April 22, 2019

A crescent Pluto shines like a jewel in the Kuiper Belt


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This image, taken 15 minutes after the New Horizons spacecraft's closest approach to Pluto on July 14, reveals the distant world's rugged terrain and atmospheric haze layers. This image, first published in early September, was re-released by NASA Thursday after further image progressing to bring out details. Credit: NASA/JHUAPL/SwRI
This image, taken 15 minutes after the New Horizons spacecraft’s closest approach to Pluto on July 14, reveals the distant world’s rugged terrain and atmospheric haze layers. This image, first published in early September, was re-released by NASA Thursday after further image progressing to bring out details. Credit: NASA/JHUAPL/SwRI

An image released Thursday, taken by NASA’s New Horizons spacecraft minutes after zipping past Pluto in July, shows the backlit world on a new scale, revealing rugged mountains, glacial plains and deep layers of atmospheric haze.

It is an expanded version of a crescent view first released in September, according to NASA, showing an entire hemisphere of Pluto with silhouetted terrain on the night side of the dwarf planet at the left side of the image. Scientists also say the subtle shadow cast by Pluto on its tenuous atmosphere is visible near the top of the picture.

Alan Stern, the New Horizons mission’s principal investigator, called the picture “mouthwatering” on Twitter.

NASA says the picture was taken when New Horizons was 11,000 miles (18,000 kilometers) from Pluto.

On the right side of the image, the vast glacial plains of Sputnik Planum are seen bordering ranges of 11,000-foot (3,500-meter) mountains dubbed Norgay Montes and Hillary Montes, after the climbing duo who first reached the summit of Mount Everest in 1953.

New Horizons is slowly beaming data recorded at Pluto back to Earth. Now traveling more than 3 billion miles away, the bandwidth of the spacecraft’s fixed communications antenna is limited, and all the data will not be in the hands of scientists until some time next year.

The spacecraft is also returning images captured on the probe’s final approach to Pluto, showing regions not seen up-close during the July 14 flyby.

This view from early July 13 from a distance of 1.03 million miles (1.7 million kilometers). It provides fascinating new details to help the science team map the informally named Krun Macula (the prominent dark spot at the bottom of the image) and the complex terrain east and northeast of Pluto’s “heart” (Tombaugh Regio). Pluto’s north pole is on the planet’s disk at the 12 o’clock position of this image. Credit: NASA/JHUAPL/SwRI
This view from early July 13 from a distance of 1.03 million miles (1.7 million kilometers). It provides fascinating new details to help the science team map the informally named Krun Macula (the prominent dark spot at the bottom of the image) and the complex terrain east and northeast of Pluto’s “heart” (Tombaugh Regio). Pluto’s north pole is on the planet’s disk at the 12 o’clock position of this image. Credit: NASA/JHUAPL/SwRI

Meanwhile, New Horizons has completed three course correction burns to budge its trajectory toward a small Kuiper Belt Object for a planned encounter Jan. 1, 2019. A fourth maneuver in the series is scheduled for Nov. 4 to finish aiming the spacecraft toward its next target.

But NASA still must approve the New Horizons team’s plan to fly past a second destination in the Kuiper Belt, a ring of mini-worlds circling the sun beyond the orbit of Neptune, of which Pluto is the largest object. The space agency granted preliminary approval for New Horizons to change its course for the 2019 fly opportunity.

Researchers also announced a new discovery on Pluto’s moon Charon that may help scientists understand its enigmatic history.

An infrared spectral scan of a fresh crater named Organa on Charon’s Pluto-facing hemisphere revealed high levels of ammonia. A nearby crater with a similar appearance mysteriously has no ammonia signature.

This composite image is based on observations from the New Horizons Ralph/LEISA instrument made at 10:25 UT (6:25 a.m. EDT) on July 14, 2015, when New Horizons was 50,000 miles (81,000 kilometers) from Charon. The spatial resolution is 3 miles (5 kilometers) per pixel. The LEISA data were downlinked Oct. 1-4, 2015, and processed into a map of Charon's 2.2 micron ammonia-ice absorption band. Long Range Reconnaissance Imager (LORRI) panchromatic images used as the background in this composite were taken about 8:33 UT (4:33 a.m. EDT) July 14 at a resolution of 0.6 miles (0.9 kilometers) per pixel and downlinked Oct. 5-6. The ammonia absorption map from LEISA is shown in green on the LORRI image. The region covered by the yellow box is 174 miles across (280 kilometers). Credits: NASA/JHUAPL/SwRI
This composite image is based on observations from the New Horizons Ralph/LEISA instrument made at 10:25 UT (6:25 a.m. EDT) on July 14, 2015, when New Horizons was 50,000 miles (81,000 kilometers) from Charon. The spatial resolution is 3 miles (5 kilometers) per pixel. The LEISA data were downlinked Oct. 1-4, 2015, and processed into a map of Charon’s 2.2 micron ammonia-ice absorption band. Long Range Reconnaissance Imager (LORRI) panchromatic images used as the background in this composite were taken about 8:33 UT (4:33 a.m. EDT) July 14 at a resolution of 0.6 miles (0.9 kilometers) per pixel and downlinked Oct. 5-6. The ammonia absorption map from LEISA is shown in green on the LORRI image. The region covered by the yellow box is 174 miles across (280 kilometers).
Credits: NASA/JHUAPL/SwRI

“Why are these two similar-looking and similar-sized craters, so near to each other, so compositionally distinct?” asked Will Grundy, New Horizons composition team lead from Lowell Observatory in Flagstaff, Arizona. “We have various ideas when it comes to the ammonia in Organa. The crater could be younger, or perhaps the impact that created it hit a pocket of ammonia-rich subsurface ice.  Alternatively, maybe Organa’s impactor delivered its own ammonia.”

Geologists are trying to piece together what the ammonia detection means. It could be a window into a more active history of cryovolcanism on Charon, when the moon’s surface may have been repaved through eruptions of liquids kept warm by the body’s internal heating.

“This is a fantastic discovery,” said Bill McKinnon, deputy lead for the New Horizons geology, geophysics and imaging team from Washington University in St. Louis. “Concentrated ammonia is a powerful antifreeze on icy worlds, and if the ammonia really is from Charon’s interior, it could help explain the formation of Charon’s surface by cryovolcanism, via the eruption of cold, ammonia-water magmas.”

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Follow Stephen Clark on Twitter: @StephenClark1.


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