Mars Sample Return Sample Receiving Project measurement definition team final report
No abstract available.
Astrobiology↗
Geology topics
Jeffrey J. Marlow
Publications and source records attributed to Jeffrey J. Marlow.
Carbonate-hosted microbial communities are prolific and pervasive methane oxidizers at geologically diverse marine methane seep sites
At marine methane seeps, vast quantities of methane move through the shallow subseafloor, where it is largely consumed by microbial communities. This process plays an important role in global methane dynamics, but we have yet to identify all of the methane sinks in the deep sea. Here, we conducted a continental-scale survey of seven geologically diverse seafloor seeps and found that carbonate rocks from all sites host methane-oxidizing microbial communities with substantial methanotrophic potential. In laboratory-based mesocosm incubations, chimney-like carbonates from the newly described Point Dume seep off the coast of Southern California exhibited the highest rates of anaerobic methane oxidation measured to date. After a thorough analysis of physicochemical, electrical, and biological factors, we attribute this substantial metabolic activity largely to higher cell density, mineral composition, kinetic parameters including an elevated V max , and the presence of specific microbial lineages. Our data also suggest that other features, such as electrical conductance, rock particle size, and microbial community alpha diversity, may influence a sample’s methanotrophic potential, but these factors did not demonstrate clear patterns with respect to methane oxidation rates. Based on the apparent pervasiveness within seep carbonates of microbial communities capable of performing anaerobic oxidation of methane, as well as the frequent occurrence of carbonates at seeps, we suggest that rock-hosted methanotrophy may be an important contributor to marine methane consumption.
Proceedings of the National Academy of Sciences (P↗
Mapping metabolic activity at single cell resolution in intact volcanic fumarole soil
Interactions among microorganisms and their mineralogical substrates govern the structure, function, and emergent properties of microbial communities. These interactions are predicated on spatial relationships, which dictate metabolite exchange and access to key substrates. To quantitatively assess links between spatial relationships and metabolic activity, this study presents a novel approach to map all organisms, the metabolically active subset, and associated mineral grains, all while maintaining spatial integrity of an environmental microbiome. We applied this method at an outgassing fumarole of Vanuatu’s Marum Crater, one of the largest point sources of several environmentally relevant gaseous compounds, including H2O, CO2, and SO2. With increasing distance from the soil-air surface and from mineral grain outer boundaries, organism abundance decreased but the proportion of metabolically active organisms often increased. These protected niches may provide more stable conditions that promote consistent metabolic activity of a streamlined community. Conversely, mineral exteriors accumulate more organisms that may cover a wider range of preferred conditions, implying that only a subset of the community will be active under any particular environmental regime. More broadly, the approach presented here allows investigators to see microbial communities “as they really are” and explore determinants of metabolic activity across a range of microbiomes.
FEMS Microbiology Letters↗
A global synthesis of lava lake dynamics
Active lava lakes represent a variety of open-vent volcanism in which a sizeable body of lava accumulates at the top of the magma column, constrained by the vent and/or crater geometry. The longevity of lava lakes reflects a balancing of cooling and outgassing occurring at the surface by input of hot and gas-rich magma from below. Due to their longevity and relative accessibility, lava lakes provide a natural laboratory for studying fundamental volcanic processes such as degassing, convection and cooling. This article examines all seven lakes that existed at the time of writing, located in the Pacific, Antarctica, Africa, and South and Central America. They span all tectonic environments, and a range of magma compositions. We focus on analysis of the lake surface motion using image velocimetry, which reveals both similarities and contrasts in outgassing and lake dynamics when comparing the different lakes. We identify two categories of lake behavior: Organized (Erta ’Ale, Nyiragongo, K¯ılauea after 2011, and Erebus) and Chaotic (Villarrica,Masaya, Marum). This division does not map directly to lake size, viscosity, gas emission rate, or temperature. Instead, when examined together, we find that the lakes follow a linear relationship between average surface speed and the ratio of total gas flux to lake surface area. This relationship points to the importance of both flux and lake size in addition to the total volumetric outgassing rate, and suggests a shared deep mechanism controls the supply of heat and gas to all lakes. On the other hand, the differences between Chaotic and Organized lakes highlight the important role of the geometry of the conduit-lake transition, which superimposes a shallow signal on that of the deep circulation. The spatial patterns of surface motion we document suggest the release of gas bubbles at Chaotic lakes is more efficient (i.e., bubbles are less likely to be retained and recycled) compared with Organized lakes. In addition, the data presented here indicate that the solidified crust of Organized lakes plays a role in regulating convection and outgassing in lava lakes.
Journal of Volcanology and Geothermal Research↗