Solar System Origin & Evolution at Imperial

尘埃和气体是如何形成一个能够维持生命的行星的？这是最基本的问题之一，从学生到科学家，每个人都参与其中。我们的星球形成于45亿年前，与太阳以及太阳系中的其他行星和小天体一起形成，它是迄今为止发现的唯一一个有生命进化的宜居世界。通过了解太阳系形成的细节，我们有望找到答案。我们现在对恒星及其伴随的行星系统的形成有了很多了解。我们知道恒星是由星际尘埃云和气体云坍缩形成的。行星是在被称为行星状星云的圆盘中构造的，由坍缩的气体云的旋转形成。在环绕着年轻太阳的太阳星云中，我们太阳系中的所有物体都是通过一种叫做吸积的过程产生的。然而，关于太阳系是如何形成的，还有一长串我们不知道的细节。例如，为什么所有的行星都如此不同？为什么金星是一个有着厚厚的二氧化碳大气层的地狱，火星是一个有着稀薄大气层的冰冻岩石，而地球是生命的天堂？答案就在这些行星形成之前的事件中，它就在星云的早期历史中，在这些事件中，细尘聚集在一起，形成了被称为星子的更大的物体，这些星子通过碰撞、加热和水的作用而改变，成为行星的基石。我们的研究旨在跟踪太阳系形成之前的行星物质的演化，通过太阳星云内的前体物体的组装到这些物体成为行星时的变化。太阳系前尘埃的来源为我们的太阳系提供了一个背景。尘埃来自哪种类型的恒星，这些不同来源的尘埃是如何在太阳星云中混合和变化的？这些问题可以通过分析陨石中高温、难熔元素的同位素来回答。陨石是保存早期太阳系历史的小行星岩石。陨石与宇宙尘埃粒子一起，也保留了来自太阳星云的细尘埃粒子。这些尘埃颗粒小于百万分之一米，但现代微量分析可以揭示它们的矿物质和成分。我们将研究陨石和宇宙尘埃的细粒成分，以了解太阳星云中细粒尘埃是如何开始积累的，早期热星云的加热和重复的短加热事件如何影响尘埃颗粒的聚集，以及磁场是否有助于控制太阳星云中尘埃的分布。除了构成行星的岩石和金属材料外，我们的研究还将研究对生命起源至关重要的有机材料的命运。通过新开发的方法，我们可以追踪陨石中有机物的历史，从它们在星际空间的形成，到太阳星云，再到星子。这项研究将考察岩石和金属细尘中记录的事件对早期行星物质有机成分的影响，而地球上最早的生物就是由这些物质构成的。一旦行星最终形成，它们的物质就会继续变化。我们的研究重点是火星，它提供了第二个可能出现生命的行星体的例子。我们将追溯水和有机物从行星形成到现在的演变过程。对火星地貌的研究将考察火星历史上的一个关键时期，当时全球气候变化使地球变成了干旱的荒地，以评估生物适应和生存的机会。对火星土壤中生存或有机化合物的研究将检验是否仍能在火星上探测到生命的迹象。

How did dust and gas produce a planet capable of supporting life? This is one of the most fundamental of questions, and engages everyone from school children to scientists. Our planet formed 4.5 billion years ago along with the Sun and the other planets and minor bodies in our Solar System, and it is the only habitable world yet discovered on which life evolved. By understanding the details of how our Solar System formed we can hope to find an answer.We now know much about how stars and their accompanying planetary systems form in general. We know that stars form by the collapse of interstellar clouds of dust and gas. Planets are constructed in disks known as planetary nebula formed by the rotation of the collapsing gas cloud. It was in the solar nebula, surrounding the young Sun, that all the objects in our Solar System were created through a process called accretion.There is, however, a long list of details we don't know about how our Solar System formed. Why, for example, are all the planets so different? Why is Venus an inferno with a thick carbon dioxide atmosphere, Mars a frozen rock with a thin atmosphere, and Earth a haven for life? The answer lies in events that predated the assembly of these planets, it lies in the early history of the nebula and the events that occurred as fine-dust stuck together to form larger objects known as planetesimals, and as those planetesimals changed through collisions, heating and the effects of water to become the building blocks of planets. Our research intends to follow the evolution of planetary materials from the sources of dust prior to solar system formation, through the assembly of precursor objects within the solar nebula to the alteration of these objects as they became planets.The source of presolar dust provides a context to our solar system. From what types of star was dust derived and how did dust from these different sources mix and change in the solar nebula? These questions can be answered by analysis of isotopes of high temperature, refractory elements, within meteorites - rocks from asteroids that preserve a history of the early solar system. Meteorites, together with cosmic dust particles, also retain the fine-dust particles from the solar nebula. These dust grains are smaller than a millionth of a metre but modern microanalysis can expose their minerals and compositions. We will study the fine-grained components of meteorites and cosmic dust to investigate how fine-dust began accumulating in the solar nebula, how heating by an early hot nebula and repeated short heating events affected aggregates of dust grains, and whether magnetic fields helped control the distribution of dust in the solar nebula.In addition to the rocky and metallic materials that make up the planets, our research will examine the fate of organic materials that were crucial to the origins of life. Through newly developed methods we can trace this history of organic matter in meteorites from their formation in interstellar space, through the solar nebula and into planetesimals. This research will examine the effect of events also recorded in rocky and metallic fine-dust on the organic components of the early planetary materials from which the first living things on Earth were constructed.Once the planets finally formed, their materials continued to change. Our research focuses on the planet Mars, which provides a second example of a planetary body on which life could have appeared. We will trace the evolution of water and organics from planetary formation to the present day. Research on landforms on Mars will examine a crucial period in the planet's history, when global climate change transformed the planet into an arid wasteland, to evaluate the opportunity for organisms to adapt and survive. Research on the survival or organic compounds in martian soil will test whether the signature of life can still be detected on the planet.