ALBERT

Description: The habitability of Mars is strongly dependent on the availability of liquid water, which is essential for life as we know it. One of the few places where liquid water might be found on Mars is in liquid perchlorate brines that could form via deliquescence. As these concentrated perchlorate salt solutions do not occur on Earth as natural environments, it is necessary to investigate in lab experiments the potential of these brines to serve as a microbial habitat. Here, we report on the sodium perchlorate (NaClO4) tolerances for the halotolerant yeast Debaryomyces hansenii and the filamentous fungus Purpureocillium lilacinum. Microbial growth was determined visually, microscopically and via counting colony forming units (CFU). With the observed growth of D. hansenii in liquid growth medium containing 2.4 M NaClO4, we found by far the highest microbial perchlorate tolerance reported to date, more than twice as high as the record reported prior (for the bacterium Planococcus halocryophilus). It is plausible to assume that putative Martian microbes could adapt to even higher perchlorate concentrations due to their long exposure to these environments occurring naturally on Mars, which also increases the likelihood of microbial life thriving in the Martian brines

Description: The accumulation of thousands of boulder-sized clasts into boulder fields in the Atacama Desert has been linked to seismic-driven downslope transport, a rare sedimentary process corroborated by this study. We surveyed boulder arrangements occurring in the Atacama Desert and identified three accumulation types for further investigation: a small circular boulder cluster (BC), a long channelized boulder stream (BS), and a wide convex-shaped boulder field (BF). Drone-based photogrammetric techniques and field observations were used to generate high-quality digital elevation models and orthophotos to determine boulder count, size, coverage, orientation, lithology and local topography. Our data shows that the arrangement of boulder accumulations corresponds with the shape of the accommodation space and the boulder input, where BCs occur at the center of completely confined topographic depressions, BSs occur along laterally confined and incised hill slopes with boulders stacked above each other, and BFs occur on largely unconfined shallow and low-relief slopes with a distinct boulder front. A general downslope increase of average boulder size and coverage was measured in all boulder accumulations and a long-axis orientation of boulders parallel to the transport direction was observed for the BS. Based on these results and the lack of fluvial transport indicators, we conclude that transport and arrangement of boulder accumulations are largely controlled by the interplay of topography and seismic-driven boulder transport, resulting in unique landscape features present in the hyper-arid Atacama Desert. Such sedimentary transport processes are rare on Earth but potentially play a greater role on other arid planetary surfaces that are covered by boulders and subject to sufficient seismic activity.

Description: Most definitions of life assume that, at a minimum, life is a physical form of matter distinct from its environment at a lower state of entropy than its surroundings, using energy from the environment for internal maintenance and activity, and capable of autonomous reproduction. These assumptions cover all of life as we know it, though more exotic entities can be envisioned, including organic forms with novel biochemistries, dynamic inorganic matter, and self-replicating machines. The probability that any particular form of life will be found on another planetary body depends on the nature and history of that alien world. So the biospheres would likely be very different on a rocky planet with an ice-covered global ocean, a barren planet devoid of surface liquid, a frigid world with abundant liquid hydrocarbons, on a rogue planet independent of a host star, on a tidally locked planet, on super-Earths, or in long-lived clouds in dense atmospheres. While life at least in microbial form is probably pervasive if rare throughout the Universe, and technologically advanced life is likely much rarer, the chance that an alternative form of life, though not intelligent life, could exist and be detected within our Solar System is a distinct possibility.

Description: Microbial enhanced oil recovery (MEOR) is an economically attractive tertiary recovery technique and fermentative bacteria are frequently suggested for MEOR, partly because microbially produced organic acids have the potential for rock matrix dissolution. In this study, the metabolic activity and the community shift of a diverse microbiome of a high-salinity oilfield upon supplying MEOR nutrients was investigated in dynamic sandpacks set-up with and without crude oil using pure quartz sand and two types of reservoir rock. Geochemical characterization of the porous media included specific surface area (SSA), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). During the experiments, substrate and metabolites, incremental oil and differential pressure were monitored and the microbial community shift was investigated via Illumina sequencing. Fermentative Halanaerobiales outcompeted other microbes and led to an incremental oil recovery of 24.5 ± 9.6 %OOIP in reservoir rock. Microbial-induced dissolution of surface minerals was indicated by a decrease in SSA and surface-bound ferrous iron and concluded to be an important MEOR mechanism. Fermentation of sucrose was primarily limited by an insufficient acid neutralization capacity (ANC), but a carbonate content of 12% sustainably buffered the pH in a favorable growth range. Even minor amounts of other non-inert minerals (1% pyrite and calcite) facilitated microbial growth significantly, resulting in six-fold higher acetate production rates compared to quartz sand. Besides emphasizing the relevance of accessory minerals in MEOR, our results imply that the ANC could serve as potential screening parameter for predicting the performance of fermentation - based MEOR in the field.

Description: Souring induced by sulfate reducing microorganisms (SRM) represents a severe problem in the petroleum industry. In addition to conventional biocides and nitrate, alternative SRM inhibitors such as molybdate have been proposed recently for controlling microbial souring. We used oilfield-derived microbial consortia, rock and fluids to test molybdate as a specific SRM inhibitor for a microbial enhanced oil recovery (MEOR) application where souring might occur as a side effect. SRM cells were quantified and dissolved molybdate, sulfate and gaseous hydrogen sulfide were measured under different dynamic conditions in sandpacks with and without residual oil. In batch experiments, 0.5 mM molybdate inhibited SRM growth whereas hydrogen sulfide and mineral precipitations were observed in bottles amended with 100 mM nitrate. However, significant molybdate adsorption onto reservoir rock occurred and maximum Langmuir saturation was estimated to be ≥ 34 μmol g−1. Residual oil allowed a further propagation of molybdate into sandpacks, but a pH 〈 6 and sulfide concentrations 〉11 μMH2S aq limited the efficiency of molybdate due to rapid adsorption. Under favorable souring conditions, we also observed the localized formation of macroscopic iron sulfide precipitations. These resulted in a four-fold permeability decrease after the injection of SRM substrates for 40 days and a calculated mean sulfate reduction rate of 52 μM h−1. However, delayed sulfate reduction in molybdate-preflushed sandpacks suggests an inhibitory effect even if molybdate is partially adsorbed. Sulfate reduction was not detected when molybdate was continuously injected with MEOR nutrients into sandpacks demonstrating its inhibitory efficiency in case it is applied in early phases of field operations with a potential risk of souring.

Description: We present a case for the exploration of Venus as an astrobiology target—(1) investigations focused on the likelihood that liquid water existed on the surface in the past, leading to the potential for the origin and evolution of life, (2) investigations into the potential for habitable zones within Venus’ present-day clouds and Venus-like exo atmospheres, (3) theoretical investigations into how active aerobiology may impact the radiative energy balance of Venus’ clouds and Venus-like atmospheres, and (4) application of these investigative approaches toward better understanding the atmospheric dynamics and habitability of exoplanets. The proximity of Venus to Earth, guidance for exoplanet habitability investigations, and access to the potential cloud habitable layer and surface for prolonged in situ extended measurements together make the planet a very attractive target for near term astrobiological exploration.

Description: The possible detection of the biomarker of phosphine as reported by Greaves et al. in the Venusian atmosphere stirred much excitement in the astrobiology community. While many in the community are adamant that the environmental conditions in the Venusian atmosphere are too extreme for life to exist, others point to the claimed detection of a convincing biomarker, the conjecture that early Venus was doubtlessly habitable, and any Venusian life might have adapted by natural selection to the harsh conditions in the Venusian clouds after the surface became uninhabitable. Here, I first briefly characterize the environmental conditions in the lower Venusian atmosphere and outline what challenges a biosphere would face to thrive there, and how some of these obstacles for life could possibly have been overcome. Then, I discuss the significance of the possible detection of phosphine and what it means (and does not mean) and provide an assessment on whether life may exist in the temperate cloud layer of the Venusian atmosphere or not.