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Arthur T Knackerbracket has found the following story:

The infernal landscape of Dallol, located in the Ethiopian depression of Danakil, extends over a volcanic crater full of salt, where toxic gases emanate and water boils in the midst of intense hydrothermal activity. It is one of the most torrid environments on Earth. There, daily temperatures in winter can exceed 45 degrees Celsius[113 F] and there are abundant hypersaline and hyperacid pools with pH values that are even negative.

A recent study, published this year, reports that certain microorganisms can develop in this multi-extreme environment (simultaneously very hot, saline and acid), which has led its authors to present this place as an example of the limits that life can support, and even to propose it as a terrestrial analogue of early Mars.

However, a French-Spanish team of scientists led by biologist Purificación Lopez Garcia of the French National Centre for Scientific Research (CNRS) has now published an article in Nature Ecology & Evolution that concludes otherwise. According to these researchers, there is no life in Dallol's multi-extreme ponds.

"After analyzing 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," says López García.

"What does exist is a great diversity of halophilic archaea (a type of primitive salt-loving microorganism) in the desert and the saline canyons around the hydrothermal site, but neither is found in the hyperacid and hypersaline pools themselves, nor in the so-called Black and Yellow lakes of Dallol, where magnesium abounds. And all this despite the fact that microbial dispersion in this area, due to the wind and to human visitors, is intense."

[...] According to the authors, this work "helps to circumscribe the limits of habitability and demands caution when interpreting morphological biosignatures on Earth and beyond," that is, one should not rely on the apparently cellular or "biological" aspect of a structure, because it could have an abiotic origin.

"In addition, our study presents evidence that there are places on the Earth's surface, such as the Dallol pools, which are sterile even though they contain liquid water," stresses Lopez Garcia. This means that the presence of liquid water on a planet, which is often used as a habitability criterion, does not directly imply that it has life.

[...] "We would not expect to find life forms in similar environments on other planets, at least not based on a biochemistry similar to terrestrial biochemistry," points out Lopez Garcia, who insists on the need to have multiple indications, to analyze all types of alternatives and to be very prudent with interpretations before reaching any conclusions in astrobiology.

Wikipedia's entry on Dallol notes:

Dallol currently holds the official record for record high average temperature for an inhabited location on Earth, and an average annual temperature of 35°C (95°F) was recorded between 1960 and 1966.

More information: Jodie Belilla et al. Hyperdiverse archaea near life limits at the polyextreme geothermal Dallol area, Nature Ecology & Evolution (2019). DOI: 10.1038/s41559-019-1005-0

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