1st Methane, Now Oxygen: Another Possible ‘Biosignature’ Gas Is Acting Weird on Mars
- 1st Methane, Now Oxygen: Another Possible ‘Biosignature’ Gas Is Acting Weird on Mars
by But don’t assume that Mars microbes are responsible.
Another possible biosignature gas is behaving strangely in Mars’ air. We already knew, thanks to NASA’s Curiosity Mars rover, that methane levels in the 96-mile-wide (154 kilometers) Gale Crater rise significantly during the summer months and that concentrations of the gas have spiked dramatically several times over the past few years, for unknown reasons. And now, a new study reports that the six-wheeled robot has observed something similar with oxygen, another potential sign of life.
“We’re beginning to see this tantalizing correlation between methane and oxygen for a good part of the Mars year,” study co-author Sushil Atreya, a professor of climate and space sciences at the University of Michigan in Ann Arbor, said in a statement. “I think there’s something to it. I just don’t have the answers yet. Nobody does.”
The newly reported results come courtesy of Curiosity’s Sample Analysis at Mars (SAM) instrument, a small chemistry lab that the rover carries on its body. The mission team has been using SAM to characterize the Red Planet’s atmosphere and analyze samples of dirt and drilled rock since Curiosity landed inside Gale Crater in August 2012.
The new study, which was published online Tuesday (Nov. 12) in the Journal of Geophysical Research: Planets, provides a detailed look at the SAM atmospheric measurements from 2012 to 2017. The data show that the air inside Gale Crater is 95% carbon dioxide (CO2) by volume, 2.6% molecular nitrogen (N2), 1.9% argon (Ar), 0.16% molecular oxygen (O2) and 0.06% carbon monoxide (CO).
There are no surprises in those numbers. But the team found that O2 levels don’t follow the same seasonal patterns as those other gases, rising considerably higher than predicted in the spring and summer and falling below expected levels during the Gale Crater winter.
And that was definitely a surprise. “The first time we saw that, it was just mind-boggling,” Atreya said.