Planetary Origins and Development

科学家们现在可以探测到地球大小的行星，它们绕着我们银河系中遥远的其他恒星运行。然而，行星如何首先形成，然后发展和功能的许多基本方面是未知的或令人惊讶的不确定性。这项提案中的研究将解决科学家在这一迷人领域寻求答案的一些问题。我们从事的学科有同位素宇宙化学、岩石学、岩石物理学和低温地球化学。四位具有不同背景的首席调查员将共同努力解决五个大问题。1.是什么过程产生了构成太阳系的原子？氢和氦主要是138亿年前大爆炸的产物。但是，所有较重的元素，如钙、钛、铬、镍、锆、钼或钯呢？自20世纪50年代以来，关于这些较重的元素是如何在大恒星中合成的，已经有了公认的理论。现在有证据表明这些理论可能是错误的。我们将测量太阳系中一些最古老的物质中这些元素的同位素比例，以测试新理论。2.在类地行星中，是什么过程控制着锡等挥发性元素的数量？我们将使用最近建造的熔炉进行实验，以确定这些中等挥发性元素从熔融小行星和行星体中的相对损失和同位素分馏。我们将评估是否在拱星盘非常早期的过程负责或是否有损失从大型行星火山进入太空。这项工作也可能告诉我们一些热的太阳系外行星的大气层。3.金属芯是如何形成和区分的？地球像所有的类地行星一样，有一个铁的核心。在地球的情况下，它是部分液体，所以对流，产生磁场。这些核心是如何形成和结晶的？我们将测量陨石中钒，铬，镍，钼，钯和钨的同位素变化，这些变化与实验一起，将为早期行星胚胎以及较大物体的核心形成和结晶提供新的见解。预计这些也将揭示月球形成撞击物Theia的性质。岩石行星内部如何对轨道应力作出反应？在地球上，我们知道来自月球的潮汐力会导致行星内部移动。月球形成后不久，它就非常接近地球--它将占据三分之一的夜空！所以潮汐力要大得多。然而，我们对岩石行星如何应对如此巨大的压力知之甚少。我们将进行实验室实验来评估这一点。5.行星壳如何影响大气演变？可居住世界发展的最重要方面之一是大气层的形成。然而，最重要和最简单的元素之一氢的释放还没有得到很好的理解。气候建模和生命起源研究中出现了一些想法，我们将通过水和岩石之间的相互作用对氢气生成进行新的实验和建模研究。

Scientists can now detect Earth-sized planets orbiting other stars far away in our Milky Way galaxy. Yet, many basic aspects of how planets first form, then develop and function are unknown or surprisingly uncertain. The research in this proposal will address some of the questions to which scientists seek answers in this fascinating area. The subjects in which we work are called isotope cosmochemistry, petrology, rock physics and low temperature geochemistry. Four lead investigators with these different backgrounds will work together to address five big questions. 1. What processes generated the atoms from which our Solar System was built? Hydrogen and helium are mainly the product of the Big Bang 13.8 billion years ago. But what about all the heavier elements like calcium, titanium, chromium, nickel, zirconium, molybdenum or palladium? Since the 1950s there have been well accepted theories for how these heavier elements were synthesised in large stars. Now there is evidence these theories may be wrong. We will measure the proportions of the isotopes of these elements in some of the oldest material in the Solar System to test the new theories. 2. What processes govern the amount of volatile elements like tin in the terrestrial planets? We will perform experiments using a recently-built furnace to determine the relative losses and isotopic fractionation of such moderately volatile elements from molten asteroidal and planetary bodies. We will evaluate whether very early processes in the circumstellar disk were responsible or whether there were losses from large planetary volcanoes into space. This work may also tell us about the atmospheres of some hot exosolar planets. 3. How do metallic cores form and differentiate? The Earth like all terrestrial planets has an iron core. In the case of Earth it is partially liquid, so convects, generating a magnetic field. How do such cores form and then crystallise? We will measure isotopic variations in vanadium, chromium, nickel, molybdenum, palladium and tungsten in meteorites, which together with experiments, will provide new insights into core formation and crystallisation in early planetary embryos as well as larger objects. These are expected to also shed light on the nature of the Moon-forming impactor Theia.4. How do rocky planetary interiors respond to orbital stresses? On Earth we are aware of tidal forces from the Moon that cause the interior of a planet to move. Shortly after the Moon formed it was very close to Earth - it would have occupied a third of the night sky! So the tidal forces would have been vastly bigger. Yet we do not know much about how a rocky planet responds to such huge stresses. We will conduct laboratory experiments to evaluate this. 5. How do planetary crusts influence atmospheric evolution? One of the most important aspects of the development of habitable worlds is the formation of an atmosphere. However, the release of one of the most important and simple of elements, hydrogen, is not well understood. There are ideas emerging from climate modelling and origins of life studies that we will test with new experimental and modelling investigations of hydrogen generation through the interactions between water and rock.