No evidence of magma ocean on Io based on Juno/JIRAM data

TL;DR

This paper critically evaluates previous claims of a magma ocean on Io based on Juno/JIRAM infrared data, arguing that the data and analysis do not support such a conclusion.

Contribution

The authors challenge prior interpretations by highlighting issues with data saturation, incomplete proxies, and statistical insignificance of the observed radiance dependence.

Findings

Data saturation issues undermine previous analysis

The M-filter is an incomplete proxy for total heat output

Latitudinal radiance dependence is not statistically significant

Abstract

A recent paper (ref. 1) used infrared images of Io acquired by the Juno/JIRAM instrument to derive a latitudinal dependence of the spectral radiance and conclude that such latitudinal dependence is consistent with a magma ocean model. We challenge their conclusions, and we draw attention to some potential issues with their analysis. In this letter, we will use three arguments to show that: (1) the (ref. 1) paper uses saturated data; (2) the M-filter of the JIRAM imager is only a weak and incomplete proxy for the total power output; and finally (3) even assuming that the radiance was correctly estimated, the latitudinal dependence of the 4.8-$\mu$m spectral radiance is not statistically significant. These facts, taken together, demonstrate that the results presented in (ref. 1) are not sufficient to confirm consistency with a magma ocean model on Io.