Where water tends to pool, life often stalls. This observation has shaped many theories of evolution since biology began and has framed how life might arise on Earth. Yet where lies the boundary? Can any aquatic life endure everywhere, or do strict conditions govern its survival? With that premise, researchers have explored the most uninhabitable and extreme places on the planet. They were surprised to discover organisms that find comfortable living conditions even there.
The case in point is ultra-small organisms called nanohaloarchaea found in an geothermally active field near the Dallol volcano in North Afar, Ethiopia. Today, this site stands as one of the most extreme environments on Earth, surpassing other “almost extraterrestrial” locales where life persists, even in places where life-sustaining extremophiles like those in Antarctica, the Atacama Desert, or Río Tinto (Huelva) have adapted. Extreme living conditions do not deter these microbes.
Ethiopia remains home to an extraordinarily harsh destination, a point of reference for researchers and explorers alike.
Archaea comprise a large group of unicellular prokaryotic microorganisms. They lack a nucleus and the membrane-bound organelles found in many other life forms, yet they form their own distinct domain. In this region, the organisms are noted to be about 1,000 times smaller than typical bacteria.
A team of Spanish and French scientists, led by researchers from the Center for Astrobiology (CAB, INTA-CSIC), reported this finding, published in Science in 2019, with related results in Scientific Reports linked to Nature. Their work established a new benchmark for habitability conditions, guiding where to search for life on Earth and potentially beyond.
The site was once regarded as a cradle of life, and many fossils tied to human history have been found in the Afar Depression. Today, it is among the most inhospitable places on the planet.
The local climate is dry and hot, with average high temperatures around 41 degrees Celsius. A hydrothermal zone exists where water rises from underground at about 100 degrees Celsius.
A strip of color marks the area: the chimneys and cones glow with hues created by minerals erupting to the surface. The palette comes from minerals such as pyrolusite, chlorargyrite, wurtzite, and halite, colored by salts and metals in the environment. Sulfate-rich yellow deposits, iron-oxide reds, and green copper-salt waters add to the surreal landscape.
And despite everything there is life
Even in such extreme, seemingly uninhabitable settings, entire communities of unknown microorganisms were found inside tiny mineral spheres within the chimneys that channel the flowing water. These beings shield themselves by coating their surfaces with regional minerals, forming protective bubbles.
Beyond that protection, they are wrapped in molecular matrices that enable them to live in consortia. They have been observed to grow very slowly, relying on chemolithotrophy to extract energy from stones rather than organic matter. Oxygen is not required, as they metabolize metals and minerals for survival.
The study demonstrates that microorganisms can endure and potentially thrive in such extreme environments, offering insights into the limits of habitability and how life might persist under harsh conditions on other worlds.
The most extreme region in the world, as described by researchers, continues to captivate the imagination.
In search of life on the red planet
The fascination with discovering life extends beyond Earth. Findings like these help define the conditions likely needed to detect life on other planets, such as Mars. Yet the red planet remains elusive, with no definitive signs that it once harbored life.
Earlier this period, NASA’s Curiosity rover observed a mix of carbon isotopes, 12 and 13, in rocks from Gale Crater. If this pattern were seen on Earth, it would be interpreted as a sign of metabolic activity by underground microorganisms. On Mars, however, researchers carefully consider multiple explanations, since past life remains a possibility but not a certainty.
Many clues in biology could also be explained by unknown aspects of Mars’ geology or chemistry, reflecting how much is still not understood about the planet’s workings and how such phenomena might be camouflaged. The search for life on Mars continues, with researchers weighing evidence and alternative explanations.
Reference research: [citation: Nature, 2019; Science report details cited within the article]
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A note on the environment and science communication: the environment sector continues to study these remarkable systems, sharing findings through peer-reviewed journals and credible scientific summaries to advance understanding of extremophiles and planetary habitability.