Despite its oft-celebrated flexibility and resilience, life is obviously not present at every point in the known Universe – either because it had never evolved or because it went extinct. Now, however, a group of French and Spanish researchers have found a place on our own planet where life is simply nowhere to be found.
The hot, saline, hyperacid ponds located in the Dallol geothermal field in Ethiopia extend over a volcanic crater that’s characterised by high amounts of toxic gases, daily temperatures over 45 degrees Celsius in winter, and negative pH values.
And although a study published this year claimed that certain microorganisms can develop in this multi-extreme environment, which the researchers claimed to be a useful model of the early conditions on Mars, the new work concludes that Dallol’s ponds are actually barren.
“After analysing many more samples than in previous works, with adequate controls so as not to contaminate them and a well-calibrated methodology, we have verified that there’s no microbial life in these salty, hot and hyperacid pools or in the adjacent magnesium-rich brine lakes,” said lead researcher Purificación López García.
Whereas the surrounding desert and saline canyons are actually teeming with a type of primitive microorganism called halophilic archaea, the pools themselves were found to be life-free by every single method deployed by the researchers, including genetic sequencing, microbial culture attempts, and chemical analysis.
The study has also shown that certain silica-rich Dallol mineral precipitates may look almost identical to microbial cells under a microscope, which has likely been what tripped up some of the studies conducted in this region in the past.
According to López García, these findings could help future studies avoid misinterpreting different structures as biological, rather than abiotic, in nature both on Earth and during attempts to pick up on the signatures of extra-terrestrial life elsewhere in the Universe.
Furthermore, the results also militate against direct associations between the presence of water and the emergence of biological life. López García proposes that astrobiologists would be wise to rely on multiple indications, analyse as many alternatives as possible (or practicable), and use a high degree of caution when making conclusions regarding life on other planets.
The study was published in the journal Nature Ecology & Evolution.