Enter the last of the big ones - Callisto
And second largest of the Jovian moons.
Here is a good graphic for comparative purposes.
By NASA / JPL / University of Arizona
NASA/JPL/DLR
National Oceanic and Atmospheric Administration
NASA/JPL/DLR(German Aerospace Center) - Own work, based on:
http://photojournal.jpl.nasa.gov/catalog/PIA02308
http://photojournal.jpl.nasa.gov/catalog/PIA00502
https://web.archive.org/web/20111028055701/http://sos.noaa.gov/images/fullsize/Solar_System/ganymede.jpg
http://photojournal.jpl.nasa.gov/catalog/PIA03456, Public Domain, Link
awesome astronomy sir,a very useful work sir @gavvet
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