Percolation clusters of organics in interstellar ice grains as the incubators of life

TL;DR

This paper proposes that organic molecule clusters in interstellar ice grains could have served as incubators for the origin of life, with micro-environments facilitating early biochemical evolution and eventual microbial emergence.

Contribution

It introduces a novel model where percolation clusters in interstellar ice act as micro-environments for abiogenesis, linking astrophysical processes to the origin of life.

Findings

Large organic clusters form in interstellar ice over million-year timescales.

Superclusters create micro-environments conducive to chemical evolution.

Microbes could survive planetary collisions and seed life on Earth.

Abstract

Biomolecules can be synthesized in interstellar ice grains subject to UV radiation and cosmic rays. I show that on time scales of $\gtrsim 10^{6}$ years, these processes lead to the formation of large percolation clusters of organic molecules. Some of these clusters would have ended up on proto-planets where large, loosely bound aggregates of clusters (superclusters) would have formed. The interior regions of such superclusters provided for chemical micro-environments that are filtered versions of the outside environment. I argue that models for abiogenesis are more likely to work when considered inside such micro-environments. As the supercluster breaks up, biochemical systems in such micro-environments gradually become subject to a less filtered environment, allowing them to get adapted to the more complex outside environment. A particular system originating from a particular location on some supercluster would have been the first to get adapted to the raw outside environment and survive there, thereby becoming the first microbe. A collision of a microbe-containing proto-planet with the Moon could have led to fragments veering off back into space, microbes in small fragments would have been able to survive a subsequent impact with the Earth.