Ethiopian ponds too extreme even for microbes
25 Nov 2019
European biologists have confirmed the one place on Earth where conditions are too extreme for life to exist.
The hot, hyper acidic ponds in the geothermal field of in Ethiopia do not even contain microbial life, according to their paper, published in Nature Ecology & Evolution. This means the presence of liquid water on a planet, which is often used as a habitability criterion, does not directly imply that it has life.
Purificación Lopez Garcia of the French National Centre for Scientific Research said: "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.
"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.
Professor Lopez Garcia said there is a great diversity of halophilic archaea – a salt-loving microorganism – in the desert and the saline canyons around the hydrothermal site, but not in the hyperacid and hypersaline pools themselves, nor in Dallol’s magnesium-rich black and yellow lakes.
Dallol’s hydrothermal springs discharge anoxic, hyper-acidic (pH <0) brines that contain more than 26 g/L of iron. The 108°C brines are also hyper-saline – almost 10 times more saline than seawater.
This new research rejects previous studies, which could have falsely confirmed microbial life in Dallol ponds due to mineral precipitates that look like microbial cells under a microscope or the contamination of samples with archaea from adjacent lands, Lopez Garcia said.
Her team used sequencing of genetic markers to detect and classify microorganisms, microbial culture attempts, fluorescent flow cytometry to identify individual cells, chemical analysis of brines and scanning electron microscopy combined with X-ray spectroscopy.
