Image: Craters on Ganymede

Description: Fresh impact craters on the grooved terrain on Ganymede by Galileo. The crater to the north is Gula (38 kilometers km in diameter). It has a distinctive central peak. The crater to the south is Achelous. It is 32 km in diameter. A characteristic feature of both craters, almost identical in size, is the "pedestal" - an outward-facing, relatively gently sloped scarp that terminates the continuous ejecta blanket. Similar features may be seen in ejecta blankets of Martian craters, suggesting impacts into a volatile (ice)-rich target material. Furthermore, both craters appear crisp and feature terraces. Gula has a prominent central peak; Achelous instead may show the remnant of a collapsed central peak or a central pit that is not fully formed. On lower-resolution images taken under higher sun illumination angle, both craters are shown to have extended bright rays, especially Achelous, which demonstrates that these two craters are younger than the respective surrounding landscape.
Title: Craters on Ganymede
Credit: http://photojournal.jpl.nasa.gov/catalog/PIA01609
Author: NASA
Permission: Public domain
Usage Terms: Public domain
License: Public domain
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