[P-CG20] Future missions and instrumentation for space and planetary science

[PCG20-05] Development of an ultra-small gas chromatograph – mass spectrometer with a jet separator for future planetary exploration

*Takamitsu Iwaya^1,2, Oya Kawashima³, Haruna Sugahara³, Kazushi Asamura³, Yoshifumi Saito^3,1 (1.University of Tokyo, 2.Ball Wave Inc., 3.JAXA)

Keywords:gas chromatograph, mass spectrometer, organic molecules

Organic molecules are major analytical target to understand the prebiotic chemistry and for search for signs of past or present life in the solar system. Mass spectrometers (MSs) are widely used for in-situ analysis in a planetary exploration, there is a limit to the separation of organic molecules with various structural isomers only by mass number information. A gas chromatograph - mass spectrometer (GC-MS), which separates each molecular species by gas chromatograph (GC), is a powerful option of the analytical instrument for organic molecules. For example, the GC-MS on Cassini-Huygens shown that the atmosphere of Saturn's moon Titan may contain complex organic matter (e.g., Niemann et al., 2010), and the GC-MS on Curiosity rover detected a variety of organic molecules in the rock sample on the Mars (e.g., Niemann et al., 2010). Furthermore, GC-MSs are also planned to be installed on ESA‘s ExoMars rover (e.g., Arevalo Jr et al., 2015) and NASA’s Dragonfly (e.g., Lorenz et al., 2018), which is scheduled for launch in the near future. Thus, GC-MS is one of the most important organic chemical analyzers for future planetary exploration.
In this study, we are developing prototype of an ultra-small GC-MS system by combining a quadrupole mass spectrometer (QMS) with rods length of 10 cm and a palm-sized GC; Sylph (e.g., Iwaya et al., 2022). The GC is originally equipped with a ball SAW sensor (e.g., Yamanaka et al., 2006) that uses surface acoustic wave (SAW) on a spherical piezoelectric element with a diameter of 3.3 mm as a detector. The ball SAW sensor can nondestructively detect molecules as changes in SAW amplitude or velocity due to adsorption and desorption of molecules on a sensitive film coated on the sensor surface. Therefore, the ball SAW sensor can be connected in series to the QMS for simultaneous measurement, enabling cross-checking of quantitative and qualitative analysis.
In addition, the GC-MS for planetary exploration cannot be equipped with a large vacuum pump like a terrestrial GC-MS, so it is essential to exhaust most of the gases introduced from the GC at the GC-MS interface. On the other hand, the GC-MS interface is known to be effective in preferentially introducing analytes to the MS through its structure. We have applied the Jet Separator (JS) as the GC-MS interface, in which carrier gas is sprayed in supersonic from the GC outlet and introduced into the inlet of the MS installed on the opposite side. Analytes heavier than carrier gas (H₂ or He) have lower diffusion coefficients, and therefore sprayed out of the GC outlet at narrower angles, allowing more molecules to pass through the MS inlet. Therefore, the concentration of the analyte in the carrier gas introduced in MS is higher than that passed through the GC (enrichment effect). Previous evaluations of the prototype JS have confirmed that the concentration of analytes introduce into the MS is about 4 times concentration at the GC outlet. As the future study, we plan to optimize the structure of the prototype JS to further improve the enrichment effect, and to demonstrate its performance in combination with a GC-MS prototype.