LAVA LAKE EXPLOSIVE ACTIVITY – THE KEY TO DETERMINING ERUPTION TEMPERATURES ON THE JOVIAN MOON IO?

Active lava lakes are open volcanic systems, where lava circulates between a magma chamber and the surface. Rare on Earth, lava lakes may be common on Io, the highly volcanic jovian moon (e.g., [1]). Io’s low atmospheric pressure means that activity within Io’s lava lakes may be explosive, exposing lava at near-eruption temperatures (poorly constrained for Io). Lava lakes are therefore important targets for future missions to Io [2, 3]. With this in mind, hand-held infrared imagers were used to collect in-situ thermal emission data from the phonolite Erebus (Antarctica) lava lake [4] and the basalt lava lake at Erta’Ale (Ethiopia). Data analysis has established surface temperature and area distributions and the integrated thermal emission spectra for each lava lake. These spectra have been used to test models developed for analysis of remote sensing data of lava lakes and lava flows on both Earth and Io, where no ground-truth exists. The silicate cooling model [5] assumes, for the lava lake model variant, that the existing surface crust has been created at a fixed rate. Model output consists of a synthesized thermal emission spectrum, estimate of surface age range, and a rate of surface crust area formation. The cooling model provides accurate reproductions of actual thermal spectra and the total emitting area to within a few percent of actual emitting area. Model resurfacing rates broadly agree with observed behaviour at both lakes. Despite different composition lavas, the integrated thermal emission spectra from the two terrestrial lava lakes studied are very similar in shape, and, importantly, bear a striking similarity to spectra of Pele, an Io volcano that has been proposed to be a persistent, active lava lake [6] and which is the source of a massive dust and gas plume. This work was conducted at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA, and is supported by the NASA PG&G Program. AGD thanks the BBC for transport to the Erta’Ale lava lake. Copyright 2010 California Institute of Technology. References: [1] Davies, (2007) Volcanism on Io, Cambridge. [2] Keszthelyi et al. (2009) LPSC abstract 1943. [3] McEwen et al. (2009) LPSC abstract 1876. [4] Davies et al., (2008) JVGR, 177, 705-724. [5] Davies (1996) Icarus, 124, 45-61. [6] Davies et al. (2001) JGR, 108, 33,079-33,104.