The Ancient Cratered Surface of the Jovian Moon Callisto
Orbiting at the outer edge of the Galilean satellites, Callisto stands as the most heavily cratered object in the Solar System. Unlike its more geologically active companions, which are reshaped by intense tidal heating and volcanic outgassing, Callisto remains a testament to the conditions of the early solar neighborhood. Its surface is a chronological ledger of impacts dating back billions of years, preserved in an icy, rigid crust that has undergone little internal evolution since the era of late heavy bombardment. The composition of this moon is a complex mixture of approximately equal parts rock and water ice. Unlike other large icy moons that show signs of tectonic resurfacing or orbital resonance-induced heating, Callisto possesses a unique interior structure. Current gravitational mapping suggests it is only partially differentiated. While it likely contains ...