Abstract_EANA2025-67

Abstract EANA2025-67

Is There Such a Thing as an Agnostic Biosignature? A Critical Review Toward a Working Framework

Max Riekeles (1), Marie Dannenmann (2), Jacob Heinz (3), Fabian Klenner (4), Iva Vilović (5) and Jean-Pierre de Vera (6)

(1) Astrobiology Group, Center of Astronomy and Astrophysics, Technical University Berlin, Berlin, Germany, (2) Freie Universität Berlin, Department of Earth Sciences, Institute of Geological Sciences, Berlin, Germany, (3) Center of Applied Space Technology and Microgravity (ZARM), University of Bremen, Bremen, Germany, (4) Department of Earth and Space Sciences, University of Washington, Seattle, USA, (5) Stellar, Solar and Exoplanetary Physics, Leibniz-Institute for Astrophysics Potsdam (AIP), An der Sternwarte 16, Potsdam, Germany, (6) German Aerospace Center (DLR), Space Operations and Astronaut Training, Microgravity User Support Center (MUSC), Köln, Germany

The search for life beyond Earth increasingly includes calls for the identification of “agnostic biosignatures”—features or phenomena that could indicate life without assuming Earth-based biochemistry. While compelling in theory, the term “agnostic” is often used inconsistently and lacks a rigorously defined scientific concept. Here, we present the early stages of a review project aimed at critically assessing the use of “agnostic” in the astrobiological literature, with the goal of clarifying its meaning, scope, and utility. We are analyzing published astrobiology papers that use the term “agnostic,” paying close attention to how the term is invoked, whether it is defined or left implicit, and what types of biosignatures or detection approaches it is associated with. We aim to classify these usages and identify recurring themes, assumptions, and gaps.

Just as the definition of life can be seen as spectrum-like rather than binary, we propose that “agnosticism” in biosignature science might also be treated as a continuum. Rather than asking whether a biosignature is or is not agnostic, we ask: To what degree is it agnostic, and along which dimensions?

We make the first steps towards a refined and possibly quantifiable framework for biosignature agnosticism, in which we aim to bridge the gap between philosophical abstraction and technical implementation. Beyond semantic clarity, we seek to address pragmatic questions of high relevance to the development of life detection missions: What exactly makes a biosignature “agnostic”? Can we define general dimensions along which the agnosticism of any biosignature can be quantified? Is a high degree of agnosticism always desirable, or are there trade-offs in terms of reliability, testability, or interpretability? How can an agnostic approach be operationalized in real-world instrument design and data interpretation? Does agnosticism imply universality? Can a working definition guide us toward better life detection strategies, or is the term more a buzzword than a useful framework? By answering these questions and clarifying the concept of agnosticism in biosignature science, we aim to transform it from a vague aspiration into a practical tool, empowering the search for life in its many possible forms beyond Earth.