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<p>Ocean worlds are important targets for life detection missions because they meet several key requirements for habitability. However, identifying potential life requires observing clear and unambiguous biosignature signals above the baseline of existing abiotic processes, which are rarely characterized rigorously enough to adequately evaluate this risk. Here we develop a quantitative framework for holistically evaluating abiotic baselines on ocean worlds to guide life detection strategies. Using Enceladus as an example, we assess the potential of using CH<sub>4</sub> isotopes and their relationship with CO<sub>2</sub>, and amino acid chirality as biosignatures, demonstrating that uncertainties in abiotic processes currently prevent hypothetical future δ<sup>13</sup>C<sub>C</sub><sub>O</sub><sub>2</sub> and δ<sup>13</sup>C<sub>C</sub><sub>H</sub><sub>4</sub> measurements from definitively inferring a biosphere on Enceladus. Neglecting the abiotic baseline thus risks ambiguous and false negative life detection claims for isotopic and chiral biosignatures, respectively. Interpreting these and other alternative biosignatures on Enceladus, Europa, Titan and similar planetary bodies therefore requires complementary geophysical observations. Abiotic ambiguity can be reduced by constraining internal temperatures to within ~10–100 °C and improving characterization of the target’s rheology, lithology, initial abiotic organic inventory and ocean transport timescales.</p>

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A framework for evaluating biosignature potential against the abiotic baseline on ocean worlds

  • 期刊论文

  • 发表日期：

    2026年6月17日

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  • Peter M. Higgins,
  • Weibin Chen,
  • Oliver Warr,
  • Lucas M. Fifer,
  • Wanying Kang,
  • Charles S. Cockell,
  • Barbara Sherwood Lollar

摘要

Ocean worlds are important targets for life detection missions because they meet several key requirements for habitability. However, identifying potential life requires observing clear and unambiguous biosignature signals above the baseline of existing abiotic processes, which are rarely characterized rigorously enough to adequately evaluate this risk. Here we develop a quantitative framework for holistically evaluating abiotic baselines on ocean worlds to guide life detection strategies. Using Enceladus as an example, we assess the potential of using CH4 isotopes and their relationship with CO2, and amino acid chirality as biosignatures, demonstrating that uncertainties in abiotic processes currently prevent hypothetical future δ13CCO2 and δ13CCH4 measurements from definitively inferring a biosphere on Enceladus. Neglecting the abiotic baseline thus risks ambiguous and false negative life detection claims for isotopic and chiral biosignatures, respectively. Interpreting these and other alternative biosignatures on Enceladus, Europa, Titan and similar planetary bodies therefore requires complementary geophysical observations. Abiotic ambiguity can be reduced by constraining internal temperatures to within ~10–100 °C and improving characterization of the target’s rheology, lithology, initial abiotic organic inventory and ocean transport timescales.