Speckle imaging of volcanic hotspots on Io with the Keck telescope
2003; Elsevier BV; Volume: 165; Issue: 1 Linguagem: Inglês
10.1016/s0019-1035(03)00168-4
ISSN1090-2643
AutoresBruce Macintosh, Donald T. Gavel, S. G. Gibbard, C. E. Max, M. J. Eckart, Imke de Pater, A. M. Ghez, J. R. Spencer,
Tópico(s)Planetary Science and Exploration
ResumoUsing speckle imaging techniques on the 10-m W.M. Keck I telescope, we observed near-infrared emission at 2.2 μm from volcanic hotspots on Io in July–August 1998. Using several hundreds of short-exposure images we reconstructed diffraction-limited images of Io on each of three nights. We measured the positions of individual hotspots to ±0.004″ or better, corresponding to a relative positional error of ∼20 km on Io's surface. The sensitivity of normal ground-based images of Io is limited by confusion between overlapping sources; by resolving these multiple points we detected up to 17 distinct hotspots, the largest number ever seen in a single image. During the month-long span of our 1998 observations, several events occurred. Loki was at the end of a long brightening, and we observed it to fade in flux by a factor of 2.8 over the course of one month. At the 3-sigma level we see evidence that Loki's position shifts by ∼100 km. This suggests that the brightening may not have been located at the "primary" Loki emission center but at a different source within the Loki caldera. We also see a bright transient source near Loki. Among many other sources we detect a dim source on the limb of Io at the latitude of Pele; this source is consistent with 2.7% of the thermal emission from the Pele volcano complex being scattered by the Pele plume, which would be the first detection of a plume through scattered infrared hotspot emission.
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