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

最近发现了南极冰盖下广泛存在的液态水和微生物生态系统，这引起了人们对研究南极冰下环境的极大兴趣。理解冰下水文学、长期与世隔绝的生命的持久性以及冰下栖息地的演变和稳定，需要一种综合的跨学科方法。麦克默多干谷生物地球化学、水文学和冰川学的微创直接冰川探测(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，以探索独特的南极冰下系统--血液瀑布。血瀑布是一种高盐度的冰下卤水，支持活跃的微生物群落。冰下卤水从泰勒冰川表面的裂缝中释放出来，提供了进入南极冰下生态系统的入口。最近的地球化学和分子分析支持血瀑布中盐类和微生物的海洋来源。上一次海水淹没麦克默多干河谷的这一部分是在第三纪晚期，这表明卤水是古老的。尽管如此，从冰下源头到血瀑布的直接样本还没有收集到，关于这种卤水的来源或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轮廓描绘了冰下基质中一个可能的断层，这可能有助于解释卤水释放的局部性和间歇性。然而，目前还不清楚是什么触发了专门在血瀑布裂缝中偶尔释放的卤水，也不清楚盐水在到达地表的过程中发生了多大程度的变化。米奇项目旨在确定血瀑布的卤水释放机制，评估河流管道内的地球化学和微生物群落的变化，并评估血瀑布水域是否对南极洲研究最多的极地冰川之一泰勒冰川的温度和应力状态产生明显影响。对冰川构造和卤水释放机制的地球物理研究将使用探地雷达、GPS和一个小型被动地震台网。与国际合作者一起，来自德国FH Aachen应用科学大学(由德国航空航天中心(DLR)资助)的“冰鼹鼠”团队将开发和部署创新的微创技术，用于清洁进入血瀑布排水系统并从深处提取盐水样本。这些技术将允许在远离地表(长达数十米)的地方收集卤水样本，以进行地球化学分析和微生物结构-功能实验。令人关切的是，钻探过程中固有的化学和生物材料污染了原始的冰下环境；Midge将提供有关热电探头清洁获取和取回具有代表性的冰下样品的功效的数据。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，是冰冷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、清洁的替代品，并将能够探索冰川下的水文和生态系统功能，同时在开发对结冰系统进行微创和清洁采样的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.