3D photographs from the New Horizons probe indicate the presence of a frozen underground ocean on Charon, Pluto's largest moon, according to an article in Icarus magazine.
The flight of the New Horizons probe past Pluto and its satellites in July 2015 showed the presence of a complex and contrasting relief on Charon. Scientists have discerned gigantic “ditches” 4-5 kilometers deep and powerful mountain ranges.
For example, on the equator of Charon there is a whole network of canyons, named "Serenity depression" in honor of the ship from the science fiction film of the same name. It is the longest structure of its kind in the solar system - its length exceeds 1,800 kilometers, which is almost five times longer than the Grand Canyon on Earth. These canyons, NASA scientists suggested in February, could have resulted from the freezing of the subglacial ocean in the bowels of Charon.
Alan Stern, mission leader for New Horizons, and his colleagues provided further evidence for this hypothesis by analyzing how stressful Charon's surface overall is from a geological perspective. The presence of some forms of global tension, as scientists suggested, should have confirmed the existence of the subsurface ocean, and their absence, on the contrary, would indicate that all the unusual landforms on Charon arose in a different way.
To do this, the scientific team combined images from a New Horizons color camera into three-dimensional stereo images that allowed them to see all the surface irregularities, small canyons and depressions that were not visible in black and white images from the Ralph camera.
After analyzing the images of the side of Charon, which was turned towards the probe during its flight through Pluto's "retinue", scientists found a large number of stretching traces on the satellite's surface. Many small and almost invisible cracks were present in the Volcano Plain and Land of Oz, the largest landforms on Charon, not only in the large canyons and troughs discovered in the early days after receiving data from New Horizons.
Such ice "stretch marks", according to estimates by Stern and his colleagues, occupy about 1% of the total area of Charon, which is quite enough to speak about the presence of a sufficiently large subglacial ocean on this moon of Pluto. Judging by the fact that such cracks are present on the oldest plains of Charon, its ocean froze long ago, several billion years ago, as a result of which the planet's diameter increased by several kilometers.
The conclusions of the scientists generally fit into the theory of the "radioactive" origin of the subsurface water layer, which arose due to the heat generated by the decay of radioactive elements in the Charon core. When the stocks of radionuclides were depleted, Charon's bowels cooled down, the ocean froze over and tectonic activity ceased forever.
Promotional video: