as a general instrument in hospitals it offers better and cheaper monitoring of patients.

Don't forget the astronauts

ESA Astronaut Luca Parmitano with temperature sensor

The experiment shows that astronauts develop a 1ºC higher temperature that never goes away after staying in space for two months. What causes this ‘space fever’ is not clear, but it has far-reaching consequences.

video
Space Station Live: Circadian Rhythms

Video above: Professor Gunga explains the temperature sensor used in the Circadian Rhythms follow-up study.

Comparing data to other studies shows a correlation with Interleukin-1, a hormone that causes fever when sick. Raising body temperature by a degree requires 20% more energy, derived from food, so mission planners need to know more about this phenomenon in order to estimate the required food supplies for long missions.

Related links:

Charite in Space – Center for Space Medicine and Extreme Environments: http://charite-in-space.de/

Thermolab experiment details: http://eea.spaceflight.esa.int/portal/exp/?id=9165

Experiment archive: http://eea.spaceflight.esa.int/

International Space Station Benefits for Humanity: http://www.esa.int/Our_Activities/Human_Spaceflight/International_Space_Station_Benefits_for_Humanity

Columbus: http://www.esa.int/Our_Activities/Human_Spaceflight/Columbus

Images, Video, Text, Credits: ESA/NASA/Charite, ZWMB/NASA TV.

Best regards, Orbiter.ch

mardi 12 mai 2015

LHC Season 2: Follow the people at the frontiers of physics












CERN - European Organization for Nuclear Research logo.

May 12, 2015

video
Welcome to LHC season 2: new frontiers in physics at #13TeV

What do physicists dream of? What do they hope to discover when they harvest new data from the world's most powerful particle accelerator, the Large Hadron Collider (LHC)? In the new video series "LHC Season 2: New frontiers in physics" the camera follows 11 physicists from the four large LHC experiments ALICE, ATLAS, CMS and LHCb.

The physicists tell of their hopes for new discoveries during the LHC's second run, now at the record-breaking energy of 13 teraelectronvolts (TeV). They speak of dark matter, supersymmetry, the Higgs boson, antimatter, current theory in particle physics and its limits as well as new theoretical models that could extend it. As they explore the nature of matter in the universe, they will soon discover a new energy frontier. Follow their search – a new video will be posted on this blog weekly.

CERN - Large Hadron Collider (LHC)

Note:

CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 22 Member States.

Related article:

LHC: Preparations for collisions at 13 TeV: http://orbiterchspacenews.blogspot.ch/2015/04/cern-lhc-preparations-for-collisions-at.html

Related links:

Large Hadron Collider (LHC): http://home.web.cern.ch/topics/large-hadron-collider

ALICE experiments: http://home.web.cern.ch/about/experiments/alice

ATLAS experiments: http://home.web.cern.ch/about/experiments/atlas

CMS experiments: http://home.web.cern.ch/about/experiments/cms

LHCb experiments: http://home.web.cern.ch/about/experiments/lhcb

For more information about the European Organization for Nuclear Research (CERN), visit: http://home.web.cern.ch/

Image, Video, Text, Credits: CERN/Cian O'Luanaigh.

Greetings, Orbiter.ch

Space Launch System Program Moving Forward with Critical Design Review












NASA - Space Launch System (SLS) logo.

May 12, 2015

NASA's Space Launch System (SLS) Program is kicking off its critical design review May 11 at NASA's Marshall Space Flight Center in Huntsville, Alabama.


Image above: Artist concept of NASA's Space Launch System wireframe design. The SLS Program is kicking off its critical design review May 11 at NASA's Marshall Space Flight Center in Huntsville, Alabama. Image Credits: NASA/MSFC.

This new rocket will be the most powerful launch vehicle ever built. It is designed to be sustainable and evolve to carry crew and cargo on deep space missions, including an asteroid and ultimately to Mars.

Milestone reviews like the critical design review are just that -- critical. The critical design review demonstrates that the SLS design meets all system requirements with acceptable risk, and accomplishes that within cost and schedule constraints. It also proves that the rocket should continue with full-scale production, assembly, integration, and testing and that the program is ready to begin the next major review covering design certification.

"We've never said building a rocket is easy," said SLS Program Manager Todd May. "We pore over every part of this rocket during these reviews. Thousands of documents and months of time are put into making sure the design is sound, safe and sustainable, and will make NASA's mission of furthering human spaceflight possible. We are making advances every day on this vehicle."

Each element for the rocket -- including boosters, engines, stages and Spacecraft and Payload Integration & Evolution (SPIE) -- undergo their own reviews before this week’s kickoff of the integrated program review. Boosters, stages and engines have passed their critical design reviews, and the SPIE Office is in the process of completing its critical design review. SPIE is responsible for the design and development of several parts of the top of the rocket, including:

- Orion stage adapter – connects the Orion spacecraft to the SLS

- Interim cryogenic propulsion stage -- gives the Orion spacecraft the big push needed to fly beyond the moon before the spacecraft returns to Earth during the first flight test of SLS

- Launch vehicle stage adapter -- used to connect the core stage and interim cryogenic propulsion stages


Image above: Artist concept highlighting the upper stage of the Block 1 configuration of NASA’s Space Launch System. The Spacecraft and Payload Integration & Evolution Office (SPIE) at NASA’s Marshall Space Flight Center in Huntsville, Alabama, is responsible for the design and development of the Orion stage adapter, interim cryogenic propulsion stage and launch vehicle stage adapter. Image Credits: NASA/MSFC.

SPIE also works to prepare for the future evolution of SLS to provide the capabilities needed for human missions to Mars. The office oversees in-house research and partners with academia, industry and other government agencies to develop new technologies and systems that will benefit not only SLS, but also the larger U.S. launch industry.

The SLS Program critical design review is targeted to conclude in late July.

Artist's view of the SLS launch. Image Credit: NASA

The first flight test of the SLS will be configured for a 70-metric-ton (77-ton) lift capacity and carry an uncrewed Orion spacecraft beyond low-Earth orbit to test the performance of the integrated system. As the SLS evolves, it will be the most powerful rocket ever built and provide an unprecedented lift capability of 130 metric tons (143 tons) to enable missions even farther into our solar system.

For more information on SLS, visit: http://www.nasa.gov/sls

Images (mentioned), Text, Credits: NASA/Marshall Space Flight Center/Kim Henry/Lee Mohon.

Best regards, Orbiter.ch

Kepler's Six Years In Science (and Counting)












NASA - Kepler Mission patch.

May 12, 2015


The graphic tells NASA's Kepler spacecraft's story by the numbers from the moment it began hunting for planets outside our solar system on May 12, 2009. From the trove of data collected, we have learned that planets are common, that most sun-like stars have at least one planet and that nature makes planets with unimaginable diversity.

Kepler launched on March 6, 2009. Its mission was to survey a portion of our galaxy to determine what fraction of stars might harbor potentially habitable, Earth-sized exoplanets or planets that orbit other stars. Of particular interest are exoplanets orbiting in the habitable zone -- the range of distance from a star in which the surface temperature of an orbiting planet might sustain liquid water. For life as we know it, liquid water is a necessary ingredient.

Of the more than 1,000 confirmed planets found by Kepler, eight are less than twice Earth-sized and in their stars' habitable zone. All eight orbit stars cooler and smaller than our sun.

During its four-year prime mission, Kepler simultaneously and continuously measured the brightness of more than 150,000 stars, looking for the telltale dimming that would indicate the presence of an orbiting planet. From these dimmings, or transits, and information about the parent star, researchers can determine a planet's size (radius), the time it takes to orbit its star and the amount of energy received from the host star.

Kepler's exquisitely precise photometer, or light sensor, was designed to detect minute changes in brightness, to infer the presence of an Earth-sized planet. For a remote observer, Earth transiting the sun would dim its light by less than 1/100th of one percent, or the equivalent of the amount of light blocked by a gnat crawling across a car’s headlight viewed from several miles away.

In May 2014, the Kepler spacecraft began a new mission, K2, to observe parts of the sky along the ecliptic plane, the orbital path of the Earth about the sun, where the familiar constellations of the zodiac lie. This new mission provides scientists with an opportunity to search for even more exoplanets, as well as opportunities to observe notable star clusters, young and old stars, active galaxies and supernovae. The spacecraft continues to collect data in its new mission.

For more information on Kepler, please visit: http://www.nasa.gov/kepler

Graphic, Text, Credits: NASA Ames/W Stenzel/Michele Johnson.

Greetings, Orbiter.ch

NASA’s New Horizons Spots Pluto’s Faintest Known Moons












NASA - New Horizons Misson logo.

May 12, 2015


It’s a complete Pluto family photo – or at least a photo of the family members we’ve already met. 

For the first time, NASA’s New Horizons spacecraft has photographed Kerberos and Styx – the smallest and faintest of Pluto’s five known moons. Following the spacecraft’s detection of Pluto’s giant moon Charon in July 2013, and Pluto’s smaller moons Hydra and Nix in July 2014 and January 2015, respectively, New Horizons is now within sight of all the known members of the Pluto system.

“New Horizons is now on the threshold of discovery,” said mission science team member John Spencer, of the Southwest Research Institute in Boulder, Colorado. “If the spacecraft observes any additional moons as we get closer to Pluto, they will be worlds that no one has seen before.”

Drawing ever closer to Pluto in mid-May, New Horizons will begin its first search for new moons or rings that might threaten the spacecraft on its passage through the Pluto system. The images of faint Styx and Kerberos shown here are allowing the search team to refine the techniques they will use to analyze those data, which will push the sensitivity limits even deeper.

Kerberos and Styx were discovered in 2011 and 2012, respectively, by New Horizons team members using the Hubble Space Telescope. Styx, circling Pluto every 20 days between the orbits of Charon and Nix, is likely just 4 to 13 miles (approximately 7 to 21 kilometers) in diameter, and Kerberos, orbiting between Nix and Hydra with a 32-day period, is just 6 to 20 miles (approximately 10 to 30 kilometers) in diameter. Each is 20 to 30 times fainter than Nix and Hydra.

The images detecting Kerberos and Styx shown here were taken with New Horizons’ most sensitive camera, the Long Range Reconnaissance Imager (LORRI), from April 25-May 1. Each observation consists of five 10-second exposures that have been added together to make the image in the left panel. Images were extensively processed to reduce the bright glare of Pluto and Charon and largely remove the dense field of background stars (center and right panels). This reveals the faint satellites, whose positions and orbits - along with those of brighter moons Nix and Hydra -  are given in the right panel.

“Detecting these tiny moons from a distance of more than 55 million miles is amazing, and a credit to the team that built our LORRI long-range camera and John Spencer’s team of moon and ring hunters,” added New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute.

Artist's view of Pluto from New Horizons Spacecraft. Image Credit: NASA

Kerberos is visible in all of the images, though is partially obscured in the second image. Styx is not visible in the first image, only in subsequent ones; on April 25 it was obscured by electronic artifacts in the camera – the black and white streaks extending to the right of the extremely overexposed images of Pluto and Charon in the center of the frame. These artifacts point in different directions in different images due to the varying orientation of the spacecraft. Other unlabeled features in the processed images include the imperfectly removed images of background stars and other residual artifacts.

Although Styx and Kerberos are more visible in some frames than others, perhaps due to brightness fluctuations as they rotate on their axes, their identity is confirmed by their positions being exactly where they are predicted to be (in the center of the circles in the right panel).

The Johns Hopkins University Applied Physics Laboratory (APL) designed, built, and operates the New Horizons spacecraft, and manages the mission for NASA’s Science Mission Directorate. SwRI leads the science team, payload operations and encounter science planning. New Horizons is part of the New Frontiers Program managed by NASA’s Marshall Space Flight Center in Huntsville, Alabama.

To view images from New Horizons and learn more about the mission, visit:
http://www.nasa.gov/newhorizons

Images & Animations (mentioned), Text, Credits: NASA/Tricia Talbert.

Greetings, Orbiter.ch

NASA Research Reveals Europa's Mystery Dark Material Could Be Sea Salt












NASA Galileo Mission patch.

May 12, 2015

Jupiter's moon Europa. Image Credits: NASA/JPL-Caltech

NASA laboratory experiments suggest the dark material coating some geological features of Jupiter's moon Europa is likely sea salt from a subsurface ocean, discolored by exposure to radiation. The presence of sea salt on Europa's surface suggests the ocean is interacting with its rocky seafloor -- an important consideration in determining whether the icy moon could support life.

The study is accepted for publication in the journal Geophysical Research Letters and is available online.


Image above: A "Europa-in-a-can" laboratory setup at NASA-JPL mimics conditions of temperature, near vacuum and heavy radiation on the surface of Jupiter's icy moon. Image Credits: NASA/JPL-Caltech.

“We have many questions about Europa, the most important and most difficult to answer being is there life? Research like this is important because it focuses on questions we can definitively answer, like whether or not Europa is inhabitable,” said Curt Niebur, Outer Planets Program scientist at NASA Headquarters in Washington. “Once we have those answers, we can tackle the bigger question about life in the ocean beneath Europa’s ice shell.”

For more than a decade, scientists have wondered about the nature of the dark material that coats long, linear fractures and other relatively young geological features on Europa’s surface. Its association with young terrains suggests the material has erupted from within Europa, but with limited data available, the material's chemical composition has remained elusive.

"If it's just salt from the ocean below, that would be a simple and elegant solution for what the dark, mysterious material is," said research lead Kevin Hand, a planetary scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California.


Image above: A close-up of salt grains discolored by radiation following exposure in a "Europa-in-a-can" test setup at JPL. Image Credits: NASA/JPL-Caltech.

One certainty is that Europa is bathed in radiation created by Jupiter's powerful magnetic field. Electrons and ions slam into the moon's surface with the intensity of a particle accelerator. Theories proposed to explain the nature of the dark material include this radiation as a likely part of the process that creates it.

Previous studies using data from NASA's Galileo spacecraft, and various telescopes, attributed the discolorations on Europa's surface to compounds containing sulfur and magnesium. While radiation-processed sulfur accounts for some of the colors on Europa, the new experiments reveal that irradiated salts could explain the color within the youngest regions of the moon's surface.


Image above: A salt sample inside a JPL test chamber is bathed in an eerie blue glow as an electron beam scans across it many times each second, delivering a powerful dose of radiation. Image Credits: NASA/JPL-Caltech.

To identify the dark material, Hand and his co-author Robert Carlson, also at JPL, created a simulated patch of Europa's surface in a laboratory test apparatus for testing possible candidate substances. For each material, they collected spectra -- which are like chemical fingerprints -- encoded in the light reflected by the compounds.

"We call it our 'Europa in a can,'" Hand said. "The lab setup mimics conditions on Europa's surface in terms of temperature, pressure and radiation exposure. The spectra of these materials can then be compared to those collected by spacecraft and telescopes."

For this particular research, the scientists tested samples of common salt -- sodium chloride -- along with mixtures of salt and water, in their vacuum chamber at Europa's chilly surface temperature of minus 280 degrees Fahrenheit (minus 173 Celsius). They then bombarded the salty samples with an electron beam to simulate the intense radiation on the moon's surface.


Image above: After tens of hours of exposure to Europa-like conditions, sodium chloride samples turned a yellowish-brown color. The color is spectrally similar to that of dark features on Europa imaged by NASA's Galileo spacecraft.
Credits: NASA/JPL-Caltech

After a few tens of hours of exposure to this harsh environment, which corresponds to as long as a century on Europa, the salt samples, which were initially white just like table salt, turned a yellowish-brown color similar to features on the icy moon. The researchers found the color of these samples, as measured in their spectra, showed a strong resemblance to the color within fractures on Europa that were imaged by NASA's Galileo mission.

"This work tells us the chemical signature of radiation-baked sodium chloride is a compelling match to spacecraft data for Europa's mystery material," Hand said.

Additionally, the longer the samples were exposed to radiation, the darker the resulting color. Hand thinks scientists could use this type of color variation to help determine the ages of geologic features and material ejected from any plumes that might exist on Europa.


Image above: A salt sample, baked to a brownish color by radiation, after exposure to Europa-like conditions. Image Credits: NASA/JPL-Caltech.

Previous telescope observations have shown tantalizing hints of the spectral features seen by the researchers in their irradiated salts. But no telescope on or near Earth can observe Europa with sufficiently high resolving power to identify them with certainty. The researchers suggest this could be accomplished by future observations with a spacecraft visiting Europa.

JPL built and managed NASA's Galileo mission for the agency's Science Mission Directorate in Washington, and is developing a concept for a future mission to Europa. The California Institute of Technology in Pasadena, manages JPL for NASA.

For more information about Europa, visit: http://europa.jpl.nasa.gov

For more information about Galileo mission, visit: http://science.nasa.gov/missions/galileo/

Images (mentioned), Text, Credits: NASA/Dwayne Brown/JPL/Preston Dyches/Sarah Ramsey.

Cheers, Orbiter.ch