Panspermia in a Milky Way-like Galaxy

TL;DR

This study models the likelihood of organic compounds traveling between stars in a Milky Way-like galaxy, revealing significant variation across the galaxy and showing that panspermia is less prevalent than naive estimates suggest.

Contribution

It applies a modified habitability model to cosmological simulations to quantify the spatial variation of panspermia probability in a galaxy.

Findings

Panspermia probability varies by orders of magnitude across the galaxy.

Only a small fraction of stars have high panspermia probabilities.

Panspermia is less effective than naive expectations based on simple ratios.

Abstract

We study the process of panspermia in Milky Way-like galaxies by modeling the probability of successful travel of organic compounds between stars harboring potentially habitable planets. To this end, we apply the modified habitability recipe of Gobat & Hong (2016) to a model galaxy from the MUGS suite of zoom-in cosmological simulations. We find that, unlike habitability, which only occupies narrow dynamic range over the entire galaxy, the panspermia probability can vary be orders of magnitude between the inner ($R, b = 1-4 {\rm kpc}$) and outer disk. However, only a small fraction of star particles have very large values of panspermia probability and, consequently, the fraction of star particles where the panspermia process is more effective than prebiotic evolution is much lower than from na\"ive expectations based on the ratio between panspermia probability and natural habitability.