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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/M000400/1
负责人：
J Davies
金额：
$ 12.59万
依托单位：
CARDIFF UNIVERSITY
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%2FM000400%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)，我们提议成立一个由七个英国机构的科学家和三个国际合作伙伴组成的联盟，以“早期地球的不稳定遗产”为中心。地球的宜居性与其挥发物的库存和循环密切相关，而如今这些挥发物又与板块构造相结合，但我们仍然不知道我们的星球如何发现自己处于这种近乎理想的“金发姑娘”状态，其中挥发物的混合“恰到好处”。这仅仅是处于正确的太阳距离和正确的挥发物供应的问题吗？或者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的发展至关重要，并且考虑到系外行星发现领域的蓬勃发展，它们对于衡量其他地方存在生命的可能性变得格外重要。在本提案中，我们研究了地球上挥发物的早期演化如何为宜居性奠定了基础。行星通过碰撞而生长，这些剧烈事件可能导致撞击天体中携带的挥发物损失。我们将通过数值模拟探索挥发物在星子碰撞中保留或损失的条件。我们还将通过研究元素 S，尤其是它的地球化学孪生元素 Se，评估挥发物“晚”被输送到地球的可能性，即在重大碰撞的漩涡结束并且地球基本建成之后。我们将限制核心损失的过程以及该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硒起源的指纹，并将查明它是否对应于任何已知的陨石类型，或者它是否可能是由彗星传递的。月球为地球的起源提供了进一步的线索，并且询问最近精炼的月球挥发物清单的重要性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融化。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地球内部或留在大气中。岩浆海中保留的挥发物可能成为深层地幔挥发物循环的一部分，或者永久封存在深层储层中。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，这些相如果通过对流岩浆海洋中的溶解度输送到很深的地方，则可能含有挥发性元素。使用地震和建模技术，我们将评估目前在地幔最深处是否“可见”此类储存挥发物的任何残留物。由于其尺寸，核心对挥发性预算的影响可能很大，但挥发性溶解度却鲜为人知。我们将研究氢、碳和氮在高压和高温下在液态金属中的溶解度。在这个联盟中，我们还将创建一批博士生和导师，他们作为一个大团队的一部分，利用钻石中的夹杂物拼凑出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不稳定的预算和通量联系起来。该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。我们的目标是更好地了解地球最初如何成为一颗宜居行星，并为英国的进一步研究能够继续在这个令人兴奋的领域发挥引领作用奠定坚实的基础。这将是该联盟的最终遗产，并通过与其他联盟的联系，成为整个主题行动的最终遗产。