History and Habitability of the LP 890-9 Planetary System

TL;DR

This paper investigates the evolution, habitability potential, and orbital dynamics of the LP 890-9 planetary system, emphasizing how initial volatile content and internal properties influence the possibility of life-supporting conditions on planet c.

Contribution

It provides new insights into the planet's atmospheric evolution, tidal circularization timescales, and habitability prospects considering various initial conditions and internal dynamics.

Findings

Planet c lies near the habitable zone's inner edge.

Water loss during magma ocean phase can be significant, but depends on initial conditions.

Tidal circularization of the planets varies from 0.5 Gyr to over 7 Gyr depending on internal properties.

Abstract

We present numerous aspects of the evolution of the LP 890-9 (SPECULOOS-2/TOI-4306) planetary system, focusing on the likelihood that planet c can support life. We find that the host star reaches the main sequence in 1 Gyr and that planet c lies close to the inner boundary of the habitable zone. We find the magma ocean stage can last up to 50 Myr, remove 8 Earth-oceans of water, and leave up to 2000 bars of oxygen in the atmosphere. However, if the planet forms with a hydrogen envelope as small as 0.1 Earth-masses, no water will be lost during the star's pre-main sequence phase from thermal escape processes. We find that the planets are unlikely to be in a 3:1 mean motion resonance and that both planets tidally circularize within 0.5 Gyr when tidal dissipation is held constant. However, if tidal dissipation is a function of mantle temperature and rheology, then we find that planet c's orbit may require more than 7 Gyr to circularize, during which time tidal heating may reach hundreds of terawatts. We thus conclude that the habitability of planet c depends most strongly on the initial volatile content and internal properties, but no data yet preclude the viability of an active biosphere on the planet.