Elucidating planet formation using chondrule oxygen fugacity

利用球粒氧逸度阐明行星形成

• 批准号: 2887731
• 金额: --
• 依托单位: University of Oxford
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2023
• 资助国家: 英国
• 起止时间: 2023 至 无数据
• 项目状态: 未结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2887731
• 关键词: Elucidating; planet; formation; using; chondrule

BackgroundRecently, there has been a dramatic shift in understanding of planet formation and the circumstellar disk, following incredible images from the ALMA telescope. They have revolutionised understanding of planetary formation and caused a suite of new theories. For example, Johansen et al. 2014 suggested that regions with increased dust and gas pressure (pressure maxima) must have been present in the protoplanetary disk to form the first planetary bodies. The origin and nature of pressure maxima is poorly understood, despite their potential importance in planetary formation. The snow line, where water transitions from solid to vapour because of disk temperature, has been suggested as a possible cause of pressure maxima. If this is true, then planetary formation is a natural result of disk evolution.AimsCondensation and vaporisation of water at the snow line affect oxygen fugacity, through altering H2:H2O in the gas. fO2 records from throughout the protoplanetary disk therefore could enable us to investigate the nature and origin of pressure maxima, as well as their consequences, with depth and clarity unprecedented in planetary science research.Chondrites are made of mm sized solids from the disk, and therefore carry fO2 records dating from the early Solar System. This is demonstrated by Sutton et al. (2017), who showed that carbonaceous chondrites (CC) recorded a more positive fO2 than non-carbonaceous (NC). This is due to the parent body oxygen fugacity, as CCs incorporated more solid water than NC bodies. In order to discover the fO2 of the actual disk, we need to record data from individual chondrules, which range from 100-1000um. Their size means that high precision, high-resolution techniques are required to recover values, this has never been done before in a systematic and focussed way.In the project, I hope to use the variable partitioning of trace elements among metal, silicates and sulphides as a proxy for fO2 values in individual chondrules. This will allow me to understand the environments in which chondrules formed, giving new understanding about the snow line and its consequences in our Solar System, and the associated pressure maxima. As such, this project could unlock several key new insights into planet building processes.Research MethodologyThe redox state of elements including Fe, Cr, W, Ti, and V varies with fO2. The thermodynamic stability of these elements in molten metal, silicates and sulphides is controlled by their redox states, and therefore fO2. As a result, we can create a proxy for oxygen fugacity in individual chondrules by looking at relative concentrations of these elements within metal, silicate and sulphide. In this project, values will be estimated through a comparison of concentration inside a chondrule to the value measured in artificial samples created under a range of controlled fO2 conditions. Concentrations would be measured using high-resolution techniques, including laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), electron probe micro-analysis (EMPA), and micro X-ray fluorescence (uXRF) at Diamond Light Source.Artificial samples will be created in the Department of Earth Sciences using specialised furnaces. The proxies discussed here have been developed and used in Oxford for decades, applied to terrestrial and martian rocks, but never before on other extra-terrestrial material, highlighting the potential of this project to unlock new information on the process of planet building.

背景是，遵循来自Alma望远镜的令人难以置信的图像，对行星形成和偶色磁盘的了解发生了巨大的转变。他们彻底改变了对行星形成的理解，并引起了一系列新理论。例如，Johansen等人。 2014年建议，尘埃和气压升高（压力最大值）的区域必须存在于原星盘中，以形成第一个行星体。最大值的起源和性质在行星形成中的潜在重要性，尽管它们的起源和性质却很少。由于磁盘温度的水从固体转变为蒸气的雪线已被认为是最大压力的可能原因。如果这是真的，那么行星形成是磁盘进化的自然结果。雪线的aimscondensation和水蒸发会通过改变气体中的H2：H2O来影响氧散热。因此，来自整个原星磁盘的FO2记录可以使我们能够调查压力最大值的性质和起源及其后果，并在行星科学研究中具有深度和清晰度，而深度和清晰度则是由磁盘的MM尺寸固体制成的，因此携带早期太阳能系统的FO2记录。 Sutton等人证明了这一点。 （2017年），他表明碳质软管（CC）的fo2比非碳质（NC）更为正。这是由于母体的氧气发酵性，因为CC融入了比NC身体更多的固体水。为了发现实际磁盘的FO2，我们需要记录来自100-1000UM的单个软骨的数据。它们的大小意味着需要高精度，高分辨率技术才能恢复值，这从未以系统的和集中的方式进行。在项目中，我希望在单个软骨中使用金属，硅酸盐和硫化物之间的痕量元素的可变分区作为fo2值的代理。这将使我能够理解软骨形成的环境，从而对雪线及其在太阳系中的后果以及相关的最大压力最大化给予新的了解。因此，该项目可以将几个关键的新见解解锁到行星构建过程中。研究方法论，包括Fe，Cr，Cr，W，Ti和V在内的氧化还原状态随FO2而变化。这些元素在熔融金属，硅酸盐和硫化物中的热力学稳定性由其氧化还原态控制，因此由FO2控制。结果，我们可以通过查看金属，硅酸盐和硫化物中的这些元素的相对浓度来创建单个软骨中的氧气散热性的代理。在该项目中，将通过将软骨内部的浓度与在一系列受控的FO2条件下创建的人工样品中测量的值进行比较来估计值。将使用高分辨率技术来测量浓度，包括激光消融能力耦合等离子质谱法（LA-ICP-MS），电子探针微分析（EMPA）和微型X射线荧光（UXRF）在钻石光源中使用钻石源。在钻石光源中，将在钻石光源中使用零件samples。此处讨论的代理已经在牛津开发和使用了数十年，用于陆地和火星岩石，但从来没有在其他地球外材料上，强调了该项目的潜力解锁有关行星建设过程的新信息。