Several craters along a general line that may be overlapping, touching, or separate from one another. A crater chain, or catena, is typically the result of either secondary impacts or Igneous rock that forms from cooling magma on the surface of a planet or asteroid. activity. Several unusual crater chains have been found on Ganymede and Callisto that appear to be the impact scars of tidally disrupted comets or asteroids. These features serve to record the characteristics of comets and support the rubble-pile model for Conglomeration of frozen water and gases (methane, ammonia, CO2) and silicates that that formed in the outer solar system and orbits the Sun. In recent years, the description of comets has shifted from dirty snowballs to snowy dirtballs with more dust than ice. However, the ratio is less than 10-to-1. Click on Term to Read More nuclei and some asteroids, in which these objects are formed of many small, loosely bound fragments. A couple of crater chains have been found on Earth, including the Aorounga Craters.