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，在地球历史的前半段，大气和海洋中几乎没有氧气。在过去的十年里，我们巩固了我们对从何时开始向富含臭氧的现代环境进行漫长而复杂的过渡的理解。然而，这次所谓的“大氧化事件”（GOE）和后来O2变化的原因仍然是地球系统科学的主要谜团之一。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见解和视角。该项目将通过结合从地核到大气顶部的新数据和计算来解决这一挑战，从而开发出一个可以解释GOE的氧气地球化学循环的综合模型。这项具体的研究计划是由一种新兴的共识所推动的，即生物氧气生产早在GOE之前就开始了。如果是这样，那么GOE很可能是由氧气消耗的变化引发的。各种各样的推理都指向了地幔中臭氧反应物质通量的变化，这可能是由地球内部逐渐但不可阻挡的冷却所驱动的。然而，具体的变化及其原因尚不清楚，并存在争议。项目团队将完善和测试过去十年中提出的一些假设。要做到这一点，它必须整合：大气化学模型；无机和有机地球化学代用物记录了地球表面氧的历史；这些代用品的实验室校准；岩石圈和地幔样品的地球化学分析；地球内部结构的地震重建；地幔混合与演化地球动力学模式；热力学计算;以及矿物物理实验的发现。这些学科社区的研究人员很少合作。因此，这项工作将在科学上具有变革意义。项目团队的目标是将这种转变扩展到其成员甚至地球科学之外。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交流和融合：举办开放的在线“无墙工作坊”；对我们的合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；并开发、部署和评估教师专业发展（PD）计划，该计划的核心是科学家如何跨越不同的学科鸿沟进行沟通，以回答复杂的问题。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认识，虽然具有广泛的社会重要性，但经常被讨论，但很少实现。

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.