The first GC-MS Spectrum Ever Recorded on a Comet using CD column

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On the 12th of November 2014 Philae module (see picture) of European Space Agency’s (ESA) Rosetta mission landed on Comet 67P/Churyumov-Gerasimenko (known as Churi). This was the first ever soft landing on a comet.

The landing was risky and didn’t go well, considering that the spacecraft would not be able to sufficiently recharge its batteries with its dedicated solar array.

The lander has several analytical instruments onboard. One of those instruments was the COmetary SAmpling and Composition (COSAC) experiment that included a Gas Chromatograph (GC) linked to a Mass Spectrometer (MS).

With its last breath a sample was taken from the surface (however not as planned) and among other measurements a GC-MS spectrum was recorded. The only column was Chirasil-Dex (consists of cyclodextrin directly bonded to dimethylpolysiloxan; CB 10 m×0.25 mm; 0.25 μm thick film).

Due to the limited power supply this was the only gas chromatogram taken.

And now the results:

Although there was no clear molecule detected within this chromatogram owing to the extremely small amount of material that arrived in the GC oven due to the non-nominal drilling, a search (both automated and manual) was initiated for signal to look for even the smallest deviations from background noise.

A 31 m/z was found, that could be ethylene glycol, but the signal-to-noise ratio (SNR) is really low, so it is not confirming this detection. However, the retention time of pure ethylene glycol on the flight spare column (reproduced experiment in the laboratory) is a strong argument for a trace detection of the compound in these data, not to mention that ethylene glycol was also detected in several comets.

This was a pioneer measurement in space research and raised open questions that future cometary missions will aim to answer in the next decades

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