Isotopic studies of solar system formation and early development

Lead Research Organisation: University of Oxford


The research in this proposal tries to answer a string of 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 a Sun and 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. Why do we have a Sun? We think the Sun formed from a huge mass of gas and dust like the clouds you see in pictures of the Orion Nebula. Stars like our Sun are not unusual, but it is hard to see them forming. It must happen by gravity pulling all the gas and dust into one spot. But what makes that happen? Does it just - happen? Some scientists think it takes a shock wave from another star to force the gas and dust to move together so that gravity starts to become really powerful - powerful enough to get everything to collapse and form a new star. The shock wave that started it all may have come from a supernova explosion. We expect to find out by analysing meteorites to find tell-tale signs of atoms that can only have been made in a supernova. Question 2. 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 much about how the disk rotated or whether stuff was thrown on to it from the Sun. 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 3. 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 tennis court 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 baby-planets. We can also tell that rocky planets like Earth took longer - roughly 50 million years. Jupiter must have formed fast because it is made of gas that would have been lost otherwise. Now we have evidence that Mars, a small planet, actually formed very fast, at the exact same time as Jupiter should have been forming a bit further away. Maybe Jupiter scoffed up all the dust and debris and did not leave much for Mars to get any bigger. The first thing to do is to check out this evidence and see if it is right. Question 4. How did the Moon form and why is it so different from Earth? We think the Moon formed from the debris left from a collision between Earth and another planet. The debris was so hot that it was vaporised and some was lost to space. Water is not the only thing that was lost. We have evidence that some of the iron metal was boiling! We need to check out this theory with more measurements and see what else evaporated when planets were made. Question 5. Why do we have an iron core in our planet? We think the core formed from an ocean of molten rock created from the incredible heat resulting from the Moon-forming Giant Impact. Somehow the Earth must have cooled down from this amazing fireball to the pleasant place it is today. We think we can now date when different bits of the core formed. In fact, this will tell us how fast the Earth was cooling down after the Moon formed. From this we should be able to figure out when the Earth might have become okay for there to be oceans of water suitable for life to develop.


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