Methane Debate Splits Mars Community

Observations over the last decade suggest that methane clouds form briefly over Mars during the summer months. The discovery has left many scientists scratching their heads, since it doesn't fit into models of the martian atmosphere.

"The reports are extraordinary," says Kevin Zahnle of NASA Ames Research Center. "They require methane to have a life time of days or weeks in the martian atmosphere, which disagrees with the known behavior of methane by at least a factor of 1000."

Zahnle and his colleagues have expressed some serious doubts about the existence of methane on Mars in a paper that appeared last December in the journal Icarus.

"What we say is that the evidence is not nearly strong enough for us to suspend our trust in the known chemical behavior of methane," he says.

But the observers are not backing down.

"We stand by our results," says Michael Mumma of NASA's Goddard Space Flight Center?, who leads one of the groups that made the methane observations. "True, the measurement is difficult, but it is not impossible."

Mumma thinks the paper by Zahnle and his coauthors has been "a disservice," so he plans to write a rebuttal. "The community needs to understand the weakness of this argument," he says.