Thirty years after the first discovery of high-temperature submarine venting, the vast majority of the global mid-ocean ridge remains unexplored for hydrothermal activity. Of particular interest are the world's ultraslow spreading ridges that were the last to be demonstrated to host high-temperature venting but may host systems particularly relevant to prebiotic chemistry and the origins of life. Here we report evidence for previously unknown, diverse, and very deep hydrothermal vents along the ∼110 km long, ultraslow spreading Mid-Cayman Rise (MCR). Our data indicate that the MCR hosts at least three discrete hydrothermal sites, each representing a different type of water-rock interaction, including both mafic and ultramafic systems and, at ∼5,000 m, the deepest known hydrothermal vent. Although submarine hydrothermal circulation, in which seawater percolates through and reacts with host lithologies, occurs on all mid-ocean ridges, the diversity of vent types identified here and their relative geographic isolation make the MCR unique in the oceans. These new sites offer prospects for an expanded range of vent-fluid compositions, varieties of abiotic organic chemical synthesis and extremophile microorganisms, and unparalleled faunal biodiversity-all in close proximity.hydrothermal activity | mid-ocean ridge | microbiology | ocean chemistry | astrobiology

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On May 31, 2010, a direct acoustic measurement method was used to quantify fluid leakage rate from the Deepwater Horizon Macondo well prior to removal of its broken riser. This method utilized an acoustic imaging sonar and acoustic Doppler sonar operating onboard a remotely operated vehicle for noncontact measurement of flow cross-section and velocity from the well's two leak sites. Over 2,500 sonar cross-sections and over 85,000 Doppler velocity measurements were recorded during the acquisition process. These data were then applied to turbulent jet and plume flow models to account for entrained water and calculate a combined hydrocarbon flow rate from the two leak sites at seafloor conditions. Based on the chemical composition of end-member samples collected from within the well, this bulk volumetric rate was then normalized to account for contributions from gases and condensates at initial leak source conditions. Results from this investigation indicate that on May 31, 2010, the well's oil flow rate was approximately 0.10 AE 0.017 m 3 s −1 at seafloor conditions, or approximately 85AE 15 kg s −1 (7.4 AE 1.3 Gg d −1 ), equivalent to approximately 57,000AE 9,800 barrels of oil per day at surface conditions. End-member chemical composition indicates that this oil release rate was accompanied by approximately an additional 24 AE 4.2 kg s −1 (2.1AE 0.37 Gg d −1 ) of natural gas (methane through pentanes), yielding a total hydrocarbon release rate of 110 AE 19 kg s −1 (9.5 AE 1.6 Gg d −1 ).Gulf of Mexico | oil spill | buoyant plume | buoyant jet | subsurface A ccurate assessment of the hydrocarbon fluid release rate from well blowouts such as that of the Deepwater Horizon Macondo well provides fundamental information for evaluating intervention options to regain well control, properly scaling oil collection and containment operations, estimating the total spill volume, assessing environmental damage, and investigating well casing or blowout preventer (BOP) failure modes. On May 31, 2010, a direct acoustic technique was used to measure the volumetric flow rate of fluids (liquid and gas) emitted from the Deepwater Horizon Macondo well. This method, which adapts acoustic techniques previously developed for deep-sea hydrothermal vent research (1), enabled observation from a remotely operated vehicle (ROV) (Fig. S1) at horizontal standoff distances of between 2 and 7 m, providing a noncontact method of measurement wherein the sensors did not disturb the flow or become fouled with oil or gas hydrate accretions. Despite the optical opacity of the fluid, this acoustic technique enabled quantitatively detailed measurement of the leaks' cross-sectional areas and velocity profiles. This acoustic flow rate assessment was conducted on a "not to interfere basis" due to the well containment operations being carried out from late April through mid-July. Data were thus collected on an opportunistic basis during short time intervals between containment procedures.Acoustic measurement commenced immediately following the unsuccessful "...

This study provides a broad look at mathematics education research published between 1982 and 1998. The ERIC database was utilized to count and categorize more than 3,000 articles from 48 educational research journals. We identified the number of articles relating to gender, ethnicity, class, and disability that were published in journals from various categories. Attention was also given to grade levels, mathematical topics, and general educational topics in conjunction with each equity group. We conclude that, in comparison with research on ethnicity, class, and disability, research on gender was more prevalent and integrated into mainstream U.S. mathematics education research. Overall, the majority of research seemed to focus on student cognition and outcomes, with less attention to contextual or cultural issues.

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Fungi can be highly efficient biogeochemical agents and accumulators of soluble and particulate forms of metals. This work aims to understand some of the physico-chemical mechanisms involved in toxic metal transformations focusing on the speciation of metals accumulated by fungi and mycorrhizal associations. The amorphous state or poor crystallinity of metal complexes within biomass and relatively low metal concentrations make the determination of metal speciation in biological systems a challenging problem but this can be overcome by using synchrotron-based element-specific X-ray absorption spectroscopy (XAS) techniques. In this research, we have exposed fungi and ectomycorrhizas to a variety of copper-, zinc- and lead-containing minerals. X-ray absorption spectroscopy studies revealed that oxygen ligands (phosphate, carboxylate) played a major role in toxic metal coordination within the fungal and ectomycorrhizal biomass during the accumulation of mobilized toxic metals. Coordination of toxic metals within biomass depended on the fungal species, initial mineral composition, the nitrogen source, and the physiological state/age of the fungal mycelium.

This paper reviews the scientific motivation and challenges, development, and use of underwater robotic vehicles designed for use in ice-covered waters, with special attention paid to the navigation systems employed for under-ice deployments. Scientific needs for routine access under fixed and moving ice by underwater robotic vehicles are reviewed in the contexts of geology and geophysics, biology, sea ice and climate, ice shelves, and seafloor mapping. The challenges of under-ice vehicle design and navigation are summarized. The paper reviews all known under-ice robotic vehicles and their associated navigation systems, categorizing them by vehicle type (tethered, untethered, hybrid, and glider) and by the type of ice they were designed for (fixed glacial or sea ice and moving sea ice).

Preliminary analysis of near-bottom, high-resolution DSL-120 sidescan and bathymetric data from the median valley in the TAG (Trans-Atlantic Geotraverse) segment near 26°N on the Mid-Atl antic Ridge, and Argo-Il photography from the associated actively venting hydrothermal mound, allows us to evaluate the structural, volcanic, and hydrothermal processes occurring in this area, and to provide baseline constraints on the pre-drilling status of the morphology of the mound and the distribution of venting. These data were collected just 2 months before ODP drilling of the active TAG mound, one of the largest volcanichosted, mid-ocean ridge hydrothermal deposits yet discovered. Sharp discontinuities and strong asymmetry in the morphology and age distribution about the spreading axis suggest a recent episode of preferential accretion of crust to the east. Such episodes have likely contributed to the long-term spreading asymmetry (13 mm/yr to the east, 11 mm/yr to the west) of the TAG segment. The active mound lies within the intersection of a zone of actively developing ridge-parallel (north-northeast) fissures and a series of pre-existing obliquely oriented (east-northeast) faults. The east-northeast faults are not continuous with faults previously described from the upper rift valley walls. This intersecting fault pattern may be important in localizing hydrothermal activity. Contemporaneous tectonic deformation and hydrothermal deposition continue to modify the three-dimensional structure and hydrogeology of the active TAG mound.