Formation and evolution of small planets and moons

小行星和卫星的形成和演化

基本信息

批准号：
ST/T000163/1
负责人：
Lidunka Vocadlo
金额：
$ 50.06万
依托单位：
University College London
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2020
资助国家：
英国
起止时间：
2020 至无数据
项目状态：
未结题

来源：
https://gtr.ukri.org/projects?ref=ST%2FT000163%2F1
关键词：
Formation evolution small planets moons

项目摘要

Our research aims to aid understanding of the formation and evolution of smaller terrestrial planetary cores (e.g., Mercury, the Moon, Mars and Ganymede) and the icy moons and smaller bodies of the outer solar system. We shall do this in the following ways: (i) by investigating core crystallisation processes (Project 1), (ii) by determining the physical properties of core-forming materials under the relevant conditions of pressure and temperature (Project 2) and (iii) by investigating the physical properties of icy materials (including their vibrational spectra) at high pressures and very low temperatures (Project 3).Key observables from recent and future missions are surface morphologies, spectroscopic observations, magnetic fields, gravity data and, for the Moon and for Mars (via the current InSight mission) seismic observations. The generation of magnetic fields relies on energy sources which include the release of gravitational energy and latent heat of crystallisation. Detailed understanding of these energy sources in small planetary cores is currently uncertain, as it is not even known whether they crystallise from the bottom up or from the top down, and this has first order implications for dynamo driving mechanisms; these are the main issues to be addressed by Project 1. Key deliverables of this project will be ab initio predictions over the entire pressure-temperature range relevant to the cores of Mercury, Ganymede, Mars and the Moon of: i) the adiabatic temperature gradients and melting curves of iron-alloys, which will allow us to determine the mode of core crystallisation, ii) the densities of the liquids and the liquid-solid density contrast, which contributes to gravitational energy release, and iii) the latent heat of fusion in iron alloy systems.Project 2 is predominantly experimental, and addresses major gaps in our knowledge of the fundamental physical properties of iron alloys and related materials at the conditions found within the smaller planetary cores. If we are to understand planetary evolution, geophysical modelling of planetary interiors - the outputs of which can be tested against data from spacecraft and ground-based observations - is essential, but these geophysical models will be reliable only if the physical properties of the constituent core-forming materials (essentially iron and iron alloys) are accurately known in the relevant pressure and temperature ranges. At present, this is often not the case for the conditions expected in the interiors of the Moon, Mercury, Mars and Ganymede. Surprisingly, even for the simplest approximation - a core of pure iron - the data currently available are inadequate. Key deliverables of the project will be the determination of the phase diagrams and physical properties of iron alloys, especially ternary systems such as Fe-Ni-Si and Fe-S-Si, at pressures up to ~40 GPa. Project 3 addresses a different class of materials - water ice and hydrated sulphate salts - which form the mantles of the icy bodies of the outer solar system. Application of pressure to these readily induces changes in crystal structure and, in the case of the hydrated sulphate salts, can lead to expulsion of water and transformation to a lower hydration state. The consequence of these structural changes is to produce a layered structure within the icy body. In addition, the large volume changes accompanying dehydration may result in global expansion and rifting and/or global contraction and crumpling of the surface. Key deliverables of this project include the phase diagrams, equations of state and thermal and electrical conductivities of these icy materials under the relevant conditions of pressure and temperature. In addition to this we shall determine the vibrational spectra of these various phases which will allow direct comparison with mission data.

我们的研究旨在帮助理解较小的陆地行星岩心（例如汞，月球，火星和甘木接受）以及外太阳系外部太阳系的较小物体的形成和演变。我们将通过以下方式进行此操作：（i）通过研究核心结晶过程（项目1），（ii）通过在压力和温度相关条件下确定核心形成材料的物理特性（项目2）和（iii）（iii），通过调查冰冷材料的物理性能（包括高温和非常低的温度）（包括非常低的温度）（包括非常低的项目3）。观察，磁场，重力数据以及月球和火星（通过当前的洞察任务）地震观测。磁场的产生依赖于能源，这些能源包括重力的释放和结晶的潜热。目前，对小行星岩心的这些能源的详细理解尚不确定，因为它们甚至还不知道它们是从自下而上还是从上到下结晶，这对发电机驾驶机制具有一阶含义。这些是项目1的主要问题。该项目的关键可交付成果将是对与汞，甘木甲，火星和月球相关的整个压力 - 温度范围的起初预测：引力能释放，以及iii）铁合金系统中的潜在融合热。项目主要是实验性的，并且在我们对较小的行星岩心中发现的条件下的铁合金和相关材料的基本物理特性的了解中探讨了我们了解的主要差距。如果我们要了解行星的演化，则必须对行星内部的地球物理建模（可以根据航天器和基于地面观测的数据进行测试，但这些地球物理模型只有在构成核心材料的物理特性（本质上是Ironal和Iron Alloys）是准确的，因此这些地球物理模型只有在构成核心材料的物理特性（本质上是核心形成材料）是相关的。目前，对于月球，汞，火星和甘木接受的预期条件通常并非如此。令人惊讶的是，即使对于最简单的近似值（纯铁的核心），当前可用的数据也不足。该项目的关键可交付成果将确定铁合金的相图和物理性能，尤其是诸如Fe-Ni-Si和Fe-S-Si之类的三元系统，最高约40 GPA。项目3解决了不同类别的材料 - 水冰和水合硫酸盐盐 - 构成了外部太阳系冰冷体的披风。将压力施加到这些很容易引起晶体结构的变化，在水合硫酸盐盐的情况下，可以导致水排出并转化为较低的水合状态。这些结构变化的结果是在冰冷体内产生分层结构。此外，伴随脱水的大容量变化可能会导致全球膨胀，裂开和/或全球收缩以及表面的弯曲。该项目的关键可交付成果包括在压力和温度的相关条件下这些冰冷材料的相图，状态和热电导率的方程。除此之外，我们还将确定这些各个阶段的振动光谱，这将允许与任务数据进行直接比较。