Detection of High-Mass Molecular Biosignatures in Antarctic Ices: Relevance for Icy Moons Exploration

Icy worlds are ubiquitous in the solar system. Among them, the Jovian and Saturnian moons Europa and Enceladus are considered the most habitable places as they host subsurface liquid oceans in direct contact with a rocky core below their icy shells. Moreover, Enceladus possesses valuable chemical ingredients, including at least five of the six basic elements for life - CHNOPS - and its porous rocky core hosts hydrothermal systems which, as sources of chemical disequilibria, are deemed necessary for the emergence of life. High-mass and low-mass organics have been detected in Enceladus icy grains with the Cosmic Dust Analyzer (CDA), a spaceborne impact mass-spectrometer. The structure of these organics comprises a variety of functional groups and moieties [1,2,3,4].

Spaceborne instruments such as CDA and future ones such as the SUrface Dust Analyzer (SUDA) onboard Europa Clipper will strongly benefit from data obtained in laboratory experiments, both in terms of data interpretation and performance.

 

In this context, our current understanding of the solar system strongly benefits from comparative planetology. Terrestrial analogue sites of icy ocean moons are specific locations on Earth that are similar in some important aspects (e.g., geological or environmental characteristics) to those on icy ocean moons, and can thus serve as natural laboratories. Their study brings substantial contribution to the scientific knowledge of ocean worlds, and can support space missions by e.g., informing on the habitability of extreme environments, the preservation of biosignatures in these environments and the relevance of specific analytical methods to detect them, as well as testing of instrumentation. The detailed analysis of terrestrial analogue samples with techniques relevant for space missions is thus a key milestone in the preparation of missions investigating habitability and searching for signs of life on icy ocean moons.

 

Here we present the first ever analysis of natural ice analogues with Laser Induced Liquid Beam Ion Desorption (LILBID) - a well-established method allowing the simulation of ice grains’ impact ionization mass spectra. Many LILBID spectra of synthetic samples have already been recorded to complement an expanding reference database [5] for e.g., Europa Clipper. Gas Chromatography linked to Mass Spectrometry (GC-MS), Raman and IR spectroscopy measurements were also carried out, in an effort to carry out an orthogonal investigation of the samples. Ice samples were collected from key locations in the Collins (a.k.a. Bellingshausen) glacier on King George Island, Antarctica, with support from the Instituto Antártico Uruguayo. Here we will discuss results from icy samples containing the microalgae Sanguina nivalis, a species highly adapted to the low temperatures of the glacier, limited nutrient availability and intense sunlight. Various low and high-mass molecular biosignatures are detected despite the complexity of the samples’ matrix, including a range of amino acids, fatty acids and larger lipids. Moreover, environmental adaptations to intense UV radiation and low temperature relevant to icy ocean worlds are reflected in the molecular biosignatures, with the respective detections of pigments and a high degree of unsaturation in the lipid profile. This marks the first ever detection of biosignatures in natural samples with LILBID. Our results highlight the detection capability of SUDA-type instruments in regards to biosignatures specifically reflecting icy moon conditions, despite the high salt levels of the ice matrix. This work and other measurements carried out at the Analogue Icy Moon Simulations (AIMS) laboratory will support preparation for ESA’s future L4 mission to Enceladus.

 

 

[1] F. Postberg et al. Nature 558, 564–568 (2018)

[2] F. Postberg et al. Nature 618, 489–493 (2023)

[3] N. Khawaja et al. Mon. Not. R. Astron. Soc 489, 4, 5231–5243 (2019)

[4] N. Khawaja et al. Nat Astron 9, 1662–1671 (2025)

[5] F. Klenner et al., Earth Space Sci., 9, e2022EA002313 (2022)