A flourishing microbial ecosystem has been found in an ice-covered Antarctic lake by Brent Christner, John Priscu, and their colleagues, raising the chances of finding life on icy moons such as Europa and Enceladus.
The team used hot water to drill a 60-centimeter-diameter hole through the overlying ice of Lake Whillans, a 60-square-kilometer subglacial lake in western Antarctica. The main problem with searching for life in ice-covered lakes is to avoid contamination from the surface during drilling, and the team took extraordinary measures to ensure sterilization by using filters, heating, ultraviolet light and hydrogen peroxide.
They found an aquatic microbial ecosystem that was surprisingly diverse, including nitrogen bacteria and microorganisms that metabolize methane. Lake Whillans lies beneath half a mile (about 800 m) of ice on the lower portion of the Whillans Ice Stream in West Antarctica, and is part of an extensive river network underneath the ice.
The new finding shows that a rich and diverse ecosystem of bacteria and single-celled organisms is possible in a pitch-dark environment without any apparent contribution from photosynthesis.
We can envision a similar situation on Jupiter’s moon Europa. In most places, the icy crust there is many miles deep, but in some areas such as the so-called chaos terrains, the ice may be only as thick as that overlying Lake Whillans.
In Europa’s chaos terrains (see the simulated flyover of one of these regions, called Conamara, above), nutrients may be brought up close to the surface by subsurface currents powered by geothermal activity and tidal forces. These nutrients might originate in Europa’s deep ocean, which by some accounts is about 100 kilometers deep. Various modeling studies have shown that Europa may have enough nutrients to support a substantial ecosystem, perhaps even simple multicellular life such as brine shrimps.
Here’s a short video from the journal Nature (which published the results) giving a behind-the-scenes look at how the team does its work: