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The Greenland ice cap is similar in many ways to the frozen worlds of the solar system and can teach us how to seek life.

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Many regions of the Earth are temperate, nutrient rich, and stable environments where life seems to thrive effortlessly. But not all of Earth. Some parts, like the Greenland ice cap, are inhospitable.

In our burgeoning search for life elsewhere in the solar system, it stands to reason that we will be looking at marginal and inhospitable worlds. Frozen worlds like Jupiter’s moon Europe and Saturn’s moon Enceladus are our most likely targets. These frozen worlds have warm oceans under layers of ice.

What can Greenland’s cryo-ecosystems tell us about the search for life on frozen bodies like Europe and Enceladus?

Any organism adapted to live on Greenland ice cap (Gray) must be hard. It is an extreme environment where life has to deal with prolonged exposure to negative temperatures. The polar regions of the Earth are also subjected to more radiation than other parts of the Earth, due to the nature of the magnetosphere. According to some scientists, the GrIS can help us in our search for life on other worlds, where conditions are just as extreme.

Laura Sánchez-García is a geoscientist at the Centro de Astrobiología in Madrid, Spain. Sanchez-Garcia visited a field site in Greenland in July 2021 to study microbial cryo-ecosystems. The GrIS is much like a laboratory to study these systems, and according to Sanchez-Garcia, the ice cap may have implications in our search for life on Europe, Enceladus and other frozen worlds.

Laura Sanchez-Garcia handling the ice drill on the GrIS. Image Credit: Laura Sanchez-Garcia / CAB (INTA-CSIC)

It is not only the GrIS itself that has attracted all this attention. There are also glacial lakes, peatlands, melted streams and permafrost. Taken together, all of these environments could host microbial environments that represent different stages of evolution for psychrophile microorganisms.

Sanchez-Garcia’s efforts have focused on something called lipid biomarkers. These are specific organic molecules that can be traced back to their source organisms. Lipids include fats and waxes, and they can be fossilized and preserved in sedimentary rocks and in ice through geological periods, unlike other markers like DNA and proteins. Breakthroughs in genomics and bioinformatics have advanced the study of lipid biomarkers and helped deepen our understanding of the history of microbial life on Earth. These same breakthroughs help shape our quest for life on other worlds in our solar system.

Sanchez-Garcia and his colleague, Daniel Carrizo, collected samples of ice cores from various locations on and around the GrIS. They sampled a combination of older ice, younger ice, and cleaner, dirtier ice at depths between 50 and 80 cm (20 to 31 inches). They also took samples of meltwater and sediment from bedrock erosion, as well as water samples from various types of lakes, including a salt lake. All samples were filtered and analyzed. The water samples were analyzed chemically, while the sediment and ice samples were analyzed for lipid biomarkers.

Sediments from erosion of glacial rocks on the Greenland ice sheet.  Image Credit: Laura Sanchez-Garcia / CAB (INTA-CSIC)
Sediments from erosion of glacial rocks on the Greenland ice sheet. Image Credit: Laura Sanchez-Garcia / CAB (INTA-CSIC)

Finally, the team collected samples of mosses, grasses, lichens and other plants. This allowed them “… to gain insight into the new isotopic signatures of vegetation contributing to the lipid footprint of the soil…” according to the team. And after?

Soil and vegetation studies at the Kangerlussuaq planetary analog field site.  Credits: Laura Sánche-García / CAB (INTA-CSIC).
Soil and vegetation studies at the Kangerlussuaq planetary analog field site. Credits: Laura Sánche-García / CAB (INTA-CSIC).

Sanchez-Garcia and Carrizo are back in the lab with their samples and intend to publish their results. The research duo focuses on three topics:

  • Detection of psychrophilic sources and metabolisms in the Greenlandic glacier Issunguata Sermia.
  • Molecular and isotopic distribution of lipid biomarkers in glacial lakes compared to stormwater in the Greenlandic region of Kangerlussuaq.
  • Biological succession on Greenland soils after the retreat of the glaciers based on molecular and isotopic lipid biomarkers.

The results of studies like this are important not only for understanding the history of Earth, but also for astrobiology. The data helps build models of how chemistry, biology, and geology interact. It gives scientists a better understanding of the Earth’s carbon cycle and how oxygen accumulates in the atmosphere, an event essential for the development of complex organisms.

Insight into the development of life on Earth aids the search for life on other worlds. This research on extremophiles on Earth is helping to develop mission profiles for places like Enceladus and Europe. Successful missions are all about asking the right questions at the right time with the right technology. Research like this helps narrow down the questions.

Artist's impression of the interior of Europe, based on data obtained by Galileo space probes Credit: NASA
Artist’s impression of the interior of Europe, based on data obtained by Galileo space probes Credit: NASA

Astrobiologists are pretty sure that for life to appear, water must be in contact with rocks. On Enceladus and Europa, scientists believe that rocks and brackish water are in contact, with ice being another prominent feature. The Greenland ice cap gives researchers like Sanchez-Garcia the opportunity to refine our understanding of how it all plays out.

One of the primary goals of astrobiology is to understand how the Earth itself became habitable. How, when and why did it become habitable? If other worlds in our solar system are habitable, how do we know?

A great final answer to these questions is unlikely. Instead, a series of smaller responses is more likely. Perhaps this research on the Greenland ice sheet will provide some.

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