Development of a gas chromatography mass spectrometry method for assembly theory measurements
Authors: Asche Silke , Weiss Gabriella M. , Sequin Frederic , Graham Heather V. 
Published: July 2024

Assembly theory (AT) is a proposed framework for an agnostic biosignature detection method based on the idea that life produces complex objects in abundance1. The complexity assignment for an object is based on the number of required steps to make the object and derived from graph theory. The consideration for the copy number of that object in the specific environment is based on the idea that functional systems selectively produce objects that are favorable for the systems stability or survival.While the underlying theory of this life detection method is well established, more experimental work is required to prove the theory&#8217;s experimental capabilities.Figure 1: Depiction of the required steps for an agnostic biosignature method for life detection. Development of the idea, laboratory testing and deployment.Experimental data has been reported from spectroscopy instruments (IR and NMR) as well as mass spectrometry (MS) instruments (direct injection ESI-MS and LC-MS)2-3. While MS is a promising technology and could enable biosignature research, LC-MS is a technique currently not developed for space exploration due to limitations rising from using solvent as analyte carrier due to their weight but also due to problems creating gradient mixtures in micro gravity.Gas chromatography (GC)-MS is a solution for this problem as no solvent carrier is required and it is a well-established and tested tool for space exploration4-5. It has been deployed in 1968 in the Viking mission, is currently used on Curiosity&#8217;s SAM instrument and will be deployed with MOMA on the Rosalind Franklin Rover, with DraMS on Dragonfly and with MASPEX on Europa Clipper6. Because of the amount of experience collected in GC-MS spaceflight and the fact that a higher number of future missions carry this specific instrument, an experimentally tested GC-MS agnostic biosignature method is needed now. We present preliminary results for AT measurements on a GC-Orbitrap-MS. Orbitrap mass spectrometer are widely used for compound identification as they allow for very precise analysis of intact molecules as well as for fragments after additional collision steps. This specific type of MS is currently under development for future lander missions6.Due to the differences between GC-MS and LC-MS or direct infusion, developing a method for AT calculation required consideration towards several parameters. The noise floor reduction and blank subtraction methods needed to be adjusted for GC-MS. &#160;Concentration limits were investigated to understand the AT capabilities of the instrument for the specific analytes. Further the choice of columns (polar/ non-polar) and derivatization methods and their impact on the AT calculation result will be presented. Developing an agnostic biosignature method that can be used on instruments that are already in space collecting data offers new opportunities in biosignature development and interpreting collected data.&#160;References:1. Sharma, A., Cz&#233;gel, D., Lachmann, M. et al. Assembly theory explains and quantifies selection and evolution. Nature 622, 321&#8211;328 (2023). https://doi.org/10.1038/s41586-023-06600-92. Jirasek, M., Sharma, A., Bame, J. R. et al.Investigating and Quantifying Molecular Complexity Using Assembly Theory and Spectroscopy. ACS Central Science (2024). https://doi.org/1021/acscentsci.4c001203. Marshall, S.M., Mathis, C., Carrick, E. et al.Identifying molecules as biosignatures with assembly theory and mass spectrometry.&#160;Nat Commun&#160;12, 3033 (2021). https://doi.org/10.1038/s41467-021-23258-x4. Mahaffy, P.R., Webster, C.R., Cabane, M. et al. The Sample Analysis at Mars Investigation and Instrument Suite. Space Sci Rev 170, 401&#8211;478 (2012). https://doi.org/10.1007/s11214-012-9879-z5. Akapo, S. O., Dimandja, J.-M.D., Kojiro, D. R. et al. Gas chromatography in space. Journal of Chromatography A, 843, 1&#8211;2, 147-162 (1999).https://doi.org/10.1016/S0021-9673(98)00947-96. Luoth, C., Mahaffy, P., Trainer, M. al. Planetary Mass Spectrometry for Agnostic Life Detection in the Solar System. Frontiers in Astronomy and Space Sciences, 8 (2021). https://doi.org/10.3389/fspas.2021.755