Callisto Impact Craters
This composite of Galileo spacecraft images of Jupiter's icy moon Callisto combines data from two orbits showing several types of impact craters. North is to the top of the picture; the Sun illuminates the surface from the east. The global image on the right shows one of the largest impact structures on Callisto, the Asgard multiring structure located near 300N latitude, 1420W longitude. The Asgard structure is approximately 1700 km across and consists of a bright central zone surrounded by discontinuous rings. The rings include degraded ridges near the central zone and troughs at the outer margin, which resulted from deformation of the icy crust following impact.
Date: 7 Dec 1998
Smaller impacts have smashed into Callisto after the formation of Asgard. The young, bright-rayed crater Burr located on the northern part of Asgard is about 75 km across. Galileo images show a third type of impact crater in this image, a dome crater named Doh, located in the bright central plains of Asgard. Doh (left image) is about 55 km in diameter, while the dome is about 25 km across. Dome craters contain a central mound instead of a bowl-shaped depression or central mountain (peak) typically seen in larger impact craters. This type of crater could represent penetration into a slushy zone beneath the surface of the Asgard impact.
The global image on the right was taken on 4 November 1996, at a distance of 111,900 km by the Solid-State Imaging Camera onboard NASA's Galileo spacecraft during its third orbit around Jupiter. The image on the left was obtained at a resolution of 90 m per picture element on 16 September 1997, during Galileo's tenth orbit when the spacecraft was less than 9500 km from Callisto.
Image Credit: Arizona State University
Credit: Lunar and Planetary Institute