ORIGIN: Towards in situ Laser Desorption Mass Spectrometry of Amino Acids, PAHs and Lipids on Ocean Worlds
A high priority topic in current space science is the detection of life, past or present, on Solar System bodies other than earth. Reliable (in situ) detection of signatures of life poses several major challenges including, but not limited to, robust and simple instrumentation suitable for flight, measurement sensitivity and dynamic range coverage, and identification of compounds which are not expected to be of importance prior to the mission. Several Solar System bodies have been (and are currently still being) investigated for the presence of extinct or extant life. More recently, two new astrobiological targets were uncovered, as the presence of oceans underneath the ice shells of Enceladus (Saturn system) and Europa (Jupiter system) was revealed by the Galileo and Cassini-Huygens missions . These so-called “Ocean worlds” are interesting targets for the detection of signatures of life, either in the oceans themselves or preserved within (near) surface ice, where they are protected from harsh radiation environment. Among the list of accepted biosignatures, amino acids, lipids, and polycyclic aromatic hydrocarbons (PAHs) show the highest molecular stability, potentially retaining their molecular structure for several billions of years. Detection and identification of these molecules is therefore of great interest for space agencies aiming to search for signs of life on Ocean Worlds .
In this contribution, we present the current measurement capabilities of our novel prototype laser desorption mass spectrometer (LDMS) called ORIGIN (ORganics Information Gathering Instrument). This system is designed for in situ space exploration missions and constructed at the University of Bern . The fully operational space prototype LDMS instrument allows for detection and identification of major and minor biomolecules. The design of the instrument is light-weight, compact and simple, and has low energy consumption, which will allow for in situ identification of major and minor biomolecules. ORIGIN is comprised of a miniature reflectron-type time-of-flight mass analyser (160 mm x Ø 60 mm) and a nanosecond pulsed laser system (wavelength λ = 266 nm, pulse repetition rate of 20 Hz, pulse width of τ ~ 3 ns) for the gentle desorption of analytes . Various sample solutions of amino acids standards, amino acids extracted out of permafrost materials, PAHs, and lipid standards were measured. The results of the tested amino acids are already published in recent research ; we extend these studies with measurements on amino acids extracted from permafrost material. Additional measurement campaigns were performed to evaluate optimal laser desorption conditions, the limits of detection, and the influence of sample holder substrate. We will discuss the measurement procedures and results of several investigations into the performance of ORIGIN when it comes to detection of several biosignatures, including amino acids, PAHs, and lipids. ORIGIN is a powerful alternative technique to those more commonly/traditionally applied in space exploration missions, such as pyr-GC-MS. The implications of our results, specifically those with respect to the suitability of the presented technique for future space missions to explore these Ocean Worlds in the search for signatures of life, will be discussed.
 I. Lunine, Acta Astronaut., 2017, 131, 123-130.
 P. Hand, et al., NASA, 2017, Report of the Europa Lander Science Definition Team.
 F.W. Ligterink, et al., Sci. Rep., 2020, 10, 9641.
 A. Riedo, et al., J. Mass Spectrom., 2013, 48, 1-15.