The Cassini space probe has taken a stunning image of Saturn's moon Mimas against the blue-grey backdrop of Saturn's rings. The image (source: NASA/JPL/Space Science Institute), taken on 7 November at a distance of 3.7m km (2.3m miles) from Saturn, shows several of Saturn's rings as well as the moon.

The tiny moon appears on the right of the picture, two thirds of the way up. Saturn appears blue, rather than golden, in the picture because of preferential scattering of blue wavelengths in Saturn's cloud-free upper atmosphere. The dark band stretching across the image is Saturn's B ring, the densest of Saturn's rings. A full explanation of the picture appears on the Cassini Imaging Team website.

Mimas is one of Saturn's innermost moons, and its surface is dominated by the Herschel Crater, which is 130 km (80 miles) wide and was caused by an impact that likely came close to destroying the moon. In the centre of the 10km deep crater is a mountain almost as high as Mount Everest.

Mimas has a low density, which means that it is probably largely composed of ice. It also has a temperature of -200C (-328F), leading scientists to think that its surface features may have been preserved since the moon's formation.

The Cassini-Huygens mission is a co-operative mission between the US space agency Nasa, the European Space Agency (Esa) and the Italian Space Agency (Asi). The Huygens probe will separate from the Cassini craft on Christmas Day, making a gradual descent to the surface of the moon, Titan, where it will make landfall in mid-January. ®

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