No matter the size, color, or species, what unites almost all of life on Earth is it’s ultimate dependence on sunlight. Plants use energy from the sun to grow, which we and other organisms then utilize through stuffing those plants (and animals that have eaten plants) into our greedy mouths. However, there are exceptions to this rule—the hydrothermal vent life at the bottom of the ocean discovered a few decades ago, for example. In ecosystems like these, life’s normal rules are overturned, and organisms thrive without sunlight by getting energy from chemical compounds found in ocean sediments and water.
A new chapter in this saga of weird, weird life opened in late August with the announcement that microbial life has been found in Lake Whillans, a body of water lurking beneath 800 meters of Antarctic ice and only 640 kilometers from the South Pole. The shallow lake, 2 meters deep on average, was created through the melting of ice by heat from deep within the Earth. Although previous research expeditions have drilled into other subglacial lakes, this is the first time such drilling has been unequivocally contamination-free (meaning no outside bacteria were introduced into the samples). Using a combination of techniques that took over six years to develop, a team of scientists managed to retrieve water from the lake in January 2013. Since then, the researchers have been analyzing these samples to determine who’s down there and what the heck they’re doing.
It turns out that there is approximately as much microbial life in Lake Whillans as exists in the deep parts of the world’s oceans (~130,000 cells per milliliter of water) and almost 4000 species of bacteria and archaea have been identified so far in the samples. This community of organisms has survived, scientists estimate, for between 120,000 and 1 million years without sunlight. Instead, microbial life beneath the ice depends on the chemical compounds of elements such as iron, sulphur, and nitrogen, which originally come from the sediment and are then utilized by the lake microbes. Efficient recycling of these energy sources, as bacteria in the lake die and decompose, have allowed life to flourish here for much longer than would otherwise be possible.
Finding organisms in this extreme environment gives us a better idea of the diversity of life on Earth and a more complete understanding of how nutrients and energy are cycled among Earth’s smallest citizens. On a more cosmic scale, this discovery should give us hope that we might find life on planets with similar conditions, where water might be lurking beneath a sheath of ice. In particular, Jupiter’s moon Europa, which scientists have already posited might contain liquid water beneath its icy exterior, could harbor microbes similar to the ones in Lake Whillans. A mission by the European Space Agency, the Jupiter Icy Moon Explorer (JUICE), is set to launch a course for Europa in 2022 and may help uncover whether microbial life there could have arisen by the same principles we see here in Lake Whillans.
For the original paper, see: http://www.nature.com/nature/journal/v512/n7514/full/nature13667.html (it’s behind a paywall, however) or http://www.nature.com/news/lakes-under-the-ice-antarctica-s-secret-garden-1.15729