Poás Volcano in Costa Rica, captured by Landsat 8 on March 5, 2025, features a barren, Mars‑like crater containing Laguna Caliente, a super‑acidic lake with an average pH just above 0. Though too harsh for plants and animals, the lake hosts acid‑loving microbes such as Acidiphilium, making Poás a valuable analog for early Martian hydrothermal environments. The volcano — about 8,848 ft (2,697 m) high and located ~10 miles (16 km) from San José — was active through much of 2025, with sulfur dioxide and ash impacts reported in May. Researchers compare Poás to Mars’ Home Plate but stress there is still no conclusive evidence Mars ever harbored life.
Poás Volcano: Costa Rica’s Mars-like 'Paradise' for Extreme Microbes
Poás Volcano in Costa Rica, captured by Landsat 8 on March 5, 2025, features a barren, Mars‑like crater containing Laguna Caliente, a super‑acidic lake with an average pH just above 0. Though too harsh for plants and animals, the lake hosts acid‑loving microbes such as Acidiphilium, making Poás a valuable analog for early Martian hydrothermal environments. The volcano — about 8,848 ft (2,697 m) high and located ~10 miles (16 km) from San José — was active through much of 2025, with sulfur dioxide and ash impacts reported in May. Researchers compare Poás to Mars’ Home Plate but stress there is still no conclusive evidence Mars ever harbored life.
09:46 PM, 11/11/2025Science
Image: Landsat 8, March 5, 2025 — Coordinates: [10.19781287, -84.238304442]
Overview
This striking satellite image shows Poás Volcano rising above Costa Rica's rainforest with a stark, almost Martian appearance. Poás sits inside Poás Volcano National Park in Alajuela province. The stratovolcano began forming roughly 1.5 million to 700,000 years ago and reaches a summit elevation of about 8,848 ft (2,697 m).
Laguna Caliente: A Super‑acidic Microbial Habitat
At the core of Poás is the main crater, roughly 0.8 miles (1.3 km) across, which contains Laguna Caliente — a super‑acidic lake with an average pH value just above 0, comparable to battery acid. The crater periodically produces geysering and emits steam, toxic gases and ash. These extreme chemical conditions exclude plants and animals, but they host thriving communities of acid‑tolerant microbes. The lake is dominated by bacteria in the genus Acidiphilium, which metabolize metal compounds dissolved in the acidic waters.
“We have a very human‑centric bias for what a nice, happy, temperate environment is to grow in,” said Rachel Harris, a microbial ecologist and geochemist at Harvard University who contributes to NASA’s Decadal Astrobiology Research and Exploration Strategy. “The Poás system may be hostile to most forms of life we are familiar with. But for a microbe adapted to acid, heat and toxic metals, it's paradise.”
Why Poás Matters to Planetary Science
Scientists study Poás because its acidic hydrothermal environment resembles volcanic settings that likely existed on early Mars more than 3 billion years ago, when the Red Planet had warmer, wetter conditions. A 2022 study found that Laguna Caliente’s low biodiversity paired with high community resilience is similar to what researchers expect could have developed in hypothetical Martian ecosystems. Poás is often compared to the Martian locality called Home Plate — a roughly 300‑ft (90 m) plateau examined by NASA’s Spirit rover — which shows geochemical evidence of past acidic hydrothermal activity.
Recent Activity and Local Impacts
Although satellite images can make Poás appear isolated, the suburbs of Costa Rica’s capital, San José, lie only about 10 miles (16 km) southeast of the volcano. Poás is one of Central America’s most active volcanoes: over the past two centuries it has produced dozens of major eruptions and many smaller outbursts. According to the Smithsonian Institution’s Global Volcanism Program, the volcano has entered 13 minor eruptive phases since 2005.
The most recent eruptive period began on Jan. 5, 2025, and continued through much of the year before likely subsiding. Activity peaked in early May 2025, when elevated sulfur dioxide briefly affected air quality in San José and ashfall damaged some nearby crops, as reported by NASA’s Earth Observatory.
Takeaway
Poás Volcano is both a popular and accessible tourist destination and a natural laboratory for studying extremophiles and planetary analogs. Its acidic crater lake provides insight into the kinds of microbial communities that might survive in extreme acidic hydrothermal systems — on Earth and potentially on other worlds. Despite tantalizing analogies and promising rover findings, there remains no definitive evidence that Mars ever hosted life.