Meteorites

"This is the core textbook for someone who is wanting to get into meteorite research professionally, so that could be an undergraduate student who’s got a project, or a post-graduate who is looking at meteorites to study. It’s a fantastic book. It’s quite recent – published in 2004 – but it’s a textbook that covers all different kinds of meteorites, all different aspects of meteorite research. This is the most up to date and the most comprehensive. It’s got lots of pictures in it, lots of tables and graphs; it’s a really good reference work. I’ve got a very well-thumbed copy on my desk. In their most basic form, a meteorite is a rock from space. They can be made out of stone or iron or a mixture of stone and iron. There are three main types. The stony ones are made out of rocky minerals, very similar to terrestrial ones. You get iron meteorites which are made mostly of iron but there’s nickel in there as well and other bits and bobs. And then the stone and iron meteorites, which are mixtures of rocky minerals and metal. Most meteorites we have on Earth come from asteroids, although there are a few from Mars and a few from the Moon and then a very few, only nine out of over 40,000 known meteorites, called the CI chondrites, which may derive from comets, but the jury’s still out. No, no, no! The asteroids live in the asteroid belt between Mars and Jupiter. These are ‘small Solar System bodies’. Asteroids are the builders’ rubble left over when the Solar System formed. These are the materials that never got into making a planet. Well, there are asteroids that cross or are near Earth’s orbit anyway, but you can get instability in the gravitational field of a Solar System object – it’s all to do with this thing called orbital resonance. When an asteroid’s orbit interacts with Jupiter’s gravitational field you can get a wobble which can cause the asteroid to be thrown out of its stable orbit, which then can result in collisions in the asteroid belt. Some of these fragments can make their way into the inner Solar System and then hit the Earth – this is the stuff we know as meteorites. The Solar System is a very, very complex place, so it’s not surprising at all that meteorites land on earth. All sorts of things. Although it’s quite a small field, there are probably about 1,000 people around the world who have meteorite research as their main research focus, and it covers a multitude of sins. Talking about the research that we do at the museum, just to give you an example of the diversity, I have colleagues who are looking at meteorites for the very first materials formed in our Solar System, and they are looking at and dating those materials and seeing what minerals they are made out of to try to get a real handle on the chemical and physical environment of the Solar System over four and a half billion years ago, prior to planets forming. These are the primordial building blocks of the Solar System. I have colleagues who are looking at meteorites from Mars to try and better understand the geology of Mars. I look at meteorites which have undergone certain amounts of geological processing but not to the extent of Earth or Mars or any of the other terrestrial planets. They are the things that were trying to become planets but didn’t; they stopped in their tracks. So looking at meteorites like that gives us an idea of the processes the Earth was undergoing at that time as well. We are also very interested in organic matter in meteorites, so some meteorites, the carbonation chondrites, contain quite considerable amounts of organic matter, and it is quite feasible that the early Earth was seeded with…well, we know that the early Earth was bombarded by meteorites and comets… Oh yes. You can see it on the surface of the Moon as well. If you think of the Earth and the Moon as one thing, as the Earth-Moon system… Well, it’s do with the Solar System sorting itself out. Well, there are still things going on. We have been whacked by large asteroids and comets in the past and undoubtedly will be in the future as well. Obviously things are a bit calmer that they were, but the Solar System is still an active place. Four billion years ago it was extremely active. So, in the first few hundred million years of the Earth’s life, material was bombarding the Earth and much of this material would have had organic matter in it. It is quite possible that the chemical building blocks you need for life, and I’m not talking about there being little bacteria on the meteorites or anything, but the chemical building blocks, all of those elements you need for life to start, could have been delivered from space by meteorites. That book, Meteorites , is actually giving you the information about the different types of meteorite – how old they are, the things that they contain – so, yes, there is information about the organic components within carbonation chondrites, for example. So if you were student trying to get into meteorites or you were starting a PhD, this book would be a very, very good starting point to give you an overview. It is a very good primary reference source."