Manchester Cosmochemistry 2011

我们关注太阳系的史前、形成和演化，以了解像地球这样能够支持生命的行星是否普遍存在。为了做到这一点，我们开创了新技术，并将其应用于外星物质的样本，特别是来自太空任务的样本，陨石，以及来自太阳系进入我们大气层的尘埃。我们还希望在目前计划的小行星、月球和火星任务将样本送回地球时，为最新、最灵敏的仪器和技术做好准备。我们的太阳系是由一团尘埃和气体云坍缩而形成的。我们通过太阳系前颗粒——陨石中幸存下来的尘埃颗粒——来研究它。这些揭示了太阳形成之前银河系的历史，以及前几代恒星的元素是如何形成的。陨石中这种物质比例的细微变化就像指纹一样，可以让我们识别出哪种类型的小行星为地球提供了物质。除了这些太阳系前的颗粒，我们还发现了太阳系中形成的第一批尘埃的样本。这些都是最终导致行星形成的一系列事件的第一步幸存下来的产物。我们试图了解它们是如何形成的，以及它们是如何被第一批小行星上的过程所改变的。早期太阳系中存在的某些放射性同位素的寿命非常短，它们一定是在附近形成的，最多在太阳和太阳系形成前几百万年。有相当多的证据表明，其中一些放射性同位素一定来自超新星爆炸。似乎我们的太阳系在这方面是不寻常的——它是如何影响生命起源和生存的地方的发展的？通过这种方式，我们更多地了解了恒星是如何制造物质的，以及这些物质是如何混入周围环境的。此外，早期太阳系的放射性衰变也让我们可以测量小行星和行星形成事件之间的时间间隔。在陨石中，我们有第一批小行星生命阶段的快照，这些快照告诉我们它们成长、升温、形成地核和岩石地幔以及冷却需要多长时间。“创世纪”号返回的太阳风样本被认为代表了太阳本身的组成（因此也代表了整个太阳系）。测量这些物质的组成可以为我们提供所有行星和太阳系天体演化的起点。这有助于我们理解行星，尤其是地球是如何演变成现在的样子的。彗星的样本，比如星尘号任务返回的彗星样本，以及从平流层收集的太阳系尘埃粒子，或者从南极冰中提取的彗星样本，提供了了解它们的组成的机会，以及它们是否能提供大部分地球生命所依赖的挥发性元素（在低温下凝结的东西，如水）。一旦行星被组装起来，故事就不完整了。像地球这样的类地行星自形成以来就受到了许多过程的影响。这些过程可以通过它们在火星和月球陨石等样本上留下的痕迹来研究。通过研究火星陨石，我们可以了解火星表面流体流动的时间以及这些流体来自什么样的环境。特别是，我们可以将它们与地球流体进行比较，寻找生命影响的证据。月球样本很好地模拟了未来将从小行星上带回的表面样本——通过将它们一粒一粒地拆开，我们可以了解月球表面的历史（包括大型撞击盆地形成的时间），同时开发和测试即将到来的任务所需的技术。

We focus on the prehistory, formation and evolution of our solar system, to understand whether planets capable of supporting life, like our Earth, are common. To do this we pioneer new technology and apply it to samples of extraterrestrial material, notably samples from space missions, meteorites, and dust from the solar system that enters our atmosphere. We also want to be ready with the latest and most sensitive instruments and techniques when samples are returned to Earth by currently planned missions to asteroids, the Moon and Mars. Our solar system formed by the collapse of a cloud of dust and gas. We study it via presolar grains - particles of the dust that survived inside meteorites. These reveal the history of the galaxy before our sun formed and how the elements were made in previous generations of stars,. Slight variations in the proportions of this material among meteorites act as fingerprints that will allow us to identify which types of asteroids contributed material to the Earth. Alongside these presolar grains we find samples of the first dust to form in our solar system. These are surviving products of the first step in a sequence of events that eventually led to the formation of planets. We seek to understand both how they formed and how they were modified by processes on the first asteroids.The lifetime of certain radioactive isotopes that were present in the early solar system is so short that they must have been made nearby, at most a few million years before the sun and solar system formed. There is considerable evidence that some of these radioactive isotopes had to come from a supernova explosion. It seems our solar system is unusual in this respect - how did it affect the development of places where life could originate and survive? In this way we learn more about how the stars made material and how it was mixed into their surroundings. Additionally, this radioactive decay in the early solar system also lets us measure the time between events as asteroids and planets formed. In meteorites we have snapshots of stages in the life of the first asteroids that tell us how long it took them to grow, heat up, form cores and rocky mantles, and cool. The Genesis mission returned a solar wind sample, which is believed to represent the composition of the bulk sun itself (and thus the bulk solar system). Measuring the composition of this material gives us the starting point from which all the planets and solar system bodies evolved. This helps us understand how the planets and particularly the Earth grew into their current form.Samples of comets, such as that returned by the Stardust missions and solar system dust particles collected in the stratosphere or extracted from Antarctic ice, provide the opportunity to understand their composition and whether they could have supplied a large fraction of the volatile elements (things that condense at low temperature, like water) on which life on Earth depends. The story wasn't complete once planets were assembled. Terrestrial planets like our Earth have been affected by many processes since they formed. These processes can be studied through the traces they have left on samples such as meteorites from Mars and the Moon. By studying Martian meteorites we can understand the timing of fluid flows on the Martian surface and what sort of environment these fluids had come from. In particular, we can compare them with terrestrial fluids and seek evidence of the effects of life. Lunar samples are good analogues of the surface samples that will be returned from asteroids in the future - by taking them apart grain by grain we can understand the history of the Moon's surface (including when the large impact basins formed) while developing and testing techniques that forthcoming missions will require.