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.

为了回应NERC主题行动（TA），我们提出了英国七个机构的科学家之间的财团，并以三个国际合作伙伴为中心，以“地球早期的动荡遗产”为中心。地球的宜居性与挥发物的库存和循环密切相关，该挥发物与板块构造相结合，但是我们仍然对我们的星球在这种近乎理想的“ Goldilocks”状态中如何找到自己的地球有几乎没有概念，而挥发性混合物则“正确”。仅仅是在正确的太阳距离上与挥发物的正确供应的问题？还是早期积聚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，并且鉴于Exo-Allanet Discovery的蓬勃发展领域，它们为衡量其他地方的生命概率而获得了额外的灵感。在这一提议中，我们调查了地球上挥发物的早期演变是如何为居住性奠定了基础。行星随着碰撞和这些暴力事件的增长可能导致撞击物体内携带的挥发物的丧失。我们将通过数值建模探索挥发物在行星碰撞中保留或丢失的条件。我们还将评估挥发物被传递到地球“迟到”的可能性，即大规模碰撞的漩涡完成后，通过研究元素S，尤其是其地球化学双胞胎SE，就可以在很大程度上建立了地球。我们将将损失过程限制为核心和该过程赋予的同位素签名。我们将进一步使用同位素测量值作为现代SE起源的手指印刷，并确定它是否对应于任何已知的陨石类型，还是彗星可能会传递。月亮为地球起源提供了进一步的线索，并审问了最近精炼的挥发性月球清单的重要性，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行星的内部或留在大气中。保留在岩浆海洋中的挥发物可能成为深幔挥发周期的一部分，或者在深层储层中永久隔离。我们将通过模拟早期岩浆海洋条件的一系列实验来纠正这个问题。我们将进一步研究下地幔中相位的稳定性，如果通过在令人对流的岩浆海洋中的溶解度传递到巨大的深度，则可能存在挥发性元素。使用地震和建模技术，我们将评估当前在最深的地幔中“可见”此类存储的挥发物的任何残余物。核心对波动预算的影响可能很大，因为它的尺寸很大，但是易变的溶解度是鲜为人知的。我们将在高压和温度下检查液体金属中氢，碳和氮的溶解度。在该财团中，我们还将创建一组博士生和主管，这些学生和主管是大型团队的一部分，以将地球挥发性进化的证据拼凑在一起，并使用包含在钻石中。这些可能是可以将地球早期进化的实验性和理论工作与当今的挥发性预算和深层地球中的通量联系起来的关键“时空”胶囊。本提案中提出的问题很复杂，需要大量信息才能提供有意义的答案。我们的目标是对地球最初如何成为一个可居住的星球建立深刻的理解，并建立一个坚实的基础，在该基础上，英国进一步的研究可以继续在这一令人兴奋的领域中引领道路。这将是该财团的最终遗产，并通过与整个主题行动的其他财团的联系。