Mars may not have much to do right now, in terms of life, but the dusty red planet may not be as inhospitable as it seems.
New experiments have shown that cyanobacteria (also known as blue-green algae) can grow successfully in atmospheric conditions on Mars.
Of course, a few more ingredients are needed, but it’s an important step toward cyanobacteria-based life support systems for human habitats when we finally make our way there.
“Here we show that cyanobacteria can use gases available in the atmosphere of Mars, at low total pressure, as their source of carbon and nitrogen,” said astrobiologist Cyprien Verseux of the University of Bremen in Germany.
“Under these conditions, cyanobacteria retained their ability to grow in water containing only Martian 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 every habitat on the planet and sometimes produces powerful toxins that can kill other organisms.
Still, we may not be without it. Scientists believe that an explosion of cyanobacteria 2.4 billion years ago was largely responsible for our breathing atmosphere. When it exploded on the scene, cyanobacteria pumped the atmosphere with oxygen, dramatically changing the entire planet.
All types of cyanobacteria produce oxygen as a photosynthetic by-product, and they are an invaluable source of it even today.
Scientists have been pondering for several years whether and how we can use the ability of cyanobacteria to make oxygen to live on Mars (and in space).
This would bring additional benefits. The atmosphere of Mars is composed mainly of carbon dioxide (95 percent) and nitrogen (3 percent), both of which are fixed by cyanobacteria, which convert them into organic compounds and nutrients, respectively.
However, the atmospheric pressure from Mars is a significant setback. It’s only 1 percent of Earth’s atmospheric pressure, too low for the presence of liquid water, and cyanobacteria can’t grow directly in it or extract enough nitrogen. But recreating the conditions of Earth’s atmosphere on Mars is also a challenge, especially the pressure.
So Verseux and his team looked for a middle ground. They developed a bioreactor called Atmos that has an atmospheric pressure of about 10 percent that of Earth, but uses only what is found on Mars, albeit in reverse proportions: 96 percent nitrogen and 4 percent carbon dioxide.
Also included in the bioreactor was water – which can be obtained on Mars from molten ice, which is abundant on the surface in certain places – and a Martian regolith simulant, a mixture of minerals created here on Earth with just some on Mars. find is. .
The system, consisting of nine glass and steel vessels, was carefully temperature and pressure controlled and monitored at all times.
Atmos. (C. Verseux / ZARM)
The team selected a species of nitrogen-fixing cyanobacteria that preliminary tests have shown are most likely to thrive under these conditions. Anabaena sp. PCC 7938 and tested under various conditions.
Some rooms used a culture medium to grow the cyanobacteria, while others used a simulation of Mars regolith. Some were exposed to Earth’s atmospheric pressure, while others were reduced to low pressure.
The scientists discovered that not only their Anabaena grow, it did so “vigorously”. It is clear that it grew better on the culture medium than on the regolith of Mars, but the fact that it grew on the regolith at all constitutes a huge success – indicating that cyanobacterial growth on Mars would not depend on imported ingredients from the soil.
Then, to assess whether the cyanobacteria grown under Mars conditions could continue to be useful, the researchers dried it and used it as a substrate to grow Escherichia coli
This showed that sugars, amino acids and other nutrients can be extracted from the cyanobacteria to feed other cultures, which can then be used for other purposes, such as producing medicines.
There is of course still a lot of work to be done.
Atmos is designed to test whether cyanobacteria can be grown under certain atmospheric conditions, not to maximize efficiency, and the parameters of the bioreactor will depend on many factors in the mission to Mars, including the mission’s payload and architecture. Anabaena may not even be the best cyanobacterium for the job.
Now that the concept has been proven, the team can get to work on optimizing a bioreactor system that could one day keep us alive on Mars.
“Our bioreactor, Atmos, is not the culture system we would use on Mars: it is designed to test the conditions on Earth that we would provide there,” said Verseux.
“But our results will help design a Martian culture system … We want to move from this proof-of-concept to a system that can be used efficiently on Mars.”
The research is published in Frontiers in Microbiology