The prospect of a Mars colony is a step closer to reality, with Dutch scientists having harvested more than a dozen crops grown in simulated Mars soil, right here on Earth.
Now the scientists are asking if plant growth can be sustained there.
Dr Wieger Wamelink, who led the team from Wageningen University and Research in successfully growing the crops, is on a mission to find out whether bacteria - which is essential in turning dead plant parts into nutrients for plant growth - can survive on the Red Planet.
"With this next step, we are moving from just growing crops to building a small but sustainable ecosystem," said Dr Wamelink, who is both a botanist and an ecologist.
He is teaming up with Dr Maaike van Agtmaal from Imperial College London, who will start the experiments this month.
Sterilised Mars and Moon soil simulants will be inoculated with bacteria from different agriculture soils and placed under controlled conditions. The bacteria's activity will then be monitored.
"My aim is to study the process of terraforming of soils, the process of making soil habitable. We will therefore also compare the results from the simulants with Sahara sand and Arctic soil," Dr van Agtmaal said.
The experiment will last a month, with samples taken every week.
Last year, Dr Wamelink got the scientific community excited after he revealed that his team had harvested tomatoes, rye, spinach, cress, peas, radishes, garden rocket, chives and leeks grown in Mars and Moon soil simulants. The Mars soil simulant came from a volcano in Hawaii, while the Moon soil simulant came from an Arizona desert.
The crops were cultivated in a regular greenhouse and post-harvest tests found that they were safe to eat, with no dangerous levels of heavy metals - such as copper, arsenic and lead - detected.
Seeds from the crops were replanted last year and successfully germinated. "So we now know the cycle is complete," said Dr Wamelink.
Preliminary findings have revealed no differences between crops grown in Earth soil and in Mars and Moon simulants, including in vitamin and protein content.
But Dr Wamelink said the harvests of crops grown in Mars and Moon soil simulants were still poorer than those grown in Earth soil. Cress, for example, produced seeds of a smaller mass, which had poorer germination.
"This could be due to lower bacterial activity," he said.
Dutch company Mars One, which is tentatively aiming to set up human colonies on the Red Planet, said it is interested in the latest project.
"It could mean an important step towards producing food more efficiently on Mars, which means less time or space would be needed to grow a healthy diet for future Mars settlers," said chief executive and co-founder Bas Lansdorp.
Dr Wamelink will embark on a study of Mars' cosmic radiation and its potentially harmful effects on plants later this year.
The researchers have been crowdfunding (https://crowdfunding. wur.nl/project/planten-kweken-op-mars) to keep the research going and have raised 60 per cent of the €25,000 (S$37,300) target.