New JIRAM Analysis Suggests Io's Lava Lakes Radiate an Order of Magnitude More Power Than M-band Surveys Reported

Overview

A new analysis of data from NASA’s Juno mission suggests that decades of thermal measurements have systematically understated how much power Io’s volcanic lava lakes radiate. According to a Universe Today write-up of an arXiv preprint by Alessandro Mura and colleagues, prior estimates that relied on a single infrared band missed the contribution of the cooler central crusts that cover most of each lake’s surface, leaving researchers with figures “an entire order of magnitude” too low.

What We Know

Io, Jupiter’s innermost large moon, hosts more than 400 “paterae” - volcanic depressions, many of which behave as active lava lakes - according to a summary published by Phys.org. Imaging from Voyager in 1979 and Galileo in the 1990s established the basic landscape, but a finer view came from the Jupiter InfraRed Auroral Mapper (JIRAM) onboard Juno.

The new study, titled “Lava Lakes on Io: crust age and implications for thermal output” and posted to arXiv on March 23, 2026, examines 32 of those paterae. Its abstract notes that JIRAM observations “have confirmed that many of Io’s volcanic hot spots are active lava lakes, characterized by a colder central crust surrounded by a hotter peripheral ring.” The authors, led by Alessandro Mura, place the central crust temperatures in the 220–230 K range and the peripheral rings at temperatures up to 900 K, as reported by Phys.org.

The core argument is that older surveys read the lakes through a narrow infrared filter that is well tuned to the hot rings but poorly suited to the much larger crustal areas. “The M-band is extremely good at picking up ‘hot spots’ like the peripheral rings, but is essentially blind to the central crust of the paterae,” Universe Today writes in summarizing the study. The same article continues: “Despite being much cooler in temperature, the crustal areas themselves are much, much more massive than the peripheral rings. As a result, their overall thermal output is much higher as well, despite being ‘cooler’ on the surface.”

The team illustrates the gap with a single patera designated P63. Earlier work pegged it at around 7 Gigawatts of thermal emission, with some models reaching 20 Gigawatts. Folding in the JIRAM-derived crust contribution, Universe Today reports the new estimate at 80 GW. Phys.org cites the same 7, 20 and 80 GW figures, framing the shift as “an entire order of magnitude” upward, per Phys.org.

Mura and colleagues also use the cooling profile of the crust to back out a resurfacing time. According to Phys.org, a crust at roughly 200 K “would be about 13 years old,” with a characteristic resurfacing timescale of 8–10 years for the lakes as a whole.

Methodology Caveats

A companion analysis by some of the same authors, published in Frontiers in Astronomy and Space Sciences and titled “Re-evaluating Io’s volcanic heat flow: critical limitations in Juno/JIRAM M-band analysis,” lays out why M-band-only estimates need a rethink. Federico Tosi, Alessandro Mura and Francesca Zambon, all affiliated with the Istituto Nazionale di Astrofisica’s Istituto di Astrofisica e Planetologia Spaziali, write that JIRAM’s M-band is “centered at 4.78 µm” with a wavelength range of “4.54–5.02 µm,” and that “the ratio between the total blackbody radiance and the radiance measured in the JIRAM M-band filter varies markedly across the range of temperatures relevant for Io’s volcanic activity,” per Frontiers.

The Frontiers paper highlights two further pitfalls. It notes that “saturation effects in the JIRAM M-band imager detector, if not discussed and treated in detail, may systematically underestimate radiance from Io’s hot spots,” and adds that data above 12,000 Digital Numbers “shows distinct departure from linearity” in the instrument’s response, as documented by Frontiers. The same authors also caution that “identical 4.8-µm radiance values can correspond to significantly different total radiance outputs depending on the hot spot’s temperature” and that, without independent temperature data, “the inferred total power remains poorly constrained,” per Frontiers.

The Frontiers analysis goes further, arguing that “no statistically robust correlation exists between spectral radiance density and absolute latitude, regardless of how the data are binned or analyzed,” undercutting earlier claims that Io’s heat flow follows a clear north-south pattern, according to Frontiers.

What We Don’t Know

The Mura et al. arXiv preprint has not yet been peer-reviewed in its public form; the abstract page lists a related DOI in the Planetary Science Journal but the full journal version of the analysis has not been verified through the cited coverage. The popular write-ups also extrapolate from a single illustrative case (P63) to the broader population of paterae without listing revised totals for every lake studied, according to Universe Today and Phys.org.

Whether the higher thermal estimates change the case for a global magma ocean inside Io is also still open. The Frontiers companion paper frames the heat-flow distribution as “critical to constraining its internal structure and tidal heating mechanisms, including the debated presence of a global magma ocean,” per Frontiers, but neither paper claims to settle that question, and Juno’s extended mission is expected to add more JIRAM observations of Io and its sibling moons.