Relaxed impact craters on Ganymede: Regional variation and high heat flows

• Published in: Icarus (New York, N.Y. 1962) N.Y. 1962), 2018-05, Vol.306, p.214-224
• Main Authors: Singer, Kelsi N., Bland, Michael T., Schenk, Paul M., McKinnon, William B.
• Format: Article
• Language: English
• ISSN: 0019-1035; 1090-2643
• DOI: 10.1016/j.icarus.2018.01.012

•Apparent depths for 180 craters on Ganymede were measured.•Many craters exhibit substantially reduced depths compared to fresh craters.•Regions near the south pole show a different depth pattern than other latitudes.•The results imply overall high heat flow and potential regional thermal variation. Viscously relaxed craters provide a window into the thermal history of Ganymede, a satellite with copious geologic signs of past high heat flows. Here we present measurements of relaxed craters in four regions for which suitable imaging exists: near Anshar Sulcus, Tiamat Sulcus, northern Marius Regio, and Ganymede's south pole. We describe a technique to measure apparent depth, or depth of the crater with respect to the surrounding terrain elevation. Measured relaxation states are compared with results from finite element modeling to constrain heat flow scenarios [see companion paper: Bland et al. (2017)]. The presence of numerous, substantially relaxed craters indicates high heat flows—in excess of 30–40 mW m−2 over 2 Gyr, with many small (