RINGS are not just for planets any more – Saturn’s moon Rhea has mysterious rings around it too.
Telltale drops in electron flow measured by the Cassini spacecraft around Rhea point to the presence of rings of debris ranging from pebble to boulder size (Science, vol 319, p 1380). Rings made of such large particles are harder to spot than those made of fine dust.
The rings are the first observed around a moon. “It is a huge surprise – we didn’t have any suspicions at all,” says Geraint Jones of University College London.
Their formation is a mystery. Planetary rings…
