“As we monitor (for) methane over time, we may be able to say more about the possibility about any sources in the Gale Crater region,” he said.

Measurements of other atmospheric gases have proven more fruitful.

An analysis of carbon, argon and other isotopes, which are variations of particular chemical elements, indicates that Mars, as suspected, has lost significant amounts of its atmosphere to space over time.

“The gases in the current atmosphere are a product of Mars’ entire history,” said Curiosity scientist Laurie Leshin of the Rensselaer Polytechnic Institute in Troy, New York.

The goal of the two-year, $2.5 billion Curiosity mission is to determine whether Mars, which is cold and dry today, ever had the chemical and environmental conditions to support and preserve microbial life.

“Did Mars once have abundant flowing water, and if so why is the climate so cold and the atmosphere so thin today as to preclude this?” Leshin said.

“By studying today’s atmosphere, we can gain clues to how Mars’ environment has changed,” she said.

Curiosity, which landed on Mars in August, is NASA’s first astrobiology mission since the 1970s-era Viking probes.