Lava tubes and basaltic caves as astrobiological targets on Earth and Mars: A review     

Richard J. Léveillé  Saugata Datta 《Planetary and Space Science》2010,58(4):592-618

Lava tubes and basaltic caves are common features in volcanic terrains on Earth. Lava tubes and cave-like features have also been identified on Mars based on orbital imagery and remote-sensing data. Caves are unique environments where both secondary mineral precipitation and microbial growth are enhanced by stable physico-chemical conditions. Thus, they represent excellent locations where traces of microbial life, or biosignatures, are formed and preserved in minerals. By analogy with terrestrial caves, caves on Mars may contain a record of secondary mineralization that would inform us on past aqueous activity. They may also represent the best locations to search for biosignatures. The study of caves on Earth can be used to test hypotheses and better understand biogeochemical processes, and the signatures that these processes leave in mineral deposits. Caves may also serve as test beds for the development of exploration strategies and novel technologies for future missions to Mars. Here we review recent evidence for the presence of caves or lava tubes on Mars, as well as the geomicrobiology of lava tubes and basaltic caves on Earth. We also propose future lines of investigation, including exploration strategies and relevant technologies.  相似文献   

Application of electrical resistivity to map the stratigraphy and salinity of fluvio-deltaic aquifers: case studies from Bangladesh that reveal benefits and pitfalls     

Pedrazas  Micaela N.  Cardenas  M. Bayani  Hosain  Alamgir  Demir  Cansu  Ahmed  Kazi Matin  Akhter  Syed Humayun  Wang  Lichun  Datta  Saugata  Knappett  Peter S. K. 《Hydrogeology Journal》2021,29(4):1601-1610

Fluvio-deltaic aquifers are the primary source of drinking water for the people of Bangladesh. Such aquifers, which comprise the Ganges-Brahmaputra-Meghna Delta, are hydrogeologically heterogeneous. Because of widespread groundwater quality issues in Bangladesh, it is crucial to know the hydrostratigraphic architecture and hydrochemistry, as some aquifer units are contaminated, whereas others are safe. Geophysical methods provide a potentially effective and noninvasive method for extensive characterization of these aquifers. This study applies and investigates the limitations of using electrical resistivity imaging (ERI) for mapping the hydrostratigraphy and salinity of an aquifer-aquitard system adjacent to the Meghna River. Some electrical resistivity (ER) sections showed excellent correlation between resistivity and grain size. These suggest that ERI is a powerful tool for mapping internal aquifer architecture and their boundaries with finer-grained aquitards which clearly appear as low-ER zones. However, in parts of some ER sections, variations in electrical properties were determined by porewater resistivity. In these cases, low ER was indicative of brine and did not indicate the presence of finer-grained materials such as silt or clay. Accordingly, the following hydrostratigraphic zones with different resistivities were detected: (1) aquifers saturated with fresh groundwater, (2) a regional silt/clay aquitard, and (3) a deeper brine-saturated formation. In addition, shallow silt/clay pockets were detected close to the river and below the vadose zone. ERI is thus a promising technique for mapping aquifers versus aquitards; however, the observations are easily confounded by porewater salinity. In such cases, borehole information and groundwater salinity measurements are necessary for ground-truthing.

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Assessing Li and other leachable geochemical proxies for paleo-salinity in lake sediments from the Mono Basin, CA (USA)     

Rahul Sahajpal  Saugata Datta  Sidney R. Hemming 《Geochimica et cosmochimica acta》2011,75(24):7855-7863

Regional climate-driven hydrological changes are accompanied by salinity changes in closed basin lakes. We have investigated acid leachable Li, along with other leachable ions including Mg, Ca and Sr, as geochemical proxies of salinity in lake sediments in the Mono Basin, California. All the elements in the acid leachable suite show a strong correlation with paleo-lake level estimates based on physical and stratigraphic evidence. The CaCO₃ content of lake sediments, which has been shown to be a reliable proxy for lake level changes in the Mono basin and the adjoining Owens Lake basin, corresponds well with our acid-leachable proxy data.  相似文献   

Groundwater arsenic biogeochemistry-Key questions and use of tracers to understand arsenic-prone groundwater systems     

David A.Polya  Charlotte Sparrenbom  Saugata Datta  Huaming Guo 《地学前缘(英文版)》2019,10(5):1635-1641

Over 100,000,000 people worldwide are exposed to high arsenic groundwater utilised for drinking or cooking.The consequent global avoidable disease burden is estimated to be of the order of 100,000 avoidable deaths or more per annum from just direct exposures — i.e.excluding indirect exposure(from rice and other foods)and excluding morbidity.Notwithstanding 1000 s of papers published on arsenic(hydro)(bio)geochemistry,there remain a number of key outstanding questions to be addressed in relation to arsenic geoscience-these include questions related to:(i)the role of human activities —irrigation,agriculture and other land uses — on arsenic mobilisation in groundwaters;(ii)the specific sources,nature and role of organics,minerals and microbial communities involved in arsenic mobilisation;(iii)the relationship to microscopic to macroscopic scale geological(including tectonic)and evolution processes;(iv)unravelling the over-printing of multiple processes in complex highly heterogeneous aquifer systems and(v)using increasing understanding of the controls of arsenic mobility in groundwaters systems to informing improved locally-relevant remediation and mitigation approaches.This article further summarises how the 9 further papers in this Special Issue address some of these questions through the use of chemical and/or isotopic tracers.  相似文献