Spatial and temporal scales of aqueous alteration in icy planetesimals

冰冷星子中水相变化的时空尺度

基本信息

批准号：
ST/G001693/1
负责人：
Martin Robert Lee
金额：
$ 44.83万
依托单位：
University of Glasgow
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2009
资助国家：
英国
起止时间：
2009 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=ST%2FG001693%2F1
关键词：
Spatial temporal scales aqueous alteration

项目摘要

This aim of this research programme is to understand better the evolution of the small bodies of rock and ice that lie in the outer parts of the solar system. These bodies are collectively called 'planetesimals', and are of great interest to planetary scientists because they have remained unchanged for most of the 4,500 million year history of the solar system. Thus, they can tell us much about how it formed and developed. This research project is concerned with planetesimals that contained liquid water, probably for a brief period soon after their formation. Pieces of these planetesimals have fallen to Earth as meteorites called 'carbonaceous chondrites', which are highly valued by scientists because their chemical compositions indicate that they are least altered rocks available for study. However, despite their very primitive chemistry, the carbonaceous chondrites are made mainly of minerals that were formed by water reacting with their parent planetesimal, and this process of aqueous alteration would be expected to have also modified the chemical composition of the rock. This contradiction between a primitive chemistry and secondary mineralogy can only be explained if water within the planetesimal was static. However, recent computer simulations of planetesimal evolution consistently predict that only the smallest bodies could have contained static water and in most it must have flowed through the rocks, modifying their chemical compositions along its path. In this research programme we will test the assumptions and predictions of these models by obtaining new information on the behavior and history of water within planetesimals using one group of carbonaceous chondrites called the CMs. These meteorites contain small crystals of minerals called carbonates that crystallized from the water. By examining the compositions, internal structures and distributions of carbonate crystals using a range of microscope-based techniques, we will address the following questions: Was the water stationary or did it flow in the same way that hot water moves through rocks on Earth? Did the water exist for only a brief period in a small body or was it present for millions of years within a larger planetesimal? Did planetesimal interiors contain water or was it present only close to their surface? Results of this research will increase our understanding of how planetesimals formed and evolved and will enable us and other scientists to assess and potentially modify the computer models of planetesimal interiors. Ultimately this work is significant for our understanding of the early history of the solar system but also of the present-day composition and internal structure of comets and asteroids. These bodies are currently the focus of a great deal of international research activity, having been visited recently by several space probes, and are targets for future unmanned and possibly manned exploration.

该研究计划的这个目的是更好地了解太阳系外部的岩石和冰的小体的演变。这些尸体集体称为“行星”，对行星科学家的兴趣非常重要，因为在太阳能系统的45亿年历史中，它们的大部分历史中的大部分都保持不变。因此，他们可以告诉我们有关其形成和开发的方式。该研究项目与含有液态水的行星有关，可能是在它们形成后不久的短时间内。这些行星的碎片已像陨石一样落在地球上，称为“碳质软管”，科学家高度重视它们，因为它们的化学成分表明它们是可用于研究的最小变化的岩石。然而，尽管它们非常原始化学反应，但碳质软管主要是由矿物质制成的，这些矿物是由水与其母的行星反应形成的，预计这种水性蚀变的过程也将修改岩石的化学成分。只有在地球内的水是静态的，才能解释原始化学与二级矿物学之间的这种矛盾。但是，最近对行星进化的计算机模拟始终预测，只有最小的身体才能包含静态水，并且在大多数情况下，它必须流过岩石，从而改变其化学成分沿其路径。在本研究计划中，我们将使用一组称为CMS的碳质软管获得有关行星范围内水的行为和历史的新信息来测试这些模型的假设和预测。这些陨石包含从水结晶的碳酸盐矿物质的小晶体。通过使用一系列基于显微镜的技术检查碳酸盐晶体的内部结构和分布，我们将解决以下问题：是水静止还是以与热水在地球上岩石移动的方式相同的方式流动？水是否仅在一个小体中存在很短的时间，还是在较大的行星中存在数百万年的水？行星内部的内饰是否含有水，还是仅存在靠近其表面？这项研究的结果将提高我们对行星的形成和进化的理解，并使我们和其他科学家能够评估和可能修改行星室内装饰的计算机模型。最终，这项工作对于我们对太阳系的早期历史的理解以及当今彗星和小行星的内部结构而言至关重要。这些机构目前是许多国际研究活动的重点，最近有几次太空探测器访问了，并且是未来无人驾驶和可能被驾驶勘探的目标。