Wanted Dead or Alive Extraterrestrial Life Forms (Thermodynamic criterion for life is a growing open system that performs self-assembly processes)

TL;DR

This paper proposes a thermodynamic criterion for identifying extraterrestrial life, emphasizing the importance of self-assembly and disequilibrium in open systems as key indicators for life detection.

Contribution

It introduces a formal thermodynamic framework defining life as a growing open system performing self-assembly, aiding the search for extraterrestrial life.

Findings

Life is characterized by out-of-equilibrium self-assembly processes.

Candidate planets should show increased inhomogeneity as a sign of life.

The thermodynamic criterion helps distinguish living matter from non-living systems.

Abstract

For more than 100 years, humanity (both specialists and enthusiastic laics) has been searching for extraterrestrial life hoping we are not alone. The first step in the quest for extraterrestrial life is to define what and where exactly to look for. Thus, the basic definition of living matter is a conditio sine qua non for the quest. The diversity of species on Earth is so large that our quest for extraterrestrial life cannot be limited to forms and shapes present and known to us from our environment. However, there are two formal conditions that must be fulfilled in order for something to be assumed as living matter. First, it should represent a growing open thermodynamic system (in biological terms - a cell), and thus be a system out of equilibrium. Second, it must perform synthesis, self-assembly and accumulation processes (in biological terms to grow, maintain homeostasis, respond to environment, reproduce, exchange matter and energy, evolve). Populated planets are consisted of two components: biosphere and its environment (geosphere, hydrosphere and atmosphere). Living matter and its environment are out of equilibrium. Thus, the candidate planets are dynamic inhomogeneous systems for two reasons. First, a planet receives energy from its star, which leads to disequilibrium for external reasons. Animate matter contributes to disequilibrium for internal reasons: accumulation of matter and self-assembly. In practice, for a screening, an astrobiologist should search for increase in inhomogeneity on a candidate planet.