Nicholson Arwen
Physics and Astronomy, University of Exeter College of Engineering Mathematics and Physical Sciences, Exeter EX4 4QL, UK.
Philos Trans R Soc Lond B Biol Sci. 2025 Aug 7;380(1931):20240098. doi: 10.1098/rstb.2024.0098.
Searching for signs of alien life-biosignatures-on distant planets requires general hypotheses on the evolution of biospheres, and how life interacts with and influences its planet. We will not be able to visit a distant planet to directly observe any alien life and thus measuring properties of a biosphere such as organism abundance or reproduction rate is impossible. This paper provides an overview of two life-environment coupled models and analyses how their results might aid in guiding our search for biosignatures. The first model is of a simple methanogen biosphere and demonstrates that the 'strength' (i.e. the concentration of a gas in the atmosphere) of the biosignature is only very minimally impacted by the population dynamics of the biosphere. This reduces the number of assumptions needed to predict biosignatures for a given metabolic pathway. The second model is of an evolving life-environment coupled system-the Tangled Nature model-and demonstrates that the most probable trajectory for an exo-biosphere is to diversify over time owing to a mechanism known as sequential selection with memory. These models can inform our search for alien life in the galaxy.This article is part of the discussion meeting issue 'Chance and purpose in the evolution of biospheres'.
在遥远的行星上寻找外星生命的迹象——生物特征，需要关于生物圈演化以及生命如何与行星相互作用和影响行星的一般假设。我们无法前往遥远的行星直接观测任何外星生命，因此测量诸如生物体丰度或繁殖率等生物圈属性是不可能的。本文概述了两个生命 - 环境耦合模型，并分析了它们的结果如何有助于指导我们寻找生物特征。第一个模型是关于简单产甲烷菌生物圈的模型，它表明生物特征的“强度”（即大气中一种气体的浓度）仅受到生物圈种群动态的极小影响。这减少了预测给定代谢途径生物特征所需的假设数量。第二个模型是一个不断演化的生命 - 环境耦合系统——“纠缠本质”模型，它表明由于一种称为具有记忆的顺序选择的机制，外星生物圈最可能的轨迹是随时间多样化。这些模型可以为我们在星系中寻找外星生命提供参考。本文是“生物圈演化中的机遇与目的”讨论会议专题的一部分。
