2,655,000,000,000,000,000,000,000 kg
orbiting the double dwarf planet further away. With diameters of 10-50 km, the moons – Nix, Hydra, Styx, and Kerberos – are all much smaller than Charon, which measures 1,212 km across, making it half as large as Pluto.
Most known moons in the Solar System are locked in predictable orbits around their planets. Earth’s moon rotates its own axis once per orbit around Earth, and the synchronic rotation means that the same side of the Moon is always facing Earth.
Pluto’s four small moons are much more rebellious, according to research by the SETI Institute in California based on data from the New Horizons mission. Hydra rotates its own axis no less than 89 times for every orbit around Pluto. According to scientists, that is so extreme that Hydra almost risks losing some of its own material. The other moons also behave very mysteriously, and astronomers are sure that Charon’s and Pluto’s partnership is the cause, but they still do not know how.
PLUTO COLOURS MOON RED
One of the most sensational discoveries resulting from New Horizon’s epoch-making visit to the dwarf planet is the characteristic red dot on Charon’s north pole.
The dot is so marked that it seems as if something coloured it, and that is probably also the case. In an article in the reputable scientific journal Nature, the scientists behind the New Horizons mission explain that the red colour could be due to reddish, organic materials known as tholins, which are produced, when methane gas from Pluto’s atmosphere is captured by Charon’s gravitational field and freezes onto the moon’s north pole. When the methane is subjected to ultraviolet sunlight, a chemical process converts it i nto heavier hydrocarbons and subsequently into tholins. Hence, you could say that Pluto has “i nfected” Charon slightly with i ts atmosphere, and the result is a nice, red top on the dwarf planet’s largest moon.
HEART HIDES LIQUID OCEAN
The surprises concerning Pluto do not stop with the moons. Based on New Horizon’s observations, astronomers have discovered that Pluto may contain a liquid ocean beneath a huge, heart-shaped feature on the surface of the dwarf planet.
If Pluto includes a liquid ocean, this could explain why the heart-shaped feature, Tombaugh Regio, is always facing Charon in a reciprocal, bound rotation. A partly frozen ocean is heavy and could provide the extra weight required to keep Pluto and Charon locked in this position.
New Horizon’s visit to Pluto lasted a month, and it took some 15 months to send all data back to Earth. The analysis will take even longer, so the probe may end up answering more questions about Pluto.