Abundant ammonium hydrosulphide embedded in cometary dust grains

Ammonium hydrosulphide has long since been postulated to exist at least in certain layers of the giant planets. Its radiation products may be reason for red colour seen on Jupiter. Several ammonium salts, NH3 and an acid, have previously detected comet 67P/Churyumov-Gerasimenko. The acid H2S is fifth most abundant molecule coma 67P followed by NH3. In order look salt NH4+SH-, we analysed situ measurements from Rosetta/ROSINA Double Focusing Mass Spectrometer during Rosetta mission. appear independent each other when sublimating directly nucleus. However, observe a strong correlation between two species dust impacts, clearly pointing salt. We find that NH4+SH- far salt, more impacts than even water. also all salts first time fluoride. amount ammonia acids balance other, confirming mostly form embedded into grains. Allotropes S2 S3 are strongly enhanced while H2S2 its fragment HS2 not detected, which probably result radiolysis NH4+SH-. This makes prestellar origin likely. Our findings explain apparent depletion nitrogen comets maybe help solve riddle missing sulphur star forming regions.