GC, MDGC

Chromatography on Comet 67P - the First Results

Aug 31 2015 Comments 0

When Philae landed on the surface of comet 67P/Churyumov–Gerasimenko — after two bounces of up a kilometre in height — it was the culmination of a 10-year journey through the solar system. But for scientists it was just the beginning — or so they hoped.

The bounces mean that the lander didn’t end up where the research teams planned, and Philae now sits in the shadow of a cliff. The lander’s primary battery was designed to power the instruments for the first few days — after that the solar powered second battery would take over. These plans had to change due to Philae’s position — and so Philae was put in hibernation.

Planet modelling

All was not lost though. The scientists instructed a few of Philae’s instruments to sample and analyse the comet at its resting place for two days before the lander went to sleep — the initial results have been published in an issue of the journal Science.

It is thought that comets are some of the oldest relics of the early solar system and by investigating them we can gain an insight into the formation of the planets. The initial results show 67P has a porous, homogeneous interior — which researchers can use to build models of planetesimal formation and accretion processes in the early solar system.

GC/MS four billion years ago

Two of the instruments that managed to sample and analyse P67 were Ptolemy and COSAC (Cometary Sampling and Composition). These instruments analyse samples as gas chromatographs or mass spectrometers with COSAC taking samples from under Philae and Ptolemy from above the lander. For more information on Ptolemy have a look at the article, What is Ptolemy?

In GC mode, the instruments separate the sample as it passes along a tube before being ionized and detected; while as an MS instrument they vaporize and strip an electron from the sample’s molecules before the mass/charge ratio is measured. In both cases the instruments present the results as a mass spectrum — how the quantity of molecules vary according to their mass/charge ratio.

The results from Philae show that both instruments detected a range of organic molecules — some are the precursors to life — and some sulphur based compounds. One of the key molecular species in the search for life is nitrogen. In the results published so far the Ptolemy and COSAC teams have different views on the abundance of nitrogen species found — with COSAC reporting that they might be relatively abundant while Ptolemy found a lower abundance.

However, this is just the start of the work as the teams have more data to analyse and hopefully build a coherent picture of what is on 67P. There is also the prospect of the instruments collecting more data and transmitting it to Earth with Philae waking up in June, although communication with the lander is patchy.

Will David Bowie change his lyrics to ‘Is there life on 67P/Churyumov–Gerasimenko?

Image By European Space Agency via Wikimedia Commons
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