Volatile Delivery to Rocky Planets through Impactors in Young Systems

For life to originate on a planet, a robust inventory of chemical species is required. These chemicals are potentially sourced exogenously through comets and asteroids; however, the amounts and timescales of their delivery remains unconstrained in exoplanetary systems. Here, we investigate impact histories in a ‘peas in a pod’ system architecture using N-body simulations. This architecture is chosen as it is the most commonly occurring architecture in observations, and has been shown to be likely to produce impacts in which organic molecules and prebiotic building blocks survive. What we seek to do here is constrain the impact fluxes and place them into the context of the system environment.

We create a model system of three tightly-packed, Earth-like, inner planets orbiting a Sun-like star, which are encircled by a ring of asteroids. This is in turn enclosed by the orbit of a gas giant, and an outer ring of mostly cometary objects that extends to the edge of the system. To explore what drives impactor flux, we vary parameters such as the presence of the gas giant, the eccentricity and inclination of the impactor disks, and the spacing of the inner planets. By integrating over a period relevant to the formation of life, we examine the nascency of impactor material and the amount of it that makes it to the inner planets. Further work involves combining this with models of chemical abundances and distributions through asteroids and comets to constrain available inventory for prebiotic chemistry, as well as extending this to other planetary system architectures. The result will give us an improved understanding of which ‘peas in a pod’ system characteristics are most favorable for abiogenesis and inform our future observations of potentially habitable systems.