One of the most surprising discoveries in recent years in the outer Solar System is that there are small moons which have oceans inside them. Jupiter’s moon Europa and Saturn’s moon Enceladus are now known to have global oceans of water beneath their icy crusts, and others are thought to as well, including Ganymede, Titan, and possibly others. These moons have a lot of ice and rock as well, and gravitational tugging and heating from the large gas giant planets helps maintain a deep layer of liquid water inside them, where otherwise they would most likely be frozen solid in the deep cold so far from the Sun. Now it seems that another moon also once had an ocean, although in this case it is thought to now be solid ice: Pluto’s largest moon, Charon.
After a lull of several weeks, the downlinking of new data from the New Horizons spacecraft has begun, including stunning new images of Pluto and its largest moon, Charon, as well as a treasure trove of other scientific data. There is so much to come that it will take about one year to downlink everything from the spacecraft and send back to Earth. Those first amazing images of Pluto and its moons were only the beginning.
The first-ever closeup view of Pluto’s surface from the flyby by New Horizons has been released, as well as the best view yet of Pluto’s largest moon, Charon. The new Pluto image shows mountains up to 3,500 metres (11,000 feet) tall in this region, unexpected on such a small, cold planetary body. They are thought to be made of solid water ice and no more than 100,000 years old, which is very young geologically. Those and other features suggest that Pluto may still be geologically active even now.
New colour and black & white images of Pluto and its largest moon Charon, taken by New Horizons on July 11 and 12, 2015. Much closer (and better) colour images are scheduled to be available tonight or tomorrow. As of this post, there are now less than 13 hours until closest approach!