Viscoelastic Models of Tidally Heated Exomoons

TL;DR

This study introduces a viscoelastic model for tidally heated exomoons, which more accurately predicts their surface temperatures and habitability potential by accounting for temperature-dependent heat flux and melting effects.

Contribution

It is the first to apply a viscoelastic model to exomoon tidal heating, improving habitability predictions over traditional fixed Q models.

Findings

Viscoelastic model predicts 2.8 times more exomoons in the Tidal Temperate Zone than fixed Q model.

The model shows that internal melting moderates surface temperature, acting as a thermostat.

Results suggest higher habitability potential for tidally heated exomoons.

Abstract

Tidal heating of exomoons may play a key role in their habitability, since the elevated temperature can melt the ice on the body even without significant solar radiation. The possibility of life is intensely studied on Solar System moons such as Europa or Enceladus, where the surface ice layer covers tidally heated water ocean. Tidal forces may be even stronger in extrasolar systems, depending on the properties of the moon and its orbit. For studying the tidally heated surface temperature of exomoons, we used a viscoelastic model for the first time. This model is more realistic than the widely used, so-called fixed Q models, because it takes into account the temperature dependency of the tidal heat flux, and the melting of the inner material. With the use of this model we introduced the circumplanetary Tidal Temperate Zone (TTZ), that strongly depends on the orbital period of the moon, and less on its radius. We compared the results with the fixed Q model and investigated the statistical volume of the TTZ using both models. We have found that the viscoelastic model predicts 2.8 times more exomoons in the TTZ with orbital periods between 0.1 and 3.5 days than the fixed Q model for plausible distributions of physical and orbital parameters. The viscoelastic model gives more promising results in terms of habitability, because the inner melting of the body moderates the surface temperature, acting like a thermostat.