Dynamical Interactions and Habitability in the TOI-700 Multi-planet System

The discovery of a second earth sized planet (TOI-700e) interior to the habitable candidate TOI-700d has prompted further research into this system, as the additional planet makes the TOI-700 system a tightly packed multi-planet system with multiple planets in the habitable zone, like TRAPPIST-1. In this work, we use the planetary evolution code VPLanet to assess the potential habitability of TOI-700d and TOI-700e. We first examine their orbital dynamics to evaluate the influence of planet–planet interactions on the planet spin, obliquity, and eccentricity. We then investigate whether these interactions are sufficient to cause either TOI-700d or e to be perturbed out of a habitable state, and whether we expect either planet could retain surface oceans over Gyr timescales. Together, these analyses allow us to assess the long-term habitability prospects of both TOI-700d and TOI-700e. We find that multi-planet interactions in the TOI-700 system do not prevent either planet from potentially retaining habitable conditions; however, we find that TOI-700e is located very near the boundary of the tidally locked habitable zone, suggesting further work is needed to determine whether it is truly habitable.