  A recent article reported experimental observations of methane and CO2
clathrate formation at conditions similar to the interstellar medium (ISM),
namely 10-30 K and 10-10 mbar. The authors conducted time-dependent
reflection-absorption infrared spectroscopy (RAIRS) of vapor-deposited H2O:CH4
and H2O:CO2 mixtures and interpreted new blue and red -shifted peaks from those
of trapped CH4 and CO2 in amorphous ice, respectively, as indicative of
clathrate formation. In this Letter to the Editor, we point out potential
pitfalls and caution against the implications drawn for the ISM.
