The potential for delayed planetesimal bombardment to deliver volatiles and reconstitute atmospheres on potentially habitable, M-dwarf-hosted planets

In recent years a paradigm shift has occurred in exoplanet science, wherein M-Dwarf systems are increasingly viewed as a foundational pillar of the search for potentially habitable worlds in the solar neighborhood. However, the processes that led to the formation of this rapidly accumulating sample of planet systems are still poorly understood. Moreover, it is unclear whether tenuous primordial atmospheres around these Earth-analogs could have survived the intense epoch of heightened stellar activity that is typical for low-mass stars. While delayed cometary delivery has the potential to reconstitute these atmospheres, the process is rather stochastic, and the typical high impact velocities can often result in net volatile depletion. However, it is well established that the tail-end (within a few hundred Myr after the planets formed) of planetesimal bombardment on the Earth has the potential to erode, enhance, or radically reshape its primordial atmosphere. We present new simulations of in-situ planet formation across the M-dwarf mass spectrum. From the left-over planetesimal and collisional fragment populations we infer the orbital structure of the remnant debris fields, and utilize high-resolution GPU-accelerated models of real M-dwarf-hosted systems to derive late mass delivery rates. While bombardment decays swiftly at small radial distances, we find that significant planetesimal fluxes persist in the habitable zone for some time.