Isotopic studies of early planetesimals and planetary embryos

这项提案中的研究试图回答关于我们为什么在这里的大问题。不只是...为什么你和我在这里。不只是...为什么人类会在这里不只是...动物进化的原因甚至...生命的起源但是...为什么我们会有地球和太阳系描述这项研究将取得什么成果的最好方法是列出一些好的问题，然后解释我们正在做什么来试图找出答案。问题1.当行星还在形成的时候，乘坐宇宙飞船绕着太阳漫游会是什么样子？它会比今天复杂得多，因为我们确信行星是由气体和尘埃的旋转盘形成的。我们不知道物质是如何移动和混合的，也不知道许多早期的物体是从哪里来的。我们可以通过精确测量存在的原子种类的微小差异来发现。这些作为一种签名的磁盘位，让我们跟踪运动，而不是像一个侦探使用指纹跟踪一个强盗。问题2.行星是如何形成的？我们认为，在这个尘埃盘中，岩石和碎片以某种方式粘在一起形成了小行星，然后通过引力将更多的岩石拖到它们身上。没有人知道这是如何开始的。这是行星科学中最大的问题之一。重力作用不大，直到物体达到一个小村庄的大小。如何让东西变得像一辆汽车甚至一个足球场那么大更难理解。如果我们知道它发生得有多快，我们就可以验证一些理论。我们将尝试通过测定一些早期原行星形成的陨石的年龄来回答这个问题。问题3.为什么类地行星有铁核？我们认为地球的核心是由一片熔岩海洋形成的，这些熔岩海洋是由像月球形成的巨大撞击这样的吸积事件产生的难以置信的热量造成的。然而，我们不知道金属最初是如何形成的，以及如何从最初的原行星中分离出来。是什么提供了热量？可能是放射性能量或撞击。通过找出熔化和金属分离发生的时间，我们可以确定它是如何发生的，因为放射性同位素和放射性热产生会随着时间而衰减。

The research in this proposal tries to answer big questions about why we are here. Not just...why you and I are here. Not just...why humans are here. Not just...why animals evolved. Not even...why life started. But...why we have an Earth and Solar System at all. The best way to describe what this research will achieve is to list some good questions and then to explain what it is we are doing to try and figure out the answers. Question 1. What would it be like to roam around the Sun in a spaceship when the planets were being made? It would have been a lot more complicated than today because we are sure the planets formed from a swirling disk of gas and dust. We do not know how material moved around and mixed nor where many early objects came from. We can find out from precise measurements of small differences in the kinds of atoms present. These act as a kind of signature of bits of the disk and allow us to track motions rather like a detective uses fingerprints to trace a robber. Question 2. How were the planets created? We think that in this dusty disk the rock and debris somehow stuck together into tiny planets, which then dragged more rock onto them by gravity. Nobody knows exactly how this gets started. It is one of the biggest problems in planetary science. Gravity does not do much until an object is about the size of a small village. How to make things the size of a car or even a football pitch is harder to understand. We could test some theories if we knew how fast it happened. We will try and answer this by dating some of the meteorites that formed from early proto-planets. Question 3. Why do we have iron cores in terrestrial planets? We think the Earth's core formed from an ocean of molten rock created from the incredible heat resulting from accretion events like the Moon-forming Giant Impact. However, we do not understand how metal first formed and segregated from the first proto-planets. What provided the heat? It could have been radioactive energy or impacts. By finding out when melting and metal segregation occurred we can determine how it happened because radioactive isotopes and radiogenic heat production decay with time.