A Most Unusual Lake

Scientists estimate that Earth is home to more than 100 million lakes. Among the most unusual is Lake Unter-See, one of Antarctica's largest and deepest surface lakes, known for its distinctive water chemistry. Its ice-covered waters have exceptionally high levels of dissolved oxygen, low dissolved carbon dioxide, and a strongly alkaline (basic) pH.

The OLI (Operational Land Imager) on Landsat 9 captured this image on February 16, 2026, during the Antarctic summer. Most of the lake's water comes from seasonal meltwater draining from the margins of the nearby Anuchin Glacier, which flows south from the Gruber Mountains in Queen Maud Land.

With mean annual temperatures of about minus 10 degrees Celsius (14 degrees Fahrenheit), Lake Unter-See remains frozen year-round, its waters sealed beneath several meters of ice. Sunlight penetrates the ice and warms the water below, but the cold surface and strong winds drive evaporation and sublimation, preventing significant surface melting. The lake's maximum depth is thought to reach nearly 170 meters (558 feet).