Collaborative Research: MIDGE: Minimally Invasive Direct Glacial Exploration of Biogeochemistry, Hydrology and Glaciology of Blood Falls, McMurdo Dry Valleys

最近在南极冰盖下广泛发现的液态水和微生物生态系统引起了人们对南极冰下环境研究的极大兴趣。了解冰下水文学、长期与世隔绝的生命持续存在以及冰下栖息地的演变和稳定性，需要采用综合的跨学科方法。麦克默多干谷血瀑布生物地球化学、水文和冰川学的微创直接冰川勘探（MIDGE）合作项目将整合地球物理测量、分子微生物生态学和地球化学分析，探索被称为血瀑布的独特南极冰下系统。血瀑布是一种高盐的冰下盐水，支持活跃的微生物群落。冰下盐水从泰勒冰川表面的裂缝中释放出来，为进入南极冰下生态系统提供了一个方便的入口。最近的地球化学和分子分析支持血瀑布中的盐和微生物的海洋来源。最后一次海水淹没麦克默多干谷的这一部分是在晚第三纪，这表明盐水是古老的。尽管如此，还没有从血瀑布的冰下水源收集到直接样本，人们对这种盐水的来源以及它被密封在泰勒冰川下的时间也知之甚少。在血瀑布附近收集的雷达剖面描绘了冰下基底中可能存在的断层，这可能有助于解释盐水释放的局域性和偶发性。然而，目前尚不清楚是什么触发了血瀑布裂缝中卤水的偶发性释放，也不清楚卤水在流向地表时发生了多大程度的改变。MIDGE项目旨在确定血瀑布的盐水释放机制，评估冰川导管内地球化学和微生物群落的变化，并评估血瀑布的水是否对泰勒冰川（南极洲研究最多的极地冰川之一）的温度和应力状态有明显影响。冰川结构和盐水释放机制的地球物理研究将使用探地雷达、GPS和小型被动地震台网。MIDGE将与来自德国亚琛应用科学大学（FH Aachen University of Applied Sciences, Germany）的“冰鼹鼠”（Ice Mole）团队（由德国航空航天中心（DLR）资助）共同开发和部署创新的微创技术，用于清洁通道和从Blood Falls排水系统深处提取盐水样本。这些技术将允许收集远离地表（高达几十米）的盐水样本，用于地球化学分析和微生物结构-功能实验。人们关切钻探过程中固有的化学和生物物质对原始冰下环境的污染；MIDGE将提供关于热电探针清洁获取和检索代表性冰下样品的有效性的数据。南极冰下环境为研究微生物生命的生存能力和适应性提供了极好的机会，并且是冰行星上生命栖息地的潜在陆地类似物。MIDGE项目为热水和机械钻探提供了一种便携、多功能、清洁的替代方案，将使冰下水文和生态系统功能的探索成为可能，同时在开发微创和清洁冰系统采样技术方面取得重大进展。

Recent discoveries of widespread liquid water and microbial ecosystems below the Antarctic ice sheets have generated considerable interest in studying Antarctic subglacial environments. Understanding subglacial hydrology, the persistence of life in extended isolation and the evolution and stability of subglacial habitats requires an integrated, interdisciplinary approach. The collaborative project, Minimally Invasive Direct Glacial Exploration (MIDGE) of the Biogeochemistry, Hydrology and Glaciology of Blood Falls, McMurdo Dry Valleys will integrate geophysical measurements, molecular microbial ecology and geochemical analyses to explore a unique Antarctic subglacial system known as Blood Falls. Blood Falls is a hypersaline, subglacial brine that supports an active microbial community. The subglacial brine is released from a crevasse at the surface of the Taylor Glacier providing an accessible portal into an Antarctic subglacial ecosystem. Recent geochemical and molecular analyses support a marine source for the salts and microorganisms in Blood Falls. The last time marine waters inundated this part of the McMurdo Dry Valleys was during the Late Tertiary, which suggests the brine is ancient. Still, no direct samples have been collected from the subglacial source to Blood Falls and little is known about the origin of this brine or the amount of time it has been sealed below Taylor Glacier. Radar profiles collected near Blood Falls delineate a possible fault in the subglacial substrate that may help explain the localized and episodic nature of brine release. However it remains unclear what triggers the episodic release of brine exclusively at the Blood Falls crevasse or the extent to which the brine is altered as it makes its way to the surface. The MIDGE project aims to determine the mechanism of brine release at Blood Falls, evaluate changes in the geochemistry and the microbial community within the englacial conduit and assess if Blood Falls waters have a distinct impact on the thermal and stress state of Taylor Glacier, one of the most studied polar glaciers in Antarctica. The geophysical study of the glaciological structure and mechanism of brine release will use GPR, GPS, and a small passive seismic network. Together with international collaborators, the 'Ice Mole' team from FH Aachen University of Applied Sciences, Germany (funded by the German Aerospace Center, DLR), MIDGE will develop and deploy innovative, minimally invasive technologies for clean access and brine sample retrieval from deep within the Blood Falls drainage system. These technologies will allow for the collection of samples of the brine away from the surface (up to tens of meters) for geochemical analyses and microbial structure-function experiments. There is concern over the contamination of pristine subglacial environments from chemical and biological materials inherent in the drilling process; and MIDGE will provide data on the efficacy of thermoelectric probes for clean access and retrieval of representative subglacial samples. Antarctic subglacial environments provide an excellent opportunity for researching survivability and adaptability of microbial life and are potential terrestrial analogues for life habitats on icy planetary bodies. The MIDGE project offers a portable, versatile, clean alternative to hot water and mechanical drilling and will enable the exploration of subglacial hydrology and ecosystem function while making significant progress towards developing technologies for minimally invasive and clean sampling of icy systems.