A central need in the field of astrobiology is generalized perspectives on life that make it possible to differentiate abiotic and biotic chemical systems McKay (2008). A key component of many past and future astrobiological measurements is the elemental ratio of various samples. Classic work on Earth’s oceans has shown that life displays a striking regularity in the ratio of elements as originally characterized by Redfield (Redfield 1958; Geider and La Roche 2002; Eighty years of Redfield 2014). The body of work since the original observations has connected this ratio with basic ecological dynamics and cell physiology, while also documenting the range of elemental ratios found in a variety of environments. Several key questions remain in considering how to best apply this knowledge to astrobiological contexts: How can the observed variation of the elemental ratios be more formally systematized using basic biological physiology and ecological or environmental dynamics? How can these elemental ratios be generalized beyond the life that we have observed on our own planet? Here, we expand recently developed generalized physiological models (Kempes et al. 2012, 2016, 2017, 2019) to create a simple framework for predicting the variation of elemental ratios found in various environments. We then discuss further generalizing the physiology for astrobiological applications. Much of our theoretical treatment is designed for in situ measurements applicable to future planetary missions. We imagine scenarios where three measurements can be made—particle/cell sizes, particle/cell stoichiometry, and fluid or environmental stoichiometry—and develop our theory in connection with these often deployed measurements.

天体生物学领域的一个核心需求是对生命的普遍看法，使区分非生物和生物化学系统成为可能 McKay (2008)。许多过去和未来的天体生物学测量的一个关键组成部分是各种样本的元素比率。关于地球海洋的经典研究表明，生命在元素比例方面表现出惊人的规律性，正如雷德菲尔德最初所描述的那样（雷德菲尔德 1958 年；盖德和拉罗什 2002 年；雷德菲尔德八十年 2014 年）。自最初观察以来的工作主体已将该比率与基本生态动力学和细胞生理学联系起来，同时还记录了在各种环境中发现的元素比率的范围。在考虑如何最好地将这些知识应用于天体生物学背景时，仍然存在几个关键问题：如何利用基本生物生理学和生态或环境动力学将观察到的元素比率的变化更正式地系统化？这些元素比例如何推广到我们在自己星球上观察到的生命之外？在这里，我们扩展了最近开发的广义生理模型（Kempes 等人，2012、2016、2017、2019），以创建一个简单的框架来预测各种环境中元素比率的变化。然后我们讨论进一步推广天体生物学应用的生理学。我们的大部分理论处理都是为适用于未来行星任务的现场测量而设计的。我们想象可以进行三种测量的场景——颗粒/细胞尺寸、颗粒/细胞化学计量以及流体或环境化学计量——并根据这些经常部署的测量发展我们的理论。