OPTIMIZING SPATIAL, SPECTRAL, AND TEMPORAL RESOLUTION FOR CONSTRAINING ERUPTION STYLE ON IO AND EARTH WITH THERMAL REMOTE SENSING

Volcanic eruptions on Io and Earth are monitored by a variety of thermal remote sensing instruments. While more resolution is always desirable, we have developed methodologies to constrain the style of eruption using low spatial, spectral, and temporal resolution data. For Io, this is necessitated by the limits of spacecraft and Earth-based telescopic observations. Eruption style can be classified using the concept of "thermal signature" that focuses on the temporal evolution of thermal emission spectra [1]. The ratio of the emission at 2 µm and 5 µm, and how this ratio changes temporally, is often diagnostic of effusive eruption style, even in low spatial resolution data [2]. Tests using ground-based thermal data for terrestrial “ground truth” cases show that this classification system is equally valid for Earth. A square meter of an active lava lake of Io looks very similar to a square meter of an active lava lake on Earth. The same goes for pahoehoe flows. This validation of “thermal signature” means that appropriate physical models can be selected to interpret the data. The scale of Io’s eruptions can defy the imagination. “Outburst” eruptions, known to be caused by extensive lava fountaining, can radiate >10¹³ W. The smallest thermal anomalies detected on Io in medium/low spatial resolution data are still larger than almost all contemporaneous subaerial volcanic activity on Earth. The large volumes of lava erupted on Io (>56 km³ at Pillan in 1997) are an expression of internal tidal heating. It may be that high compressive stresses in the lower lithosphere inhibit magma ascent, and so only relatively large volumes of magma can overcome this stress barrier and reach the surface. The results of the “thermal signature” analysis [2] can be used to aid in the planning of future space-borne instruments that can be used for volcano monitoring on Io, as well as Earth. This work was performed at the Jet Propulsion Laboratory-California Institute of Technology, under NASA contract, with support from the NASA Outer Planets Research Program. © 2009. All rights reserved. References: [1] Davies, A., 2007, Volcanism on Io, Cambridge University Press, pp372. [2] Davies, A., Keszthelyi, L., and Harris, A., 2009, The Thermal Signature of Volcanic Eruptions on Io and Earth, JVGR, submitted.