Saturn's moonlet Methone - egg (or space ball)

Methone was discovered by Cassini in 2004. This is moonlet with sizes 4 x 2.5 kilometers, orbiting Saturn in 24 hours (familiar number?), with radius of orbit 194 000 kilometers. For the long time it was the only we knew about Methone, until in 2012, Cassini passed in 4000 kilometers from its surface and took its first detailed images. Cassini met many strange moons in Saturn system before: ravioli moons Pan and Atlant, but this time we have an egg:

 Image: NASA/JPL - Methone from the distance 4000 km. Resolution - 27 meter per pixel

There are no craters or another features on the surface of Methone, it is absolutely smooth. However, the moon is didvided in two parts: dark, with albedo only 13%, and bright - albedo more than 70%. Another strange feature - average density of Methone is only 0.31 g/cm3, which is three times less than density of water ice, the lowest value among all bodies in the Solar System. There are two explanations of its low density:

1. Realistic - this is pile of ice dust, formed by gravity of Saturn and nearby relatively large moon Mimas ;

2. Sci-fi - This is alien construction, with hollows inside (beware xenomorphs!)

Near to Methone, there are two other moonlets of similar sizes - Pallene and Anthe, but have no detailed images for them.  Methone, Pallene and Anthe, all orbit at similar distances from Saturn and they are in a dynamical relationship between themselves. The larger Mimas strongly perturbs the three moons, all of which orbit between Mimas and Enceladus. The vastly more massive Mimas causes the Methonean orbit to vary by as much as (20 km), it causes Pallene to vary by a slightly smaller amount and it has the greatest effect on Anthe. 

Probably, the creator of this moon was inspired by Space balls movie xD