Saturn has a smorgasbord of little moons, some of them orbiting within or just next to聽its rings. In the聽鈥淕rand Finale鈥澛爏tage of the聽NASA Cassini spacecraft鈥檚 mission, which ended in聽2017, it聽observed five of the planet鈥檚 small inner moons up close, which have now been analysed by researchers.
The Cassini observations showed that ring particles are constantly falling onto them, and they are all slightly different in聽shape and characteristics. The innermost moons are much redder, because the rings contain iron and red organic material, and the outermost ones are bluer because of ice and water vapour from the liquid plumes of the larger and further-out moon Enceladus.聽These small moons are just a taste of the diversity in Saturn鈥檚 system: it has 62 moons, each different from the next.
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Pan: Saturn鈥檚 reddest inner moon
Pan is a shepherd moon, orbiting in a gap in the rings and keeping the area free of stray bits of ice and dust. This process also gives it its weird equatorial ridge as the strays stick to the moon鈥檚 equator. It is the reddest of the inner moons.
Daphnis:聽The moon that makes waves
Daphnis has the lowest density of the inner moons at about 274 kilograms per cubic metre 鈥� about a quarter the density of cool water 鈥� which means it is probably extremely porous and spongy. Like Pan, it orbits within the rings, creating a wavy gap as it passes by and building up a small bump around its middle.
Atlas: A flattened, fluffy pita
Atlas鈥檚 equatorial ridge makes up 25 per cent of its total volume, giving it a flattened, pita bread-like shape. Parts of its surface seem to be covered with at least 10 metres of soft, fluffy dust.
Pandora: Bumpy with a smooth patch
Pandora is more heavily cratered than its neighbours. Despite being only about 100 kilometres across at its widest point, it has at least two craters that are 30 kilometres wide. Pandora doesn鈥檛 have a ridge like the other moons that orbit within the rings, but it does have a remarkably smooth patch that probably comes from the rings.
Epimetheus: Strange grooves
Epimetheus is the densest of the small inner moons, and also one of the largest. It shares a nearly identical orbit with another moon, called Janus. Its entire surface is covered in strange grooves, which may have formed like stretch marks as Saturn鈥檚 gravity constantly stretched and warped Epimetheus.
Read more: Saturn鈥檚 other moons
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