# The Effect of Multiple Heat Sources on Exomoon Habitable Zones

## TL;DR

This paper investigates how multiple heat sources, especially tidal heating, influence the habitable zones of exomoons around giant exoplanets, highlighting the importance of viscoelastic models in assessing habitability.

## Contribution

It compares tidal heating models and maps habitable zones considering various heat sources, advancing understanding of exomoon habitability beyond stellar radiation alone.

## Key findings

- Tidal heating dominates energy input for moons beyond certain distances from stars.
- Viscoelastic models show a significant thermostat effect affecting habitability.
- Habitable zones depend on moon eccentricity and star-planet distance, influencing detection prospects.

## Abstract

With dozens of Jovian and super-Jovian exoplanets known to orbit their host stars in or near the stellar habitable zones, it has recently been suggested that moons the size of Mars could offer abundant surface habitats beyond the solar system. Several searches for such exomoons are now underway, and the exquisite astronomical data quality of upcoming space missions and ground-based extremely large telescopes could make the detection and characterization of exomoons possible in the near future. Here we explore the effects of tidal heating on the potential of Mars- to Earth-sized satellites to host liquid surface water, and we compare the tidal heating rates predicted by tidal equilibrium model and a viscoelastic model. In addition to tidal heating, we consider stellar radiation, planetary illumination and thermal heat from the planet. However, the effects of a possible moon atmosphere are neglected. We map the circumplanetary habitable zone for different stellar distances in specific star-planet-satellite configurations, and determine those regions where tidal heating dominates over stellar radiation. We find that the `thermostat effect' of the viscoelastic model is significant not just at large distances from the star, but also in the stellar habitable zone, where stellar radiation is prevalent. We also find that tidal heating of Mars-sized moons with eccentricities between 0.001 and 0.01 is the dominant energy source beyond 3--5 AU from a Sun-like star and beyond 0.4--0.6 AU from an M3 dwarf star. The latter would be easier to detect (if they exist), but their orbital stability might be under jeopardy due to the gravitational perturbations from the star.