Planetary Geoscience

Image Credit: JPL/NASA

The Jupiter System

The lack of a solid surface makes geological investigation of Jupiter itself a somewhat tricky proposition, but Jupiter has a host of moons with solid surfaces, including four of the largest moons in the Solar System.  These Galilean moons (so-called because they were discovered by Galileo himself in 1609) are, in fact, among the most geologically interesting bodies in the Solar System.  Continuous tidal stretching and squeezing of Io – the closest of the four to Jupiter – heats the interior so much that volcanic eruptions are constant, including some that throw plumes high off the surface.  Similar, though less intense, heating of the interior of Europa apparently supports a global ocean underneath its icy crust.  This ocean is widely held to be the most likely place within the Solar System, aside from Earth, where life could exist.  Unfortunately, the ocean is hidden beneath 10 – 50 km of ice.  The icy surface of Europa is very young from recent resurfacing, which could indicate some communication between the surface and underlying ocean.  Ganymede, the third Galilean moon outward from Jupiter, has a much older looking icy surface and supports its own magnetic field – a sign of likely differentiation with an iron core and perhaps its own liquid water layer beneath the surface.  Callisto, on the other hand, has a highly cratered surface and no evidence for differentiation.  Though still icy, Callisto’s surface is much darker than those of Europa and Ganymede, apparently from a coating of low albedo material.

Researchers in the UT EPS department are investigating the surface compositions of Jupiter’s Galilean moons using data from ground-based telescopes and from NASA spacecraft that have viewed them up-close.  Determining and mapping surface compositions and correlating compositional units with geology will address the question of how the surfaces are influenced by subsurface conditions.  Of particular interest is whether a material from Europa’s subsurface ocean ever makes it to the surface, or vice versa.