for National Geographic News
Data obtained by the Mars Express probe that is currently orbiting the red planet show that water vapor and methane gas are concentrated in the same regions of the Martian atmosphere, the European Space Agency recently announced.
The finding may have important implications for the possibility that microbial life could exist on Mars. If microbes are making methane in the Martian atmosphere as part of their living process, they would rely on water.
Some scientists remain skeptical, however. They are not convinced that the new methane measurements are real and statistically valid. Even if the overlap exists, they say, it could just as easily be explained by other processes.
Vittorio Formisano of the Institute of Physics and Interplanetary Science in Rome, Italy, lead the team that made the recent announcement. In March the same researchers said they had detected methane in the Martian atmosphere. The scientists used the Planetary Fourier Spectrometer (PFS) on Mars Express, an instrument that maps infrared radiation on Mars.
Now new PFS data shows that at 10 to 15 kilometers (6.2 to 9.3 miles) above the Martian surface, water vapor is well mixed and uniform. Close to the planet's surface, however, water vapor is two to three times more concentrated in three equatorial regions than in other areas.
The data also shows concentrations of methane in the same areas where water vapor and underground water ice are more concentrated. A water-ice layer a few tens of centimeters (8 to 12 inches) below the surface was detected by NASA's Odyssey spacecraft, which is also orbiting Mars.
"This overlap [of methane and water vapor] points to a common underground source in the same regions," Formisano said in an e-mail interview.
Formisano stresses that an underground source doesn't prove there is microbial life. The methane could be a byproduct of volcanic gassing. Or it could be the chemical reaction between water and rocks in the soil and crust.
However, there is a possibility that the methane is produced by organisms called methanogens, which are microbes that produce methane as a waste product of their life process. The gas would be released to the surface and into the atmosphere.
Scientists have speculated that the methane-producing bacteria may live in water below the presumed ice table.
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