Geoscience and the Search for Life Beyond the Solar System

TL;DR

This paper discusses how geophysical and geochemical insights are crucial for interpreting potential biosignatures on exoplanets, emphasizing the need for models to distinguish biological signals from abiotic features in upcoming observations.

Contribution

It highlights the importance of integrating geophysical and geochemical models to interpret exoplanet biosignatures and identifies key areas for future research in this interdisciplinary field.

Findings

Exoplanet interior properties can be constrained by atmospheric and stellar observations.

Plausible models are needed to interpret biosignatures and rule out abiotic explanations.

Understanding Earth's biogeochemical evolution informs exoplanet habitability assessments.

Abstract

How can scientists conclude with high confidence that an exoplanet hosts life? As telescopes come on line over the next 20 years that can directly observe photons from terrestrial exoplanets, this question will dictate the activities of many scientists across many fields. The expected data will be sparse and with low signal-to-noise, which will make disentangling biosignatures from abiotic features challenging. Our Earth is not just unique in that it hosts life, it is also the only terrestrial planet with direct observations of its interior through seismic waves, and compositional evolution through field and laboratory measurements. This extensive research reveals a planet born from collisions between worlds, followed by a complicated biogeochemical evolution. Exoplanet interiors, on the other hand, can only be constrained by the following observations: 1) photometric and spectroscopic analysis of the planet's atmosphere, 2) spectroscopic and photometric analysis of the host star, and 3) companion planet properties. From these (future) data, astrobiologists must generate plausible compositional and evolutionary models that constrain a potentially habitable exoplanet's internal properties and history, provide environmental context, and rule out geochemical explanations for any putative biosignatures. The goal of this white paper is to frame the role of geophysical and geochemical processes relevant to the search for life beyond the Solar System and to identify critical, but understudied, areas of future research.