Molecular diversity as a biosignature

TL;DR

This paper proposes a new biosignature detection method based on molecular diversity metrics, distinguishing biotic from abiotic samples across terrestrial and extraterrestrial contexts, even under degradation.

Contribution

It introduces a statistical framework for biosignatures based on molecular assemblage diversity, applicable to planetary mission data without requiring specific molecular features.

Findings

Biotic samples show higher molecular diversity than abiotic ones.

Diversity-based biosignatures are consistent across amino acids and fatty acids.

The method remains effective under simulated space-like degradation.

Abstract

The search for life in the Solar System hinges on data from planetary missions. Detecting biosignatures based on molecular identity, isotopic composition, or chiral excess requires measurements that current and planned missions can only partially provide. We introduce a new class of biosignatures, defined by the statistical organization of molecular assemblages and quantified using diversity metrics. Using this framework, we analyze amino-acid diversity across a dataset spanning terrestrial and extraterrestrial contexts. We find that biotic samples are consistently more diverse -- and therefore distinct -- from their sparser abiotic counterparts. This distinction also holds for fatty acids, indicating that the diversity signal reflects a fundamental biosynthetic signature. It also proves persistent under modeled space-like degradation. Relying only on relative abundances, this biogenicity assessment strategy is applicable to any molecular composition data from archived, current, and planned planetary missions. By capturing a fundamental statistical property of life's chemical organization, it may also transcend biosignatures that are contingent on Earth's evolutionary history.