Abstract_EANA2026-68

Abstract EANA2026-68

Detectability of cellular biosignatures under simulated Enceladus surface conditions

Mirandah Ackley (1), Marie Dannenmann (1), Alvaro Del Moral Jimenez (2), Zoe Emerland (3), Matthew Sylvest (3), Karen Olsson-Francis (2), Frank Postberg (1), Manish Patel (3)

(1) Planetary Sciences and Remote Sensing Group, Institute of Geological Sciences, Freie Universität Berlin, Berlin, Germany, (2) AstrobiologyOU, Faculty of Science, Technology, Engineering & Mathematics, The Open University, Milton Keynes, UK, (3) HyperVelocity Impact & Space and Planetary Environments Laboratories, School of Physical Sciences, The Open University, Milton Keynes, UK

Icy moons with a subsurface ocean, such as Saturn’s moon Enceladus, are considered prime targets in the search for extraterrestrial life in the Solar System [1,2]. Using impact ionization mass spectrometry, analyses of ice grains from Enceladus have already identified a variety of organic material originating from the moon’s cryovolcanic plume, as demonstrated by CDA onboard the Cassini-Huygens mission [3,4]. Enceladus is the target of ESA’s upcoming large-class mission (L4), which aims to land on the surface of the icy moon and analyze plume ice grains and surface material for potential biosignatures using onboard mass spectrometers.

The Planetary Sciences group at Freie Universität Berlin is specialized in mass spectral analysis of simulated ice grains in space by a laser-induced liquid beam ion desorption mass spectrometer (LILBID-MS) [5]. Preliminary experiments using simulated ice grains have accurately identified biomolecules such as amino acids, peptides, sugars, and fatty acids from cellular material [6], while also distinguishing between molecular patterns with biotic or abiotic origins [7]. Furthermore, it has been demonstrated that cellular material contained within a single ice grain emitted from Enceladus or Europa can be detected using LILBID-MS [8].

However, there are significant gaps in our understanding of how detectable cellular biosignatures may be altered by the harsh environmental conditions present on the surface of Enceladus or within its plume, with its cryogenic temperatures (~75 K), ultra-high vacuum conditions, and high levels of attenuated solar UV radiation (~1.5 W m⁻²).

In this work, we investigate how extreme environmental conditions characteristic of Enceladus' surface or its plume may affect the mass spectral biosignatures of model organism Sphingopyxis alaskensis. Using a planetary surface simulation chamber at The Open University, microorganisms were exposed to conditions relevant to the surface of Enceladus: 173 K, 5 millibar, and UV doses equivalent to up to 2 days on Enceladus’ surface. The mass spectra of the microorganisms were then measured using the LILBID-MS laboratory setup to determine whether detectable biosignatures were altered by these simulated conditions and to what extent. In our anion mass spectra, we found that smaller key cellular fatty acid structures (m/z 199-450) showed little to no degradation under the simulated conditions. However, higher abundances of lipid and fatty acid fragments were observed over time, suggesting a breakdown of large lipid structures (> m/z 600).

These results advance our understanding of how potential cellular biosignatures might be altered by extreme planetary conditions, directly informing biosignature detection strategies for future planetary exploration missions, such as L4.

[1] M. L. Cable et al. The Planetary Science Journal, 2(4), 132 (2021)

[2] O. Mousis et al. The Planetary Science Journal, 3(12):268 (2022)

[3] F. Postberg, et al. Nature, 558(7711), 564-568 (2018)

[4] N. Khawaja et al. Monthly Notices of the Royal Astronomical Society, 489(4), 5231-5243 (2019)

[5] F. Klenner et al. Rapid Communications in Mass Spectrometry, 33(22), 1751–1760 (2019)

[6] M. Dannenmann et al. Astrobiology, 23(1), 60-75 (2023)

[7] F. Klenner et al. Astrobiology, 20(2), 179-189 (2020)

[8] F. Klenner & J. Bönigk et al. Science Advances, 10(12) (2024)