The Poás volcano, located in the middle of the Costa Rican rainforest, most recently erupted in 2017 and 2019. The area immediately around the volcano is devoid of life due to the toxic gases it releases.
On the edge of the top of the Poás volcano is one of the most acidic lakes on Earth, bright blue in color and full of toxic metals, temperatures can fluctuate between 100 degrees Fahrenheit (38 degrees Celsius) and 194 degrees Fahrenheit (90 degrees Celsius), this place is visited by some very lucky scientists who come to learn more about how life can develop on the planet Mars, observing how frequent phreatic eruptions occur, these occur when groundwater is heated by volcanic activity, releasing explosions of ash, rock, and steam.
One of the scientists who has managed to access the acid lake and carry out a study of this supernatural phenomenon is Justin Wang, a graduate student and research assistant at the University of Colorado, Boulder, Colorado. He has explained the numerous experitments carried out on the surface of the lake, one of the most recent was published in Frontiers in Astronomy and Space Science, which shows how some microbes have found a way to live in this environment, one of the most hostile on the planet.
Although the diversity of life in this lake is not high, it has managed to adapt and persist in a multitude of forms. “Our finding shows that life persists in the most extreme environments on Earth. It’s hard to imagine anything more hostile to life than an ultra-acid volcanic lake with frequent eruptions,” said Wang.
The Poás volcano is a supernatural wonder in which life could develop?
This otherworldly ecosystem could suggest how life could 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. The two crater lakes near the top of the volcano, both formed after the craters filled with rainwater, couldn’t be more different from each other.
An inactive crater contains Lake Botos, 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, damaging 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 of the 2019 excursion are still pending, it’s a trip Wang will never forget.
Wang and his collaborators hiked to the volcano in November, a month after the crater lake was reformed. They were very careful where they stepped on the loose soil caused by acidity breaking down the surface material. Parts of the lake boiled and volcanic vents called fumaroles spewed out hot sulfurous gases.
Can microorganisms survive in this environment?
In 2013, researchers explained that Acidiphilium bacteria live in the lake. These microbes are often found in acid mine drainage, as well as in hydrothermal systems, such as Laguna Caliente. Acidiphilium bacteria have multiple genes that allow them to adapt to survive in different environments.
More eruptions occurred at the site before the team returned in 2017. After collecting more samples, the researchers found that there was slightly more biodiversity among the bacteria in the lake than expected. Furthermore, sequencing of its DNA revealed that the Acidiphilium bacterium has evolved ways of converting elements such as sulfur, iron and arsenic to create the energy it needs to survive.
“A leading hypothesis of our study is that life on Poás volcano is capable of surviving on the fringes during these extreme environments. Therefore, we would love to sample not only the crater lake, but also the shoreline, connected groundwater and any nearby place where life may be harbored”, reported the researcher.
The genetic adaptations discovered by Wang and his colleagues during their study suggest that life could have survived in hydrothermal environments on Mars as it does in some of the most extreme places on Earth.
Hydrothermal systems provide heat, water and energy, everything necessary for the formation and evolution of life. While previous Martian exploration has looked at ancient water sources such as craters and rivers, researchers believe that ancient hot spring sites are another key target in the search for extraterrestrial life.
Research to understand tiny organisms that live in extreme environments is changing the way scientists view the limits of life, whether inside an active volcanic crater lake or along hot hydrothermal vents on the ocean floor.
While that helps researchers change the way they think about how life could exist within the hostile conditions on other planets, Wang cautions that scientists shouldn’t be too “Earth-centric” in their approach. Life on Earth is usually found in the presence of water, but the existence of water on Mars was much more limited and episodic in the past, he said.
“I think we need to change the way we think about life on other worlds,” Wang said. “We need to consider the unique geological histories of our extraterrestrial environments and put that in context with what we have here on Earth. If rivers were unstable on Mars while hot springs were common, then perhaps life in hydrothermal environments is the most likely place where life could have existed.”