mercredi 1 juillet 2015

New Horizons - Methane Detected; New Images of Pluto and Charon; Sunrise & Sunset Observations












NASA - New Horizons Mission logo.

July 1, 2015

Yes, there is methane on Pluto, and, no, it doesn’t come from cows. The infrared spectrometer on NASA’s Pluto-bound New Horizons spacecraft has detected frozen methane on Pluto’s surface; Earth-based astronomers first observed the chemical compound on Pluto in 1976.

“We already knew there was methane on Pluto, but these are our first detections,” said Will Grundy, the New Horizons Surface Composition team leader with the Lowell Observatory in Flagstaff, Arizona. “Soon we will know if there are differences in the presence of methane ice from one part of Pluto to another.”


Image above: The location of the New Horizons Ralph instrument, which detected methane on Pluto, is shown. The inset is a false color image of Pluto and Charon in infrared light; pink indicates methane on Pluto’s surface. Image Credits: NASA/Johns Hopkins Applied Physics Laboratory/Southwest Research Institute.

Methane (chemical formula CH4) is an odorless, colorless gas that is present underground and in the atmosphere on Earth. On Pluto, methane may be primordial, inherited from the solar nebula from which the solar system formed 4.5 billion years ago. Methane was originally detected on Pluto’s surface by a team of ground-based astronomers led by New Horizons team member Dale Cruikshank, of NASA’s Ames Research Center, Mountain View, California.

Come Fly with New Horizons on its Approach to Pluto


Images from New Horizons show the view from aboard the spacecraft closes in on the Pluto system for a July 14 flyby. Image Credits: NASA/Johns Hopkins Applied Physics Laboratory/Southwest Research Institute.

This time-lapse approach movie was made from images from the Long Range Reconnaissance Imager (LORRI) camera aboard New Horizons spacecraft taken between May 28 and June 25, 2015. During that time the spacecraft distance to Pluto decreased almost threefold, from about 35 million miles to 14 million miles (56 million kilometers to 22 million kilometers). The images show Pluto and its largest moon, Charon, growing in apparent size as New Horizons closes in. As it rotates, Pluto displays a strongly contrasting surface dominated by a bright northern hemisphere, with a discontinuous band of darker material running along the equator. Charon has a dark polar region, and there are indications of brightness variations at lower latitudes.

June 30, 2015, View of Pluto and Charon from New Horizons

Video above: This movie, from New Horizons’ highest-resolution imager, shows Pluto and Charon as the spacecraft closes in. In the annotated version, Pluto’s prime meridian (the region of the planet that faces Charon) is shown in yellow and the equator is shown in pink. Video Credits: NASA/Johns Hopkins Applied Physics Laboratory/Southwest Research Institute.

“Alice” Instrument Practices for Sunset and Sunrise Observations of Pluto’s Atmosphere 


Image above: The location of the Alice ultraviolet imaging spectrograph on the New Horizons spacecraft is indicated. Image Credits: Photo credit: NASA/Johns Hopkins Applied Physics Laboratory/Southwest Research Institute.

The New Horizons spacecraft has made a critical observation in preparation for its upcoming observations of Pluto’s tenuous atmosphere. Just hours after its flyby of Pluto on July 14, the spacecraft will observe sunlight passing through the planet’s atmosphere, to help scientists determine the atmosphere’s composition. “It will be as if Pluto were illuminated from behind by a trillion-watt light bulb,” said Randy Gladstone, a New Horizons scientist from Southwest Research Institute, San Antonio. On June 16, New Horizons’ Alice ultraviolet imaging spectrograph successfully performed a test observation of the sun from 3.1 billion miles away (5 billion kilometers), which will be used to interpret the July 14 observations.


Image above: This is how the Sun looked in ultraviolet light to NASA’s SOHO spacecraft on June 16, 2015, when New Horizons observed the Sun at similar ultraviolet wavelengths. Image Credit: NASA.

New Horizons is now less than 11 million miles (18 million kilometers) from the Pluto system. The spacecraft is healthy and all systems are operating normally.


Image above: This spectrum of the Sun obtained by New Horizons’ Alice instrument on June 16, 2015, will be used to interpret the spacecraft’s upcoming observations of Pluto’s atmosphere. Image Credits: Photo credit: NASA/Johns Hopkins Applied Physics Laboratory/Southwest Research Institute.

NASA’s New Horizons Spacecraft Stays the Course to Pluto

NASA’s New Horizons spacecraft is getting a final “all clear” as it speeds closer to its historic July 14 flyby of Pluto and the dwarf planet’s five moons.


Image above: These images show the difference between two sets of 48 combined 10-second exposures with New Horizons' Long Range Reconnaissance Imager (LORRI) camera, taken at 8:40 UTC and 10:25 UTC on June 26, 2015, from a range of 21.5 million kilometers (approximately 13 million miles) to Pluto. The known small moons, Nix, Hydra, Kerberos and Styx, are visible as adjacent bright and dark pairs of dots, due to their motion in the 105 minutes between the two image sets. Images Credits: NASA/JHU-APL/SwRI.

After seven weeks of detailed searches for dust clouds, rings, and other potential hazards, the New Horizons team has decided the spacecraft will remain on its original path through the Pluto system instead of making a late course correction to detour around any hazards. Because New Horizons is traveling at 30,800 mph (49,600 kph), a particle as small as a grain of rice could be lethal.

“We’re breathing a collective sigh of relief knowing that the way appears to be clear,” said Jim Green, director of planetary science at NASA. “The science payoff will be richer as we gather data from the optimal flight path, as opposed to having to conduct observations from one of the back-up trajectories.”

Mission scientists have been using the spacecraft’s most powerful telescopic camera, the Long Range Reconnaissance Imager (LORRI), to look for potential hazards, such as small moons, rings, or dust, since mid-May. The decision on whether to keep the spacecraft on its original course or adopt a Safe Haven by Other Trajectory, or "SHBOT" path, had to be made this week since the last opportunity to maneuver New Horizons onto an alternate trajectory is July 4.

“Not finding new moons or rings present is a bit of a scientific surprise to most of us,” said principal investigator Alan Stern of the Southwest Research Institute (SwRI) in Boulder, Colorado. “But as a result, no engine burn is needed to steer clear of potential hazards. We presented these data to NASA for review and received approval to proceed on course and plan. We are ‘go’ for the best of our planned Pluto encounter trajectories.”

New Horizons formed a hazard analysis team in 2011, after the discovery of Pluto’s fourth moon, Kerberos, raised concerns the cratering of these moons by small debris from the outer area of the solar system known as the Kuiper Belt, could spread additional hazardous debris into New Horizons’ path. Mission engineers re-tested spare spacecraft blanketing and parts back on Earth to determine how well they would stand up to particle impacts, and scientists modeled the likely formation and locations of rings and debris in the Pluto system. By the time New Horizons’ cameras were close enough to Pluto to start the search last month, the team had already estimated the chances of a catastrophic incident at far less than one percent.


Image above: Pluto and its largest moon, Charon seen from 35 million miles. Image Credits: NASA/Johns Hopkins Applied Physics Laboratory/Southwest Research Institute.

The images used in the latest searches that cleared the mission to stay on its current course were taken June 22, 23 and 26. Pluto and all five of its known moons are visible in the images, but scientists saw no rings, new moons, or hazards of any kind. The hazards team determined that satellites as faint as about 15 times dimmer than Pluto’s faintest known moon, Styx, would have been seen if they existed beyond the orbit of Pluto’s largest and closest moon, Charon.

If any rings do exist, the hazard team determined they must be extremely faint, reflecting less than one 5-millionth of the incoming sunlight.

“The suspense – at least most of it – is behind us,” says John Spencer, of SwRI, who leads the New Horizons hazard analysis team. “As a scientist I’m a bit disappointed that we didn’t spot additional moons to study, but as a New Horizons team member I am much more relieved that we didn’t find something that could harm the spacecraft. New Horizons already has six amazing objects to analyze in this incredible system.”

The Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, designed, built, and operates the New Horizons spacecraft, and manages the mission for NASA’s Science Mission Directorate. The Southwest Research Institute, based in San Antonio, 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 and http://pluto.jhuapl.edu and http://solarsystem.nasa.gov/planets/plutotoolkit.cfm

Follow the New Horizons mission on social media, and use the hashtag #PlutoFlyby to join the conversation. The mission’s official NASA Twitter account is @NASANewHorizons. Live updates will be available on Facebook at: https://www.facebook.com/new.horizons1

Images (mentioned), Animation (mentioned), Video (mentioned), Text, Credits: NASA/Lillian Gipson/Dwayne Brown/Laurie Cantillo/Karen Northon/Johns Hopkins University Applied Physics Laboratory/Mike Buckley/Southwest Research Institute/Maria Stothoff.

Best regards, Orbiter.ch

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