CoRoT-7 b: Super-Earth or Super-Io?

TL;DR

This paper explores whether CoRoT-7 b is a super-Earth or a super-Io, suggesting tidal heating could cause extreme volcanism, making it more akin to a volcanic moon than a rocky planet.

Contribution

It introduces the idea that tidal heating may dominate CoRoT-7 b's geophysics, challenging previous assumptions based solely on insolation.

Findings

Tidal decay could have placed CoRoT-7 b on a wider orbit.

Tidal heating might cause extreme volcanism similar to Io.

A small eccentricity (~10^-5) can produce significant tidal heating.

Abstract

CoRoT-7 b, a planet about 70% larger than the Earth orbiting a Sun-like star, is the first-discovered rocky exoplanet, and hence has been dubbed a "super-Earth". Some initial studies suggested that since the planet is so close to its host star, it receives enough insolation to partially melt its surface. However, these past studies failed to take into consideration the role that tides may play in this system. Even if the planet's eccentricity has always been zero, we show that tidal decay of semi-major axis could have been large enough that the planet formed on a wider orbit which received less insolation. Moreover, CoRoT-7 b could be tidally heated at a rate that dominates its geophysics and drives extreme volcanism. In this case, CoRoT-7 b is a "super-Io" that, like Jupiter's volcanic moon, is dominated by volcanism and rapid resurfacing. Such heating could occur with an eccentricity of just 10^-5. This small value could be driven by CoRoT-7 c if its own eccentricity is larger than ~10^-4. CoRoT-7 b may be the first of a class of planetary super-Ios likely to be revealed by the CoRoT and Kepler spacecraft.