How to Study a Meteorite?

Basically we wanted to study first its surface morphology to find some amazing features caused by the atmospheric entry and then measure its elemental composition to find out about its past. The preparations for the first part were rather simple as we just had to clean the small meteorite from organic and inorganic contamination by ultrasonification in deionized water and organic solvents. After that, the meteorite was attached to a special holder with a vacuum-friendly carbon tape and inserted into a very expensive scanning electron microscope that originally costed slightly less than million euros. In that device, we scanned row by row across the meteorite and measured the generated signals. From those signals the computer generated an image of the surface with far greater resolution than ever possible with a conventional optical microscope. When we started getting the first images, our jaws literally dropped to the floor. It was nothing we had ever seen before because it was indeed something out of this world. The meteorite was covered with crystalline microscopic features and I shit you not – one of them actually looked like a duck :D
Anyhow, our next goal was to study the composition of the meteorite and for that purpose we had to create a high quality polished surface with as much flat area as possible. This was achieved by drowning the meteorite in a vacuum epoxy and cut in half with special tools. After a final polish and cleaning the sample was ready for elemental analysis. In our first attempt we used energy dispersive X-ray microanalysis in the same scanning electron microscope, where we essentially bombarded the meteorite with high velocity electrons and measured the resulting characteristic X-rays. Those measurements revealed that the meteorite consisted mostly of iron and nickel but oddly enough we also saw a small content of iridium. This truly peaked our interest because the asteroid that killed the dinosaurs 65 to 66 million years ago also contained iridium. In order to verify the presence of that element, we had to do another measurement with an instrument that is solely dedicated to precise elemental analysis – a wavelength dispersive X-ray spectrometer. In that device, the meteorite was irradiated with energetic X-rays and the resulting characteristic X-rays that originated from the sample, were measured. This measurement unfortunately showed us that we actually didn’t have iridium in our sample but instead the previously observed peak in the spectrum belonged to gallium instead. But this was also exciting for us because we use gallium as a source for our ion gun.
This study was carried out by Captain Corrosion OÜ in collaboration with the FMTDK doctoral school and the department of materials science of the Institute of Physics, University of Tartu.