Fig. 1. DFMS mass spectra in the m/z ranges of 36 and 38.

The spectra demonstrate the clear identification of the two isotopes ³⁶Ar and ³⁸Ar and of the interfering molecules. The exact m/z locations are given in the text. The spacecraft background spectra were obtained before the cometary signal became apparent (2 August 2014, heliocentric distance of 3.6 AU, almost 800 km from the nucleus).