Supercritical CO2 and Subcritical H2O Analysis (SCHAN) Instru-ment: Automated Lipid Analysis for in-situ Planetary Life Detection

The search for extraterrestrial extant or extinct life in our Solar System will require more capable instrumentation and methods for detecting low abundances of biosignatures. This paper introduces the Supercritical CO2 and Subcritical H2O Analysis (SCHAN) instrument, a portable and automated system that integrates supercritical fluid extraction (SFE), supercritical fluid chromatog-raphy (SFC), and subcritical water extraction coupled with liquid chromatography. The instrument is compact, weighing 6.2 kg, making it suitable for spaceflight missions to planetary bodies. Traditional techniques, such as gas chromatography–mass spec-trometry (MS), face challenges with involatile and thermally labile analytes, necessitating derivatization. The SCHAN instrument, however, eliminates the need for derivatization and co-solvents by utilizing neat supercritical CO2 with water as an additive. This SFE-SFC-MS method gives efficient lipid biosignature separations with median detection limits of 10 pg/g (ppt) for fatty acids and 50 pg/g (ppt) for sterols. Several free fatty acids and cholesterol were detected in biologically lean samples from the Atacama Desert, demonstrating the instrument's potential for in-situ life detection missions. The SCHAN instrument addresses the chal-lenges of conventional systems, offering a compact, portable, and spaceflight-compatible tool for the analysis of biosignatures such as lipids.