Volcanism on Io: the view from Galileo

Abstract

Io, Jupiter’s innermost Galilean satellite, is the most volcanically active body in the solar system. Ashley Gerard Davies reviews the wealth of data returned by NASA's veteran spacecraft Galileo, that has led to a better understanding of the volcanic processes wracking Io. Jupiter’s moon Io is the only other body in the solar system known to have active, high‐temperature volcanism like that found on Earth. The Galileo spacecraft has been observing Io regularly since June 1996, and the data that it has returned have led to many new insights into the volcanic processes that have shaped not only Io, but Earth in its distant past.

Keck AO survey of Io global volcanic activity between 2 and 5 μm

“…Combining the three broadband brightnesses, we derived the type of activity using a basaltic cooling lava flow model (Davies, 1996). Pele exhibits the same style of activity previously observed by NIMS and SSI (Davies et al, 2001) indicating that the style of activity (the continual disruption of the crust on the surface of a lava lake; see Davies et al (2001) and Radebaugh et al (2004a)) is continuing. At Isum, an areally small but thermally very vigorous eruption is under way, indicative of either (i) a tightly areally-confined eruption, perhaps in a patera or caldera, where flows cannot spread out; or (ii) a small fire fountaining eruption, yielding constant areas at high temperatures.…”

“…A eruption style has been determined at a number of volcanoes on Io from a series of observations obtained throughout the Galileo mission. Early on it was recognized that different effusive styles had different spectra as seen by NIMS (Davies, 2001). Attempts have been made to classify different eruption styles on Io, for example, "Pele-type" and "Prometheustype" on the basis of plume type (McEwen and Soderblom, 1983), and Pillanean (large pyroclastic deposits, short-lived, high volumetric eruption rate) and Promethean (long-lived, insulated flow fields with a sustained plume) .…”

High-Resolution Keck Adaptive Optics Imaging of Violent Volcanic Activity on Io

“…Comparing the thermal signature of the Surt eruption with others seen by Galileo NIMS (Davies 2001), one can see that the thermal output [(7.8 ± 0.6) × 10…”

Post-solidification cooling and the age of Io's lava flows

“…In all cases, a surfaceintegrated thermal emission spectrum is produced. As more and more data from both Io and Earth are analyzed, different eruption signatures (Davies, 1996(Davies, , 2001Howell, 1997) and emission temporal evolutions (Davies, 2001(Davies, , 2003a(Davies, , 2003bDavies et al, 1997Davies et al, , 2000Keszthelyi et al, 2001;) are recognized, indicative of different eruption styles and mass eruption rates. Despite their limitations, these relatively simple models have been successfully applied to Galileo Near Infrared Mapping Spectrometer (NIMS) and solid state imaging experiment (SSI) data.…”