Near the center of Costa Rica is its famous volcano called Volcán Poás, whose peaks house two crater lakes: the inactive southern Lake Botos and the active northern Laguna Caliente. A team of scientists took samples from the northern volcanic lake, known for being one of the most acidic in the world and for having liquid sulfur (S) floating near its bottom, and found that the organisms there employed a wide gamut of genes to allow them to survive such harsh conditions—a fact that the research team believes might hold clues as to how organisms, if any, might survive on our neighbor planet Mars.
Published in the journal Frontiers in Astronomy and Space Sciences, the study encompassed a genetic study of the microbes that lived in the lake water; this included the single microbial genus Acidiphilium, which was described in a study published in the journal Astrobiology back in 2018.
The current research team, led by the University of Colorado Boulder astrobiologist Justin Wang, returned to the volcanic lake after Volcán Poás erupted back in 2017; their goal was to examine what effect the recent eruptions had on the biodiversity present in the lake water.
Sweeping genetic analyses revealed that while Acidiphilium was still the predominant genus present in the water, a couple of other microorganisms were also present in the mix. Additionally, these microorganisms possessed genes that conferred to these microbes both acid and heat resistance—no doubt necessary adaptations that helped them survive post-eruption.
Alongside these survival genes, the team also found additional genes that allowed these microbes to metabolize substances that other organisms might consider toxic, like sulfur (S) and arsenic (As). This was paired with genes for carbon fixation—genes that are commonly found in plants, which allow them to convert carbon into organic compounds, among other functions.
Said Wang: “We expected a lot of the genes that we found, but we didn’t expect this many given the lake’s low biodiversity. This was quite a surprise, but it is absolutely elegant. It makes sense that this is how life would adapt to living in an active volcanic crater lake.”
What’s important to Wang and the team is that these organisms found ways to harness energy from chemical reactions, other than the Sun, to power their biological processes; this, in turn, gave scientists insights into how organisms may evolve in worlds beyond Earth, whose surfaces won’t receive as much sunlight as Earth does.
Experts also think that life on early Earth may have started in environments similar to those in Laguna Caliente—hydrothermal environments deep underwater, where organisms would have been shielded from the then-harsher effects of ultraviolet radiation from the Sun, given that Earth wouldn’t develop a distinct ozone layer until the onset of the Great Oxidation Event (GOE) some 2.4 to 2 billion years ago.
To Wang and team, early Mars may have been a similarly wet and volcanically-active world, same as early Earth; thus, organisms that may have existed (or perhaps may still exist) on the Martian surface did so using similar processes that sustained Earth’s microorganisms until the onset of our current oxygen-rich atmosphere.
“Our research provides a framework for how ‘Earth life’ could have existed in hydrothermal environments on Mars,” Wang followed. “But whether life ever existed on Mars and whether or not it resembles the microorganisms we have here is still a big question. We hope that our research steers the conversation to prioritize searching for signs of life in these environments.”
References
- Frontiers. (2022, January 28). Extremely harsh volcanic lake shows how life might have existed on Mars. EurekAlert! https://www.eurekalert.org/news-releases/941049
- Hynek, B. M., Rogers, K. L., Antunovich, M., Avard, G., & Alvarado, G. E. (2018). Lack of microbial diversity in an extreme mars analog setting: Poás volcano, costa rica. Astrobiology, 18(7), 923–933. https://doi.org/10.1089/ast.2017.1719
- Klemetti, E. (2017, April 21). A costa rican volcano sees its biggest blast in years. WIRED. https://www.wired.com/2017/04/costa-rican-volcano-sees-biggest-blast-years/
- Starr, M. (2022, January 29). This extremely toxic lake could show us how life may have survived on mars. ScienceAlert. https://www.sciencealert.com/a-toxic-volcanic-lake-could-show-us-how-life-may-have-survived-on-mars
- Wang, J. L., Dragone, N. B., Avard, G., & Hynek, B. M. (2022). Microbial survival in an extreme martian analog ecosystem: Poás volcano, costa rica. Frontiers in Astronomy and Space Sciences, 9. https://www.frontiersin.org/article/10.3389/fspas.2022.817900
