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A surprise closeup of Charon courtesy of New Horizons

David Dickinson, Correspondent
Jul 17, 2015, 3:39 UTC

Sen—In a surprise release today, NASA gave us our best look yet at Pluto’s largest moon Charon, courtesy of New Horizons. The image shows the now familiar face of the 750 mile (1,208 km) diameter moon, complete with amazing world-spanning chasms and its mysterious polar dark spot. The new inset takes us a step closer, revealing craters, rills and scarps reminiscent of Mercury or even Earth’s Moon.   

“The most intriguing feature is a large mountain sitting in a moat,” said New Horizons Geology, Geophysics and Imaging team leader Jeff Moore of NASA’s Ames Research Center in a press release, referring to the feature in the bottom-left hand side of the image. “This is a feature that has geologists stunned and stumped.”

This image was taken with New Horizons’ Long Range Reconnaissance Imager (LORRI) around 10:30 UTC on July 14, just 80 minutes prior to the spacecraft’s closest approach to Pluto. The close-up inset image was captured from a range of just 49,000 miles (79,000 km) as the spacecraft passed through the Pluto system at over 8 miles a second. For context, 49,000 miles is about twice the distance of the geosynchronous satellites orbiting the Earth, and 20 per cent of the distance from Earth to the Moon.

New Horizons made its closest pass near Charon at 17,931 miles (28,858 km) distant at 12:04 UTC (8.04 EDT), just 14 minutes after it passed Pluto. The spacecraft then went on to pass through the shadows of both Pluto and Charon to perform a series of radio astronomy experiments, the results of which are forthcoming.

The image is highly compressed, though the New Horizons team hinted today on the spacecraft's official NASA Twitter feed (@NASANewHorizons) that “we took more than 1,200 pictures of Pluto” during the historic flyby.

The return rate from a distance of 32 Astronomical Units (where one AU is the Earth-Sun distance of 150 million km) is extremely slow at about two kilobytes per second, resulting in a data retrieval process that will take 16 months for all the flyby information to be returned home.

And there’s more in store, as another press conference is set for tomorrow live on NASA TV starting at 17:00 UTC. Will we see a crescent Pluto? An iconic image of the Pluto-Charon pair? Are there any new moons still awaiting discovery in the data? Stay tuned!