It was two years ago today that NASA’s New Horizons spacecraft became the first-ever probe to visit Pluto in the cold, outer fringes of the Solar System. To help celebrate the occasion, NASA has posted a new video of the epic flyby, when the spacecraft soared over the tall mountains and vast icy plains of this small but active world.
As Cassini’s “Grand Finale” journey continues, the spacecraft has completed its eighth dive past the innermost rings of Saturn (known as a ring crossing), and there are now just under 100 days left until it plunges into the giant planet’s atmosphere, never to come back. Although time may be running out, Cassini continues to devour every drop of science data that it can, which builds upon other data that has transformed our view of the Saturnian system – a complex array of worlds like a miniature Solar System. This includes, of course, more fantastic images of Saturn and its rings and moons. The detail seen in the rings is nothing short of staggering.
Moons are exceedingly common in the Solar System – Jupiter alone has 67! But smaller planets do as well of course, except for Mercury and Venus, and even some dwarf planets and asteroids have moons. This includes dwarf planets such as Pluto, which has five moons despite being so small itself. Most of the larger dwarf planets are now known to possess moons, and now another one has been discovered, by the Hubble Space Telescope and two other telescopes, orbiting the third largest known dwarf planet known as 2007 OR10.
Some great new views from the Cassini spacecraft of Saturn’s tiny moon Atlas were released today. Atlas is similar to another Saturnian “ravioli” or “flying saucer” moon, Pan – a central roughly spherical or oblate body with an unusual broad equatorial ridge. Like Pan, the ridge is thought to have formed from material coming from Saturn’s rings, and also like Pan, the ridge on Atlas appears very smooth, but is significantly larger. Atlas orbits just outside the outer edge of Saturn’s A ring and is very small, only about 15 kilometres (9.4 miles) across, but still larger than Pan.
Saturn is, of course, famous for its exquisite ring system, but other planets have rings as well – Jupiter, Uranus and Neptune all have them, they just aren’t nearly as prominent. Now it turns out that Mars may also have once had rings, and could have them again in the future.
Twelve years ago today, one of the most incredible space missions ever was accomplished: the first landing of a probe on an alien moon. And this wasn’t just any moon, but Titan, largest moon of Saturn and one of the most fascinating worlds in the Solar System. Although much colder than Earth, Titan mimics some of the processes found here such as its hydrological cycle, but with liquid methane/ethane instead of water. Titan had been observed extensively by telescopes and from Saturnian orbit, but this was the first time the surface could be seen up close.
Charon is Pluto’s largest moon and, despite being so cold and remote from the Sun, has been revealed to be a fascinating and active world, just like Pluto itself. Residing in the far outskirts of the Solar System, it had been expected that Charon – and Pluto for that matter – would be little more than frozen, dead worlds. But just like the rest of the Solar System, there were surprises waiting to be found. Thanks to the New Horizons spacecraft, we got our first close-up views of the Pluto system in July 2015. It soon became evident that not only were Pluto and Charon geologically active in the ancient past, but they perhaps still are in some ways even now. One of the most surprising findings was both Pluto and Charon likely had subsurface water oceans; while it is thought that Pluto’s is probably still liquid, Charon’s is likely completely frozen, and now additional evidence for its existence has been published by researchers.