ETD

• abitabilità
• atmosfera
• atmosphere
• dinamica
• dynamics
• esopianeta
• exoplanet
• habitability
• K2-3d
• LHS 1140b
• simulations
• simulazioni

In this work, we model K2-3 and LHS 1140, currently the two best-characterized multiplanet exosystems that contain possible habitable planets K2-3d and LHS 1140b.

To evaluate their habitability, we first studied the dynamics of both systems by running dynamical simulations backwards in time for 10^9 orbits. The LHS 1140 system is stable, with very low variability in the star-planet distances in all sets of simulations. In contrast, one sixth of all K2-3 system simulations resulted in collisions. We used these simulations to compute a minimum, mean, and maximum star–planet distance for both K2-3d and LHS 1140b to be used as constraints for the atmospheric modelling.

We developed an original one-dimensional hydrostatic radiative-diffusive atmospheric structure code. We included planetary surface reflection, photochemistry, diffusion, water vapour saturation, convection in the lower atmosphere, and atmospheric escape. We also computed radiative transfer throughout our 1D atmosphere. Our program can easily implement different surface and atmospheric compositions and different stellar spectra.

We conclude that both K2-3d and LHS 1140b could retain an Earth-like atmosphere at least on the timescale of our dynamical simulations (~0.1 Gyr). K2-3d could have habitable surface conditions were it to orbit near the outer edge of the computed star-planet distance range, while LHS 1140b has surface temperatures below the freezing point of water, making it mostly uninhabitable.