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Searching for Life in the Ice of Antarctica - and Mars?
Once thought to be barren of life, the ice covers of alpine and polar lakes are home to rich microbial communities. Advances in laser induced fluorescence emission (L.I.F.E.) imaging and spectroscopy now make it possible to detect and monitor photosynthetic cyanobacteria living within the ice.
Non-destructive, non-contact L.I.F.E. detection of microbes living within Antarctic lake ice was first accomplished during the 2008 Tawani Expedition to Lake Untersee, Dronning Maud Land, Antarctica. The observation has since been confirmed by studies at Lake Fryxell in the McMurdo Dry Valleys.
The findings mean that it may one day be possible to search from orbit for L.I.F.E. signatures of photosynthetic organisms in the polar regions of Mars, the ice moons of the outer planets, and the frozen regions of exoplanets in neighboring star systems.
The dry valleys of Schirmacher Oasis and Untersee lie due south of Cape Town, South Africa in the Russian sector of Antarctica.
Orbital images courtesy of Google Earth. Annotated to indicate Schirmacherr Oasis, Dry Valleys, and Untersee expedition sites.
Untersee has been ice-covered for the past 10,000 yearrs. Fed by the massive Anuchin Glacier the mouth of the lake nearest the glacier contains water that is highly oxygenated. At the far end of the lake, at a depth of 180 meters, the water is anoxic.
Untersee is an alkaline, high salinity "soap lake" whose underwater inhabitants have been protected for 10,000 years by 2-6 meters of translucent ice.
At current global warming rates this protective ice cap should be lost in 1-2 decades.
For now, the cold, dry rocky land offers a "Mars analog" extreme environment for field testing life detection technology prior to deployment on human or robotic missions to Mars.
Landing at Anuchin glacier entrance to Untersee.
Unloading supplies from the DC-3 at the top of the Anuchin Glacier.
Accumulations of wind-blown dust can collect as fist-sized lumps of soil and sink beneath the glacier ice to form erie "eyes". At the base of each of these "cryoconites" is an accumulation of soil and complex microbial communities.
Cryoconite
These eyes can extend as chains running several kilometers along a fissure in the slowly moving glacier ice.
Cryoconite Chain
The boundary between the glacier and the lake is marked by an intriguing "ice monster" - actually a simple folding of the lake ice much like an ocean wave as the glacier pushes against the lake ice cover.
Ripple in Ice - an ice wave
During the winter dry winds remove the upper layers of ice from the lake allowing giant boulders to apparently "rise" to the surface.
Boulders riding surface of the frozen lake
Not surprisingly, the summer sun warms the boulders. The heat from the boulders melts the ice to form moats containing films of liquid water. The boulders will slowly sink into the ice only to reappear the following season.
The moats and associated cracks and fissure contain a rich microbial community dominated by photosynthetic organisms such as cyanobacteria.
But microorganisms also inhabit the millions of bubbles found throughout the translucent ice of this ancient lake.
A 532 nm laser penlight excites a photosynthetic pigment found in the cyanobacteria inhabiting these bubbles resulting in a pale yellow fluorescence captured in these images.
These organisms were amongst the earliest inhabitants of our planet and once were most likely the dominant species on Earth. As life evolved to include "grazing" organisms, cyanobacterial communities were devastated. These organisms at Untersee are protected with an ice barrier surrounding small, millimeter scale, miniature "Earths". The microbes dwell in the liquid water boundary zone between soil and ice.
These miniature cryoconites filled with cyanobacteria-dominated microbial colonies slowly sink through the Untersee ice cover. The image shows one meter of an ice core with a sample of the colonies illuminated with a 532 nm laser.
Once the organisms arrive at the lake bottom they join a massive microbial mat community. Portions of the mat have created living stromatolites which appear in the next image. A diver's fingers are included for scale.
When a stromatolite is brought to the surface the outer living layer appears to be rich in a variety of photopigments that absorb blue and green light, producing a deep red color in the growth tip at the apex of the formation.
Transection of the stromatolite reveals the characteristic layering. Only the outermost layer is alive. The others layers are the fossil remains of progressively more ancient microbial mat communities.
For more information on stromatolites see Ancient Complexity.
Using L.I.F.E. Technology to Estimate Photosynthetic Productivity
In a joint effort between investigators at the Kinohi Institute, Harvey Mudd College, and the Ecology Institute of the University of Innsbruck, Innsbruck, Austria, non-destructive, non-contact L.I.F.E. field cameras and spectrometers are being developed to annually estimate the productivity of polar and alpine ice photosynthesis here on Earth. For more information see Life in Lava Tubes.
Employing similar devices from an orbiting satellite could help us rapidly estimate the impact of global climate change on Arctic, Antarctic, and Alpine ecosystems. The technology could provide a cost-efficient way to monitor the health of food crops around the world.
References
Weisleitner, K., Hunger, L., Kohstall, C., Frisch, A., Storrie-Lombardi, M. C., Sattler, B.,(2019) Laser-induced fluorescence emission (L.I.F.E.) as novel non-invasive tool for in-situ measurements of biomarkers in cryospheric habitats. J. Vis. Exp. 152, e60447.
Sattler, B., M.C. Storrie-Lombardi, C.M. Foreman, M. Tilg, and Psenner, R. (2010) Laser induced fluorescence emission (L.I.F.E.) from Lake Fryxell cryoconites. Annal. Glaciol., 2010. 51(56): p. 145-152.
Storrie-Lombardi, M.C., Muller, J.-P., Fisk, M.R., Cousins, C., Sattler, B., Griffiths, A.D. and Coates, A.J. (2009) Laser induced fluorescence emission (L.I.F.E.): searching for Mars organics with a UV-Enhanced PanCam. Astrobiology 9(10): 953-964.
Storrie-Lombardi, M.C. and Sattler, B. (2009) Laser induced fluorescence emission (L.I.F.E.): Detection of microbial life in the Ice covers of Antarctic lakes. Astrobiology 9(7): 659-672.
Storrie-Lombardi, M.C. and Williamson, S. (2009) Possible role of bacteriophage-mediated horizontal gene transfer on microbial adaptation to environmnetal stressors in polar ecosystems. In Polar Microbiology: The Ecology, Biodiversity and Bioremediation Potential of Microorganisms in Extremely Cold Environments. A. K. Bej, J. Aislabie and R. M. Atlas. London, Taylor and Francis: 179-200.
Gerakines, P.A. and Storrie-Lombardi, M.C. (2009) Sources of organic matter for the Archean cryosphere. In Polar Microbiology: The Ecology, Biodiversity and Bioremediation Potential of Microorganisms in Extremely Cold Environments. A. K. Bej, J. Aislabie and R. M. Atlas. London, Taylor and Francis: 201-214.
Sattler, B. and Storrie-Lombardi, M.C. (2009) L.I.F.E. in Antarctic lakes. In Polar Microbiology: The Ecology, Biodiversity and Bioremediation Potential of Microorganisms in Extremely Cold Environments. A. K. Bej, J. Aislabie and R. M. Atlas. London, Taylor and Francis: 95-114.
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