Ever since the Mars Curiosity rover touched down on the dusty surface of the far-distant planet, observers back on Earth have been hoping for signs of alien life. We would be thrilled with even the hint of a microbe, but it's starting to look more like wishful thinking than a scientific possibility.
Methane is considered to be an indication of the existence of microbes on other planets, just as it is on Earth. A paper published in the journal Science, titled "Low Upper Limit to Methane Abundance on Mars," analyzes the results from Curiosity's search for methane and concludes that it simply isn't to be found on the planet's surface.
Curiosity has been looking for signs of methane by using a Tunable Laser Spectrometer, a device that looks for spectral patterns unique to methane. An analysis of the findings shows no atmospheric methane within detectable parameters.
The paper's abstract concludes that this "reduces the probability of current methanogenic microbial activity on Mars."
This is a setback in the search for life, especially after reports that plumes of methane emerged on Mars in 2003. It casts doubt on those earlier observations, leaving scientists with a whole new tangle of questions to be answered. Were those really methane plumes? If so, why are there no traces now?
Though the study has put a damper on hopes for Martian life, scientists aren't yet ready to completely rule out the possibility. Curiosity mission project scientist John Grotzinger told The New York Times only that the findings discount the chance for life.
Curiosity's mission continues and the rover will keep up the search, but people eager for signs of life might want to prepare for disappointment.