Ganymede and Callisto

Studying the Ice Shells of the Galilean Satellites

I have been modeling large impact craters and impact basins on the surfaces of Ganymede and Callisto to understand what they can tell us about the ice surrounding these moons.


Icy impact craters on the surface of Ganymede.

Complex impact craters, or those with a peak at the center as those shown above, can give us hints as to how warm the ice shell is near the surface. We can then use these temperatures to understand how quickly or slowly the moons are cooling off through time - these critical estimates allow planetary scientists to untangle how our Solar System formed.

Multiring basins, the largest and some of the most striking features observed, may form after very large impacts. Valhalla Basin on Callisto, pictured to the right, is one such basin I am modeling. By reproducing these large impact structures, I hope to understand not only how warm the ice is but also if we can determine how thick the ice is.

I've presented some of this work at the 49th Lunar and Planetary Science Conference. Please see my abstract below for more information!

Formation of Impact Craters on Ganymede and Callisto as a Constraint on Ice Shell Structure (2018) Bjonnes, E. and Johnson, B. C.. In Lunar and Planetary Science XLIX, Abstract # 1548, Lunar and Planetary Institute, Houston.