The evolution of the protosolar disk

原太阳盘的演化

基本信息

批准号：
PP/D001714/1
负责人：
Sara Russell
金额：
$ 21.4万
依托单位：
Natural History Museum
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2007
资助国家：
英国
起止时间：
2007 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=PP%2FD001714%2F1
关键词：
evolution protosolar disk

项目摘要

The aim of this proposal is to determine the formation environment of the solid materials that later made up the planets in the Solar System. From studies of meteorites, combined with astronomical observations and modelling, we believe that the planets formed from a disk around the Sun (the protosolar disk) composed of dust and gas. Much of this disk spiralled into the forming Sun, but some remained, that probably accreted firstly into mm-cm sized solid lumps that went on to become part of bigger and bigger objects and eventually into the terrestrial planets. These millimetre-sized objects have been preserved inside some meteorites and are called chondrules. By looking at them in detail we can learn about what the disk was made of, how these first solids formed and how the conditions in the disk may have evolved. The chemistry / specifically, the abundance of each of the elements- of chondrules can tell us something about their origins and evolution. Each element has a different chemical character, and their behaviour will be dictated by conditions such as temperature, pressure and the amount of oxygen and hydrogen present. By measuring the abundance of as many elements as possible, we can build up a picture of the conditions in which the chondrules formed, as well as an idea about what the chondrule precursors were made of. Some elements have more than one isotope- nuclei of the same element that have different mass. Isotopes of a single element will have broadly the same chemical properties, but will slightly differ in their physical properties, for example their volatility. We plan to measure the isotopic composition of the four most common elements silicon, iron, oxygen and magnesium in chondrules, we can build up a better picture of their history. In addition to thermal history, a couple of the elements we propose to measure for isotopes have some special properties. The oxygen isotopic composition of solar system objects is very diverse, and points to an initial variation in the composition of solar system oxygen. This initial heterogeneity can be used as a tracer of the original composition of the solid. Magnesium isotopes are also particularly interesting for another reason. The isotope 26Mg can be radiogenic, formed from the decay of the radioactive, and now extinct, isotope 26Al. Monitoring the abundance of 26Mg can tell us something about the distribution of 26Al, a potentially critical heat source, in the early solar system. These measurements can also potentially tell us something about timescales / early-formed objects are likely to have contained more 26Al when they solidified than solids that formed when most of the 26Al had already decayed away. Measuring silicon and iron isotopes is somewhat more exploratory / there are not very many measurements already reported of these two elements, and so we do not already have a good picture of what diversity in isotopic composition we can expect. It is likely that these isotopes can be used as tools to determine the thermal history of chondrules and how they interacted with the neighbouring gas (that may have contained some Fe and Si in gaseous form). There is a lack of accurate, systematically acquired data about the chemistry and isotopic composition of these objects, and especially of several of these parameters on the same object. By building up a database of the major and minor element composition of these objects, and the isotopic composition of the major elements oxygen, silicon, iron and magnesium, we can determine the diversity of compositions of material in the accretion disk. This in turn will allow us to determine the degree of mixing and turbulence in the disk, the timescales of formation of disk solids and the thermal history of these objects. We can use this information to compare to astronomical disk observations, and assess if there was anything unusual about the evolution of our own planetary system.

该提案的目的是确定后来构成太阳系行星的固体材料的形成环境。通过对陨石的研究，结合天文观测和建模，我们认为行星是由尘埃和气体组成的围绕太阳的圆盘（原太阳盘）形成的。这个圆盘的大部分螺旋状进入正在形成的太阳，但还有一些留下来，它们可能首先吸积成毫米-厘米大小的固体块，然后成为越来越大物体的一部分，最终形成类地行星。这些毫米大小的物体被保存在一些陨石内部，被称为球粒。通过详细观察它们，我们可以了解圆盘是由什么构成的，这些最初的固体是如何形成的，以及圆盘中的条件是如何演变的。球粒的化学成分/具体来说，每种元素的丰度可以告诉我们一些关于它们的起源和演化的信息。每种元素都有不同的化学特性，它们的行为取决于温度、压力以及氧和氢含量等条件。通过测量尽可能多的元素的丰度，我们可以了解球粒形成的条件，以及了解球粒前身的成分。有些元素具有多个具有不同质量的同一元素的同位素核。单一元素的同位素具有大致相同的化学性质，但其物理性质略有不同，例如挥发性。我们计划测量球粒中四种最常见元素硅、铁、氧和镁的同位素组成，我们可以更好地了解它们的历史。除了热历史之外，我们建议测量同位素的几种元素还具有一些特殊性质。太阳系天体的氧同位素组成非常多样化，这表明太阳系氧的组成存在初始变化。这种初始异质性可以用作固体原始成分的示踪剂。镁同位素也特别令人感兴趣还有另一个原因。同位素 26Mg 可能是放射性的，由放射性同位素 26Al 衰变形成，现已灭绝。监测 26Mg 的丰度可以告诉我们有关 26Al（一种潜在的关键热源）在早期太阳系中的分布情况。这些测量结果还可以告诉我们一些有关时间尺度的信息/早期形成的物体在凝固时可能含有比大多数 26Al 已经衰变时形成的固体更多的 26Al。测量硅和铁同位素在某种程度上更具探索性/这两种元素的测量报告并不多，因此我们还没有很好地了解我们可以预期的同位素组成的多样性。这些同位素很可能可以用作确定球粒热历史以及它们如何与邻近气体（可能含有一些气态形式的铁和硅）相互作用的工具。缺乏关于这些物体的化学和同位素组成的准确、系统获取的数据，特别是同一物体上的其中几个参数。通过建立这些物体的主量元素和微量元素组成以及主量元素氧、硅、铁、镁的同位素组成的数据库，我们可以确定吸积盘中物质成分的多样性。这反过来将使我们能够确定圆盘中的混合和湍流程度、圆盘固体形成的时间尺度以及这些物体的热历史。我们可以利用这些信息与天文盘观测进行比较，并评估我们自己的行星系统的演化是否存在任何异常。

项目成果

期刊论文数量（10）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

Insights into the thermal history of AOAs in carbonaceous chondrites

深入了解碳质球粒陨石中 AOA 的热历史

DOI：
发表时间：
2007
期刊：
METEORITICS & PLANETARY SCIENCE
影响因子：
2.2
作者：
Howard L. E.
通讯作者：
Howard L. E.

Origin and chronology of chondritic components: A review

DOI：
10.1016/j.gca.2008.09.039
发表时间：
2009-09-01
期刊：
GEOCHIMICA ET COSMOCHIMICA ACTA
影响因子：
5
作者：
Krot, A. N.;Amelin, Y.;Yin, Q. -Z.
通讯作者：
Yin, Q. -Z.

A nebula setting as the origin for bulk chondrule Fe isotope variations in CV chondrites

DOI：
10.1016/j.epsl.2010.05.029
发表时间：
2010-08
期刊：
Earth and Planetary Science Letters
影响因子：
5.3
作者：
D. Hezel;A. Needham;R. Armytage;B. Georg;R. Abel;E. Kurahashi;B. Coles;M. Rehkämper;S. Russell
通讯作者：
D. Hezel;A. Needham;R. Armytage;B. Georg;R. Abel;E. Kurahashi;B. Coles;M. Rehkämper;S. Russell

EVOLUTION OF CHONDRULE MG ISOTOPE COMPOSITIONS DURING MULTIPLE HEATING EVENTS

多次加热事件期间球粒 MG 同位素组成的演变