Planetary Origins and Evolution at Imperial (2016-2019)

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How from a cloud of dust and gas did we arrive at a planet capable of supporting life? This is one of the most fundamental of questions, and engages everyone from school children to scientists. We now know much of the answer: We know that stars, such as our Sun, form by the collapse of interstellar clouds of dust and gas. We know that planets, such as Earth, are constructed in a disk around their host star known as the planetary nebula, formed by the rotation of the collapsing cloud of dust and gas. We know that 4.5 billion years ago in the solar nebula, surrounding the young Sun, all the objects in our Solar System were created through a process called accretion. And among all those bodies the only habitable world yet discovered on which life evolved is Earth.There is, however, much that we still do not 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 in how those planetesimals changed through collisions, heating and the effects of water to become the building blocks of planets. Our research will follow the evolution of planetary materials from the origins of the first dust grains in the protoplanetary disk, through the assembly of planetesimals within the solar nebula to the modification of these objects as and after they became planets.Evidence preserved in meteorites provides a record of our Solar System's evolution. Meteorites, together with cosmic dust particles, 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 from collisions affected aggregates of dust grains; and whether magnetic fields helped control the distribution of dust in the solar nebula. We will also use numerical models to simulate how the first, fluffy aggregates of dust were compacted to become rock.As well as the rocky and metallic materials that make up the planets, our research will examine the source of Earth's water and the fate of organic materials that were crucial to the origins of life. By analysing the isotopes of the volatile elements Zn, Cd and Te in meteorites and samples of Earth, Moon and Mars we will establish the source and timing of water and other volatiles delivered to the planets in the inner Solar System. In addition, through newly developed methods we can trace the history of organic matter in meteorites from their formation in interstellar space, through the solar nebula and into planetesimals. Reading the highly sensitive record in organic matter will reveal how cosmic chemistry furnished the Solar System with the raw materials for life. Once the planets finally formed, their materials continued to change by surface processes such as impacts and the flow of water. Our research will examine how impacts of asteroids and comets shaped planetary crusts and whether this bombardment endangered or aided the emergence of life. We will also study the planet Mars, which provides a second example of a planetary body on which life could have appeared. Imagery of ancient lakes on Mars will reveal 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 and identify targets for future rover and sample return missions.