Not only has New Horizons sent back some intriguing images of the far side of Pluto this weekend, it has also provided more detailed imaging of the dwarf planet’s major moon Charon.
It shows chasms, craters, and a dark north polar region feature prominently on the surface. The annotated version of the imaging, above, includes a diagram showing Charon’s north pole, equator, and central meridian, with the features highlighted.
Charon’s most pronounced chasm, which lies in the southern hemisphere, is longer and kilometres deeper than Earth’s Grand Canyon, according to William McKinnon, deputy lead scientist with New Horizon’s Geology and Geophysics investigation team.
“This is the first clear evidence of faulting and surface disruption on Charon,” says McKinnon, who is based at the Washington University in St. Louis. “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.”
The most prominent crater, which lies near the south pole of Charon in an image taken July 11 and radioed to Earth today, is about 100 kilometres 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 body some time in the last billion million years.
The darkness of the crater’s floor is especially intriguing, says McKinnon. 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.
More detailed images that New Horizons will take around the time of closest approach to the moon tomorrow may provide hints about the dark region’s origin.
Previous Cosmos news coverage of the New Horizons mission and related material here or read more about this historic mission in our Cosmos coverage here.
Bill Condie is a science journalist based in Adelaide, Australia.
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