For many experts, the methane deposits discovered nine years ago in the atmosphere of the inhospitable planet were considered an indication of extraterrestrial life.
The international team of scientists had irradiated parts of a meteorite under mars conditions with ultraviolet light, whereupon the gas molecules formed. "Methane is formed from countless small micro-meteorites and interplanetary dust particles that land on the surface of mars from space," explained atmospheric chemist frank keppler. "The energy is provided by the extremely strong ultraviolet radiation."The results have been published in the scientific journal "nature".
Since scientists found coarser amounts of methane on mars, there is much speculation about the source. One hypothesis is that microorganisms form the gas and that this could be an indication of life on the red planet. Geological methane sources such as volcanoes are also being discussed. According to projections, mars produces 200 to 300 tons of methane per year, keppler said.
Without a mars expedition, but with the help of the meteorite murchison, the researchers from mainz and the universities of utrecht and edinburgh found that uv light decomposes the carbon compounds in the meteorite rock. "Unlike earth, mars lacks a protective ozone layer that could absorb most of the uv radiation from space," keppler explained. The mars atmosphere is very dark, so that a much smaller fraction of the meteorite material burns up than on earth.
The meteorite murchison contains several percent carbon and has a similar chemical composition as the coarse part of the meteorite rock that lands on mars, explained the cosmochemist ulrich ott from mainz, germany. The 4.6-billion-year-old meteorite hit the australian town of murchison in 1969. When samples were exposed to UV radiation, considerable amounts of methane escaped almost immediately.
The results may disappoint all those who firmly believe in the biological origin of methane, the max planck institute announced. But the researchers could not rule out the hypothesis of martian microbes. It is quite possible that other processes contribute to methane production, said keppler.