Physical properties of the small moon Aegaeon (Saturn LIII)

Aegaeon (Saturn LIII) is located within an arc of debris near the inner edge of Saturn’s G ring [1], and is the currently the smallest isolated moon of Saturn known [2]. On January 27, 2010 the Cassini spacecraft flew within 15,000 km of Aegaeon, obtaining images with sufficient spatial resolution (better than 100 meters/pixel) to resolve this tiny moon. These data reveal that the moon is strongly prolate, being between 1.2 and 1.6 km long but only 0.3-0.6 km wide, and that the long axis was aligned with Saturn during these observations. Images taken through different filters show that Aegaeon is red, and that its albedo is much lower than those of the other icy moons interior to Titan. Finally, long exposure images document structures in the nearby G-ring arc that appear to be generated by Aegaeon’s gravitational perturbations and thus can be used to constrain the moon’s mass and density.