The Abiotic Background: Challenges and Opportunities in the Search for Evidence of Life Beyond Earth

The "Exploring the Abiotic Background for Life Detection" workshop was convened between March 31, 2025, and April 3, 2025, at the Carnegie Institution for Science in Washington, D.C. The workshop gathered scientists and technologists from different disciplines and career stages to consider the "abiotic background": recognizing, characterizing, and understanding the set of abiotic substances, structures, and processes that may result in potential false-positive or false-negative results in the search for evidence of life beyond Earth. To frame the conversation and ensure programmatic relevance, the workshop emphasized Ocean Worlds, while also leveraging lessons learned from modern and early Earth and Mars. Salient takeaways include the following: (1) a large abiotic background, potentially sustained over geologic timescales, could mimic, obscure, and alter biosignatures, posing risks of false positives and false negatives. Addressing these challenges requires balancing targeted and untargeted measurements within the constraints of robotic spacecraft payloads; (2) the search for signatures of life beyond Earth represents a sharp inflection point in spacecraft mission complexity and design. Stakeholders of such missions must strike a difficult balance between scientific aspirations and the technological constraints inherent to robotic spaceflight; (3) Ocean Worlds are a distinct class of habitable environments, each with unique evolutionary pathways, but collectively offering new opportunities to study organic chemical evolution; (4) there is a need to establish community-wide experimental standards and laboratory simulations to better constrain the range of abiotic chemistry and improve abiotic chemistry models to guide the design of spacecraft missions; (5) a unifying, predictive framework for abiotic chemical evolution could provide a robust baseline for interpreting mission data and guiding future exploration. This report seeks to catalyze a sustained and focused dialogue on how to best account for the abiotic background in the design of astrobiology spacecraft missions. By framing the issue both in terms of risks and scientific opportunities, we lay the groundwork for a richer, more integrated approach to the exploration of other worlds that benefits from continued cross-disciplinary input. We contend that advancing our understanding of the abiotic background now will directly inform and improve future astrobiological spacecraft missions, particularly in terms of payload selection and data interpretation.