Methone is a small (3-kilometer) moon of Saturn that orbits between Mimas and Enceladus near Anthe and Pallene. Cassini captured high-resolution views of it on May 20, 2012.
The reason for its egg-like shape comes down to its size, or more specifically its mass. Methone is only 3 kilometers (2 miles) wide and doesn't quite have the mass to create a gravity to pull all parts of the moon into a spherical shape. When a world does have the gravitational 'oomph' to do so, scientists will recognize the celestial body as being in 'hydrostatic equilibrium.'
Many of the gas giants' moons aren't massive enough to attain hydrostatic equilibrium, so there's a veritable menagerie of weird shaped satellites out there. What makes Methone even more interesting is the fact that its surface appears very smooth, like an egg shell. No craters or other surface features are obvious. Cassini snapped this image on May 20 when it was 4,000 kilometers (2,500 miles) from the moon.
Methone was discovered in 2004 -- and was originally designated S/2004 S 1 or Saturn XXXII -- by the Cassini Imaging Team
after analyzing photographs from the mission. It was named after one of the Alkyonides, the seven beautiful daughters of the Giant Alkyoneus in Greek mythology
. Another two Saturnian moons are named after the Alkyonides -- Anthe and Pallene.