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 .