FESD Type I: The Dynamics of Earth System Oxygenation

氧气以O2分子的形式存在于地球的大气层和海洋中，对包括人类在内的所有多细胞生命都至关重要。然而，在地球历史的前半部分，大气和海洋中几乎没有氧气。在过去的十年里，我们巩固了我们对向现代富氧环境的漫长而复杂的过渡始于何时的理解。然而，这一所谓的“大氧化事件”(GOE)以及后来O2的变化的原因仍然是地球系统科学中的主要谜团之一。解决这个问题不仅仅是学术上的兴趣，因为它将帮助我们了解地球是如何支持生命的，并为人类活动带来的一些环境挑战提供洞察力和视角。该项目将通过结合从地核到大气层顶部的新数据和计算来解决这一挑战，以开发一个可以解释GOE的O2地球化学循环的综合模型。具体的研究计划是由一个新的共识推动的，即生物产生O2的时间早于GOE。如果是这样，那么GOE很可能是由氧气消耗的变化引发的。不同的推理路线指出，来自地幔的氧气反应物质的流量发生了变化，这可能是由地球内部逐渐但不可阻挡的冷却驱动的。然而，具体的变化及其原因尚不清楚，也存在争议。项目团队将完善和测试过去十年提出的一些假设。为了做到这一点，它必须包括：大气化学模型；根据无机和有机地球化学指标编制的地球表面氧气历史记录；这些指标的实验室校准；岩石圈和地幔样本的地球化学分析；地球内部结构的地震重建；地幔混合和演化的地球动力学模型；热力学计算；以及矿物物理实验的结论。这些学科社区的研究人员很少合作。因此，这项工作将是科学上的变革。项目团队的目标是将这种变革扩展到其成员之外，甚至超越地球科学。除了典型的培训和传播活动外，我们还将通过以下方式促进跨学科的沟通和整合：举办关于O2谜题的开放式在线“无墙工作坊”；对我们的协作研究挑战和实践进行学术研究，以确定和传播跨学科团队科学的最佳实践；以及开发、部署和评估教师专业发展(PD)计划，该计划以科学家如何跨不同的学科部门沟通来回答复杂问题为中心。这些更广泛的活动，连同科学研究计划，将推动对地球系统的整体愿景，尽管具有广泛的社会重要性，但经常被讨论，但很少被实现。

Oxygen, in the form of the molecule O2, is abundant in the Earth's atmosphere and oceans, where it is vital for all multi-cellular life, including humans. However, O2 was nearly absent from the atmosphere and oceans during the first half of Earth's history. In the past decade, we solidified our understanding of when the prolonged and complex transition to the modern, O2-rich environment began. However, the cause of this so-called "Great Oxidation Event" (GOE) and later changes in O2 remains one of the major mysteries in Earth System Science. Solving it is of more than academic interest because it will help us understand how the Earth supports life, and provide insights and perspective on some of the environmental challenges posed by human activity. This project will tackle this challenge by combining new data and calculations that reach from the Earth's core to the top of the atmosphere to develop a comprehensive model of the geochemical cycle of O2 that can explain the GOE.The specific research program is motivated by an emerging consensus that biological O2 production began long before the GOE. If so, then the GOE was most likely triggered by a change in O2 consumption. Various lines of reasoning point to changes in the flux of O2-reactive material from the Earth's mantle, perhaps driven by the gradual but inexorable cooling of the planet's interior. However, the specific changes and their causes are unclear and debated. The project team will refine and test a number of hypotheses proposed in the past decade. To do so it necessarily integrates: models of atmospheric chemistry; records of Earth's surface O2 history developed from inorganic and organic geochemical proxies; laboratory calibrations of these proxies; geochemical analyses of samples from the lithosphere and mantle; seismic reconstructions of Earth's interior structure; geodynamic models of mantle mixing and evolution; thermodynamic calculations; and findings from mineral physics experiments. Researchers in these disciplinary communities rarely collaborate. Therefore, the work will be scientifically transformative.The project team aims to extend this transformation beyond its members and even beyond the geosciences. In addition to the typical training and dissemination activities, we will foster communication and integration across disciplinary boundaries by: conducting open, online "workshops without walls" on the O2 puzzle; perform scholarly research into our collaborative research challenges and practices to identify and disseminate best practices for transdisciplinary team science; and develop, deploy, and assess a teacher professional development (PD) program centered on how scientists communicate across diverse disciplinary divides to answer complex questions. These broader activities, together with the science research program, will advance a holistic vision of the Earth System that, while of broad societal importance, is often discussed but rarely realized.