A journey from the solar nebula to planetary bodies: cycling of heat, water and organics

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In this research programme, planetary scientists and engineers from the University of Glasgow and the Scottish Universities Environmental Research Centre have joined forces to answer important questions concerning the origin and evolution of asteroids, the Moon and Mars. The emphasis of our work is on understanding the thermal histories of these planetary bodies over a range of time and distance scales, and how water and carbon-rich molecules have been transported within and between them.One part of the consortium will explore the formation and subsequent history of asteroids. Our focus is on primitive asteroids, which have changed little since they formed 4500 million years ago within a cloud of dust and gas called the solar nebula. These bodies are far smaller than the planets, but are scientifically very important because they contain water and carbon-rich molecules, both of which are essential to life. We want to understand the full range of materials that went to form these asteroids, and where in the solar nebular they came from. Although they are very primitive, most of these asteroids have been changed by chemical reactions that were driven by liquid water, itself generated by the melting of ice. We will ask whether the heat needed to melt this ice was produced by the decay of radioactive elements, or by collisions with other asteroids. The answer to this question has important implications for understanding how asteroids of all types evolved, and what we may find when samples of primitive asteroids are collected and returned to Earth. Pieces of primitive asteroids also fall to Earth as meteorites, and bring with them some of their primordial water, along with molecules that are rich in carbon. Many scientists think that much of the water on Earth today was obtained from outer space, and consortium researchers would like to test this idea. In order to understand the nature and volume of water and carbon that would have been delivered by meteorites, we first need to develop reliable ways to distinguish extraterrestrial carbon and water from the carbon and water that has been added to the meteorite after it fell to Earth. We plan to do this by identifying 'fingerprints' of terrestrial water and carbon so that they can be subtracted from the extraterrestrial components. One of the main ways in which this carbon was delivered to Earth during its earliest times was by large meteorites colliding with the surface of our planet at high velocities. Thus we also wish to understand the extent to which the extraterrestrial carbon was preserved or transformed during these energetic impact events.The formation and early thermal history of the moon is another area of interest for the consortium. In particular, we will ask when its rocky crust was formed, and use its impact history to determine meteorite flux throughout the inner solar system. To answer these questions we will analyse meteorites and samples collected by the Apollo and Luna missions to determine the amounts of chemical elements including argon and lead that these rocks contain. Information on the temperature of surface and sub-surface regions of Mars can help us to understand processes including the interaction of the planet's crust with liquid water. In order to be able to explore these processes using information on the thermal properties of martian rocks that will soon to be obtained by the NASA InSight lander, we will undertake a laboratory study of the effects of heating and cooling on a simulated martian surface. Hot water reaching the surface of Mars from its interior may once have created environments that were suitable for life to develop, and minerals formed by this water could have preserved the traces of any microorganisms that were present. We will assess the possibility that such springs could have preserved traces of past martian life by examining a unique high-altitude hot spring system on Earth.