My journey in science began with the study of volcanic gases, sparking an interest in the origin, and ultimate fate, of the volatile elements in the interior of our planet. How did these elements, so crucial to life and our surface environment, come to be sequestered within the deepest regions of the Earth, and what can they tell us about the processes occurring there? My approach has been to establish geochemical links between the noble gases, physical tracers par excellence, with major volatile elements of environmental importance, such as water, carbon and nitrogen, in mantle-derived rocks and gases. From these analyses we have learned that the Earth is relatively depleted in volatile elements when compared to its potential cosmochemical ancestors (e.g., ~2 ppm nitrogen compared to several hundreds of ppm in primitive meteorites) and that natural fluxes of carbon are two orders of magnitude lower than those emitted by current anthropogenic activity. Further insights into the origin of terrestrial volatiles have come from space missions that documented the composition of the protosolar nebula and the outer solar system.The consensus behind the origin of the atmosphere and the oceans is evolving constantly, although recently a general picture has started to emerge. At the dawn of the solar system, the volatile-forming elements (H, C, N, noble gases) that form the majority of our atmosphere and oceans were trapped in solid dusty phases (mostly in ice beyond the snowline and organics everywhere). These phases condensed from the proto-solar nebula gas, and/or were inherited from the interstellar medium. These accreted together within the next few million years to form the first planetesimals, some of which underwent differentiation very early on. The isotopic signatures of volatiles were also fixed very early and may even have preceded the first episodes of condensation and accretion. Throughout the accretion of the Earth, volatile elements were delivered by material from both the inner (dry, volatile-poor) and outer (volatile-rich) solar system. This delivery was concomitant with the metals and silicates that form the bulk of the planet. The contribution of bodies that formed in the far outer solar system, a region now populated by comets, is likely to have been very limited. In that sense, volatile elements were contributed continuously throughout Earth’s accretion from inner solar system reservoirs, which also provided the silicates and metal building blocks of the inner planets.Following accretion, it took a few hundred million years for the Earth’s atmosphere and oceans to stabilise. Luckily, we have been able to access a compositional record of the early atmosphere and oceans through the analysis of palaeo-atmospheric fluids trapped in Archean hydrothermal quartz. From these analyses, it appears that the surface reservoirs of the Earth evolved due to interactions between the early Sun and the top of the atmosphere, as well as the development of an early biosphere that progressively altered its chemistry.

中文翻译：

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大气和海洋的起源和早期演化

我的科学之旅始于研究火山气体，引起了人们对地球内部挥发性元素的起源和最终命运的兴趣。这些对生命和我们的地表环境至关重要的元素是如何被隔离在地球最深的区域中的，它们如何告诉我们那里发生的过程？我的方法是在稀有气体，卓越的物理示踪剂与地幔衍生的岩石和气体中具有环境重要性的主要挥发性元素（例如水，碳和氮）之间建立地球化学联系。通过这些分析，我们了解到，与潜在的宇宙化学祖先相比，地球上的挥发性元素相对较少（例如，约2 ppm的氮，而原始陨石中的数百ppm），并且自然的碳通量比当前的人为活动释放的碳通量低两个数量级。太空飞行任务进一步记录了地球挥发物的起源，这些任务记录了原太阳云和外层太阳系的组成。大气和海洋起源背后的共识正在不断发展，尽管最近总的情况已经开始出现。在太阳系黎明时，形成我们大部分大气层和海洋的易挥发元素（H，C，N，稀有气体）被困在固体多尘相中（大部分被冰雪覆盖的冰层和各处的有机物）。这些相是从原始太阳云气体中凝结而来的，和/或从星际媒体继承而来。这些在接下来的几百万年内共同积累，形成了第一个小行星，其中一些很早就进行了分化。挥发物的同位素特征也很早就被固定了，甚至可能早于凝结和积聚的第一阶段。在整个地球的积聚过程中，挥发性元素都是由内部（干燥的，挥发性较差的）和外部（富含挥发性的）太阳系的物质传递的。这种交付伴随着构成地球主体的金属和硅酸盐。在遥远的太阳系中形成的天体的贡献可能非常有限，该太阳系现在是由彗星组成的区域。从这个意义上讲 挥发性元素是在整个太阳吸积过程中不断从内部太阳系储层中贡献出来的，这也提供了内部行星的硅酸盐和金属构造基块。随着吸积，地球的大气层和海洋稳定了几亿年。幸运的是，通过分析捕获在太古宙热液石英中的古大气流体，我们已经能够获得早期大气和海洋的成分记录。从这些分析看来，由于早期太阳与大气层之间的相互作用，以及早期生物圈的发展逐渐改变了其化学性质，因此地球的表面储层得以演化。地球大气和海洋稳定需要花费数亿年的时间。幸运的是，通过分析捕获在太古宙热液石英中的古大气流体，我们已经能够获得早期大气和海洋的成分记录。从这些分析看来，由于早期太阳与大气层之间的相互作用，以及早期生物圈的发展逐渐改变了其化学性质，因此地球的表面储层得以演化。地球大气和海洋稳定需要花费数亿年的时间。幸运的是，通过分析捕获在太古宙热液石英中的古大气流体，我们已经能够获得早期大气和海洋的成分记录。从这些分析看来，由于早期太阳与大气层之间的相互作用，以及早期生物圈的发展逐渐改变了其化学性质，因此地球的表面储层得以演化。