I wasn’t really looking forward to Thursday’s ‘Extraterrestrial Sample Analysis’ talk. The title is dull because of the words sample and analysis and the extraterrestrial I felt was sure to be a false hope.

I was very wrong. It turns out that a team at the OU analyses meteorites, comet samples and even material from the Sun and Mars. I knew nothing about this topic until today’s talk which was not only extremely well-done and informative but also very cool because chunks of various objects were passed around the room.

You may remember a few years ago now when a team declared that they had found what they believed to be a fossilised bacteria on a meteorite that came from Mars. They found this meteorite in Antarctica and it had apparently fallen to the Earth 1,300 years ago. This was front-page news not too long ago and they are still unable to prove it beyond doubt. Regardless of the authenticity of the ‘lifeform’ embedded in the rock, my question was always ‘how do they know that it came from Mars?’.

I have read countless articles over the years that speak of rocks that come from space but never realised that scientists can now tell you which Solar System body they originated from! I find this quite incredible.

The science is reasonably simple once you see that every body created in the Solar System has a unique signature of Oxygen isotopes. If you don’t know what an isotope is, don’t worry. The gist is that there are several slightly different , but fairly common forms (isotopes) of the element Oxygen (with 16, 17 and 18 neutrons each). Oxygen is part of what makes rocks and most things in the Solar System are made of rocks!. So material on the Earth, formed in the exact conditions that the Earth was: i.e. the formative temperatures, pressures etc, have a particular ratio of these three types of Oxygen inside them. Martian rocks have another ratio. Every separately created body has its own magic number.

So when a rock here on Earth falls from the sky they can analyze it and keep track of where ii has come from. Over the past few decades we have been sending probes to other worlds and have analysed the Oxygen isotope ratios that have been found.

We now know that we are in possession of 40 meteorites that were once a part o the Moon. We have 31 pieces of Mars too. Several of the members of the asteroid belt are regular donators of meteorites and we have lots of chunks of Vespa and Pallas.

So the photo at the top shows an 8 kg chunk of iron that was originally a part of Vespa. It is worth around £20,000. In this picture here, a small 5g piece of Mars. It comes from the same rock that was found in Alan Hills in Antarctica, in which the bacteria was possibly found and is also worth around £20,000 - thats £4,000 per gram!

I apologise for the quality of the pictures; it was dark and I only has my cameraphone on me.

I also had explained to me during this talk something else that I had long held with suspicion. There is a theory that the Moon was formed when a giant body the size of Mars collided with the young, molten Earth. The collision threw out material which eventually formed the Moon and the Earth absorbed the colliding body, known as Theia.

This talk and the same Oxygen isotope ratios provide the reason and evidence for this theory - which is ever more generally accepted. When these ratios started to be measured, they found something startling: the rocks brought back from the Moon have exactly the same Oxygen isotope composition as Earth samples! That is to say that the Earth and Moon have to have been formed as one body and then at some point been divided. Its incredible what can be found when people look deep enough into things. Especially into rocks, it seems.