The Greening of Mars

A hardy microbe from Earth might one day transform the barren ground of Mars into arable soil.

Although Mars may once have been warm and wet, the Red Planet today is a frozen wasteland. Most scientists agree, it's highly unlikely that any living creature - even a microbe - could survive for long on the surface of Mars.

When the first humans travel there to explore the Red Planet up close, they will have to grow their food in airtight, heated greenhouses. The Martian atmosphere is far too cold and dry for edible plants to grow in the open air. But if humans ever hope to establish long-term colonies on their planetary neighbour, they will no doubt want to find a way to farm outdoors. Imre Friedmann has an idea of how they might take the first step.

Friedmann is a microbiologist on the NASA Astrobiology Institute team at the Ames Research Centre. Friedmann was one of the invited speakers at a NASA-sponsored conference, "The Physics and Biology of Making Mars Habitable," held at Ames late last year. His talk focused on an organism that could be used to begin the process of converting the Martian surface into arable soil.

Mars is covered by a layer of ground-up rock and fine dust, known as regolith. To convert regolith into soil, it will be necessary to add organic matter, much as organic farmers on Earth fertilise their soil by adding compost to it.

On Earth, compost is made up primarily of decayed vegetable matter. Micro-organisms play an important role in breaking down dead plants, recycling their nutrients back into the soil so that living plants can reuse them. But on Mars, says Friedmann, where there is no vegetation to decay, the dead bodies of the micro-organisms themselves will provide the organic matter needed to build up the soil.

The trick is finding the right microbe.

"Among the organisms that are known today," says Friedmann, "Chroococcidiopsis is most suitable" for the task.

Chroococcidiopsis is one of the most primitive bacteria known. What makes it such a good candidate is its ability to survive in a wide range of extreme environments that are hostile to most other forms of life. Chroococcidiopsis has been found growing in hot springs, in hypersaline (high-salt) habitats, in a number of hot, arid deserts throughout the world, and in the frigid Ross Desert in Antarctica.