Even when viewed through a typical amateur telescope, Saturn’s rings offer a jaw-dropping spectacle that always satisfies. But looked at through the eyes of NASA’s now-departed Cassini spacecraft, the view is unlike anything else in the solar system, a stunning tapestry of mind-boggling complexity. This image, taken on 22 August, 2009, by Cassini’s narrow-angle camera at a distance of 2 million kilometres (1.27 million miles) employed red, green and blue filters to produce a natural colour view. The rings are made up mostly of water ice, with particles as small as grains of sand and as large as mountains. The precise nature of the icy material that gives the rings their colour remains a topic of debate.
Janus and Tethys demonstrate the main difference between small moons and large ones; it’s all about their shape. Moons like Tethys are large enough that their own gravity is sufficient to overcome the material strength of the substances they are made of and mould them into spherical shapes, but small moons like Janus are not massive enough for their gravity to form them into a sphere.
On the morning of Sunday, 22 May planet Mars reached opposition in the constellation of Scorpius and is closest to the Earth on 30 May — its best showing in a decade for Southern Hemisphere observers. As seen from the UK the Red Planet will be low in the south at 1am BST, but on nights of good seeing surface detail will be visible in amateur telescopes. Use our interactive Mars Mapper to identify its features.