Isotopic studies of early planetesimals and planetary embryos

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.