Scientists have discovered evidence of an ancient seawater reservoir hidden beneath Antarctica ice after detecting marine microbial DNA in an iron rich red brine pool in the McMurdo Dry Valleys, according to a study published in Nature Geoscience.
Researchers found environmental DNA belonging to marine microorganisms in the highly saline underground brine, supporting the theory that ancient seawater became trapped beneath expanding glaciers and remained isolated for thousands of years.
The study explains that the brine’s distinctive red colour is caused by iron rich water reacting with oxygen when it reaches the surface, rather than by algae or pigmented microbes.
The McMurdo Dry Valleys, the largest ice free region in Antarctica, receive very little snowfall and have extremely low humidity. Although surrounded by glaciers, much of the landscape remains free of permanent ice making it a unique environment for studying ancient geological and climatic processes.
According to the researchers seawater was trapped as glaciers advanced and coastlines shifted over time. As freezing removed freshwater, salts became concentrated in the remaining liquid, creating a dense brine with a freezing point low enough to remain liquid beneath the ice.
Analysis of the environmental DNA revealed genetic material closely related to microorganisms found in modern marine environments, indicating that the underground brine originated from an ancient ocean rather than freshwater sources.
Scientists said the findings provide valuable insights into Antarctica’s environmental history, preserving evidence of past marine chemistry and ancient microbial communities that existed before the region was sealed beneath ice.
The study also highlights that isolated, salt rich subglacial brines can preserve biological evidence for long periods, offering scientists a rare opportunity to reconstruct past Antarctic environments and understand how coastlines and ice sheets evolved over time.
Researchers said the discovery could improve understanding of the limits of life in extreme environments and may also provide clues for searching for life in icy worlds beyond Earth.
However, several questions remain unanswered, including how long the microorganisms have been isolated, whether they are still biologically active, and how the brine’s chemistry has changed over thousands of years.
The researchers said further exploration of hidden Antarctic brine systems could reveal more evidence of ancient ecosystems and improve understanding of how microbial communities responded to past climate and ice sheet changes.