“…14 C-DIC (5798 years) supported recent reports that the Zondereinde mine fracture water was influenced by paleometeoric water (Table 1, Fig. 3) 13 Figure 2Zondereinde-Bierspruit system. Google Earth image of Western Bushveld Igneous Complex mining region and mining map of Zondereinde juxtaposed upon it.…”
Section: Resultssupporting
confidence: 84%
“…The age and origin of fracture fluids (modern vs. paleometeoric) in South Africa have been well characterized using a number of approaches 12 . The δ 18 O-H 2 O and δD-H 2 O values are consistent with groundwater supply wells in the area 13 . The 14 C-DIC (<1 to 2768 years) and 3 H (7–10 years) results show (Table 1, Fig.…”
Eukarya have been discovered in the deep subsurface at several locations in South Africa, but how organisms reach the subsurface remains unknown. We studied river-subsurface fissure water systems and identified Eukarya from a river that are genetically identical for 18S rDNA. To further confirm that these are identical species one metazoan species recovered from the overlying river interbred successfully with specimen recovered from an underlying mine at −1.4 km.
In situ
seismic simulation experiments were carried out and show seismic activity to be a major force increasing the hydraulic conductivity in faults allowing organisms to create ecosystems in the deep subsurface. As seismic activity is a non-selective force we recovered specimen of algae and Insecta that defy any obvious other explanation at a depth of −3.4 km. Our results show there is a steady flow of surface organisms to the deep subsurface where some survive and adapt and others perish. As seismic activity is also present on other planets and moons in our solar system the mechanism elucidated here may be relevant for future search and selection of landing sites in planetary exploration.
“…14 C-DIC (5798 years) supported recent reports that the Zondereinde mine fracture water was influenced by paleometeoric water (Table 1, Fig. 3) 13 Figure 2Zondereinde-Bierspruit system. Google Earth image of Western Bushveld Igneous Complex mining region and mining map of Zondereinde juxtaposed upon it.…”
Section: Resultssupporting
confidence: 84%
“…The age and origin of fracture fluids (modern vs. paleometeoric) in South Africa have been well characterized using a number of approaches 12 . The δ 18 O-H 2 O and δD-H 2 O values are consistent with groundwater supply wells in the area 13 . The 14 C-DIC (<1 to 2768 years) and 3 H (7–10 years) results show (Table 1, Fig.…”
Eukarya have been discovered in the deep subsurface at several locations in South Africa, but how organisms reach the subsurface remains unknown. We studied river-subsurface fissure water systems and identified Eukarya from a river that are genetically identical for 18S rDNA. To further confirm that these are identical species one metazoan species recovered from the overlying river interbred successfully with specimen recovered from an underlying mine at −1.4 km.
In situ
seismic simulation experiments were carried out and show seismic activity to be a major force increasing the hydraulic conductivity in faults allowing organisms to create ecosystems in the deep subsurface. As seismic activity is a non-selective force we recovered specimen of algae and Insecta that defy any obvious other explanation at a depth of −3.4 km. Our results show there is a steady flow of surface organisms to the deep subsurface where some survive and adapt and others perish. As seismic activity is also present on other planets and moons in our solar system the mechanism elucidated here may be relevant for future search and selection of landing sites in planetary exploration.
“…Exploration of the deep martian subsurface could be the focus of missions to detect extant martian life, as this potentially habitable environment may be the most similar to its Earth analog, which has hosted active microbial ecosystems living in isolation from surface processes for hundreds of millions to billions of years (e.g., Lippmann-Pipke et al, 2011;Lau et al, 2016;Li et al, 2016;Heard et al, 2018;Warr et al, 2018;Lollar et al, 2019). In the deep subsurface, we can infer potential types of metabolisms to look for, including what processes could produce their driving oxidants and reductants, and what materials might be required for those processes to operate (radionuclides, H 2 O, sulfides, ferrous silicates, CO 2 , and CH 4 ).…”
Section: Exploration Opportunities and Challengesmentioning
786 1. Introduction 786 2. Organization of the Ideas Presented and Discussed at the Conference 787 2.1. Definition of key terms 787 3. Martian Environments Deemed to Be Most Prospective for Extant Martian Life 788 3.1. Caves 790 3.2. Deep subsurface 790 3.3. Ice 793 3.4. Salts 796 4. Methodologies: A Summary of Possible Approaches and Strategies to Search for Extant Life on Mars 797 4.1. Geologically guided search strategies 797 4.2. Possible detection methods for extant martian life 799 4.3. Possible constraints relevant to the search for extant martian life derived from laboratory experiments 802 5. Discussion 804 Acknowledgments 805 References 805
“…Abundant fractures developed over the history of these igneous rocks host a large terrestrial subsurface water reservoir of up to 30% of the planet's total groundwater inventory (Warr et al, 2018). Geochemical signatures (e.g., salinity, major and trace elemental compositions, dissolved gas contents, redox condition, 18 O and 2 H) of these fluids indicate that they have been strongly influenced by water-rock reactions, and, in some cases, affected by mixing with varying amounts of secondary (paleo-)meteoric water (e.g., Ward et al, 2004;Onstott et al, 2006;Li et al, 2016;Heard et al, 2018;Warr et al, 2021a and references therein). Most of these deep subsurface fracture water systems have been hydrogeologically isolated over geological time scales, e.g., up to hundreds of million years to billions of years in the Canadian Shield (Holland et al, 2013;Warr et al, 2018), up to tens to hundreds of million years in the Fennoscandian Shield (Kietäväinen et al, 2014) and the Witwatersrand Basin in the Kaapvaal Craton, South Africa (Heard et al, 2018;Lippmann et al, 2003).…”
Section: Introductionmentioning
confidence: 99%
“…Geochemical signatures (e.g., salinity, major and trace elemental compositions, dissolved gas contents, redox condition, 18 O and 2 H) of these fluids indicate that they have been strongly influenced by water-rock reactions, and, in some cases, affected by mixing with varying amounts of secondary (paleo-)meteoric water (e.g., Ward et al, 2004;Onstott et al, 2006;Li et al, 2016;Heard et al, 2018;Warr et al, 2021a and references therein). Most of these deep subsurface fracture water systems have been hydrogeologically isolated over geological time scales, e.g., up to hundreds of million years to billions of years in the Canadian Shield (Holland et al, 2013;Warr et al, 2018), up to tens to hundreds of million years in the Fennoscandian Shield (Kietäväinen et al, 2014) and the Witwatersrand Basin in the Kaapvaal Craton, South Africa (Heard et al, 2018;Lippmann et al, 2003). Closed-system water-rock interactions over these extended time periods has progressively produced chemicals (e.g., H2, hydrocarbons, sulfate) and highly reducing habitable environments favorable for chemo(litho)trophic microbes (Lin et al, 2005(Lin et al, , 2006Li et al, 2016;Magnabosco et al, 2018;Lollar et al, 2019).…”
In addition to high concentrations of CH4 and H2, abundant dissolved N2 is found in subsurface fracture fluids in Precambrian cratons around the world. These fracture fluids have hydrogeological isolation times on order of thousands to millions and even billions of years. Assessing the sources and sinks of N2 and related (bio)geochemical processes that drive the nitrogen cycle in these long isolated systems can shed insights into the nitrogen cycles on early Earth with implications for other planets and moons. In this study, we collected dissolved gas samples from deep subsurface fracture fluids at seven sites (Kidd Creek, LaRonde, Nickel Rim, Fraser, Copper Cliff South, Thompson, and Birchtree) in the Canadian Shield. Multiple gas components (e.g., H2, O2 and Ar) were integrated with δ 15 NN2 values to characterize the N2 signatures. Results show that the dissolved N2 in deep subsurface fracture fluids from the Canadian Shield sites are more 15 N-enriched than those from the Fennoscandian Shield and the Witwatersrand Basin in the Kaapvaal Craton. The nitrogen isotopic signatures of the Canadian Shield samples coupled with their hydrogeological framework indicate the N2 was sourced from fixed ammonium in silicate minerals in host rocks and was generated by metamorphic devolatilization.Modeling of nitrogen devolatilization from host rocks supports this interpretation, but also suggests that a second process, likely abiotic N2 reduction, is required to account for the observed 15 N enrichment in the N2 samples from the Canadian Shield. A 10-year monitoring study for one of the boreholes, at 2.4 km of the Kidd Creek Observatory, shows a steady decrease in 15 NN2 values with time, which coincides with the temporal isotopic evolution of some other gas components in this borehole. Although it cannot be confirmed at this time, this isotopic shift in N2 may be potentially attributed to microbial processes (e.g., anaerobic oxidation of ammonium). Nevertheless, the large 15 N enrichments for the majority of the samples in this study suggest that the nitrogen cycle in the deep saline fracture fluids in the Canadian Shield is dominated by abiotic processes. This is in contrast to the nitrogen cycles in the subsurface fracture fluids in the Fennoscandian Shield and the Witwatersrand Basin, which have been shown to be strongly affected by extant microbial ecosystems discovered in those fracture waters.
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