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.
To say that 2015 has been a great year for planetary exploration would be an understatement, with fantastic new discoveries from around the Solar System. From our first ever close-up look at Pluto and its moons, to more evidence for ancient lakes and rivers on Mars (and current briny streams) to weird bright spots and mountains on Ceres, to the continuing study of Saturn and its moons, notably Enceladus, to spectacular close-up views of a comet, it has indeed been quite a year.
Phobos is the largest of Mars’ two tiny moons, but 50 million years from now, that may no longer be the case. According to new research, Phobos is gradually being pulled apart by Mars’ gravity and will eventually be destroyed. The unusual long grooves on Phobos’ surface, which have been a puzzle for planetary scientists, are a key piece of evidence that point to eventual structural failure of this little worldlet.
The Cassini spacecraft has just successfully completed the first of three final close flybys of Saturn’s moon Enceladus, and has sent back some spectacular images of the northern regions of this icy and watery world, the best views ever seen so far. Two more upcoming flybys will dive back into the water vapor plumes at the south pole and measure how much heat is emanating from the tiny moon’s interior.
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.
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!
Jupiter’s moon Europa, with its subsurface ocean, is considered by many to be the best place in the Solar System to search for extraterrestrial life. With NASA now committing itself to a new mission sometime in the 2020s, the focus is turning to what would be the best strategy for looking for any life which may be there. Over 200 scientists and engineers met at NASA’s Ames Research Center in Mountain View, Calif., last week for a workshop called The Potential for Finding Life in a Europa Plume to do just that.
Saturn’s largest moon Titan is a fascinating world, uniquely alien yet eerily Earth-like in many ways, with its rain, rivers, lakes, seas, and massive sand dunes. But in this extremely cold environment, it is liquid methane and ethane which act as “water,” mimicking the hydrological cycle on Earth. Also, due to the perpetual and global hazy cloud cover, the only way to see these features from orbit is by using radar, which is what the Cassini spacecraft has done on a regular basis for quite a few years now. As good as they are, though, the radar images contain electronic noise, which reduces sharpness and clarity. But now a new technique is letting planetary scientists see Titan’s surface more clearly than ever before.