Toxic volcanic lake reveals how life may have been possible on ancient Mars

The Poás volcano crater and Laguna Caliente are shown, as seen from the crater edge.

(CNN)Near the summit of Costa Rica's Poás volcano is one of Earth's most acidic lakes, bright blue and full of toxic metals.

The harsh conditions of Laguna Caliente, where temperatures can fluctuate between 100 degrees Fahrenheit (38 degrees Celsius) and 194 degrees Fahrenheit (90 degrees Celsius), are where a few lucky scientists go to learn more about Mars.
Frequent phreatic eruptions occur when groundwater is heated by volcanic activity, releasing explosions of ash, rock and steam.
    Yet microbes have found a way to live in this environment, one of the most hostile on our planet, according to multiple studies of the lake and new research published last week in Frontiers in Astronomy and Space Sciences.
      Although the diversity of the life in this lake isn't high, it has managed to adapt and persist in a multitude of ways.
      Toxic, stinging steam surrounds the lake and volcano.
      "Our finding shows that life persists in the most extreme environments on Earth," said study author Justin Wang, graduate student and research assistant at the University of Colorado Boulder.
      "It's hard to imagine something more hostile to life than an ultra-acidic volcanic lake with frequent eruptions," Wang said. "The low biodiversity coupled with numerous adaptations and metabolisms in our sample suggests the lake hosts highly specialized microbes for this kind of environment."
        This otherworldly environment could suggest how life might have existed on Mars billions of years ago and reveal new places to search for evidence of ancient life on the red planet, according to the researchers.

        A tale of two lakes

        The two crater lakes near the volcano's summit, both formed after craters filled with rainwater, couldn't be more different from each other. One inactive crater holds Botos lake, which is surrounded by tropical vegetation. The active crater is home to Laguna Caliente, which contains liquid sulfur and iron. Gases from the lake create acid rain and acid fog, harming nearby ecosystems and irritating the eyes and lungs of intrepid explorers.
        Researchers conducted active field studies at the lake in 2013, 2017 and 2019. While the results from the 2019 excursion are still pending, it's a trip Wang will never forget.
        Poás volcano, located in the middle of the Costa Rican rainforest, erupted most recently in 2017 and 2019. The area immediately around the volcano is devoid of life due to the toxic gases it releases.
        Wang and his collaborators hiked to the volcano in November, a month after the crater lake reformed. They were mindful of where they stepped in the loose soil caused by acidity breaking down the surface material. Parts of the lake boiled and volcanic openings called fumaroles belched out hot sulfurous gases.