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Project Progress

During 2015, we made substantial progress in understanding how Antarctic lakes provide insights into diverse astrobiological research questions. With regards to Mars, graduate student Rivera-Hernandez identified several new processes affecting sedimentation in ice-covered lakes that would leave preservable signatures in lacustrine rock records. Specifically, sediment blown or washed onto the ice can filter down into the lake below, and transport of sediment through the ice is affected by grain size, grain color, and ice properties, among other parameters. She continuing to compile data from both sediment on the ice and in the lake to develop a facies model for sedimentation in ice-covered lakes with a focus on features that distinguish them from open water lakes (Fig. 1). She is also preparing these facies models to compare with lacustrine sediments of the Murray formation, Gale Crater, Mars, using Curiosity data. If the martian lakes were ice covered, their presence would not require as warm and dense an atmosphere as does the possible presence of very long-lived open water lakes. Thus, understanding the details of the lacustrine facies, in the context of possible ice cover, has substantial implications for the ancient martian atmosphere.

The development of a new facies model for ice-covered lakes is also the foundation of a new collaboration to identify possible Cryogenian ice-covered lake deposits in the Marinoan Wilsonbreen Formation, Svalbard (Benn et al., 2015). Mackey, Rivera-Hernandez, and Sumner are now working with Prof. Ian Fairchild, Univ. of Birmingham, on evaluating whether or not any of the glacially associated lake deposits they described might have been ice covered. Mackey will be starting at postdoc position at MIT to specifically address these facies questions.

The importance of whether or not Cryogenian ice-covered lakes were present was highlighted through collaborations within the Complex Life NAI node: ice-covered lakes may have been an important ecological refuge during Snowball Earth glaciation, in particular because they can have unusual redox distributions. In collaboration with Dr. Anne Jungblut, Natural History Museum, Prof. Ian Hawes, Univ. of Canterbury, and Prof. Peter Doran, Louisiana State University, Sumner, Mackey, and Krusor published two papers on the microbiology of O₂ oases in Lake Fryxell, an Antarctic ice-covered lake (Sumner et al., 2015; Jungblut et al., 2016). The initial evaluation of the O₂ oases focused on them as an analog for Archean benthic mats containing the first cyanobacteria. However, through discussions within the context of NAI and the Astrobiology Science Conference, it became clear that similar environments may have been present during Snowball Earths. Benthic O₂ production in ice-covered lakes may have provided O₂-rich environments for the early proliferation of animals – during global glaciation. This will be the second focus of Mackey’s postdoctoral research.

Ar MIT, graduate student documents the lipid contents of stromatolite pinnacle from Lake Vanda. We hope this will be the first part of a detailed description of biosignatures that characterise microbialites from oxygen-rich ice covered lakes.

In addition to these results, the project has produced insights into stromatolite and mat growth as a function of both biological and environmental processes as well as environmental change in the McMurdo Dry Valleys, Antarctica (e.g. Mackey et al, 2015, Jungblut et al., 2016, papers in review and prep.)