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New Horizons detects methane as it stays on course for Pluto

David Dickinson, Correspondent
Jul 2, 2015, 22:10 UTC

Sen—NASA’s New Horizons spacecraft has been given the all clear as it heads towards its historic flyby of Pluto and its moons this month on July 14.

Engineers announced yesterday that no further course correction would be required to steer New Horizons clear of debris. “We’re breathing a collective sigh of relief knowing that the way appears to be clear,” NASA’s director of Planetary Science, Jim Green, said in a statement.

New Horizons has been using its Long Range Reconnaissance Imager (LORRI) to scout ahead for any new moons or rings surrounding Pluto.

The spacecraft is targeting a point 12,500 km (7,750 miles) above the surface of Pluto at 11:50 UTC on July 14, the closest point of its flyby. July 4 is the cut-off date for any course correction for an alternate Safe Haven By Other Trajectory (SHBOT) path.


A false color infrared image of Pluto and Charon (inset) showing the detection of methane by the Ralph instrument. Image credit: NASA/Johns Hopkins APL/SW Research Institute.

Researchers announced on Tuesday that frozen methane had been detected on the surface of Pluto by New Horizons. The detection was made using the infrared spectrometer aboard the Ralph instrument package. Methane was first detected on Pluto in 1976. “Soon we will know if there are differences in the presence of methane ice from one part of Pluto to another,” said New Horizons Surface Composition team leader Will Grundy in a June 30 press release.

NASA’s flying SOFIA observatory and an extensive ground-based campaign were also successful this week in catching an occultation of a background star by Pluto on June 29. This data will provide an excellent comparison study for what New Horizons sees when it takes radio occultation measurements of its own on July 14, as it flies through the shadows of Pluto and Charon and witnesses the most distant solar eclipse ever.

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The June 29 occultation of a star by Pluto captured by the Auckland University Bootes-3 team. Credit: NASASolarSystem

New Horizons is now only 15.5 million km (9.3 million miles) from Pluto, and closing fast at 14 km per second. For comparison, that is just under 40 times the distance from Earth to the Moon, and New Horizons will cover that in a sprint lasting less than two weeks.

The latest imagery is starting to show both Pluto and Charon in stark contrast, revealing Pluto as a two-faced spotted world with an orange tint. 


The latest true-color images of Pluto and Charon depicting two distinct hemispheres of Pluto and the mysterious 'dark patch' on Charon. Image credit: NASA/New Horizons

This promises to be a historic month for planetary exploration, as Pluto and its moons snap into focus in the eyes of both New Horizons and the public imagination. Be sure to get out there and observe Pluto for yourself if you own a large telescope as it nears opposition on July 6, or simply enjoy the high noon of “Pluto time” here on Earth.