A new image of the largest of Pluto’s five known moons shows various craters and chasms (canyons).
Chasms, craters, and a dark north polar region are revealed in this image of Pluto’s largest moon Charon taken by New Horizons on July 11, 2015. The annotated version includes a diagram showing Charon’s north pole, equator, and central meridian, with the features highlighted. Image credit: NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute.
“The most pronounced chasm, which lies in the southern hemisphere, is longer and miles deeper than Earth’s Grand Canyon,” said New Horizon team member Dr William McKinnon of the Washington University in St. Louis. “This is the first clear evidence of faulting and surface disruption on Charon.”
“New Horizons has transformed our view of this distant moon from a nearly featureless ball of ice to a world displaying all kinds of geologic activity,” he said.
The most prominent crater, which lies near the south pole of the moon, is about 60 miles (96.5 km) across. The brightness of the rays of material blasted out of the crater suggest it formed relatively recently in geologic terms, during a collision with a small Kuiper Belt Object (KBO) some time in the last billion years.
In this artist’s rendering, Charon rises over the frozen south pole surface of Pluto, casting a faint silvery luminescence across the distant planetary landscape. If you stood on the night region of the dwarf planet at that moment of closest approach by New Horizons – looking up at a distinctly gray Charon – it would appear about 7 times larger in the sky than Earth’s Moon. Charon is so close to Pluto and so ice-covered that it would be only 5 times dimmer than the full Moon seen from Earth. At your feet, the icy surface – resembling a sooty snow bank – would be bathed in Charon’s faint glow. The area around you would be dim, but not so dark that you would bump into things. On your moonlight stroll on Pluto you’d notice that your shadow, cast by Charon, is much less defined than your shadow from moonlight on Earth. A wisp of cloud might even pass in front of Charon as you look up. Image credit: Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute.
“The darkness of the crater’s floor is especially intriguing,” Dr McKinnon said.
One explanation is that the crater has exposed a different type of icy material than the more reflective ices that lie on the surface.
Another possibility is that the ice in the crater floor is the same material as its surroundings but has a larger ice grain size, which reflects less sunlight. In this scenario, the impactor that gouged the crater melted the ice in the crater floor, which then refroze into larger grains.
An intriguing dark region near Charon’s north pole stretches for 200 miles (322 km). More detailed images that New Horizons will take around the time of closest approach to the moon on July 14 may provide hints about the origin of this region.
