Charon, the largest of Pluto’s five moons, once had a huge underground liquid ocean that froze and expanded, thus fracturing its surface, say NASA’s New Horizons scientists who have been analyzing new images sent back from the interplanetary space probe.
The subsurface ocean froze, expanded and pushed out Charon’s surface causing it to stretch and fracture ‘on a massive scale’, NASA scientists say.
The side of Charon observed by the passing New Horizons space probe in July last year is characterized by a system of ‘pull apart’ tectonic faults, which are expressed as valleys, scarps (steep banks/slopes) and ridges.
Sharon’s surface fractured when its subsurface ocean froze and expanded. (Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)
Super deep valleys in Charon
Some of the valleys on that side of Charon were found to be over 6.5 kilometres (4 miles) deep.
Charon’s tectonic landscape suggests that Pluto’s largest moon somehow expanded a long time ago – a bit like Bruce Banner in the Incredible Hulk series who would tear his shirt as he turned into the muscle-bound giant green man-monster. As the moon’s surface stretched it fractured.
Charon’s outer layer consists mainly of water ice. When the moon was considerably younger, this layer was warmed by the decomposition of radioactive elements, as well as the moon’s own internal heat of formation.
NASA researchers believe that Charon might have been warm enough to cause the water ice to melt deep below the surface, creating an underground ocean.
The Interplanetary space probe New Horizons was launched on 19th January, 2006, with the primary mission to perform a flyby study of the Pluto system, and a secondary mission to fly by and study objects in the Kuiper belt. (Image: nssdc.gsfc.nasa.gov)
Charon cooled and the subsurface ocean froze
However, Charon then started to cool down, and this ocean would have frozen and expanded – when water turns into ice it expands. The expanding ice would have pushed the surface outward and produced the enormous chasms visible today.
The top image on this page focuses on a section of the feature nicknamed Serenity Chasma, which forms part of a vast equatorial belt of chasms on Charon.
Charon’s system of chasms is one of the longest we know of in our Solar System – it is about 1,800 kilometres (1,100 miles) long and reaches depths exceeding 7.5 kilometres (4.5 miles).
They make the Grand Canyon in the United States – which is just 446 kilometres (277 miles) long and just over 1.6 kilometres (one mile) deep – seem quite small in comparison.
In the lower portion of the image, you can see color-coded topography of the same scene. Measurements of the shape of this feature suggest to scientists that Charon’s water-ice layer was probably at least partially liquid in its early history, and has since frozen over again.
The image was obtained by LORRI (Long-Range Reconnaissance Imager) on New Horizons.
Pluto has five moons
NASA scientists believe that Pluto’s entire moon system formed when the dwarf planet (Pluto) and another planet-sized body collided early in the history of our Solar System.
Up until 11 years ago, we only knew of one of Pluto’s moon (Charon). How many more will we discover over the next ten years? (Image: solarsystem.nasa.gov)
When they crashed into each other, material was flung out and later coalesced into a family of satellites around Pluto.
Mark Showalter, of the SETI Institute in Mountain View, California, said: “The moons form a series of neatly nested orbits, a bit like Russian dolls.”
Pluto’s five moons are:
Charon: this moon, about half the size of Pluto, was discovered in 1978. It is Pluto’s largest moon, but considerably smaller than our Moon.
Nix and Hydra: two very small moons. They were discovered by a Hubble Space Telescope team that was studying the Pluto system in 2005.
Kerberos: a tiny moon that is located between the orbits of Hydra and Nix. It was discovered in 2011.
Styx: this small moon was discovered by a team of researchers who were looking for potential hazards to the New Horizon’s flyby in 2015.
Pluto may have more moons we don’t know of. Scientists are currently actively searching around to determine whether there are any. They are also trying to find a possible debris field that would have been generated by the theoretical impact billions of years ago.
Video – Charon may have had a subsurface ocean