samedi 1 août 2015

The United Arab Emirates to the conquest of Mars







UAE Space Agency logo.

August 1, 2015

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UAE Space Agency Launch Event

The UAE now aim higher than the skyscrapers of Dubai. The country aims to become the leader in space exploration; his new goal: Mars.

The Space Agency of the United Arab Emirates, born in July 2014, presented last May at MBRSC (Centre Spatial de Mohamed Bin Rashid) in Dubai, the first mission entirely planned and managed by the UAE.

Agency researchers are currently building the probe "Al Amal" ("Hope" in Arabic), which will leave for Mars in July 2020 in order to land there a year later. The choice of the year has not been left to chance: in 2021, we will celebrate the 50th anniversary of the birth of the United Arab Emirates.


Image Above: The UAE Space Agency and the Centre National d'Etudes Spatiales (the National Centre of Space Studies of France) - CNES sign a Memorandum of Understanding (MoU) to create a strategic partnership space entre les two entities. Image Credit: UAE Space Agency.

The objective of the mission is to study changes in the atmosphere of Mars during the diurnal and seasonal cycles and observe clouds and dust storms. The probe will also measure changes in temperature, dust, ice and gas in the different layers of the atmosphere. But above all, it seeks to unravel the mysteries of the red planet trying to find the reasons for the disappearance of the Martian atmosphere into space.

After 200 days of travel, the data collected by the probe will understand the changes in the atmosphere of the Earth over the past million years. More than 1,000 gigabytes of data will be analyzed by the Emirati researchers and shared with over 200 institutions worldwide. The Space Agency of the UAE has signed a collaboration agreement with the Space Agency of the UK and with the National Centre for Space Studies (CNES) in France.


Images Above: Emirates Mars Mission Journey. Images Credit: Mohammed Bin Rashid Space Centre.

Investments of the UAE in space technologies have already exceeded $ 5.5 billion and to date, the Agency has seven satellites in orbit, with the help of the European company EADS, American Boeing and the South Korean Setrac.

Space Agency of the young researchers are aware of the race against time to complete their mission. For example, the launch window - the time when Earth and Mars are closest - repeated only every two years. In fact, the mission can not afford to fall behind at risk of failing.

More importantly, these researchers feel invested with a historical mission, as they explain in a video. For them it is an important step for the Islamic civilization, which in the Middle Ages gave to humanity its first mathematicians and astronomers.


Image above:  Artist's view of the probe "Hope" arrival at Mars. Images Credit: Mohammed Bin Rashid Space Centre.

Today, it is with some pride that UAE scientists this challenge. "If a small Arab state can reach Mars, then, really, everything is possible", they argue.

For more information about the United Arab Emirates (UAE) Space Agency, visit: http://www.space.gov.ae/about-the-agency

Images (Mentioned), Video, Text, Credits: ATS/UAE Space Agency/Orbiter.ch Aerospace.

Best regards, Orbiter.ch

Earth Flyby of 'Space Peanut' Captured in New Video










Asteroid Watch logo.

August 1, 2015

NASA scientists have used two giant, Earth-based radio telescopes to bounce radar signals off a passing asteroid and produce images of the peanut-shaped body as it approached close to Earth this past weekend.


Images above: Radar images of asteroid 1999 JD6 were obtained on July 25, 2015. The asteroid is between 660 - 980 feet (200 - 300 meters) in diameter. Images Credits: NASA/JPL-Caltech/GSSR.

The asteroid appears to be a contact binary -- an asteroid with two lobes that are stuck together.

The images show the rotation of the asteroid, named 1999 JD6, which made its closest approach on July 24 at 9:55 p.m. PDT (12:55 a.m. EDT on July 25) at a distance of about 4.5 million miles (7.2 million kilometers, or about 19 times the distance from Earth to the moon).

"Radar imaging has shown that about 15 percent of near-Earth asteroids larger than 600 feet [about 180 meters], including 1999 JD6, have this sort of lobed, peanut shape," said Lance Benner of NASA's Jet Propulsion Laboratory in Pasadena, California, who leads NASA's asteroid radar research program.


Image above: NASA's 230-foot-wide (70-meter) Deep Space Network antenna at Goldstone, California. Image Credit: NASA/DSN.

To obtain the views, researchers paired NASA's 230-foot-wide (70-meter) Deep Space Network antenna at Goldstone, California, with the 330-foot (100-meter) National Science Foundation Green Bank Telescope in West Virginia. Using this approach, the Goldstone antenna beams a radar signal at an asteroid and Green Bank receives the reflections. The technique, referred to as a bistatic observation, dramatically improves the amount of detail that can be seen in radar images. The new views obtained with the technique show features as small as about 25 feet (7.5 meters) wide.


Image above: National Science Foundation Green Bank Telescope in West Virginia. Image Credit: Wikipedia.

The individual images used in the movie were generated from data collected on July 25. They show the asteroid is highly elongated, with a length of approximately 1.2 miles (2 kilometers) on its long axis. The movie spans a period of about seven hours, 40 minutes.

This week's flyby was the closest approach the asteroid will make to Earth for about the next 40 years. The next time it will approach Earth this closely is in 2054, at approximately the same distance of this week's flyby.

Data from the new observations will be particularly useful to Sean Marshall, a graduate student at Cornell University in Ithaca, New York, whose doctoral research on 1999 JD6 is funded by NASA's Near-Earth Object Program. "I'm interested in this particular asteroid because estimates of its size from previous observations, at infrared wavelengths, have not agreed. The radar data will allow us to conclusively resolve the mystery of its size to better understand this interesting little world," he said.

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Radar Observations of Asteroid 1999 JD6

 Video above: Radar data of asteroid 1999 JD6 revealed the object is a contact binary consisting of two lobes. The data was collected over seven and a half hours on July 25, 2015, when the asteroid was about 4.5 million miles (7.2 million kilometers) from Earth.

Despite the uncertainty about its size, asteroid 1999 JD6 has been studied extensively and many of its physical properties, as well as its trajectory, are well known. It rotates in just over seven-and-a-half hours and is thought to be a relatively dark object. Asteroid 1999 JD6 was discovered on May 12, 1999, by the Lowell Observatory Near-Earth-Object Search, located in Flagstaff, Arizona.

Radar is a powerful technique for studying an asteroid's size, shape, rotation, surface features and surface roughness, and for improving the calculation of asteroid orbits. Radar measurements of asteroid distances and velocities often enable computation of asteroid orbits much further into the future than would be possible otherwise.

NASA places a high priority on tracking asteroids and protecting our home planet from them. In fact, the U.S. has the most robust and productive survey and detection program for discovering near-Earth objects (NEOs). To date, U.S. assets have discovered over 98 percent of the known NEOs.

In addition to the resources NASA puts into understanding asteroids, it also partners with other U.S. government agencies, university-based astronomers, and space science institutes across the country, often with grants, interagency transfers and other contracts from NASA, and also with international space agencies and institutions that are working to track and better understand these objects.

NASA's Near-Earth Object Program at NASA Headquarters, Washington, manages and funds the search, study and monitoring of asteroids and comets whose orbits periodically bring them close to Earth. 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 available at: http://neo.jpl.nasa.gov and http://www.jpl.nasa.gov/asteroidwatch and via Twitter at http://www.twitter.com/asteroidwatch

More information about asteroid radar research is at: http://echo.jpl.nasa.gov

More information about the Deep Space Network is at: http://deepspace.jpl.nasa.gov/dsn

Images (mentioned), Video, Text, Credits: NASA/JPL/DC Agle/Preston Dyches.

Best regards, Orbiter.ch

vendredi 31 juillet 2015

Veteran NASA Astronaut and Spacewalker Michael Foreman Retires From NASA











NASA logo.

July 31, 2015

Veteran astronaut Mike Foreman has retired from NASA to join a Houston-based consulting firm. A retired captain in the U.S. Navy, Foreman’s last day with the agency today July 31.

“Mike is a great American who has served our nation for 35 years,” said Chris Cassidy, chief of the Astronaut Office at NASA’s Johnson Space Center in Houston. “We have been lucky to have him as part of our NASA team, and wish him and his family the best.”

Foreman grew up in Wadsworth, Ohio. He holds degrees from the U.S. Naval Academy in Annapolis, Maryland, and the U.S. Naval Postgraduate School in Monterey, California. Designated a Naval Aviator in 1981, Foreman has flown more than 7,000 hours in 50 different aircraft.

Astronaut Michael Foreman

Foreman was selected as a NASA astronaut candidate in 1998 and flew on two space shuttle missions, accumulating more than 26 days in space. He also performed five spacewalks, spending 32 hours and 19 minutes outside performing space station assembly tasks. He flew as a mission specialist for STS-123 on space shuttle Endeavour in March 2008. The mission delivered the Japanese Experiment Logistics Module and the Canadian-built Dextre, also known as the Special Purpose Dexterous Manipulator, to the station. His next mission was STS-129 on space shuttle Atlantis in November 2009. The mission delivered two logistics carriers and approximately 30,000 pounds of replacement parts for station power systems.

When not flying in space, Foreman held a variety of technical assignments in the Astronaut Office. He also served as chief of External Programs at NASA’s Glenn Research Center in Cleveland from June 2010 through May 2011. He most recently served as the Safety Branch chief in the Astronaut Office. There, he also supported the Exploration Branch, working on the Commercial Crew Development Program.

Foreman’s complete biography is available at: http://www.jsc.nasa.gov/Bios/htmlbios/foreman.html

Image, Text, Credits: NASA/Johnson Space Center/Nicole Cloutier-Lemasters/Christina Canales.

Greetings, Orbiter.ch

A Tale of Two Extremes: Rainfall Across the US








NASA / JAXA - Global Precipitation Measurement (GPM) logo.

July 31, 2015

The United States has seen a tale of two extremes this year, with drenching rains in the eastern half of the country and persistent drought in the west. A new visualization of rainfall data collected from space shows the stark contrast between east and west for the first half of 2015.

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Rainfall Accumulation Across the United States (1/1/2015 - 7/16/2015)

Video above: The accumulated precipitation product visualized here begins on Jan. 1, 2015, and runs through July 16, 2015. This visualization shows the heavy rainfall throughout Northern Texas and across Oklahoma as well as the drought in Southern California. Video Credits: NASA Goddard's Scientific Visualization Studio.

The precipitation data shown here, from Jan. 1 through July 16, is from the joint NASA-Japan Aerospace Exploration Agency's Global Precipitation Measurement mission.  Accumulated rain totals are shown in different colors: 0 to 1 inch is light blue, up to 12 inches is green, up to 20 inches is yellow, and up to 40 inches is red. Purple shows an up to 76 inches in southern Louisiana, central Illinois, and a swath of Texas and Oklahoma that all saw severe flooding associated with heavy rainfall this spring and summer.

From the Rockies westward, rainfall has been much sparser over the last six months. California and the southwest received little relief from their punishing drought. The Pacific northwest has received below average rainfall and not enough snowfall which they, like California, rely on for part of their water supply.

Global Precipitation Measurement (GPM) satellite. Image Credits: NASA/JAXA

The GPM mission's Core Observatory satellite launched February 2014, and unites precipitation data from an international network of 12 satellites into a single dataset. The result is NASA's Integrated Multi-satellite Retrievals for GPM, or IMERG, data product, which seamlessly shows rain and snowfall across world in 30-minute timesteps.

For more information about GPM (Global Precipitation Measurement) mission, visit: http://www.nasa.gov/mission_pages/GPM/main/index.html

Download the full data visualization from NASA Goddard's Scientific Visualization Studio: http://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=4337

To learn more about NASA's GPM Mission, visit: http://www.nasa.gov/gpm

JAXA - GPM/DPR: http://global.jaxa.jp/projects/sat/gpm/

Related Links:

A Tale of Two Extremes: Droughts and Floods Visualizations: http://svs.gsfc.nasa.gov/cgi-bin/details.cgi?aid=11966

California "Rain Debt" Equal to Average Full Year of Precipitation: http://www.nasa.gov/press-release/california-rain-debt-equal-to-average-full-year-of-precipitation

NASA's Precipitation Measurement Missions website: http://pmm.nasa.gov/

Image (mentioned), Video (mentioned), Text, Credits: NASA's Earth Science News Team/Ellen Gray/Rob Garner.

Greetings, Orbiter.ch

Powerful Auroras Found at Brown Dwarf












NASA patch.

July 31, 2015

Mysterious objects called brown dwarfs are sometimes called "failed stars." They are too small to fuse hydrogen in their cores, the way most stars do, but also too large to be classified as planets. But a new study in the journal Nature suggests they succeed in creating powerful auroral displays, similar to the kind seen around the magnetic poles on Earth.


Image above: This artist's concept shows an auroral display on a brown dwarf. If you could see an aurora on a brown dwarf, it would be a million times brighter than an aurora on Earth. Image Credits: Chuck Carter and Gregg Hallinan/Caltech.

"This is a whole new manifestation of magnetic activity for that kind of object," said Leon Harding, a technologist at NASA's Jet Propulsion Laboratory, Pasadena, California, and co-author on the study.

On Earth, auroras are created when charged particles from the solar wind enter our planet's magnetosphere, a region where Earth's magnetic field accelerates and sends them toward the poles. There, they collide with atoms of gas in the atmosphere, resulting in a brilliant display of colors in the sky.

"As the electrons spiral down toward the atmosphere, they produce radio emissions, and then when they hit the atmosphere, they excite hydrogen in a process that occurs at Earth and other planets," said Gregg Hallinan, assistant professor of astronomy at the California Institute of Technology in Pasadena, who led the team. "We now know that this kind of auroral behavior is extending all the way from planets up to brown dwarfs."

Brown dwarfs are generally cool, dim objects, but their auroras are about a million times more powerful than auroras on Earth, and if we could somehow see them, they'd be about a million times brighter, Hallinan said. Additionally, while green is the dominant color of earthly auroras, a vivid red color would stand out in a brown dwarf's aurora because of the higher hydrogen content of the object's atmosphere.

The foundation for this discovery began in the early 2000s, when astronomers began finding radio emissions from brown dwarfs. This was surprising because brown dwarfs do not generate large flares and charged-particle emissions the way the sun and other kinds of stars do. The cause of these radio emissions was a big question.

Hallinan discovered in 2006 that brown dwarfs can pulse at radio frequencies, too. This pulsing phenomenon is similar to what is seen from planets in our solar system that have auroras.

Harding, working as part of Hallinan's group while pursuing his doctoral studies, found that there was also periodic variability in the optical wavelength of light coming from brown dwarfs that pulse at radio frequencies. He published these findings in the Astrophysical Journal. Harding built an instrument called an optical high-speed photometer, which looks for changes in the light intensity of celestial objects, to examine this phenomenon.

The combination of results made scientists wonder: Could this variability in light from brown dwarfs be caused by auroras?

In this new study, researchers examined brown dwarf LSRJ1835+3259, located about 20 light-years from Earth. Scientists studied it using some of the world's most powerful telescopes -- the National Radio Astronomy Observatory's Very Large Array, Socorro, New Mexico, and the W.M. Keck Observatory's telescopes in Hawaii -- in addition to the Hale Telescope at the Palomar Observatory in California.

National Radio Astronomy Observatory's Very Large Array, Socorro, New Mexico

Given that there's no stellar wind to create an aurora on a brown dwarf, researchers are unsure what is generating it on LSRJ1835+3259. An orbiting planet moving through the magnetosphere of the brown dwarf could be generating a current, but scientists will have to map the aurora to figure out its source.

W.M. Keck Observatory's telescopes in Hawaii

The discovery reported in the July 30 issue of Nature could help scientists better understand how brown dwarfs generate magnetic fields. Additionally, brown dwarfs will help scientists study exoplanets, planets outside our solar system, as the atmosphere of cool brown dwarfs is similar to what astronomers expect to find at many exoplanets.

Hale Telescope at the Palomar Observatory in California

"It's challenging to study the atmosphere of an exoplanet because there's often a much brighter star nearby, whose light muddles observations. But we can look at the atmosphere of a brown dwarf without this difficulty," Hallinan said.

Hallinan also hopes to measure the magnetic field of exoplanets using the newly built Owens Valley Long Wavelength Array, funded by Caltech, JPL, NASA and the National Science Foundation.

Caltech manages JPL for NASA.

For more information about exoplanets and NASA's planet-finding program, visit: http://planetquest.jpl.nasa.gov

National Radio Astronomy Observatory Array Operations Center: http://www.nrao.edu/

Hale Telescope at the Palomar Observatory:http://www.astro.caltech.edu/palomar/homepage.html

W.M. Keck Observatory telescopes in Hawaii: http://www.keckobservatory.org/

Images, Text, Credits: NASA/Tony Greicius/JPL/Elizabeth Landau/NRAO/Wikimedia.

Best regards, Orbiter.ch

Exoplanets 20/20: Looking Back to the Future










Many Worlds - Exoplanets.

July 31, 2015

Geoff Marcy remembers the hair standing up on the back of his neck. Paul Butler remembers being dead tired. The two men had just made history: the first confirmation of a planet orbiting another star.


Image above: Artist's rendering of a Jupiter-sized exoplanet and its host, a star slightly more massive than our sun. Image Credits: ESO.

The groundbreaking discovery had been announced less than week earlier by the European team of Michel Mayor and Didier Queloz. But the news was met with some initial skepticism in the astronomical community. By a stroke of good luck, Marcy and Butler happened to have previously scheduled observation time on a 120-inch telescope at the Lick Observatory, atop California's Mount Hamilton.

The scientists, who would become two of the world's most famous planet hunters, remember driving down the mountainside together in October 1995. They'd spent four straight nights making their observations. And while further processing would be needed to make the scientific case, their data seemed clear and unmistakable -- and almost impossible. A huge planet, at least half the size of Jupiter, was not only orbiting its host star more tightly than Mercury hugs the sun. It was racing around that star, making a complete orbit in just four days.

The planet, called 51 Pegasi b, would open a new era in humanity's exploration of our galactic neighborhood. It would be the first in a series of "hot Jupiters" -- giant planets in fast, tight orbits -- discovered in rapid succession. The rush of new worlds would propel Marcy, Butler and their research team into the media spotlight, and forever change our view of the cosmos.

'A spine-tingling experience'

But for the moment, on that solemn drive down the mountainside, Marcy and Butler were alone with their world-altering news. "We knew we were the only people on the planet to be sure that 51 Peg, the planet, really did exist," Marcy said recently. "It was exhilarating. We were absolutely thrilled to know an historic moment in science history was happening before our eyes. It was a truly spine-tingling experience."

Still, the astronomical pioneers had a few struggles ahead to gain the acceptance of the scientific community. The hunt for extrasolar planets -- exoplanets, for short -- had a poor track record, with decades' worth of false detections. Among them was the thrilling discovery of a planet orbiting Barnard's star in the 1960s; it turned out to be an unnoticed shift of a telescope lens. Once the shift was accounted for, the "planet" disappeared.

The early '90s had seen the actual detection of "pulsar planets," but these seemed too strange to count, orbiting a rapidly spinning, radiation-spewing stellar remnant called a pulsar. Most scientists would reserve the "first" designation for a planet orbiting a normal star.

"The whole field had a snake-oil sort of feel to it," Butler said in a recent interview. "For the previous fifty years or so, there were many announcements, all proved to be wrong. If we went to a meeting and said we were looking for extrasolar planets, we might as well have said we were looking for little green men."

Even Marcy greeted the announcement of 51 Peg, made at a scientific conference in Florence, Italy, by Mayor and Queloz, with a bit of a yawn -- at first.

"This claim on October 6, 1995, of the first planet ever discovered was sort of business as usual," he said. "Here's another false claim. This one is more obviously a false claim. The orbital period is claimed to be 4.3 days. Nobody in their right mind thought planets could orbit so close to a star."

But the four nights of observations at the Lick Observatory -- perfectly coinciding with 51 Peg's four-day orbit -- changed all that. Both the Mayor and Marcy teams had been trying to develop a planet-hunting technique based on wobbling stars. The wobbles, known as the star's "radial velocity," were induced by the gravitational tugs of orbiting planets. The starlight wavelength was compressed, then stretched, as the star moved toward and away from astronomers' telescopes.

Now, Mayor and Queloz had proven that the technique worked. And a few days later, Marcy and Butler validated both the method used by Mayor's team and their own very similar detection method.

But Marcy and his team realized something more. The only thing that had kept them from beating Mayor's group to that first detection was a perfectly reasonable assumption: that big planets moved in stately orbits, like the 12 years it took Jupiter to take one lap around the sun.

Either they would have to watch stars for a very long time, or they would have to refine their wobble detector until it could pick up the very tiny shifts in a star's position caused by small planets in tighter, faster orbits.

They were working on just this type of refinement when Mayor announced his discovery. More importantly, they had been recording observations with their wobble-detecting device, known as a spectrograph. Sure enough, when they took another look, big, star-hugging planets began popping out of their data.


Images above: Giant planet 51 Pegasi b was discovered in October 1995. It is about half the size of Jupiter and orbits its star in about four days. "51 Peg" helped launch a whole new field of exploration. Images Credits: NASA/JPL-Caltech.

Planets proper

At a meeting of the American Astronomical Society in January 1996, Marcy announced two more planet discoveries: 70 Virginis and 47 Ursae Majoris. The first had a 116-day orbit -- far more reasonable than 51 Peg's scorching four days -- and its orbit was elliptical, making it unlikely to be anything but a planet. The orbit of 47 Ursae Majoris was more reasonable still: 2.5 years. Together, they provided a "bridge" to our own solar system, Marcy said, with planets behaving themselves as proper planets should.

The discoveries vaulted Marcy and his team into scientific celebrity status, with appearances on nationwide nightly news shows; their new planets even made the cover of Time magazine.

And the Marcy-Butler team was just warming up. The floodgates were opened. They discovered at least 70 of the first 100 exoplanets that were found in the years that followed. Their pioneering, planet-hunting safari went on for a decade. Soon, however, the landscape would change yet again.

The gold rush of planet finding kicked into high gear with the launch of the Kepler Space Telescope in 2009. This spacecraft nestled into an Earth-trailing orbit, then fixed its eye on a small patch of sky -- and kept it there for four years.

Within that patch were more than 150,000 stars, a kind of cross-section of an arm of our own Milky Way galaxy, as if Kepler were shining a searchlight into deep space. Kepler was looking for planetary transits -- the infinitesimally tiny dip in starlight that occurs when a planet crosses the face of the star it is orbiting.

The method only works for distant solar systems whose planets' orbits, from our perspective, are seen edge-on. This way, an exoplanet is silhouetted as it passes between Kepler and its host star, reducing the starlight measured by Kepler.

The fifth time's the charm

Kepler was the brainchild of William Borucki of the NASA Ames Research Center in Moffet Field, California. Borucki, who retired in early July 2015, doggedly pressed his case for Kepler. During the '90s, his proposed designs were rejected no less than four times. He finally won approval from NASA in 2001.

But no one knew what Kepler might find, or even if it would find anything at all.

"We launched Kepler, to some extent, like Magellan or Columbus went to sea, not knowing quite what we were going to encounter," said James Fanson, deputy manager in the Instruments Division at NASA's Jet Propulsion Laboratory in Pasadena, California. Fanson was Kepler's project manager when the spacecraft was launched.

"We knew we were going to make history," he said. "We just didn't know what history we were going to make."

Artist's impression of  Kepler Space Telescope. Image Credit: NASA

Kepler's transit watch paid off, however, identifying more than 4,600 candidate planets hundreds to thousands of light-years distant. So far, 1,028 of those have been confirmed -- some of them Earth-sized planets that orbit within their star's so-called habitable zone, where liquid water can exist on a planet. Scientists are still mining Kepler data, regularly turning up new planetary candidates and confirming earlier finds.

Kepler itself ended its initial mission in 2013, when two of four reaction wheels used to keep the spacecraft in a stable position failed. But the Kepler science team developed clever ways to continue squeezing useful data out of the space telescope, relying on the subtle pressure of sunlight to stabilize it on one axis. Kepler is now in its second phase of life, and it's still discovering planets.

Preceding Kepler was the groundbreaking COROT satellite, a European venture launched in 2006 that discovered numerous planets before it ceased functioning in 2012 -- including the first rocky planet found to orbit a sun-like star. COROT used the transit method to detect exoplanets, and was the first space mission dedicated to that purpose.

Artist's impression of the COROT satellite. Image Credit: ESA

The prolific discoveries still flowing from the Hubble Space Telescope include not only exoplanets, but characterizations of exoplanet atmospheres, identifying a variety of gases. And the Spitzer Space Telescope has found water vapor in exoplanetary atmospheres as well as weather patterns.

Both the wobble and transit methods, relied upon by the exoplanet pioneers, are still in use today, along with several other techniques. And 20 years after the first discovery, the exoplanet total is up to more than 5,000 candidates, with more than 1,800 of those confirmed.

A new reality

The galaxy, it seems, is crowded with planets. Yet we are not yet able to answer the big question: Are we alone?

A new generation of telescopes in the years and decades ahead, on the ground and in space, will continue to search for an answer. One critical tool will be the same one pioneered by Marcy and the other early planet hunters: spectroscopy. They used this method to dissect the light coming from distant stars, revealing their back-and-forth, planet-induced wobbling as the starlight was stretched and compressed; the newest generation of instruments will do the same thing to the light from the atmospheres of exoplanets. Splitting this planetary light into its constituent parts, a little like the rainbow colors of sunlight shining through a prism, should reveal which gases and chemicals are present in those alien skies.

And one day, some of those atmospheric constituents might suggest the presence of life far beyond planet Earth.

For more information about exoplanets and NASA's planet-finding program, visit: http://planetquest.jpl.nasa.gov

Images (mentioned), Text, Credits: NASA/Tony Greicius.

Greetings, Orbiter.ch

Hubble Sees a Dying Star's Final Moments











NASA - Hubble Space Telescope patch.

July 31, 2015


A dying star’s final moments are captured in this image from the NASA/ESA Hubble Space Telescope. The death throes of this star may only last mere moments on a cosmological timescale, but this star’s demise is still quite lengthy by our standards, lasting tens of thousands of years!

The star’s agony has culminated in a wonderful planetary nebula known as NGC 6565, a cloud of gas that was ejected from the star after strong stellar winds pushed the star’s outer layers away into space. Once enough material was ejected, the star’s luminous core was exposed, enabling its ultraviolet radiation to excite the surrounding gas to varying degrees and causing it to radiate in an attractive array of colors. These same colors can be seen in the famous and impressive Ring Nebula (heic1310), a prominent example of a nebula like this one.

video
Hubble and the sunrise over Earth

Planetary nebulae are illuminated for around 10,000 years before the central star begins to cool and shrink to become a white dwarf. When this happens, the star’s light drastically diminishes and ceases to excite the surrounding gas, so the nebula fades from view.

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

Hubble Space Telescope: http://www.nasa.gov/mission_pages/hubble/main/index.html

Hubble websites: http://www.spacetelescope.org/ and http://hubblesite.org/

Image, Video, Credits: ESA/Hubble & NASA, Acknowledgement: Matej Novak/Text credit: European Space Agency (ESA)/Ashley Morrow.

Best regards, Orbiter.ch

jeudi 30 juillet 2015

Crew Getting Ready for Spacewalk and Japanese Cargo Mission










ISS - Expedition 44 Mission patch.

July 30, 2015

NASA astronauts Scott Kelly and Kjell Lindgren are wrapping up U.S. spacesuit maintenance today. Cosmonauts Gennady Padalka and Mikhail Kornienko are also moving along with their preparations for an Aug. 10 spacewalk.

All three cosmonauts, including Flight Engineer Oleg Kononenko, also worked on Russian biomedical experiments. The trio explored such things as stress caused by living in space as well as the causes and countermeasures of bone loss in microgravity.


Image above: Japan’s first H-II Transfer Vehicle is seen in 2009 attached to the end of the International Space Station’s robotic arm, Canadarm2.

Japanese astronaut Kimiya Yui worked on setting up and running a session with the Capillary Flow Experiment-2 fluid physics study. He also assisted Kelly and Lindgren with spacesuit maintenance.

Meanwhile, the Japan Aerospace Exploration Agency (JAXA) is getting ready for its fifth resupply mission to the International Space Station. JAXA will launch the H-II Transfer Vehicle-5 (HTV-5) no earlier than Aug. 16 delivering new science gear to the space station.

Related links:

Stress caused by living in space: http://www.energia.ru/en/iss/researches/human/22.html

Causes and countermeasures of bone loss in microgravity: http://www.energia.ru/en/iss/researches/human/21.html

Capillary Flow Experiment-2: http://www.nasa.gov/mission_pages/station/research/experiments/459.html

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

Image, Text, Credit: NASA.

Greetings, Orbiter.ch

Telescopes Team Up to Find Distant Uranus-Sized Planet Through Microlensing














NASA - Hubble Space Telescope patch / W. M. Keck Observatory logo.

July 30, 2015

NASA’s Hubble Space Telescope and the W.M. Keck Observatory in Hawaii have made independent confirmations of an exoplanet orbiting far from its central star. The planet was discovered through a technique called gravitational microlensing.

Hubble Space Telescope. Image Credit: NASA

This finding opens a new piece of discovery space in the extrasolar planet hunt: to uncover planets as far from their central stars as Jupiter and Saturn are from our sun. The Hubble and Keck Observatory results will appear in two papers in the July 30 edition of The Astrophysical Journal.

The large majority of exoplanets cataloged so far are very close to their host stars because several current planet-hunting techniques favor finding planets in short-period orbits. But this is not the case with the microlensing technique, which can find more distant and colder planets in long-period orbits that other methods cannot detect.

Microlensing occurs when a foreground star amplifies the light of a background star that momentarily aligns with it.  If the foreground star has planets, then the planets may also amplify the light of the background star, but for a much shorter period of time than their host star.   The exact timing and amount of light amplification can reveal clues to the nature of the foreground star and its accompanying planets.

The system, cataloged as OGLE-2005-BLG-169, was discovered in 2005 by the Optical Gravitational Lensing Experiment (OGLE), the Microlensing Follow-Up Network (MicroFUN), and members of the Microlensing Observations in Astrophysics (MOA) collaborations—groups that search for extrasolar planets through gravitational microlensing.


Image above: This diagram shows how astronomers observed a distant gas giant planet around OGLE-2005-BLG-169 using microlensing. Image Credits: Hubble/STScI.

Without conclusively identifying and characterizing the foreground star, however, astronomers have had a difficult time determining the properties of the accompanying planet. Using Hubble and the Keck Observatory, two teams of astronomers have now found that the system consists of a Uranus-sized planet orbiting about 370 million miles from its parent star, slightly less than the distance between Jupiter and the Sun. The host star, however, is about 70 percent as massive as our Sun.

“These chance alignments are rare, occurring only about once every 1 million years for a given planet, so it was thought that a very long wait would be required before the planetary microlensing signal could be confirmed,” said David Bennett, the lead of the team that analyzed the Hubble data. “Fortunately, the planetary signal predicts how fast the apparent positions of the background star and planetary host star will separate, and our observations have confirmed this prediction. The Hubble and Keck Observatory data, therefore, provide the first confirmation of a planetary microlensing signal.”

In fact, microlensing is such a powerful tool that it can uncover planets whose host stars cannot be seen by most telescopes. “It is remarkable that we can detect planets orbiting unseen stars, but we’d really like to know something about the stars that these planets orbit,” explained Virginie Batista, leader of the Keck Observatory analysis. “The Keck and Hubble telescopes allow us to detect these faint planetary host stars and determine their properties.”

video
Simulation of Gravitational Microlensing

Video above: This simulation shows the 22-year journey of a star moving through space and passing directly in front of a more distant background star. All stars drift through space. Occasionally, a star lines up perfectly in front of a more distant star. The momentary alignment magnifies and brightens the light from the background star, an effect called gravitational microlensing. Video Credits: NASA, ESA, D. Bennett (University of Notre Dame), Wiggle Puppy Productions, and G. Bacon (STScI).

Planets are small and faint compared to their host stars; only a few have been observed directly outside our solar system. Astronomers often rely on two indirect techniques to hunt for extrasolar planets. The first method detects planets by the subtle gravitational tug they give to their host stars. In another method, astronomers watch for small dips in the amount of light from a star as a planet passes in front of it.

Both of these techniques work best when the planets are either extremely massive or when they orbit very close to their parent stars. In these cases, astronomers can reliably determine their short orbital periods, ranging from hours to days to a couple years.

W.M. Keck Observatory in Hawaii. Image Credit: Wikipedia

But to fully understand the architecture of distant planetary systems, astronomers must map the entire distribution of planets around a star. Astronomers, therefore, need to look farther away from the star—from about the distance of Jupiter is from our sun, and beyond.

“It’s important to understand how these systems compare with our solar system,” said team member Jay Anderson of the Space Telescope Science Institute in Baltimore, MD. “So we need a complete census of planets in these systems. Gravitational microlensing is critical in helping astronomers gain insights into planetary formation theories.”

The planet in the OGLE system is probably an example of a “failed-Jupiter” planet, an object that begins to form a Jupiter-like core of rock and ice weighing around 10 Earth masses, but it doesn’t grow fast enough to accrete a significant mass of hydrogen and helium. So it ends up with a mass more than 20 times smaller than that of Jupiter. “Failed-Jupiter planets, like OGLE-2005-BLG-169Lb, are predicted to be more common than Jupiters, especially around stars less massive than the sun, according to the preferred theory of planet formation. So this type of planet is thought to be quite common,” Bennett said.

Microlensing takes advantage of the random motion of stars, which are generally too small to be noticed without precise measurements. If one star, however, passes nearly precisely in front of a farther background star, the gravity of the foreground star acts like a giant lens, magnifying the light from the background star.

A planetary companion around the foreground star can produce a variation in the brightening of the background star. This brightening fluctuation can reveal the planet, which can be too faint, in some cases, to be seen by telescopes. The duration of an entire microlensing event is several months, while the variation in brightening due to a planet lasts a few hours to a couple of days.

The initial microlensing data of OGLE-2005-BLG-169 had indicated a combined system of foreground and background stars plus a planet. But due to the blurring effects of our atmosphere, a number of unrelated stars are also blended with the foreground and background stars in the very crowded star field in the direction of our galaxy’s center.

The sharp Hubble and Keck Observatory images allowed the research teams to separate out the background source star from its neighbors in the very crowded star field in the direction of our galaxy’s center. Although the Hubble images were taken 6.5 years after the lensing event, the source and lens star were still so close together on the sky that their images merged into what looked like an elongated stellar image.

Astronomers can measure the brightness of both the source and planetary host stars from the elongated image. When combined with the information from the microlensing light curve, the lens brightness reveals the masses and orbital separation of the planet and its host star, as well as the distance of the planetary system from Earth. The foreground and background stars were observed in several different colors with Hubble’s Wide Field Camera 3 (WFC3), allowing independent confirmations of the mass and distance determinations.

The observations, taken with the Near Infrared Camera 2 (NIRC2) on the Keck 2 telescope more than eight years after the microlensing event, provided a precise measurement of the foreground and background stars’ relative motion. “It is the first time we were able to completely resolve the source star and the lensing star after a microlensing event. This enabled us to discriminate between two models that fit the data of the microlensing light curve,” Batista said.

The Hubble and Keck Observatory data are providing proof of concept for the primary method of exoplanet detection that will be used by NASA’s planned, space-based Wide-Field Infrared Survey Telescope (WFIRST), which will allow astronomers to determine the masses of planets found with microlensing. WFIRST will have Hubble’s sharpness to search for exoplanets using the microlensing technique. The telescope will be able to observe foreground, planetary host stars approaching the background source stars prior to the microlensing events, and receding from the background source stars after the microlensing events.

“WFIRST will make measurements like we have made for OGLE-2005-BLG-169 for virtually all the planetary microlensing events it observes. We’ll know the masses and distances for the thousands of planets discovered by WFIRST,” Bennett explained.

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

For images and more about this study and the Hubble Space Telescope, visit:

http://www.nasa.gov/hubble & http://www.spacetelescope.org

http://hubblesite.org/news/2015/27

W.M. Keck Observatory in Hawaii: http://www.keckobservatory.org/

Images (mentioned), Video (mentioned), Text, Credits: NASA/Space Telescope Science Institute/Karl Hille.

Best regards, Orbiter.ch

Nearing 3000 Comets: SOHO Solar Observatory Greatest Comet Hunter of All Time












ESA / NASA - SOHO Mission patch.

July 30, 2015

In 1995, a new solar observatory was launched. A joint project of ESA and NASA, the Solar and Heliospheric Observatory – SOHO – has been sending home images of our dynamic sun ever since. SOHO was planned to open up a new era of solar observations, dramatically extending our understanding of the star we live with. . . and it delivered.

But no one could have predicted SOHO's other observational triumph: In the last two decades, SOHO has become the greatest comet finder of all time. In August 2015, SOHO is expected to discover its 3000th comet. Prior to the SOHO launch, only a dozen or so comets had ever even been discovered from space, and some 900 had been discovered from the ground since 1761.

video
Why are We Seeing So Many Sungrazing Comets?

Video above: Before 1979, there were less than a dozen known sungrazing comets – comets that swing by incredibly close to the sun. But that was before the ESA/NASA Solar and Heliospheric Observatory launched in 2000. Since then, SOHO has become the greatest sungrazing comet hunter of all time with comet finds numbering in the thousands. Video Credits: NASA/Duberstein.

"SOHO has a view of about 12 and a half million miles beyond the sun," said Joe Gurman, the mission scientist for SOHO at NASA's Goddard Space Flight Center in Greenbelt, Maryland. "So we expected it might from time to time see a bright comet near the sun. But nobody dreamed we'd approach 200 a year."

More than just a celebrated bright vision in the night sky, comets can tell scientists a great deal about the place and time where they originated. Comets are essentially a clump of frozen gases mixed with dust. They are often pristine relics that can hold clues about the very formation of our solar system. On the other hand, if they have made previous trips around the sun, they can hold information about the distant reaches of the solar system through which they've traveled. We have a variety of tools to determine what comets are made of from afar. One is to watch how material evaporates off its surface when it comes close to the sun, and here's where SOHO can provide remarkable information.

SOHO is unique in that it is able to spot comets that skim extremely close to the sun, known as sungrazers. One of SOHO's instruments, called a coronagraph, specifically blocks out the bright light of the sun to examine its atmosphere – which is a billion times fainter than the star itself. To this day, SOHO is one of our best sources for views of the giant explosions regularly produced by the sun called coronal mass ejections, or CMEs, which can hurl a million tons of solar particles off into space. This field of view is large enough to see a sungrazing comet as it sling shots around the sun.

The overwhelming bulk – some 85% -- of SOHO's comet discoveries are what's called Kreutz comets. Scientists think a single extremely large sungrazing comet broke up thousands of years ago, leading to thousands of leftover fragments, which continue to follow the same Kreutz path. On average, a new member of the Kreutz family is discovered every three days. Unfortunately, the long journey for these fragments invariably ends as they pass the sun. If they're close enough to the sun to be seen by SOHO, they're too close to survive.


Image above: A sun grazing comet as witnessed by the ESA/NASA Solar Heliospheric Observatory, or SOHO, as it dived toward the sun on July 5 and July 6, 2011. SOHO is the overwhelming leader in spotting sungrazers, with almost 3000 spotted to date. SOHO can see the faint light of a comet, because the much brighter light of the sun is blocked by what's known as a coronograph.Image Credits: ESA & NASA/SOHO.

"They just disintegrate every time we observe one," said Karl Battams, a solar scientist at the Naval Research Labs in Washington, D.C., who has been in charge of running the SOHO comet-sighting website since 2003. "There's only one Kreutz comet that made it around the sun – Comet Lovejoy. And we are pretty confident it fell apart a couple of weeks afterwards."

Other, non-Kreutz comets have survived, however. One frequent visitor is comet 96P Machholz. Orbiting the sun approximately every 6 years, SOHO has now seen this comet four times. Such comets survive by virtue of the fact that they don't travel as close to the sun – so they experience less intense solar radiation and are not subject to gravitational stretching and pulling from the sun. Information about the composition of comets is something SOHO can help with. Depending on how a comet reacts to the sun gives clues about the very substance out of which these visitors from the outer solar system are made.

Watching these sungrazing comets also help us learn about the sun. Their tails of ionized gas illuminate magnetic fields around the sun, so they can act as a tracer that helps scientists observe these invisible fields. Such fields have even ripped off comet tails allowing astronomers to watch the lost tails blowing in the steady outpouring of solar particles streaming off the sun. The tails act as a giant windsock in this solar wind, showing researchers the details of the wind's movement.

SOHO's great success as a comet finder is, of course, dependent on the people who sift through SOHO's data – a task open to the world as the data is publicly available online in real time. A cadre of volunteer amateur astronomers dedicate themselves to searching the data via the NASA-funded Sungrazer Project. While scientists often search the imagery for very specific events, various members of the astronomy community choose to comb through all the imagery in fine detail. The result: 75% of SOHO comets have been found by these citizen scientists.

Whenever someone spots a comet, they report it to Battams. He goes over the imagery to confirm the sighting and then submits it to the Central Bureau for Astronomical Telegrams, which gives it an official name. While comets spotted from the ground are named after the person who first discovered them, comets first observed by a space-based telescope are named after the spacecraft.

"As I joined the team when we already had found 500 comets, I've been in charge of confirming 2,500 so far," said Battams. "I think it's safe to say I've looked at more images of comets than any other person in history. Each comet is visible in at least 15 images, so that's more than 40,000 images of comets."


Image above: One of the more well-known comets observed by SOHO is Comet ISON, seen in the this time lapse photo from Nov. 28, 2013. Comet ISON comes in from the bottom right and moves out toward the upper right, getting fainter and fainter. The image of the sun at the center is from NASA's Solar Dynamics Observatory. Image Credits: ESA/NASA/SOHO/SDO/GSFC.

SOHO has also helped provide images for comets discovered by others. In 2012, a sungrazer was found the old-fashioned way – from the ground. Known as Comet ISON, scientists quickly realized it would make a swing by the sun close enough to be spotted by a variety of solar telescopes including SOHO. A large campaign of observations was launched, as telescopes from around the world and across the solar system watched the comet -- a fossil from the original days of the solar system formation – sweep in. The final observatory to see Comet ISON was SOHO, which watched the comet curve in toward the sun. . . and disintegrate.

Observations from SOHO were key to helping describe ISON's last hours – something that no other observatory captured.

ESA/NASA Solar and Heliospheric Observatory (SOHO). Image Credits: ESA/NASA

"When SOHO launched, its sensors were some 100 times more sensitive than previous imagers," said Gurman. "That was crucial to seeing the faint light from the solar particles in a CME. SOHO allowed us to see a range of brightness and details never before seen. It was great luck that the same exposures allowed us to see comets – not just extremely bright ones, but a whole range of fainter ones, too."

At almost 20 years old, the SOHO mission is a respected elder in NASA's Heliophysics System Observatory – the fleet of spacecraft that both watch the sun and measure its effects near Earth and throughout the solar system. SOHO is a cooperative effort between ESA (European Space Agency) and NASA. Mission control is based at NASA Goddard. The Large Angle and Spectrometric Coronagraph Experiment, or LASCO, which is the instrument that provides comet imagery, was built at the Naval Research Lab in Washington, D.C.

For more about SOHO: http://www.nasa.gov/soho and http://sci.esa.int/soho/

For more on the SOHO Sungrazer Project: http://sungrazer.nrl.navy.mil

Images (mentioned), Video (mentioned), Text, Credits: NASA's Goddard Space Flight Center/Karen C. Fox/Holly Zell.

Best regards, Orbiter.ch

Frosty Gullies on the Northern Plains of Mars












NASA - Mars Reconnaissance Orbiter (MRO) patch.

July 30, 2015


Seasonal frost commonly forms at middle and high latitudes on Mars, much like winter snow on Earth. However, on Mars most frost is carbon dioxide (dry ice) rather than water ice. This frost appears to cause surface activity, including flows in gullies.

This image, acquired on April 11, 2015, by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter, shows frost in gully alcoves in a crater on the Northern plains. The frost highlights details of the alcoves, since it forms in different amounts depending on slopes and shadows as well as the type of material making up the ground. Rugged rock outcrops appear dark and shadowed, while frost highlights the upper alcove and the steepest route down the slope.

Most changes associated with gullies are observed in the Southern hemisphere. However, some are seen in the Northern hemisphere, where steep slopes are less common. HiRISE is monitoring these gullies to look for changes and to understand the behavior of the frost.

More information and image products: http://www.uahirise.org/ESP_040811_2410

Mars Reconnaissance Orbiter (MRO)

The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., Boulder, Colorado. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter Project and Mars Science Laboratory Project for NASA's Science Mission Directorate, Washington.

For more information about Mars Reconnaissance Orbiter (MRO), visit: http://www.nasa.gov/mission_pages/MRO/main/index.html

Images, Text, Credits: NASA/JPL/University of Arizona/Caption: Colin Dundas/Sarah Loff.

Greetings, Orbiter.ch

Science on the surface of a comet












ESA - Rosetta Mission patch.

30 July 2015

Complex molecules that could be key building blocks of life, the daily rise and fall of temperature, and an assessment of the surface properties and internal structure of the comet are just some of the highlights of the first scientific analysis of the data returned by Rosetta’s lander Philae last November. 

Early results from Philae’s first suite of scientific observations of Comet 67P/Churyumov­-Gerasimenko were published today in a special edition of the journal Science.

Descending to a comet

Data were obtained during the lander’s seven-hour descent to its first touchdown at the Agilkia landing site, which then triggered the start of a sequence of predefined experiments. But shortly after touchdown, it became apparent that Philae had rebounded and so a number of measurements were carried out as the lander took flight for an additional two hours some 100 m above the comet, before finally landing at Abydos.

Some 80% of the first science sequence was completed in the 64 hours following separation before Philae fell into hibernation, with the unexpected bonus that data were ultimately collected at more than one location, allowing comparisons between the touchdown sites.

Inflight science

After the first touchdown at Agilkia, the gas-sniffing instruments Ptolemy and COSAC analysed samples entering the lander and determined the chemical composition of the comet’s gas and dust, important tracers of the raw materials present in the early Solar System.

COSAC analysed samples entering tubes at the bottom of the lander kicked up during the first touchdown, dominated by the volatile ingredients of ice-poor dust grains. This revealed a suite of 16 organic compounds comprising numerous carbon and nitrogen-rich compounds, including four compounds – methyl isocyanate, acetone, propionaldehyde and acetamide – that have never before been detected in comets.

CIVA camera 4 view

Meanwhile, Ptolemy sampled ambient gas entering tubes at the top of the lander and detected the main components of coma gases – water vapour, carbon monoxide and carbon dioxide, along with smaller amounts of carbon-bearing organic compounds, including formaldehyde.

 Importantly, some of these compounds detected by Ptolemy and COSAC play a key role in the prebiotic synthesis of amino acids, sugars and nucleobases: the ingredients for life. For example, formaldehyde is implicated in the formation of ribose, which ultimately features in molecules like DNA.

The existence of such complex molecules in a comet, a relic of the early Solar System, imply that chemical processes at work during that time could have played a key role in fostering the formation of prebiotic material.

Comparing touchdown sites

Thanks to the images taken by ROLIS on the descent to Agilkia, and the CIVA images taken at Abydos, a visual comparison of the topography at these two locations could be made.

ROLIS images taken shortly before the first touchdown revealed a surface comprising metre-size blocks of diverse shapes, coarse regolith with grain sizes of 10–50 cm, and granules less than 10 cm across.

The regolith at Agilkia is thought to extend to a depth of 2 m in places, but seems to be free from fine-grained dust deposits at the resolution of the images.

3D view of large boulder at Agilkia

The largest boulder in the ROLIS field-of-view measures about 5 m high, with a peculiar bumpy structure and fracture lines running through it that suggest erosional forces are working to fragment the comet’s boulders into smaller pieces.

The boulder also has a tapered ‘tail’ of debris behind it, similar to others seen in images taken by Rosetta from orbit, yielding clues as to how particles lifted up from one part of the eroding comet are deposited elsewhere.

Over a kilometre away at Abydos, not only did the images taken by CIVA’s seven microcameras reveal details in the surrounding terrain down to the millimetre scale, but also helped decipher Philae’s orientation.

Brightness variations of comet surface

The lander is angled up against a cliff face that is roughly 1 m from the open ‘balcony’ side of Philae, with stereo imagery showing further topography up to 7 m away, and one camera with open sky above.

The images reveal fractures in the comet’s cliff walls that are ubiquitous at all scales. Importantly, the material surrounding Philae is dominated by dark agglomerates, perhaps comprising organic-rich grains. Brighter spots likely represent differences in mineral composition, and may even point to ice-rich materials.

From the surface to the interior

The MUPUS suite of instruments provided insight into the physical properties of Abydos. Its penetrating ‘hammer’ showed the surface and subsurface material sampled to be substantially harder than that at Agilkia, as inferred from the mechanical analysis of the first landing.

The results point to a thin layer of dust less than 3 cm thick overlying a much harder compacted mixture of dust and ice at Abydos. At Agilkia, this harder layer may well exist at a greater depth than that encountered by Philae.

MUPUS investigations at Abydos

The MUPUS thermal sensor, on Philae’s balcony, revealed a variation in the local temperature between about –180ºC and –145ºC in sync with the comet’s 12.4 hour day. The thermal inertia implied by the measured rapid rise and fall in the temperature also indicates a thin layer of dust atop a compacted dust-ice crust.

Moving below the surface, unique information concerning the global interior structure of the comet was provided by CONSERT, which passed radio waves through the nucleus between the lander and the orbiter.

The results show that the small lobe of the comet is consistent with a very loosely compacted (porosity 75–85%) mixture of dust and ice (dust-to-ice ratio 0.4–2.6 by volume) that is fairly homogeneous on the scale of tens of metres.

In addition, CONSERT was used to help triangulate Philae’s location on the surface, with the best fit solution currently pointing to a 21 x 34 m area.

Philae best fit search ellipse

“Taken together, these first pioneering measurements performed on the surface of a comet are profoundly changing our view of these worlds and continuing to shape our impression of the history of the Solar System,” says Jean-Pierre Bibring, a lead lander scientist and principal investigator of the CIVA instrument at the IAS in Orsay, France.

“The reactivation would allow us to complete the characterisation of the elemental, isotopic and molecular composition of the cometary material, in particular of its refractory phases, by APXS, CIVA-M, Ptolemy and COSAC.”

“With Philae making contact again in mid-June, we still hope that it can be reactivated to continue this exciting adventure, with the chance for more scientific measurements and new images which could show us surface changes or shifts in Philae’s position since landing over eight months ago,” says DLR’s Lander Manager Stephan Ulamec.

“These ground-truth observations at a couple of locations anchor the extensive remote measurements performed by Rosetta covering the whole comet from above over the last year,” says Nicolas Altobelli, ESA’s acting Rosetta project scientist.

“With perihelion fast approaching, we are busy monitoring the comet’s activity from a safe distance and looking for any changes in the surface features, and we hope that Philae will be able to send us complementary reports from its location on the surface.”

Notes for editors:

The 31 July 2015 Science special issue includes the following papers:

“The nonmagnetic nucleus of comet 67P/Churyumov–Gerasimenko,” by H.-U. Auster et al. (Covered in a previous press release: Rosetta and Philae find comet not magnetised): http://www.esa.int/Our_Activities/Space_Science/Rosetta/Rosetta_and_Philae_find_comet_not_magnetised

“67P/Churyumov-Gerasimenko surface properties as derived from CIVA panoramic images,” by J-P. Bibring et al.

“The landing(s) of Philae and inferences about comet surface mechanical properties,” by J. Biele et al.

“Organic compounds on comet 67P/Churyumov-Gerasimenko revealed by COSAC mass spectrometry,”by F. Goesmann et al.

“Properties of the 67P/Churyumov–Gerasimenko interior revealed by CONSERT radar,” by W. Kofman et al.

“The structure of the regolith on 67P/ Churyumov–Gerasimenko from ROLIS descent imaging,” by S. Mottola et al.

“Thermal and mechanical properties of the near-surface layers of comet 67P/Churyumov–Gerasimenko,” by T. Spohn et al.

“CHO-bearing organic compounds at the surface of 67P/Churyumov–Gerasimenko revealed by Ptolemy,” by I.P. Wright et al.

Individual ROLIS and CIVA images are available via our "Landing on a comet" gallery: http://www.esa.int/Our_Activities/Space_Science/Rosetta/Highlights/Landing_on_a_comet

About Rosetta:

Rosetta is an ESA mission with contributions from its Member States and NASA. Rosetta’s Philae lander is contributed by a consortium led by DLR, MPS, CNES and ASI.

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

Where is Rosetta?: http://sci.esa.int/where_is_rosetta/

Rosetta overview: http://www.esa.int/Our_Activities/Space_Science/Rosetta_overview

Rosetta in depth:http://sci.esa.int/rosetta

Rosetta factsheet: http://www.esa.int/Our_Activities/Space_Science/Rosetta/Rosetta_factsheet

Frequently asked questions: http://www.esa.int/Our_Activities/Space_Science/Rosetta/Frequently_asked_questions

Images, Animation, Text, Credits: ESA/Rosetta/Philae/ROLIS/DLR/CIVA/CONSERT/ATG medialab; data from Spohn et al (2015).

Best regards, Orbiter.ch