Adaptive Optics Mapping of Io's Volcanism in the Thermal IR (3.8 μm)

✍ Scribed by Franck Marchis; Renée Prangé; Julian Christou

• Publisher: Elsevier Science
• Year: 2000
• Tongue: English
• Weight: 498 KB
• Volume: 148
• Category: Article
• ISSN: 0019-1035
• DOI: 10.1006/icar.2000.6506

✦ Synopsis

Two opposite hemispheres of Io were observed on October 20 and 21, 1996, through an L broadband filter, using the high-resolution capability of the Adaptive Optics (AO) system implemented on the ESO 3.6-m telescope at La Silla, Chile. These observations, performed at thermal wavelengths when Io is in daylight, have been carefully processed to improve the sharpness of the initial, diffraction-limited, images. The myopic deconvolution process used (idac) achieved an angular resolution estimated to be 0.15 arcsec, corresponding to a spatial resolution of ∼570 km on Io's disc at the time of the observations. The final images show a number of bright features which have been compared with the Galileo/NIMS data, the only data set with a comparable resolution available for the anti-Jovian side of the satellite as well as its Jupiter-facing side. Our maps of the hot spot distribution are quite consistent with the Galileo data. The Jupiter-facing side is dominated by emission from Loki, which accounts for ∼25% of the total hot spot emission from that side (and 45% of that we were able to resolve and identify), although Loki was in a phase of decreasing activity (but not yet quiescent), as derived from ground-based monitoring observations. A few more hot sources are detected, including Pele-Pillan. The other hemisphere is characterized by a large number of moderately bright hot spots which are distributed around Bosphorus Regio. These preliminary observations fully demonstrate the capabilities of an AO system coupled with a thermal camera to monitor the volcanic activity of Io, in terms of morphology as well as thermal output. These monitoring capabilities will become especially important when the Galileo mission ends.