Putative microbial life on Mars would encounter a severe scarcity of liquid water due to the prevailing freezing and hyperarid climate conditions. Interestingly, hygroscopic salts were discovered on Mars that enable water absorption from the atmosphere and lower the freezing point, potentially allowing the temporary occurrence of liquid briny water [1]. However, these brines contain high...
Liquid water, an essential compound for life on Earth, is not stable on the Martian surface, but the presence of hygroscopic salts like chlorates and perchlorates in the regolith could enable the formation of, at least temporarily, stable liquid brines[1]. In the near-subsurface, a thin regolith layer could prevent water sublimation, thus extending the lifetime of the brine [2]. Regolith...
Today, liquid water is not thermodynamically stable at the surface of Mars due to the low temperature and pressure conditions. However, liquid groundwater may still exist in the Martian subsurface [1, 2].
In this study, we use fully dynamical 3D thermal evolution models [3] to calculate the depth at which favorable conditions for liquid water are present, assuming that a global subsurface...
Light is the fundamental energy source for photosynthesis, enabling the synthesis of organic compounds. Over billions of years, photosynthetic organisms have profoundly transformed our planet into a diverse global ecosystem (1,2). Therefore, understanding an (exo)planet in the context of its stellar environment is an essential step in assessing its habitability. K-dwarf stars have gained a lot...
Astrobiological studies are fundamental to understanding how extraterrestrial environments might alter the survivability of complex biological systems. An optimal biological model for space research would need to lower its metabolic rate, possess enhanced defenses against the space environment, and be able to survive prolonged periods of space flight [1]. The crustacean Artemia salina has...
Enceladus’s subsurface global ocean (1) can be probed by sampling the gaseous and icy material the moon expels into its cryovolcanic plume and - even further out - into Saturn’s E ring (2,3,4,5). Hydrothermal outflows supported by tidal heating (4,5,6), together with rich organic chemistry (7,8) imply that the moon appears to be one of most habitable places in our solar system. Among the...
A rhythmic pattern of motion due to breathing and circulation processes is observed within macroscopic organisms such as animals. The question is whether we could observe something like this – on a much smaller scale – also in microbial life forms. We know that there is motion within any type of cell from the myriad of internal processes and also at the cell boundaries when an organism...
Cyanobacteria are ubiquitous in the world. They have successfully colonised both land and sea and were the first to oxygenate the atmosphere in what is known as the Great Oxidation Event (GOE) (1). Cyanobacteria are also the only prokaryotes capable of photosynthesis and are considered a pre-evolutionary stage of today's chloroplasts (2). This is predicted on the endosymbiont theory, which...
Terrestrial life is characterized by significant complexity combined with a high degree of order. Life needs complexity and order combined to develop functionality, exactly this functionality that life uses to keep up its ordered state against the second law of thermodynamics. Essentially, life is a form of self-sustaining complex order. Consequently, the combination of complexity and...
Evidence for water-rock interactions and hydrothermal (HT) reactions at the ocean-floor of Enceladus was found via the mass spectrometers onboard the Cassini spacecraft – the Cosmic Dust Analyzer and the Ion and Neutral Mass Spectrometer. Organic material of astrobiological interest, containing various moieties (N-, O- and aryl groups), was detected in ice grains coming from vents on...
The search for signs of biological activity on Mars is among the main objectives of Mars exploration programs [1]. Here, molecular biosignatures, i. e. molecular traces of life such as biomolecules, are of particular interest. It has to be noted though that biomolecules are highly susceptible to alteration by extreme conditions on extraterrestrial bodies. On Mars specifically, such conditions...
In planetary exploration and analog studies, the fusion of diverse datasets and collaborative research outcomes from multidisciplinary teams presents an exciting yet complex challenge. This abstract outlines an approach to address this challenge, as demonstrated during the 2023 Vulcano Summer School on Vulcano Island, Italy. Vulcano Island's unique geological setting, characterized by an...
Chemolithoautotrophic organisms thrive under extreme conditions (e.g., high metal concentrations, high temperatures, and low pH) through redox-altering minerals by oxidizing inorganic molecules (e.g., iron, sulfur, and other reduced inorganic sulfur compounds). As the early planetary phases of Earth and Mars are similar, this metabolomic path makes these microbial organisms good candidates for...
Early cellular membranes may have emerged and survived harsh temperature, pressure, pH or ionic strength gradients, presumably occurring in diverse geological environments, such as pumice rafts, volcanic splash pools, submarine hydrothermal vents and subaerial springs [1-2]. A wide variety of thermotropic phases could appear in the amphiphilic membranes under these environmental conditions,...
Research in the field of astrobiology requires the study of geological and biological features in harsh environments, such as arid, cave or volcanic environments as analogs for Mars and Venus. Evaluation of in-situ measurements and laboratory analysis of samples are important for life detection and habitability characterization, but are limited if context information such as spatial relations...
Bioproduction systems that rely on diazotrophic, rock-weathering cyanobacteria for in situ resource utilization have been described as potential ways of increasing the sustainability of crewed missions to Mars. According to this concept, cyanobacteria would be fed with water mined from the ground; carbon and nitrogen sourced from the atmosphere; and the local regolith, from which it has been...
Europa’s hydro- and cryosphere is of primary interest in the quest for habitable environments in the solar system (e.g., Coustenis & Encrenaz et al., 2013). The ice shell, which connects the potential subsurface ocean to the surface, may itself provide niches for life if liquid brine pockets can form and exist for extended periods of time. It is thus crucial to understand the dynamics of the...
Currently we do not yet know, if Earth did have a reducing atmosphere or not during the first few hundreds of Myrs of its history. However, this would have a strong impact, as shown in the Miller-Urey experiment and several follow-up studies, on prebiotic chemistry and therefore possibly the origin of life on Earth.
It has been recently suggested, that rocky planets being more massive than...
The volcanic settings of the Eolian Islands, Italy, offer access to various types of volcanic terrains, with diverse morphology and mineralogy. The current signs of volcanic activity on the island of Vulcano, whose last eruption is dated to 1890, include e.g. the presence of large fumarole fields on ground and underwater. The dry landscape and easy access to layers of older and more recent...
In the last decade Polar Research in Germany became increasingly an important focus in Space Research activities, particularly in Planetary Research and Astrobiology. The reason is obvious, because the planets and moons in our Solar System, with a potential to be habitable and also being promising candidates for the search for life beyond Earth, are icy worlds. These icy conditions on those...
The Barrancas Blancas Plain (~5000 m a.s.l., 68°39' W, 27°02' S) in the high Atacama Andes of Chile is a unique place that combines the harsh characteristics of the mountain desert environment with the presence of ice-rich permafrost. This place is situated in a Mars analog region and is therefore considered to be a natural laboratory for the study of extremophilic microbes, aiming to...
One of the main objectives of the ESA EnVision and NASA VERITAS missions is to understand the evolution of Venus by characterizing the composition and origin of its major geological terrains. The best Venus' dataset comes from the VIRTIS instrument on-board Venus Express, which used a near-infrared sensor [1,2,3], because the dense CO2 atmosphere of Venus only allows observations in narrow...
The terrestrial deep subsurface is a vast and enduring habitat, representing one of Earth's most extensive and consistent ecosystems. Microorganisms thriving within the deep biosphere are pivotal in maintaining the planet's biodiversity and represent analogs for the search for life in extraterrestrial settings. However, our understanding of microbial colonization and persistence in Earth’s...
In the context of the search for life on other bodies of the solar system, much time has been invested in research and discourse about what constitutes a good biosignature. Ideally, we would want something that is unique to life (has no abiotic origin), is easily detectable and is not prone to false positives (from eg. forward contamination). It seems to be consensus now that no single...
A major indicator for the presence of microbial life is motility, or the ability to move independently using metabolic energy. Motility can be observed and quantified by analyzing the trajectories of individual cells in microscopic videos and by comparing them with the movement of abiotic particles due to Brownian motion or drifts.
Using microscopy for detecting possible extraterrestrial...
Since the discovery of the first exoplanet, several thousand have been found, including some Earth-like planets. A new generation of space telescopes (e.g., James Webb Space Telescope and Transiting Exoplanet Survey Satellite) are now taking the search for potential extra-terrestrial life one step further. With these new missions, direct imaging of exoplanets and spectral resolution of...
Context. The possible detection of phosphine (PH3) in the clouds of Venus has raised the question as to which processes could produce such large abundances of PH3. Previous studies suggested that abiotic processes including photochemical production cannot explain the claimed PH3 concentrations. However, the photochemistry of phosphorus-bearing species in the atmosphere of Venus is not well...
Ocean worlds, such as Jupiter’s icy moon Europa, are key targets in the search for extraterrestrial life. One powerful approach involves searching for biochemical signatures at the molecular level - both specific biosignature molecules and their distribution patterns. These include amino acids and fatty acids, the latter being considered as universal biomarkers of extraterrestrial life [1],...
The possibility of extraterrestrial life has fascinated humanity for centuries. Currently, a number of space research projects are at least partly dedicated to the search for life on other worlds such as Mars and Enceladus. Against this backdrop, terrestrial laboratory experiments simulating extraterrestrial physical and geochemical conditions that might alter molecular traces of life are...
Ocean worlds in the outer Solar System are prime targets for the search of life beyond Earth [1]. So far, Enceladus is the only extraterrestrial ocean world whose subsurface material was sampled by the Cassini spacecraft. Enceladus throws its subsurface material into space in the form of ice grains and gas from the moon’s south polar region. Most of the ice grains fall back onto the surface...
Observations of Enceladus have shown water jets expelling from the surface. These jets originate from a subsurface ocean and formed Saturn’s E-ring. Further observations of the plumes have led to the consensus that Enceladus likely holds a porous chondritic mineralogy, hydrothermal environments, and several building blocks necessary for the formation of life (e.g., HCN, NH3, CO2). Numerous...
