Perchlorate and Volatiles of the Brine of Lake Vida (Antarctica): Implication for the in Situ Analysis of Mars Sediments

The cold (-13.4 C), cryoencapsulated, anoxic, interstitial brine of the 27 m-thick ice of Lake Vida (Victoria Valley, Antarctica) contains 49 microgram L-1 of perchlorate and 11 microgram L-1 of chlorate. Lake Vida brine (LVBr) may provide an analog for potential oxychlorine-rich subsurface brine on Mars. LVBr volatiles were analyzed by solid-phase microextraction (SPME) gas chromatography-mass spectrometry (GC-MS) with two different SPME fibers. With the exception of volatile organic sulfur compounds, most other volatiles observed were artifacts produced in the GC injector when the thermal decomposition products of oxychlorines reacted with reduced carbon derived from LVBr and the SPME fiber phases. Analysis of MilliQ water with perchlorate (40 microgram L-1) showed low level of organic artifacts, reflecting carbon limitation. In order to observe sample-derived organic compounds, both in analog samples and on Mars, the molar abundance of reduced carbon in a sample must exceed those of O2 and Cl2 produced during decomposition of oxychlorines. This suggests that the abundance of compounds observed by the Sample Analysis at Mars (SAM) instruments in Sheepbed samples (CB-3, CB5, and CB6) may be controlled by an increase in the reduced-carbon/oxychlorine ratio of these samples. To increase chances of in situ detection of Martian organics during pyrolysis-GC-MS, we propose that the derivatization agents stored on SAM may be used as an external source of reduced carbon, increasing artificially the reduced-carbon to perchlorate ratio during pyrolysis, allowing the expression of more abundant and perhaps more diverse Martian organic matter

Camilla: A Centaur reconnaissance and impact mission concept

Centaurs, minor planets with a semi-major axis between the orbits of Jupiter and Neptune (5–30 AU), are thought to be among the most diverse small bodies in the solar system. These important targets for future missions may have recently been Kuiper Belt Objects (KBOs), which are thought to be chemically and physically primitive remnants of the early solar system. While the Kuiper Belt spans distances of 30–50 AU, making direct observations difficult, Centaurs' proximity to the Earth and Sun make them more accessible targets for robotic missions. Thus, we outline a mission concept designed to reconnoiter 10199 Chariklo, the largest Centaur and smallest ringed body yet discovered. Named for a legendary Centaur tamer, the conceptual Camilla mission is designed to fit under the cost cap of the National Aeronautics and Space Administration (NASA) New Frontiers program, leveraging a conservative payload to support a foundational scientific investigation to these primitive bodies. Specifically, the single flyby encounter utilizes a combined high-resolution camera/VIS-IR mapping spectrometer, a sub-mm point spectrometer, and a UV mapping spectrometer. In addition, the mission concept utilizes a kinetic impactor, which would provide the first opportunity to sample the composition of potentially primitive subsurface material beyond Saturn, thus providing key insights into solar system origins. Such a flyby of the Chariklo system would provide a linchpin in the understanding of small body composition, evolution, and transport of materials in the solar system

Towards a more universal life detection strategy

This white paper argues for a more universal approach to life detection. We recommend that life detection missions focus on looking for signatures of life deemed to be shared by all possible types of life, independent of their specific biochemistries, rather than looking for signatures of life that could arguably be specific to Terran-life

Planetary mass spectrometry for agnostic life detection in the Solar system

For the past fifty years of space exploration, mass spectrometry has provided unique chemical and physical insights on the characteristics of other planetary bodies in the Solar System. A variety of mass spectrometer types, including magnetic sector, quadrupole, time-of-flight, and ion trap, have and will continue to deepen our understanding of the formation and evolution of exploration targets like the surfaces and atmospheres of planets and their moons. An important impetus for the continuing exploration of Mars, Europa, Enceladus, Titan, and Venus involves assessing the habitability of solar system bodies and, ultimately, the search for life—a monumental effort that can be advanced by mass spectrometry. Modern flight-capable mass spectrometers, in combination with various sample processing, separation, and ionization techniques enable sensitive detection of chemical biosignatures. While our canonical knowledge of biosignatures is rooted in Terran-based examples, agnostic approaches in astrobiology can cast a wider net, to search for signs of life that may not be based on Terran-like biochemistry. Here, we delve into the search for extraterrestrial chemical and morphological biosignatures and examine several possible approaches to agnostic life detection using mass spectrometry. We discuss how future missions can help ensure that our search strategies are inclusive of unfamiliar life forms.https://www.frontiersin.org/articles/10.3389/fspas.2021.755100/ful

The Organic Matter of Lake Vida, Antarctica: Biogeochemistry of an Icy Planetary World Analog

The biogeochemistry of Lake Vida brine, Antarctica, was investigated by studying the organic matter composition in a cold, isolated, subzero, hypersaline, anoxic, and aphotic brine environment. The brine of Lake Vida, encapsulated within the thick (27+ m) of Lake Vida ice, harbors an exclusively bacterial community that is metabolically active at maintenance level. Lake Vida brine is a unique analog for icy planetary worlds. Studying the organic biosignatures that are produced, processed, and transformed in Lake Vida brine can enhance our understanding of life in subzero habitats and inform our search for extant biosignatures of life on other icy worlds, such as Mars, Europa, or Enceladus. First, I investigated the standing crop of organic biosignatures in Lake Vida brine using environmental metabolomics. Analysis of the dissolved metabolites of Lake Vida brine revealed that legacy paleometabolites from past environmental conditions remained in the brine after millennia of isolation. Second, I characterized novel organic sulfones in a fraction of the dissolved organic matter in Lake Vida brine in order to further understand the ancient and modern processes that dominate the Lake Vida brine environment. Third, I investigated the particulate organic matter of Lake Vida brine using combined lipidomics and targeted metagenomics approaches in order to distinguish modern from ancient metabolites by interrogating the genetic capacity of the modern Lake Vida brine microbial community. Eukaryotic cellular detritus and legacy lipids that were indicative of a different, possibly photosynthetic, community were detected. Results indicate that Lake Vida brine contains abundant legacy organic matter in both the dissolved and particulate fraction. However, metagenomics analysis suggests that some of the lipids observed in the particulate organic matter fraction could potentially be modern. Ultimately, the presence of legacy biosignatures in the Lake Vida brine organic matter suggests that organic biosignatures of previous ecosystems may be preserved in cold, isolated ecosystems for long timescales. The prevalence of legacy in Lake Vida brine is due to the slow-growing, cold-limited lifestyle of the modern microbial assemblage. I posit that the abundance of legacy in other cold-limited, slow-growing ecosystems, on Earth and on other icy worlds, is not likely trivial and may affect the standing crop of the organic biosignatures of an environment at a given time. However, combined with metagenomics analysis, potentially achieved by space-capable sequencing technology, may allow for an integrated investigation of organic biosignatures, providing an avenue for detecting modern biosignatures, and thus, the presence of extant life

Effects of legacy metabolites from previous ecosystems on the environmental metabolomics of the brine of Lake Vida, East Antarctica

© 2018 Elsevier Ltd Lake Vida, located in a closed basin in the McMurdo Dry Valleys, East Antarctica, permanently encapsulates an interstitial anoxic, aphotic, cold (−13 °C), brine ecosystem within 27+ m of ice. Metabolically active, but cold-limited, slow-growing bacteria were detected in the brine. Lake Vida brine is derived from the evaporation of a body of water that occupied the same basin prior to ∼2800 years ago. The characteristics of this body of water changed over time and, at one point, likely resembled other modern well-studied perennial ice-covered lakes of the Dry Valleys. We characterized the dichloromethane-extractable fraction of the environmental metabolome of Lake Vida brine in order to constrain current and ancient biogeochemical processes. Analysis of the dichloromethane-extract of Lake Vida brine by gas chromatography-mass spectrometry and comprehensive multidimensional gas chromatography-time of flight-mass spectrometry reveals the presence of legacy compounds (i.e. diagenetic products of chlorophylls and carotenoids) deriving from photosynthetic algae and anaerobic, anoxygenic photosynthetic bacteria. This legacy component dilutes the environmental signal of metabolites deriving from the extant bacterial community. The persistence of legacy metabolites (paleometabolites), apparent in Lake Vida brine, is a result of the slow turnover rates of the extant bacterial population due to low metabolic activities caused by the cold limitation. Such paleometabolites may also be preserved in other cold-limited or nutrient-depleted slow-growing ecosystems. When analyzing ecosystems with low metabolic rates, the presence of legacy metabolites must first be addressed in order to confidently recognize and interpret the environmental metabolome of the extant ecosystem

Secondary Electrons as an Energy Source for Life

13 páginas.-- 3 figuras.-- 3 tablas.-- 69 referenciasLife on Earth is found in a wide range of environments as long as the basic requirements of a liquid solvent, a nutrient source, and free energy are met. Previous hypotheses have speculated how extraterrestrial microbial life may function, among them that particle radiation might power living cells indirectly through radiolytic products. On Earth, so-called electrophilic organisms can harness electron flow from an extracellular cathode to build biomolecules. Here, we describe two hypothetical mechanisms, termed “direct electrophy” and “indirect electrophy” or “fluorosynthesis,” by which organisms could harness extracellular free electrons to synthesize organic matter, thus expanding the ensemble of potential habitats in which extraterrestrial organisms might be found in the Solar System and beyond. The first mechanism involves the direct flow of secondary electrons from particle radiation to a microbial cell to power the organism. The second involves the indirect utilization of impinging secondary electrons and a fluorescing molecule, either biotic or abiotic in origin, to drive photosynthesis. Both mechanisms involve the attenuation of an incoming particle's energy to create low-energy secondary electrons. The validity of the hypotheses is assessed through simple calculations showing the biomass density attainable from the energy supplied. Also discussed are potential survival strategies that could be used by organisms living in possible habitats with a plentiful supply of secondary electrons, such as near the surface of an icy moon. While we acknowledge that the only definitive test for the hypothesis is to collect specimens, we also describe experiments or terrestrial observations that could support or nullify the hypotheses.Peer reviewe

Leveraging Open Science Machine Learning Challenges for Data Constrained Planetary Mission Instruments

International audienceWe set up two open-science machine learning (ML) challenges focusing on building models to automatically analyze massspectrometry (MS) data for Mars exploration. ML challenges provide an excellent way to engage a diverse set of experts withbenchmark training data, explore a wide range of ML and data science approaches, and identify promising models based onempirical results, as well as to get independent external analyses to compare to those of the internal team. These two challengeswere proof-of-concept projects to analyze the feasibility of combining data collected from different instruments in a singleML application. We selected mass spectrometry data from 1) commercial instruments and 2) the Sample Analysis at Mars(SAM, an instrument suite that includes a mass spectrometer subsystem onboard the Curiosity rover) testbed. These challenges,organized with DrivenData, gathered more than 1,150 unique participants from all over the world, and obtained more than 600solutions contributing powerful models to the analysis of rock and soil samples relevant to planetary science using various massspectrometry datasets. These two challenges demonstrated the suitability and value of multiple ML approaches to classifyingplanetary analog datasets from both commercial and flight-like instruments.We present the processes from the problem identification, challenge setups, and challenge results that gathered creative anddiverse solutions from worldwide participants, in some cases with no backgrounds in mass spectrometry. We also present thepotential and limitations of these solutions for ML application in future planetary missions. Our longer-term goal is to deploythese powerful methods onboard the spacecraft to autonomously guide space operations and reduce ground-in-the-loop reliance

Detection of Short Peptides as Putative Biosignatures of Psychrophiles via Laser Desorption Mass Spectrometry

International audienceStudies of psychrophilic life on Earth provide chemical clues as to how extraterrestrial life could maintain viability in cryogenic environments. If living systems in ocean worlds (e.g., Enceladus) share a similar set of 3-mer and 4-mer peptides to the psychrophile Colwellia psychrerythraea on Earth, spaceflight technologies and analytical methods need to be developed to detect and sequence these putative biosignatures. We demonstrate that laser desorption mass spectrometry, as implemented by the CORALS spaceflight prototype instrument, enables the detection of protonated peptides, their dimers, and metal adducts. The addition of silicon nanoparticles promotes the ionization efficiency, improves mass resolving power and mass accuracies via reduction of metastable decay, and facilitates peptide de novo sequencing. The CORALS instrument, which integrates a pulsed UV laser source and an Orbitrap™ mass analyzer capable of ultrahigh mass resolving powers and mass accuracies, represents an emerging technology for planetary exploration and a pathfinder for advanced technique development for astrobiological objectives. Teaser: Current spaceflight prototype instrument proposed to visit ocean worlds can detect and sequence peptides that are found enriched in at least one strain of microbe surviving in subzero icy brines via silicon nanoparticle-assisted laser desorption analysis

The grayness of the origin of life

In the search for life beyond Earth, distinguishing the living from the non-living is paramount. However, this distinction is often elusive, as the origin of life is likely a stepwise evolutionary process, not a singular event. Regardless of the favored origin of life model, an inherent “grayness” blurs the theorized threshold defining life. Here, we explore the ambiguities between the biotic and the abiotic at the origin of life. The role of grayness extends into later transitions as well. By recognizing the limitations posed by grayness, life detection researchers will be better able to develop methods sensitive to prebiotic chemical systems and life with alternative biochemistries