2015 Annual Science Report
Massachusetts Institute of Technology Reporting | JAN 2015 – DEC 2015
Mars Analog Studies: Ice Covered Lakes on Earth and Mars
Ice-covered lakes in Antarctica provide models for sedimentary processes on ancient Mars and microbial ecosystems for early Earth. Ice affects sedimentation because sand grains can be blown onto the ice, where they can eventually go through the ice into the lake below. Understanding the details of these processes and resulting sediments will allow us to better reconstruct details of lake environments and their implications for climate on early Mars. Early Earth ecosystems, and those on early Mars if life ever existed there, consist exclusively of microorganisms, which is also true for many Antarctic lakes. Thus, these lakes provide the opportunities to investigate ecological principles for early ecosystems. Data from the microbial mats in these lakes are providing insights into the growth of stromatolite, the geochemical impacts of oxygen-producing photosynthesis, and environments that may have promoted the early diversification of animals.
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.)
PROJECT INVESTIGATORS:Dawn Sumner
PROJECT MEMBERS:Jonathan Eisen
RELATED OBJECTIVES:Objective 2.1
Earth's early biosphere.
Production of complex life.
Environment-dependent, molecular evolution in microorganisms
Co-evolution of microbial communities
Effects of environmental changes on microbial ecosystems