Relative Likelihood for Life as a Function of Cosmic Time

TL;DR

This paper models the probability of life emerging over cosmic time, suggesting that if low-mass star habitability isn't suppressed, most life may exist around such stars in the distant future, influencing search strategies.

Contribution

It provides a cosmological framework for understanding the timing of life emergence and highlights the importance of low-mass stars in future biosignature searches.

Findings

Life likely peaks around 0.1 solar-mass stars in 10 trillion years

Current habitability assumptions impact the timing of life's emergence

Spectroscopic searches can test the model's predictions

Abstract

Is life most likely to emerge at the present cosmic time near a star like the Sun? We address this question by calculating the relative formation probability per unit time of habitable Earth-like planets within a fixed comoving volume of the Universe, dP(t)/dt, starting from the first stars and continuing to the distant cosmic future. We conservatively restrict our attention to the context of "life as we know it" and the standard cosmological model, LCDM. We find that unless habitability around low mass stars is suppressed, life is most likely to exist near 0.1 solar-mass stars ten trillion years from now. Spectroscopic searches for biosignatures in the atmospheres of transiting Earth-mass planets around low mass stars will determine whether present-day life is indeed premature or typical from a cosmic perspective.