The discovery of living bacteria embedded in salt deposited in super-saturated and acidic hot water inside an Ethiopian volcano offers a viable analogue for possible life on Mars- researchers suggest.
The bacteria – spherical- ultra-small members of the order Nanohaloarchaeles – were found buried near a hydro-thermal vent inside the crater of the still-active Dallol volcano in Ethiopia- by researchers led by Felipe Gómez from Spanish Astrobiology Centre in Torrejón de Ardoz- Spain.
The environment- which features a water temperature of 89 degrees Celsius- an air temperature average of 38 degrees Celsius- and a highly acidic pH reading of 0.25- is recognised as one of the most life-unfriendly places on Earth.
It is also thought to be rather similar to conditions that existed early in the life of Mars- when it was geologically more active: notably in the Gusev Crater- where NASA’s Spirit Mars Exploration Rover landed. It was a comparison that Gómez and colleagues made recently- in a paper published in the journal Astrobiology.
“The Dallol area represents an excellent Mars analogue environment given that the active volcanic environment- the associated diffuse hydrothermalism and hydrothermal alteration- and the vast acidic sulfate deposits are reminiscent of past hydrothermal activity on Mars-” they conclude.
The latest work- describing the bacteria- appears in the journal Scientific Reports.
The harsh conditions in the Dallol volcano- which lies in an area known as the Danakil Depression- 125 metres below sea level- arise because it sits at the intersection of three lithospheric plates- which are moving apart.
The activity allows for precipitation by superheated water saturated with various salts- including silver chloride- zinc iron sulphide- manganese dioxide and normal rock-salt – creating an environment- it was thought- that was as barren as it is colourful.
During a two-year investigation- however- Gómez and colleagues discovered the existence of ultra-small microbes – some 20 times smaller than normal bacteria – inside salt deposits on a yellow “chimney stack”- and in magma-heated blue water adjacent.
“This is an exotic- multi-extreme environment- with organisms that need to love high temperature- high salt content and very low pH in order to survive-” says Gómez.
The nanobacteria- in situ- were surrounded by small needle-like crystals- leading the scientists to suggest that they may be an active catalyst in the biomineralisation process that creates the salt deposits.
And- given that nanohaloarchaeles are definitively living on Earth- might something similar once have inhabited the hydrothermal vents of Mars? The researchers certainly don’t rule the possibility out.
“The results from this study suggest the microorganisms can survive- and potentially live- within this extreme environment– which has implications for understanding the limits of habitability on Earth and on (early) Mars-” the conclude.
