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“Tidally Heated Exomoons”

Vera Dobos (Konkoly Observatory of the Hungarian Academy of Sciences)
Wednesday, 1455, Lecture Room 106

Significant tidal heating on exomoons cause elevated temperature that can melt the ice on the surface. Hence tidal heating may play a key role in their habitability even without significant solar radiation. The Solar System provides examples for tidally heated moons, such as Europa or Enceladus, where the surface ice sheet covers water ocean that is tidally heated. The possibility of life is intensely studied on these satellites. Tidal forces may be even stronger in extrasolar systems, depending on the properties of the moon and its orbit. For studying the surface temperature of tidally heated exomoons, I applied a viscoelastic model for the first time. This model includes the temperature dependency of the tidal heat flux, and the melting of the inner material, unlike the widely used, so-called fixed Q models. Using the more realistic viscoelastic model I introduced the Tidal Temperate Zone (TTZ), which is the region around a planet where the surface temperature of the satellite is between 0 and 100°C, not considering other energy sources than tidal heating. The location and width of the TTZ depends on the orbital period, eccentricity, density and radius of the moon. I made similar calculations with the fixed Q model and investigated the statistical volume of the TTZ using both models. I have found that the viscoelastic model predicts 2.8 times more exomoons in the TTZ than the fixed Q model with orbital periods between 0.1 and 3.5 days 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.