  Detections of molecules in the atmosphere of gas giant exoplanets allow us to
investigate the physico-chemical properties of the atmospheres. Their inferred
chemical composition is used as tracer of planet formation and evolution
mechanisms. Currently, an increasing number of detections is showing a possible
rich chemistry of the hotter gaseous planets, but whether this extends to
cooler giants is still unknown. We observed four transits of WASP-80 b, a warm
transiting giant planet orbiting a late-K dwarf star with the near-infrared
GIANO-B spectrograph installed at the Telescopio Nazionale Galileo and
performed high resolution transmission spectroscopy analysis. We report the
detection of several molecular species in its atmosphere. Combining the four
nights and comparing our transmission spectrum to planetary atmosphere models
containing the signature of individual molecules within the cross-correlation
framework, we find the presence of H2O, CH4, NH3 and HCN with high
significance, tentative detection of CO2, and inconclusive results for C2H2 and
CO. A qualitative interpretation of these results, using physically motivated
models, suggests an atmosphere consistent with solar composition and the
presence of disequilibrium chemistry and we therefore recommend the inclusion
of the latter in future modelling of sub-1000K planets.
