New analysis of material collected by Apollo 17, the last of the six Apollo moon landings, 1969-1972, has identified the presence of a molecule known as a graphite whisker.
Whiskers in this sense are essentially very large carbon nanotubes. They turned up in the sample of moonrock when it was exposed to a test known as Raman spectroscopy. This is a process by which photons are shone onto a sample, causing electrons in molecules and atoms contained within the sample to rise (be excited) from one energy level to a higher one. Electrons that then relax into their original state do so by emitting a photon of light of the same frequency as the original one shone onto it. Electrons relaxing into a higher state will emit light of a higher frequency, while those settling into a lower than the original energy state will emit a lower frequency light wave. These latter two are Raman and anti-Raman effects. Just as in other forms of spectra, materials can have characteristic responses to this type of spectroscopy. That of the grey whiskers was observed here.
Whiskers have been found before, in samples of meteorites. Their appearance in the samples of moonrock are concentrated in a particular splodge, meaning they can’t’ve been delivered by the more homogeneous influence of the solar wind, which was distributed throughout the sample. Furthermore, the solar wind would not deliver carbon in this form, which requires special conditions to create it. Previous results had identified carbon in the sample, but not pinpointed its distribution nor the form that it took.
It is likely that the whiskers were delivered by an impact, either delivered straight to the surface or condensing out of the gas that followed the impact. But the most interesting facet of the discovery is cosmological as the whiskers have known effects on light that have to be taken into account given the distance light travels to get from an astronomical source to a telescope. Reddening and absorption by dust has been noted and estimated by many an observer and this may help to quantify as well as qualify part of this if we can now get an idea of the density and distribution of grey whiskers in space.