| Summary: | The search for life beyond Earth is a primary goal of NASA, and in our solar system ocean worlds such as Jupiter’s moon Europa are among the most promising targets. Europa has a global outer shell of ice which is likely to be tens of km thick – but also a lower mass meaning pressures and temperatures in the upper ocean below the shell may be similar to Earth’s polar oceans. Models for the habitability of Europa’s hydrosphere suggest that exchange between the ice shell and ocean, controlled by melting and freezing processes, is important for Europa’s overall habitability. Ahead of the Europa Clipper mission which is anticipated to reach the Jovian system by ~2030, we turn to Antarctica’s ice-covered oceans to build our understanding of how sub-ice ecosystems operate while simultaneously applying these lessons to other oceans worlds in our solar system. Around the edge of the Antarctic continent, floating extensions of the ice sheet called ice shelves cover 1.5 million square kilometers of the coastal ocean, an area the size of Mongolia, in ice hundreds to thousands of meters thick. Ross Ice Shelf represents a third of this area alone but the thick ice poses a significant barrier to exploration and since the late 1970s only four projects (two of which are included here) have accessed the ocean below. Sub- ice shelf ocean and ecosystem dynamics are understudied – by analogy this would be like trying to sort out the weather in a region the size of France based on launching one weather balloon a decade. Here, we used a novel remotely-operated underwater vehicle designed for sub-ice oceanography, ROV Icefin, to study the environments and ecosystems beneath Earth’s ice shelves. Over several field seasons below Ross and McMurdo Ice Shelves, we have contributed a new understanding of interactions between ice shelves, ocean, and seafloor processes. By pairing oceanographic observations with a complementary survey of bacteria and archaeal diversity under the shelf, we provide additional evidence for the importance of ...
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