My next paper is out now in the journal ‘Meteoritics and Planetary Science’ and it focusses on some work I did in collaboration with Ian Franchi (Open University) and Conel Alexander (Carnegie Institute of Washington). This research was the culmination of quite a few years of work and a lot of days spent in the lab, not my normal NanoSIMS lab though but in the Raman spectroscopy lab down the corridor. The Raman instrument uses a laser to analyse the type of bonding in samples and I was using it to look at the electronic configuration of the carbon present in comet and asteroid dust samples. The carbon can tell us about the type of history the sample has experienced – things like whether the rock was altered by being heated up or by interacting with water, we would say that this tells us how much ‘processing’ the sample has undergone. This is important for us to understand because it means we can start to piece together when and where the samples formed which allows us to build up a picture of the early Solar System.
The dust samples I analyse are called interplanetary dust particles (IDPs) and these are the dust samples collected by the NASA Cosmic Dust Lab using high-flying aircraft in the stratosphere. The majority of these IDP samples are thought to originate from Jupiter-family comets, but some may be from asteroids. Because of their potential cometary source, they are very important samples because we don’t have many comet samples on Earth (our only truly confirmed ones are from the NASA Stardust mission). These IDPs make up the bulk of my research but they are very tricky to analyse because they are so small (often only 10 microns in size), but they are important because of their rarity and what they can tell us about the early Solar System. Because we understand quite a lot about the processing history of meteorite samples, generally assumed to be from asteroids, from the other analyses we can perform on them using all manner of instruments, I decided to use meteorites to see if they could help me understand the IDPs, that are otherwise really hard to measure in many normal lab instruments because of their small size. I have managed to achieve a comparison between the two sets of samples in this paper and I show that the IDPs are very primitive because the Raman analyses show that their carbon is unlike that in the meteorite samples. This tells me that the comet samples have undoubtedly undergone very little processing and so retain pristine material from the early Solar System whereas the meteorites have undergone processing that has changed their original composition meaning they are not as good for telling us about the composition of the early Solar System. The primitive composition of IDPs is important because it means they reflect a starting point in terms of the composition of the Solar System so allow us to figure out how we got from there to where we are now. Although this finding is not particularly new in itself, my study shows that you can analyse the more well-known meteorites and use them as a framework to understand these very minute and rare dust samples so that we can glean more information from them. Raman is also a non-destructive analytical technique so my samples remain intact ready to go into the next instrument to reveal some more information about their history. I’ve already in fact analysed this batch of samples in the NanoSIMS and that work was published earlier this year (sorry, this paper is behind a paywall too)…it just took me a bit longer to write-up the Raman work.