New Horizons sees Pluto’s “bright fringe,” Charon’s “dark pole”

These images, taken by New Horizons’ Long Range Reconnaissance Imager (LORRI), show numerous large-scale features on Pluto’s surface. When various large, dark, and bright regions appear near limbs, they give Pluto a distinct, but false, non-spherical appearance. Pluto is known to be almost perfectly spherical from previous data. These images are displayed at four times the native LORRI image size and have been processed using a method called deconvolution, which sharpens the original images to enhance features on Pluto.

NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute

NASA’s New Horizons spacecraft doesn’t pass Pluto until July 14, but the mission team is making new discoveries as the piano-sized probe bears down on the Pluto system.

In a long series of images obtained by New Horizons’ telescopic Long Range Reconnaissance Imager (LORRI) May 29–June 19, Pluto and its largest moon, Charon, appear to more than double in size. From this rapidly improving imagery, scientists on the New Horizons team have found that the “close approach hemisphere” on Pluto that New Horizons will fly over has the greatest variety of terrain types seen on the planet so far. They also have discovered that Charon has a “dark pole” — a mysterious dark region that forms a kind of anti-polar cap.

“This system is just amazing,” said Alan Stern from the Southwest Research Institute in Boulder, Colorado. “The science team is just ecstatic with what we see on Pluto’s close approach hemisphere. Every terrain type we see on the planet, including both the brightest and darkest surface areas, are represented there; it’s a wonderland!

“And about Charon — wow — I don’t think anyone expected Charon to reveal a mystery like dark terrains at its pole,” Stern said. “Who ordered that?”

New Horizons scientists use a technique called deconvolution to sharpen the raw unprocessed pictures that the spacecraft beams back to Earth; the contrast in these latest images has also been stretched to bring out additional details. Deconvolution can occasionally produce artifacts, so the team will be carefully reviewing newer images taken from closer range to determine whether some of the tantalizing details seen in these images persist. Pluto’s non-spherical appearance in these images is not real; it results from a combination of the image-processing technique and Pluto’s large variations in surface brightness.

“The unambiguous detection of bright and dark terrain units on both Pluto and Charon indicates a wide range of diverse landscapes across the pair,” said Jeff Moore of NASA Ames Research Center in Mountain View, California. “For example, the bright fringe we see on Pluto may represent frost deposited from an evaporating polar cap, which is now in summer sun.”

New Horizons is approximately 2.9 billion miles (4.7 billion kilometers) from Earth and just 16 million miles (25 million km) from Pluto. The spacecraft and payload are in good health and operating normally.

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