How small is small?

Our RELAX instrument measures the ratios of different xenon isotopes. We can analyse samples so small that they contain fewer than a thousand atoms of xenon. The graphic below gives you an idea of how small an amount of material a thousand atoms is.

Our RELAX instrument can analyse amounts of xenon so tiny, it's hard to imagine them!

Over the next few months we are going to be investigating the xenon in some very small samples including:

  • grains of carbonate minerals from the carbonaceous chondrite meteorite, Orgueil. This meteorite was found almost 150 years ago and has a very primitive (unchanged) chemical composition, essentially the same as the Sun’s. The carbonate minerals in Orgueil were precipitated from a liquid and by studying them we can learn more about the role of water in the early solar system.
  • nanodiamonds – these are diamonds only a few nanometers in size (a nanometer is only a millionth of a millimeter long!). These are so small that each nanodiamond contains far fewer than 500 atoms of 132Xe. This means we cannot analyse them individually. Nanodiamonds are not very well understood and it is not certain whether or not they originated outside the solar system. By measuring the isotopic ratios of different chemical “components” contained in nanodiamonds we can learn more about where they came from and what processes they have experienced.
  • silicon carbide grains – these presolar grains (older than the solar system) are found in meteorites. They are thought to have formed around other stars and provide us with samples of stellar material from AGB stars and supernovae. They are 10-100 times bigger than nanodiamonds and, by focussing on grains with unusually high xenon contents, we hope to be able to measure xenon ratios in individual silicon carbide grains. The average silicon carbide grain is thought to contain ~30 atoms of 132Xe which is not enough for us to measure. However, if the xenon in silicon carbide grains is not evenly distributed and is concentrated in fewer then 1 grain in 20, a xenon-abundant grain may contain over 600 atoms, which we can detect. Whether we succeed in detecting it or not, we will learn more about how xenon is incorporated into these grains.

We will keep you posted on the results of these experiments!

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About Jennifer Claydon

I'm a PhD student studing xenon in meteorites. I am interested in what the chemical and physical environment of the early solar system was like. I also study the timing of events in the early solar system.
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