quinta-feira, 31 de maio de 2012
Meteorites brought methane to Mars
Methane in the Martian atmosphere was generated from organic matter in meteorites that landed on the surface of the planet, say European scientists. A multinational team was involved in the study, in which particles of the Murchison meteorite, which is similar to those that fall onto the Martian surface, were irradiated with UV light.
As reported in Nature, irradiation at UV levels believed to be the same as those on Mars released significant amounts of methane. The gas originated from carbonaceous material embedded in the meteorite.
Carbon dioxide (95%), nitrogen and argon form most of the atmosphere, with methane a trace component. Its lifetime on Mars is quite short at a few hundred years, so it needs to be constantly replenished to maintain a steady concentration. This new discovery offers an explanation for its continuous production and for the involvement of meteorites, which had been ruled out previously.
Hydrogen isotope ratio measurements confirmed that the released methane is definitely extraterrestrial and not a terrestrial anomaly. However, stable carbon isotope measurements are similar to those of terrestrial microbes, so they will be of limited value in future Mars missions.
The results might help to cast some light on the recently observed variations of methane levels across the Martian surface and will be invaluable in trying to establish whether any methane on Mars is produced by microbial life.
Publicado por Jorge M. Gonçalves às 10:36 da tarde