Although the question of whether there is life on Mars has long been a source of fascination, a more pertinent issue for human missions to the Red Planet is whether new life could grow there.
This is vital if expeditions are to be sustainable – and new research in Germany indicates that bacteria can be cultured in conditions that could be recreated on Mars.
One of the biggest potential hurdles to growing organisms on Mars is the low pressure of the atmosphere there, which is just one-hundredth that of Earth’s.
To look at whether bacteria could grow in low-pressure conditions, Dr Cyprien Verseux and colleagues from the University of Bremen's Centre of Applied Space Technology and Microgravity, or Zarm, developed a "bioreactor". This is called Atmos, or Atmosphere Tester for Mars-bound Organic Systems, and will try to grow cyanobacteria – a blue-green algae found naturally in water that can photosynthesise its own food
"If you can grow the cyanobacteria at low pressure, it's much easier," Dr Verseux said. "If not, you have a big pressure difference and you need something which is very robust and very heavy. Every kilogram increases the cost of the mission."
The bioreactor consists of nine glass and steel vessels in which the contents are stirred and the pressure kept to about one-tenth that on Earth or about 10 times that on Mars.
There were rich supplies of nitrogen and carbon dioxide, conditions that could be recreated on the surface of Mars. In one set of experiments, a growth medium – based on the nutrients found on Mars – was included.
Last summer, when Dr Verseux, who heads Zarm’s laboratory of applied space microbiology, opened up the system, he was delighted with what he saw.
“I was quite excited when I found out,” he said. “I saw the cultures were a very dense green colour, which means they had proliferated. That’s when I realised it was working.”
The key finding is that, even at low pressure, cyanobacteria can use the gases available on Mars and the nutrients in Martian dust to grow and reproduce.
Those used in the study, a filamentous type called Anabaena, use carbon dioxide and nitrogen and incorporate it into nutrients.
For a mission to Mars, cyanobacteria could potentially be used as food themselves or to produce biofuels. They could also provide nutrients for other organisms, and the researchers found that other bacteria, including Escherichia coli, a source of food and medicines, could grow on a medium made from the cyanobacteria produced in Atmos.
On Mars, the oxygen produced by the cyanobacteria could potentially be collected and used by astronauts.
After publishing the research in the Frontiers in Microbiology journal, Dr Verseux and his colleagues are now working to optimise the system, as this could encourage space agencies to look at using the technology.
“We need to do the work of being able to tell them: ‘Here’s what you can get from that technology,’” he said.
“Now we are improving the system. We’re adding some new features. We’re going to start using it again soon.”
Nasa is among the organisations with plans for human missions to Mars, with the space agency hoping to undertake them in the 2030s.
A scientist not linked to the research, Dr Paul Byrne, an associate professor of planetary science at North Carolina State University in the US, said using Martian soil and materials present on Mars to sustain humans there would “reduce the amount of stuff we have to bring from Earth”.
While cautioning that he could not say if the technology in the latest study would be adopted, he said such efforts could make missions more feasible.
“Anything in support of human exploration is going to make it cheaper, and if it makes it cheaper it makes it more possible, because fundamentally these things are bound by cost,” he said.