Infrared Spectra of Organic and Salt-Bearing Ices under Titan Conditions: Constraints on Detection of Ocean Materials

Titan, with its organic rich atmosphere and global subsurface ocean, has long been considered a7 prime candidate to potentially host life beyond Earth. The detection of species frozen within8 ocean fluids when extruded on the surface via cryovolcanism, or other means, presents an9 intriguing possibility for the characterization of the ocean composition and its habitability. To10 this end, we present infrared (IR) reflectance spectra of organic/water ice mixtures under Titan11 surface conditions, which could potentially serve as evidence of life in the ocean below, as well12 as determination of salts or other nutrients that might be present. For a subset of these species, a13 dilution series of spectra is presented to begin to constrain the limits of detection for Titan.14 Ultimately, this work shows that IR reflectance spectroscopy has little hope of detecting such15 species frozen in water ice from orbit, or even from a landed spacecraft. Such detections would16 require more sensitive in situ analytical techniques such as fluorescence or mass spectrometry,17 along with the sampling systems such methods would require.