AFRICANGLOBE – Can life develop in the most extreme conditions on Earth? Scientists from France’s National Center for Scientific Research (CNRS) are trying to find out. It has led the first scientific expedition into the Dallol salt dome in the Danakil Desert in Ethiopia. At 128 metres below sea level, the site sits on a two-kilometre-thick layer of salt, the remains of an evaporated arm of the Red Sea, under which lies an active magma chamber. “There is a very acidic pH and very high salinity around the dome,” says CNRS research director Purificación López-García. “It’s 50 per cent salt, almost twice that of the Dead Sea.” Liquids can reach 118°C, and geysers spit toxic gas and hot springs bubble with acid.
The international team of microbiologists, geologists and crystallographers spent two weeks in January exploring the dome and its surroundings, hoping to find bacteria that can live in these extreme conditions. “We went last year and came back to get more samples from the dome, the underground salt lake, the black pond containing lots of magnesium chlorides,” says López-García, 51. “We hardly recognised the place: sources get obturated by salt and other springs open next to them.”
The site was difficult to access. “We were not allowed to go there without military protection,” López-García recalls. But the effort yielded results and the team collected samples for testing. Using electron microscopes and DNA sequencing, they observed samples with extremophilic micro-organisms: bacteria and archaea (domains of single-celled micro-organisms) that not only resist Dallol’s depredations, but even reproduce. “We found a variety of archaea that has no close neighbour,” says López-García.
In the short term, culturing these extremely adaptable microbial organisms in the lab may help scientists explain why some species are able to grow in salt and acid. In the long term – there are still many samples left to collect and analyse – they could show why life on Earth started to develop.
Life – in the form of single-celled organisms – appeared on Earth around 3.8 billion years ago, during the Archean eon, as the Earth’s crust first began to poke out of the sea. In this hot, acidic and volcanic environment, geology prevailed over biology – much like it does in Dallol. “The very special environmental conditions of this site might resemble those of the early Earth,” says López-García. “This is particularly true for the presence of high hydrothermal activity in a setting where life does not yet dominate, and possibly by the presence of organic compounds. In the case of Dallol, they are likely derived from buried sediments and mobilised by ascending hydrothermal fluids.” Dallol’s hellish conditions recreate the beginning of it all – and by analysing life’s ability to find a way, even here, the scientists hope to discover an answer to the biggest question of all.