土星の衛星レアに環が発見される?

確認されれば衛星では初の発見だろう。環というと土星や天王星が有名だが、衛星に環があるケースは見つかっていなかった。

The Dust Halo of Saturn's Largest Icy Moon, Rhea Science

Saturn's moon Rhea had been considered massive enough to retain a thin, externally generated atmosphere capable of locally affecting Saturn's magnetosphere. The Cassini spacecraft's in situ observations reveal that energetic electrons are depleted in the moon's vicinity. The absence of a substantial exosphere implies that Rhea's magnetospheric interaction region, rather than being exclusively induced by sputtered gas and its products, likely contains solid material that can absorb magnetospheric particles. Combined observations from several instruments suggest that this material is in the form of grains and boulders up to several decimetres in size and orbits Rhea as an equatorial debris disk. Within this disk may reside denser, discrete rings or arcs of material.

Saturn's Moon Rhea Also May Have Rings NASA

PASADENA, Calif. -- NASA's Cassini spacecraft has found evidence of material orbiting Rhea, Saturn's second largest moon. This is the first time rings may have been found around a moon.