The ancient Mars had a source of energy for underground life

If life had taken hold in the Martian basement a long time ago, she could have benefited from a source of abundant chemical energy, suggests a new study.

This source was hydrogen, generated when radiation separated groundwater into its components. And there was probably enough hydrogen available out there to support a considerable community of Mars microbes for hundreds of millions of years, from about 4 billion years ago, according to the study.

"We have shown, on the basis of physical and chemical calculations, that the ancient Martian subsoil probably had enough dissolved hydrogen to feed a global underground biosphere," said Jesse Tarnas, a senior student at Brown University. Rhode Island. . "The conditions in this habitable zone would have been similar to those of the Earth where the underground life exists". [The Search for Life on Mars (A Photo Timeline)]

With the help of data collected by NASA's Mars Odyssey orbiter, Tarnas and his colleagues have established the abundance of radioactive elements thorium, potassium and uranium in the crust of the red planet. Since these elements are degrading at known rates, the team can extrapolate backwards, determining the levels in the old times.

The researchers also analyzed measurements of the density of the Martian crust, as well as the results of the geothermal and climatic models, to determine the amount of water likely to be divided by this natural radiation when the planet was young.

They concluded that the red planet was probably home to an underground "habitable zone" several kilometers thick about 4 billion years ago, the same time that liquid water was flowing through the surface Martian.

Scientists do not know exactly what this surface looked like at the time, whether it was relatively hot and humid most of the time, or whether the old Mars was a deep cold place where water flowed only transiently .

A cold, ancient Mars would probably make life more difficult to flower and radiate to the surface, but the same is not true of hypothetical underground organisms. Indeed, the overlying ice would make the subsurface area more habitable, preventing the newly divided hydrogen from escaping into the atmosphere.

"People have the impression that a cold climate in early March is bad for life, but what we are showing is that there is actually more chemical energy for life underground in a cold climate "said Tarnas. "We think this could change people's perception of the relationship between climate and life on Mars."

The new study, to be published in the November 15 issue of Earth and Planetary Science Letters, could help future missions look for signs of life on the red planet, such as NASA's March 2020 rover.

For example, members of the study team estimated that the 2020 rover could target "megabreccia blocks", pieces of previously buried rock exposed to meteorite impacts. It is known that such blocks are present on at least two of NASA's four landing sites for the 2020 rover, said study co-author Jack Mustard, a professor in the Department of Earth Sciences. of the environment and planets of Brown University. (These two sites are Northeast Syrtis Major and Midway.)

"The 2020 rover's mission is to look for signs of past life," Mustard said in the same release. "The areas where you can have leftovers from this underground livable area – which may have been the largest habitable area on the planet – seem to be a good place to target."

Follow Mike Wall on Twitter @ michaeldwall and Google+. follow us @Spacedotcom, Facebook or Google+. Originally posted on Space.com.