Comparative metagenomics at Solfatara and Pisciarelli hydrothermal systems in Italy reveal that ecological differences across substrates are not ubiquitous.

Introduction: Continental hydrothermal systems (CHSs) are geochemically complex, and they support microbial communities that vary across substrates. However, our understanding of these variations across the complete range of substrates in CHS is limited because many previous studies have focused predominantly on aqueous settings. Methods: Here we used metagenomes in the context of their environmental geochemistry to investigate the ecology of different substrates (i.e., water, mud and fumarolic deposits) from Solfatara and Pisciarelli. Results and Discussion: Results indicate that both locations are lithologically similar with distinct fluid geochemistry. In particular, all substrates from Solfatara have similar chemistry whereas Pisciarelli substrates have varying chemistry; with water and mud from bubbling pools exhibiting high SO4 2- and NH4 + concentrations. Species alpha diversity was found to be different between locations but not across substrates, and pH was shown to be the most important driver of both diversity and microbial community composition. Based on cluster analysis, microbial community structure differed significantly between Pisciarelli substrates but not between Solfatara substrates. Pisciarelli mud pools, were dominated by (hyper)thermophilic archaea, and on average, bacteria dominated Pisciarelli fumarolic deposits and all investigated Solfatara environments. Carbon fixation and sulfur oxidation were the most important metabolic pathways fueled by volcanic outgassing at both locations. Together, results demonstrate that ecological differences across substrates are not a widespread phenomenon but specific to the system. Therefore, this study demonstrates the importance of analyzing different substrates of a CHS to understand the full range of microbial ecology to avoid biased ecological assessments.

COSPAR Sample Safety Assessment Framework (SSAF).

The Committee on Space Research (COSPAR) Sample Safety Assessment Framework (SSAF) has been developed by a COSPAR appointed Working Group. The objective of the sample safety assessment would be to evaluate whether samples returned from Mars could be harmful for Earth's systems (e.g., environment, biosphere, geochemical cycles). During the Working Group's deliberations, it became clear that a comprehensive assessment to predict the effects of introducing life in new environments or ecologies is difficult and practically impossible, even for terrestrial life and certainly more so for unknown extraterrestrial life. To manage expectations, the scope of the SSAF was adjusted to evaluate only whether the presence of martian life can be excluded in samples returned from Mars. If the presence of martian life cannot be excluded, a Hold & Critical Review must be established to evaluate the risk management measures and decide on the next steps. The SSAF starts from a positive hypothesis (there is martian life in the samples), which is complementary to the null-hypothesis (there is no martian life in the samples) typically used for science. Testing the positive hypothesis includes four elements: (1) Bayesian statistics, (2) subsampling strategy, (3) test sequence, and (4) decision criteria. The test sequence capability covers self-replicating and non-self-replicating biology and biologically active molecules. Most of the investigations associated with the SSAF would need to be carried out within biological containment. The SSAF is described in sufficient detail to support planning activities for a Sample Receiving Facility (SRF) and for preparing science announcements, while at the same time acknowledging that further work is required before a detailed Sample Safety Assessment Protocol (SSAP) can be developed. The three major open issues to be addressed to optimize and implement the SSAF are (1) setting a value for the level of assurance to effectively exclude the presence of martian life in the samples, (2) carrying out an analogue test program, and (3) acquiring relevant contamination knowledge from all Mars Sample Return (MSR) flight and ground elements. Although the SSAF was developed specifically for assessing samples from Mars in the context of the currently planned NASA-ESA MSR Campaign, this framework and the basic safety approach are applicable to any other Mars sample return mission concept, with minor adjustments in the execution part related to the specific nature of the samples to be returned. The SSAF is also considered a sound basis for other COSPAR Planetary Protection Category V, restricted Earth return missions beyond Mars. It is anticipated that the SSAF will be subject to future review by the various MSR stakeholders.

Characterization of microplastics in indoor and ambient air in northern New Jersey.

Airborne microplastics (MPs) could have negative impacts on human health and pollute water, soil, and sediment. This study explored the distributions, compositions, and morphology of airborne microplastics in the indoor and ambient air in New Jersey, United States. Microplastic fibers, films, and fragments of Polystyrene (PS), Polyethylene terephthalate (PET), Polyethyelene (PE), Polyvinyl chloride (PVC) and Polypropylene (PP) were identified in office, hallway, classroom, and single-family house in this study. The deposition rates of synthetic fibers with length from 35 µm to 1000 µm were highest in the single-family house ((1.96 ± 1.09) × 104 fibers/m2/day) and lowest in the classroom ((6.20 ± 0.57) × 103 fibers/m2/day), suggesting that residential houses are a major source of microplastic fibers. However, for film-like plastics with surface areas ranging from 200 µm2 to 5000 µm2, a high deposition rate of (8.13 ± 2.17) × 103 films/m2/day was observed in the classroom, whereas the lowest deposition rate of (4.45 ± 0.27) × 103 films/m2/day was found in the hallway, probably because plastic films such as PE are intensively used in the classroom environments. The deposition rate of microplastics in the ambient air acquired on a building roof was only about 2-8% of the indoor deposition rates. The microplastics with similar textures but different sizes were identified in both total atmospheric deposition and particulate samples (PM2.5 and PM10), suggesting degradation from microplastics to nanoplastics. The main microplastics found in indoor air samples were PE fragments or fibers, different from those in the outdoor ambient air that were dominated by PVC fragments. These results unravel the properties of airborne microplastics in urban environments that are important to understanding their fate, transport, and potential health risks.

Raman spectroscopy provides insight into carbonate rock fabric based on calcite and dolomite crystal orientation.

Carbonate rocks record the oldest forms of life on Earth, and their geologic reconstruction requires multiple methods to determine physical and chemical processes before conclusions of ancient biosignatures are made. Since crystal orientation within rock fabric may be used to infer geologic settings, we present here a complementary Raman method to study the orientation of calcite (CaCO3) and dolomite [CaMg (CO3)2] minerals. The relative peak intensity ratio of the carbonate lattice Eg modes T and L reveals the crystallographic orientation of calcite and dolomite with respect to the incident light polarization. Our results for calcite show that when the incident laser light propagates down the crystallographic a/b axis: (1) the L mode is always greater in intensity than the T mode (I T < I L), and (2) the spectra are most intense at 45° and least intense at 90° polarization angles measured from around the c axis. Our results for dolomite show that (1) I T > I L when the incident light propagation is down the crystallographic c axis and (2) I T < I L when the incident light propagation is down the crystallographic a/b axis. This study reveals mineral orientation variation related to deposition and paragenesis within limestone and dolostone samples. The method presented yields information related to growth and deformation during diagenetic and metamorphic alteration and may be used in research seeking to identify the fabric parameters of any calcite or dolomite containing rock. The compositional and structural data obtained from Raman mapping is useful in structural geology, materials science, and biosignature research.

Subsurface Microbial Ecology at Sediment-Groundwater Interface in Sulfate-Rich Playa; White Sands National Monument, New Mexico.

The hypersaline sediment and groundwater of playa lake, Lake Lucero, at the White Sands National Monument in New Mexico were examined for microbial community composition, geochemical gradients, and mineralogy during the dry season along a meter and a half depth profile of the sediment vs. the groundwater interface. Lake Lucero is a highly dynamic environment, strongly characterized by the capillary action of the groundwater, the extreme seasonality of the climate, and the hypersalinity. Sediments are predominantly composed of gypsum with minor quartz, thenardite, halite, quartz, epsomite, celestine, and clays. Geochemical analysis has revealed the predominance of nitrates over ammonium in all of the analyzed samples, indicating oxygenated conditions throughout the sediment column and in groundwater. Conversely, the microbial communities are primarily aerobic, gram-negative, and are largely characterized by their survival adaptations. Halophiles and oligotrophs are ubiquitous for all the samples. The very diverse communities contain methanogens, phototrophs, heterotrophs, saprophytes, ammonia-oxidizers, sulfur-oxidizers, sulfate-reducers, iron-reducers, and nitrifiers. The microbial diversity varied significantly between groundwater and sediment samples as their temperature adaptation inferences that revealed potential psychrophiles inhabiting the groundwater and thermophiles and mesophiles being present in the sediment. The dynamism of this environment manifests in the relatively even character of the sediment hosted microbial communities, where significant taxonomic distinctions were observed. Therefore, sediment and groundwater substrates are considered as separate ecological entities. We hope that the variety of the discussed playa environments and the microorganisms may be considered a useful terrestrial analog providing valuable information to aid future astrobiological explorations.

Microbial Diversity of Hypersaline Sediments from Lake Lucero Playa in White Sands National Monument, New Mexico, USA.

Lake Lucero is a gypsum-rich, hypersaline, ephemeral playa located on the southern part of the Alkali Flat at the White Sands National Monument (WSNM), New Mexico, USA. This modern playa setting provides a dynamic extreme environment that changes from a freshwater lake to a hypersaline dry desert during the year. We investigated the microbial diversity (bacteria, archaea, and microbial eukaryotes) of the Lake Lucero sediments using 16S- and 18S-based amplicon sequencing approach and explored the diversity patterns in different geochemical microenvironments. Our results indicated that similar microbial communities, in particular bacterial communities colonized, were remarkably consistent across our depth profiles. Therefore, these communities show a first-order relevance on the environmental conditions (moisture content, oxygen content, and mineral composition). We found that Proteobacteria, Actinobacteria, Bacteroidetes, Firmicutes, and Gemmatimonadetes were the major bacterial phyla, while Cyanobacteria were present in relatively low abundances and appeared only at the surface. Genus level assessment reflected that Truepera, Delftia, and Pseudomonas were the predominant bacterial genera across all samples. Euryarchaeota was the major archaeal phylum in all the samples, while Candidatus Halobonum and Candidatus Nitrososphaera were the main genera. Diatoms were the dominant eukaryotic group in surface samples and Fungi, Ciliophora, Metazoa, and Nematodes were the other major groups. As expected, metabolic inference indicated that aerobic microbial communities were near surface colonizers, with anaerobic communities dominating with increasing depth. We demonstrated that these microbial communities could be used to characterize unique geochemical microenvironments enabling us to extrapolate these results into other terrestrial and possibly extraterrestrial environments with comparable geochemical characteristics.

Unique meteorite from early Amazonian Mars: water-rich basaltic breccia Northwest Africa 7034.

We report data on the martian meteorite Northwest Africa (NWA) 7034, which shares some petrologic and geochemical characteristics with known martian meteorites of the SNC (i.e., shergottite, nakhlite, and chassignite) group, but also has some unique characteristics that would exclude it from that group. NWA 7034 is a geochemically enriched crustal rock compositionally similar to basalts and average martian crust measured by recent Rover and Orbiter missions. It formed 2.089 ± 0.081 billion years ago, during the early Amazonian epoch in Mars' geologic history. NWA 7034 has an order of magnitude more indigenous water than most SNC meteorites, with up to 6000 parts per million extraterrestrial H(2)O released during stepped heating. It also has bulk oxygen isotope values of Δ(17)O = 0.58 ± 0.05 per mil and a heat-released water oxygen isotope average value of Δ(17)O = 0.330 ± 0.011 per mil, suggesting the existence of multiple oxygen reservoirs on Mars.