09:15 〜 09:30
[PPS01-02] Loki Patera and the Lava Lakes on Io: Insights from Juno
キーワード：Volcanism, Io, Galilean moons, Lava lakes
JIRAM (Jovian Infrared Auroral Mapper) is an imager/spectrometer onboard Juno, primarily designed for studying Jupiter's atmosphere and auroral emissions. During its mission, JIRAM also obtained extensive data on Io, the most volcanically active body in the solar system. The instrument combines imaging and spectroscopy in a single device. The imager operates in two bands: the "L" band at 3.45 µm, which primarily detects surface albedo, and the "M" band at 4.75 µm, optimized for mapping thermal structures. The spectrometer covers a range of 2 to 5 µm with a spectral resolution of 9 µm. With an angular resolution of 0.01°/pixel, JIRAM achieved a spatial resolution of up to 300 m during close flybys of Io.
This work summarizes JIRAM’s observations of Io during the first 62 Juno orbits, and in particular the last ones, where the observation conditions were more favourable. Detailed thermal maps reveal a multitude of volcanic hotspots, including ring-shaped near-infrared emissions from numerous lava lakes. The evolution of Loki Patera, the
largest and most active lava lake on Io, was monitored over nearly two years, providing new insights into its thermal characteristics.
We observed that Loki has a thermal structure unlike other active lava lakes previously reported, with some brightening near the lake’s perimeter but lacking the continuous “hot ring” seen in others. Modeling the slow rate of cool-ing of the crust suggests there is significant magma beneath the crust to provide the latent heat necessary to decelerate the cooling rate. A resurfacing wave, initiated in the southwest of the lake and moving toward its northern extent, was observed with a ve-locity of ~2–3 km/day. Data collected on February 3 and April 9, 2024, may indicate the onset of a new resurfacing wave originating from a point source, rather than the foundering of a linear section of the crust.
We also observed many small (~3 km wide), closely spaced islands (~10 km apart) that have persisted in the same locations for at least 45 years, since first being imaged by Voyager 1. The persistence of these islands challenges resurfacing models of Loki, as they have remained fixed—likely anchored to the lava lake floor—and have not notice-ably changed in size, arguing against large-scale thermal erosion. The large central island of Loki is hotter than the surrounding terrain and shows a few thermal structures associated with the fractures that cross the island, indicating that the fractures are like-ly full of lava.
This work summarizes JIRAM’s observations of Io during the first 62 Juno orbits, and in particular the last ones, where the observation conditions were more favourable. Detailed thermal maps reveal a multitude of volcanic hotspots, including ring-shaped near-infrared emissions from numerous lava lakes. The evolution of Loki Patera, the
largest and most active lava lake on Io, was monitored over nearly two years, providing new insights into its thermal characteristics.
We observed that Loki has a thermal structure unlike other active lava lakes previously reported, with some brightening near the lake’s perimeter but lacking the continuous “hot ring” seen in others. Modeling the slow rate of cool-ing of the crust suggests there is significant magma beneath the crust to provide the latent heat necessary to decelerate the cooling rate. A resurfacing wave, initiated in the southwest of the lake and moving toward its northern extent, was observed with a ve-locity of ~2–3 km/day. Data collected on February 3 and April 9, 2024, may indicate the onset of a new resurfacing wave originating from a point source, rather than the foundering of a linear section of the crust.
We also observed many small (~3 km wide), closely spaced islands (~10 km apart) that have persisted in the same locations for at least 45 years, since first being imaged by Voyager 1. The persistence of these islands challenges resurfacing models of Loki, as they have remained fixed—likely anchored to the lava lake floor—and have not notice-ably changed in size, arguing against large-scale thermal erosion. The large central island of Loki is hotter than the surrounding terrain and shows a few thermal structures associated with the fractures that cross the island, indicating that the fractures are like-ly full of lava.