A statistical analysis of Io's hot spots

As the most volcanically-active body in the Solar System, Io represents an extreme case of tidal heating and silicate volcanism. To better constrain the mechanics of Io's volcanism, we have performed a variety of statistical tests on a recently-published catalog of Io's hot spots, as imaged by recent Juno flybys. A spherical harmonic decomposition of Io's hot spots finds a negative Y 44 component ( p = 0.00064) to Io's volcanic spatial heat flow distribution and no other signals of spatial heterogeneity, which is not predicted by any of the three end-member models for melt generation in Io's interior. We infer that the lateral transport of melt in Io's interior could obscure signals of spatial heterogeneity; if so, then the negative Y 44 component may reflect near-surface processes rather than melt generation depth. Second, taking Io's hot spots as instances of a spatial point process, we calculated Ripley's K function and Moran's I to find that Io's hot spots do not cluster, but have positive autocorrelation ( z = +8.57). Third, we used kernel density estimation to calculate the magnitude-frequency distribution of Io's hot spots. Io's largest 20 hot spots abide by a power law n(q) ∝ q -α , where α = 2.26. In aggregate, these findings prioritize the need for new theoretical models exploring how melt is transported to the surface, not just where it's generated. • Io's surface volcanic expression is not correlated to depth of tidal dissipation. • Io's hot spots do not cluster, but their heat flows have positive spatial auto-correlation. • Io's largest hot spots follow a different magnitude-frequency distribution than the rest.