The Implications of 'Oumuamua on Panspermia

TL;DR

This paper evaluates the plausibility of interstellar panspermia facilitated by 'Oumuamua, estimating ejecta densities and impact probabilities, and concludes it could seed up to 10^5 habitable planets in our galaxy.

Contribution

It introduces a new model using 'Oumuamua's properties to estimate ejecta density and impact likelihood, refining previous panspermia assessments.

Findings

Panspermia probability for Earth is less than 10^-5.

Potentially up to 10^5 habitable planets could be seeded.

Ejecta density estimates depend on 'Oumuamua's observed properties.

Abstract

Panspermia is the hypothesis that life originated on Earth from the bombardment of foreign interstellar ejecta harboring polyextremophile microorganisms. Since the 2017 discovery of the interstellar body 'Oumuamua (1I/2017 U1) by the Pans-STARRS telescope, various studies have re-examined panspermia based on updated number density models that accommodate for 'Oumuamua's properties. By utilizing 'Oumuamua's properties as an anchor, we estimate the mass and number density of ejecta in the ISM (rho_m [kg au^-3] and rho_n [au^-3]). We build upon prior work by first accounting for the minimum ejecta size to shield microbes from supernova radiation. Second, we estimate the total number of impact events C_n on Earth after its formation and prior to the emergence of life (~0.8Gyr). We derive a conditional probability relation for the likelihood of panspermia for Earth specifically of <10^-5, given a number of factors including f_B, the fraction of ejecta harboring extremophiles and other factors that are poorly constrained. However, we find that panspermia is a plausible potential life-seeding mechanism for (optimistically) potentially up to ~10^5 of the ~10^9 Earth-sized habitable zone worlds in our Galaxy.