Quantitative study of methane-nitrogen mixed clathrates using gas chromatography and Raman spectroscopy for their detection in icy surfaces of the outer solar system

Multicomponent clathrates may be present at the surface of icy bodies. However, their potential identification remains difficult in the absence of reliable spectral data. In this work, we focus on clathrates synthesized in laboratory from a gas mixture of N2 and CH4, which are particularly relevant for Titan, Triton or Pluto, and investigate their spectral signatures at low temperature (~94 K) and low pressure (down to 2 × 10−6 MPa). The molar composition of the synthesized clathrates for various gas composition were monitored using gas chromatography. Raman scattering from 50 to 4000 cm−1 was carried out, in order to identify discriminating criteria for possible detection by remote and in-situ observations of icy bodies of the outer Solar System. Our experimental results indicate that the identification of CH4-N2 binary clathrate from in-situ Raman spectroscopy may provide a clear determination of clathrate composition. •Molar compositions of CH4-N2 clathrates were determined by gas chromatography.•Dinitrogen contributes to the trapping of methane into CH4-N2 clathrates.•For Titan surface conditions, CH4 is preferentially sequestered in the clathrate.•Raman spectroscopy produce unique spectral fingerprints of CH4-N2 clathrates.•Compositional characterization of clathrates by Raman scattering is very reliable.