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The Volatile Legacy of the Early Earth

早期地球的不稳定遗产

基本信息

批准号：
NE/M000346/1
负责人：
Geoffrey Bromiley
金额：
$ 35.29万
依托单位：
University of Edinburgh
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2014
资助国家：
英国
起止时间：
2014 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FM000346%2F1
关键词：
Volatile Legacy Early Earth

项目摘要

In response to the NERC Theme Action (TA) we propose a consortium among scientists at seven UK institutions and with three international partners centred on 'The Volatile Legacy of the Early Earth'. Earth's habitability is strongly linked to its inventory and cycling of volatiles, which today are coupled to plate tectonics, but we still have little notion as to how our planet found itself in this near-ideal 'Goldilocks' state where the volatile mix is 'just right'. Was it simply a matter of being at the right solar distance with the right supply of volatiles? Or were the details of the chemistry and dynamics of early accretion and differentiation crucial to the eventual outcome? Such questions are of critical importance for understanding our own planets development, and given the burgeoning field of exo-planet discovery, they gain extra piquancy for gauging the probability of life elsewhere. In this proposal we investigate how the early evolution of volatiles on Earth set the stage for habitability.Planets grow by collisions and these violent events may lead to loss of the volatiles carried within the impacting bodies. We will explore with numerical modeling the conditions under which the volatiles are retained or lost in planetesimal collisions. We will also assess the likelihood that volatiles were delivered to Earth 'late', namely after the maelstrom of major collisions was finished and the planet was largely constructed, by studying the element S and notably its geochemical twin, Se. We will constrain the process of loss to the core and the isotopic signature imparted by this process. We will further use isotopic measurements as finger-prints of the origin of modern Se, and will find out whether it corresponds to any known meteorite type, or if it was possibly delivered by comets. The Moon provides further clues to the origin of the Earth, and Interrogating the significance of the recently refined volatile inventory of the Moon requires new experiments under appropriate conditions.The energy generated by planetary collisions inevitably results in large-scale melting. The solubility and chemical nature of volatiles within a magma ocean controls whether or not gases are carried into the interior of the planet or left in the atmosphere. Volatiles retained in the magma ocean may become part of a deep mantle volatile cycle or become permanently sequestered in deep reservoirs. We will redress this issue with a series of experiments that simulate conditions of the early magma ocean. We will further investigate the stability of phases in the lower mantle that can potentially hold volatile elements if delivered to great depths by solubility in a convecting magma ocean. Using seismic and modeling techniques, we will assess if any remnants of such stored volatiles are currently 'visible' in the deepest mantle. The influence of the core on volatile budgets is potentially great because of its size, but volatile solubility is poorly known. We will examine the solubility of hydrogen, carbon and nitrogen in liquid metal at high pressures and temperatures.In this consortium we will also create a cohort of PhD students and supervisors who work as part of a large team to piece together the evidence for Earth's volatile evolution using inclusions trapped in diamonds. These may be the key 'space-time' capsules that can link experimental and theoretical work on early Earth evolution to present-day volatile budgets and fluxes in the deep Earth. The questions raised in this proposal are complex and require a wide range of information in order to provide meaningful answers. It is our goal to establish a much-improved understanding of how Earth initially became a habitable planet, and to build a solid foundation on which further UK research can continue to lead the way in this exciting field. This will be the ultimate legacy of this consortium, and through links to other consortia, of the entire Theme Action.

为了响应NERC主题行动（TA），我们提议在七个英国机构的科学家之间建立一个联盟，并与三个国际合作伙伴围绕“早期地球的挥发性遗产”。地球的可居住性与其挥发物的库存和循环密切相关，这与今天的板块构造有关，但我们仍然不知道我们的星球是如何发现自己处于这种近乎理想的“金发姑娘”状态的，在这种状态下，挥发性混合物“恰到好处”。这仅仅是一个问题，在正确的太阳距离与正确的挥发物供应？还是早期吸积和分化的化学和动力学细节对最终结果至关重要？这些问题对于理解我们自己的行星发展至关重要，考虑到系外行星发现领域的蓬勃发展，它们在衡量其他地方生命的可能性方面获得了额外的乐趣。在这个提议中，我们研究了地球上挥发物的早期演化是如何为可居住性奠定基础的。行星通过碰撞成长，这些剧烈的事件可能导致撞击物体内携带的挥发物的损失。我们将探索与数值模拟的条件下，挥发物保留或在星子碰撞丢失。我们还将通过研究元素S及其地球化学孪生兄弟Se，评估挥发物“晚”被传递到地球的可能性，即在主要碰撞的漩涡结束之后，地球基本上被构造。我们将限制核心的损失过程和这个过程所赋予的同位素特征。我们将进一步使用同位素测量作为现代Se起源的指纹，并将查明它是否对应于任何已知的陨石类型，或者它是否可能由彗星提供。月球为地球的起源提供了进一步的线索，而要探究最近提炼出的月球挥发物清单的意义，需要在适当的条件下进行新的实验。行星碰撞产生的能量不可避免地会导致大规模的熔化。岩浆海洋中挥发物的溶解度和化学性质控制着气体是否被带入行星内部或留在大气中。保留在岩浆海洋中的挥发分可能成为深部地幔挥发分循环的一部分，或者永久地封存在深部储层中。我们将通过一系列模拟早期岩浆海洋条件的实验来解决这个问题。我们将进一步研究下地幔中相的稳定性，如果通过对流岩浆海洋中的溶解度传递到很深的地方，这些相可能含有挥发性元素。使用地震和建模技术，我们将评估是否有任何残余的这种存储挥发物目前是“可见的”在最深的地幔。核心的影响，对挥发预算是潜在的，因为它的大小，但挥发物的溶解度知之甚少。我们将研究氢、碳和氮在高温高压下在液态金属中的溶解度。在这个联盟中，我们还将建立一个由博士生和导师组成的团队，他们将作为一个大型团队的一部分，利用钻石中捕获的包裹体来拼凑地球挥发性演化的证据。这些可能是关键的“时空”胶囊，可以将早期地球演化的实验和理论工作与当今地球深处的波动预算和通量联系起来。本提案中提出的问题很复杂，需要广泛的信息才能提供有意义的答案。我们的目标是建立一个更好的了解地球最初是如何成为一个可居住的星球，并建立一个坚实的基础上，进一步英国的研究可以继续在这个令人兴奋的领域领先。这将是这个联盟的最终遗产，并通过与其他联盟的联系，整个主题行动。