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A Belgian instrument discovered argon in a comet’s atmosphere

29 September 2015 - An article published only recently in the scientific journal Science disclosed Rosetta’s discovery of traces of argon in the atmosphere of  the comet 67P/Churyumov-Gerasimenko.

We owe this discovery to the DFMS mass spectrometer of the ROSINA instrument. This instrument, which is carried on board the Rosetta probe, was finalised in collaboration with the scientists and engineers of the Royal Belgian Institute for Space Aeronomy (BIRA-IASB). The high resolution of this instrument enables it to detect two variants of argon (isotopes 36Ar and 38Ar).

The argon detection will help scientists to arrive at a better or more profound understanding of the processes that are involved in a comet’s formation. The argon atoms seem to be easily embedded into the ice structure of the comet’s core at the very low temperatures
(-230 °C) that occur during its formation.


This discovery constitutes an additional argument in the discussion about the different ingredients comets may have brought to Earth during the formation of our solar system.

These new results bear witness of the gas’ volatility – it is much more volatile than water, which is rather comparable to nitrogen’s (N2).

Left: Typical mass spectra used for the detection of 36Ar and 38Ar by the ROSINA-DFMS instrument. These elements can only be distinguished thanks to the instrument’s high resolution.

The Science article in question: “Detection of argon in the coma of comet 67P/Churyumov-Gerasimenko,” by H. Balsiger et al.

Read more about this discovery on

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