Radial Variation and Galactic Structure Constraints on Panspermia in Milky Way–like Galaxies

To the point

Galactic structure strongly limits panspermia between stars with potentially habitable planets in Milky Way–like galaxies, causing huge differences between the inner disk and outer regions and an overall likelihood far lower than naive probability ratios would predict.

Panspermia in a Milky Way-like Galaxy
arxiv.org

Panspermia in a Milky Way-like Galaxy

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 naïve expectations based on the ratio between panspermia probability and natural habitability.