Microbes found thriving in Mars-like conditions
The discovery of microbes in any icy lava tube in Oregon raises hope that similar microorganisms could survive in the very similar conditions to be found on Mars.
The microbes are coping with near-freezing temperatures and low levels of oxygen, and can even grow in the absence of organic food. Their metabolism is driven by the oxidation of iron from olivine, a common volcanic mineral found in the rocks of the lava tube.
These factors make the microbes capable of living in the subsurface of Mars and other planetary bodies, the scientists say.
"This microbe is from one of the most common genera of bacteria on Earth," says Amy Smith, a doctoral student at Oregon State University.
"You can find its cousins in caves, on your skin, at the bottom of the ocean and just about anywhere. What is different, in this case, is its unique qualities that allow it to grow in Mars-like conditions."
In a laboratory setting at room temperature and with normal oxygen levels, the scientists demonstrated that the microbes can consume organic material - sugar.
But when the sugar was removed and the temperature and oxygen levels lowered, the microbes began to use the iron within olivine – a common silicate material found in volcanic rocks on Earth and on Mars – as its energy source.
"This reaction involving a common mineral from volcanic rocks just hasn’t been documented before," says professor Martin Fisk.
"In volcanic rocks directly exposed to air and at warmer temperatures, the oxygen in the atmosphere oxidizes the iron before the microbes can use it. But in the lava tube, where the bacteria are covered in ice and thus sheltered from the atmosphere, they out-compete the oxygen for the iron."
The conditions in which the microbes were found, says the team, are very similar to those in some subsurface areas on Mars.
Indeed, Fisk says he's examined a meteorite originating from Mars that contained tracks – which could indicate consumption by microbes – though no living material was discovered. Similar tracks were found on the rocks from the Newberry Crater lava tube, he says.
“Conditions in the lava tube are not as harsh as on Mars. On Mars, temperatures rarely get to the freezing point, oxygen levels are lower and at the surface, liquid water is not present. But water is hypothesized to be present in the warmer subsurface of Mars," says Fisk.
"Although this study does not exactly duplicate what you would find on Mars, it does show that bacteria can live in similar conditions. We know from direct examination, as well as satellite imagery, that olivine is in Martian rocks - and now we know that olivine can sustain microbial life."
Even if life isn't present on Mars now, says the team, it could have flourished in the past, when temperatures and atmospheric pressure were higher.