The NASA spacecraft New Horizons has finished its first flyby of Pluto’s largest moon, Charon, on July 14, 2015 and pictures are beginning to arrive back on Earth as of September 21. The details shown in the high-resolution images raise more questions than answers.
The landscape of Charon is exceedingly complex- extensive mountain ranges, deep canyons, and a wide array of colors. Previously, scientists assumed the dwarf planet’s moon was a more boring version of our own moon- monotonous and covered with craters.
Yet after seeing these pictures, scientists are left in awe by the geological history Charon must have experienced.
Of particular interest is a gigantic canyon that runs nearly the entire diameter of the moon. It is estimated to be four times as long and twice as deep as the Grand Canyon.
“It looks like the entire crust of Charon has been split open,” said John Spencer, of the Southwest Research Institute in Boulder, Colorado. “With respect to its size relative to Charon, this feature is much like the vast Valles Marineris canyon system on Mars.”
Although such chasms have been seen before on other planets- notably the Valles Marineris canyons on Mars- such a feature has never been observed on a satellite so small. Charon is only half the size of Pluto.
The theory behind the canyon is even stranger. Researchers believe that a long, long time ago, an ocean existed beneath the surface of Charon. As the ocean began to freeze, the liquid expanded. This caused the moon’s surface to rip open and leave behind the huge scar we see today.
The sub-surface ocean would actually be more similar to lava than water. Scientists believe it was a form of cold volcanic activity known as cryovolcanism.
“The team is discussing the possibility that an internal water ocean could have frozen long ago, and the resulting volume change could have led to Charon cracking open, allowing water-based lavas to reach the surface at that time,” said Paul Schenk, a New Horizons team member from the Lunar and Planetary Institute in Houston.
The smooth southern region of Charon is unofficially dubbed Vulcan Planum after the famous Star Trek planet. Beneath the moon’s equator is a vast region utterly unblemished by large craters. This supports the sub-surface ocean theory be indicating a period of violent upheaval occurring shortly after Charon’s formation. The cold lavas may have smoothed out the surface.
As for the strange reddish colors of the moon’s polar region, they are in fact quite similar to the red terrain on Pluto’s equatorial region. The images of the New Horizons spacecraft combine blue, red, and infrared images taken by the Ralph/Multispectral Visual Imaging Camera (MVIC) of the craft. This allows for a direct comparison between Pluto and Charon.
“We thought the probability of seeing such interesting features on this satellite of a world at the far edge of our solar system was low,” said Ross Beyer, a scientific affiliate at the Search for Extra-Terrestrial Intelligence institute (SETI) in California. “But I couldn’t be more delighted with what we see.”
SETI’s involvement in analyzing the New Horizons’ images does not mean that NASA suspects life forms once existed on Charon. Rather, due to the vast amounts of data that will be sent from the spacecraft over the next twelve months, NASA has asked SETI for help in examining the images.
Charon is proportional in size to Pluto, however, its orbit goes farther afield than the moons of most other planets. This long-range gravitial pull causes Pluto to wobble when Charon is at the farthest point of orbit.
As more and more pictures are received, we may learn still more about the strange geological past of Pluto’s largest moon, Charon.
“I predict Charon’s story will become even more amazing!” said Hal Weaver, mission Project Scientist of the Johns Hopkins University Applied Physics Laboratory in Maryland.
New Horizons in already 3.1 billion miles away from Earth. NASA affirms that all systems of the spacecraft are functioning normally and should be able to continue its journey out of our solar system without hindrance.
The New Horizons project is part of NASA’s New Frontiers Program, managed by the Marshall Space Flight Center.