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.
The Cassini spacecraft has successfully completed its first close pass of Saturn’s ring system, part of the Ring-Grazing Orbits phase of its mission, NASA said yesterday. As might be expected, Cassini has sent back some spectacular new images; these first images show Saturn’s northern hemisphere in incredible detail, including the famous “hexagon” jet stream surrounding the north pole.