March maybe not much at the moment, vividly, but the dusty red planet may not be as hospitable as it seems.
New experiments have shown it cyanobacteria (aka blue-green algae) can successfully grow under March atmospheric conditions.
Of course, a few more ingredients are required, but it’s an important step towards cyanobacteria – based life support systems for human habitats when we finally find our way over there.
“Here we show that cyanobacteria can use gases available in the Martian atmosphere at a low total pressure as their source of carbon and nitrogen,” said astrobiologist Cyprien Verseux from the University of Bremen in Germany.
“Under these conditions, cyanobacteria retained their ability to grow in water that contained only Mars – like dust and could still be used to feed other microbes. This could help make long-term missions to Mars sustainable.”
Here on earth, cyanobacteria are not always the most compatible with other life. It can be found in almost each habitat on the planet and sometimes produces powerful toxins there can kill other organisms.
Yet we may not be here without it. Scientists believe that a boom for cyanobacteria 2.4 billion years ago was largely responsible for our breathable atmosphere. When it exploded on stage, cyanobacteria pumped the atmosphere with oxygen and dramatically changed the entire planet.
All species of cyanobacteria produce oxygen as a photosynthetic by-product, and they are an invaluable source of it, even today.
This would bring additional benefits. Mars’ atmosphere consists mainly of carbon dioxide (95 percent) and nitrogen (3 percent), both of which are fixed by cyanobacteria that convert them to organic compounds and nutrients respectively.
However, Mars’ atmospheric pressure is a significant setback. It is only 1 percent of the earth’s atmospheric pressure, too low for the presence of liquid water, and cyanobacteria can not grow directly in it or extract enough nitrogen. But recreating the conditions in the Earth’s atmosphere on Mars is also challenging, especially the pressure.
So Verseux and his team sought a middle ground. They developed a bioreactor called Atmos, which has an atmospheric pressure of about 10 percent of Earth’s, but uses only what is found on Mars, even though it is in inverse proportions: 96 percent nitrogen and 4 percent carbon dioxide.
Also included in the bioreactor were water – which can be obtained on Mars from molten ice, which is abundant on the surface in some places – and a Mars regolith simulator, a mixture of minerals created here on Earth using only what is found on Mars.
The system, consisting of nine glass and steel containers, was carefully temperature and pressure controlled and monitored at all times.
The team chose a species of nitrogen-fixing cyanobacteria, which preliminary experiments showed that they would most likely thrive under these conditions, Anabaena sp. PCC 7938 and tested it under a variety of conditions.
Some chambers used a culture medium to grow the cyanobacteria, while others used simulated Mars regolith. Some were exposed to the atmospheric pressure of the earth, while others were reduced to low pressure.
The researchers found that not only did theirs Anabaena grow, it made it “powerful”. It obviously grew better on the culture medium than on the Mars regolith, but the fact that it grew on the regolith at all represents a massive success – indicating that the growth of cyanobacteria on Mars does not have to rely on imported ingredients from Earth.
To assess whether the cyanobacteria grown under martistic conditions could continue to be useful, the researchers dried it and used it as a substrate to grow Escherichia coli.
This showed that sugar, amino acids and other nutrients can be obtained from the cyanobacteria to feed other cultures, which can then be used for other purposes, such as producing medicine.
There is obviously a lot more work to be done.
Atmos was designed to test whether cyanobacteria could be grown under certain atmospheric conditions, not to maximize efficiency, and the parameters of the bioreactor will depend on many factors in the Mars mission, including the mission payload and architecture. Anabaena may not even be the best cyanobacteria for the job.
Now that the concept is proven, however, the team can start optimizing a bioreactor system that can one day keep us alive on Mars.
“Our bioreactor, Atmos, is not the cultivation system we would use on Mars: it is meant to test the conditions we would provide there on Earth,” Said Verseux.
“But our results will help steer the design of a Mars culture system … We will move from this proof-of-concept to a system that can be used on Mars effectively.”
The research is published in Limits in microbiology.
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