Air test suggests life possible on Mars

Could the red planet now be hosting life?

(CNN) -- A strange and hardy terrestrial microorganism can grow in atmospheric and soil conditions that resemble Mars, suggesting that life could thrive on the red planet, according to scientists.

The creatures, known as methanogens, survived in a thin atmosphere of hydrogen and carbon dioxide and in a special brew of volcanic ash altered to simulate the properties of martian soil, including its density, grain size and magnetic properties.

The results, in addition to the presence of vast stores of underground water on Mars, lend support to the theory that the planet once hosted or now hosts life.

"With the recent successful missions to Mars -- Pathfinder, Global Surveyor, Odyssey -- and especially the discovery that there is probably a vast ocean of frozen water below the surface, there is a greater possibility that life may exist below the surface today," said Tim Kral, a researcher at the University of Arkansas in Fayetteville.

Kral and colleagues grew the test microbes in a pressure chamber with about half the density of the atmosphere on Earth. They documented the growth by studying how much methane was produced.

If life were to exist below Mars, it would need another energy source besides photosynthesis, the process plants use to make fuel from sunlight.

Methanogens, which thrive in some of the most inhospitable places such as peat bogs and sea floor vents, tap their energy not from the sun but from the oxidation of inorganic matter, in their case hydrogen and carbon dioxide.

"Assuming that hydrogen and some water are present under the surface, the basic requirements for methanogen growth are met on Mars," the scientists said in a statement.

Even if Mars does not have life, Kral speculates that methanogens brought along by colonizers could take root, and perhaps help make the cold planet more comfortable for humans by releasing methane, a greenhouse gas.

But such "terraforming" might require hundreds or thousands of years before it could support more conventional forms of Earth life. And there are other drawbacks as well.

"Of course, there are many potential ethical and environmental problems with this," Kral said.