Methane is an organic molecule found in Earth’s atmosphere Most are produced by living things, most famously taking cows. Detection enabled MarsOn the other hand, it is a strange puzzle for planetary scientists.
In recent years, NASA’s Curiosity probe has found tiny traces of methane many in number on the red planet. While these emissions may come from some geological process, they could indicate the presence of some kind of life on Mars (couldn’t be cows, of course).
As you might expect, scientists are excited about this possibility, but the data are confusing. Higher in the atmosphere, orbital technology from the European Space Agency (ESA) detected No methane in any concentration.
That’s odd, because even though lumps of methane would melt in the Martian atmosphere, like a pinch of salt in an Olympic-sized swimming pool, our instruments are sensitive enough to still detect these bright clues.
“[W]When the European team announced that they had not seen methane, I was certainly surprised,”” say Planetary scientist Chris Webster of NASA’s Jet Propulsion Laboratory.
Why the contradiction? Webster and his colleagues looked at the data again, ruling out any minor factors that might have contributed to the methane rover’s discovery.
“So we see interconnections with rover steering, earth, rock crushing, wheel breakage – you name it,” Webster explain.
“I can’t overstate the effort the team has put into looking at every little detail to make sure these measurements are correct, and they are.”
As it turned out, the methane plumes measured by Curiosity were not punctured. Instead, the difference in measurements boils down to the Sun. The team found that methane on Mars can ebb and flow over time, and Curiosity’s energy-intensive instruments that detect methane operate mostly at night.
This occurs when the Martian atmosphere is calmer, meaning that methane doesn’t rise and melt in the atmosphere as it does on a hot day. As a result, the researchers believe, the gas sticks close to the planet’s surface at night, and during the day, the methane is so dilute that the European Space Agency’s rotating instruments (which need sunlight to function) cannot detect it remotely.
To confirm their prediction, the research team collected high-resolution measurements of Martian methane over two days, the first time Curiosity has done so in broad daylight. They also take measurements at night.
As expected, the leaked methane is near the planet’s surface at night and then melts into the atmosphere during the day.
“John [E. Moores, another member of Curiosity’s science team] I predict that methane will fall effectively to zero during the day, and our measurements during the day confirm that.” explain Planetary scientist Paul Mahaffey of NASA’s Goddard Space Flight Center.
“That’s one way of dealing with this great inconsistency.”
However, it’s still unclear why methane doesn’t appear to have accumulated in the Martian atmosphere over time – according to the researchers, methane must persist for at least 300 years before it degrades in radiation from the Sun.
Since Gale crater is unlikely to be the only source of minor methane leaks on the planet (because Gale crater isn’t that special from a geological perspective), they believe that something had to destroy or absorb all that methane before it could. They gathered in the air.
The team is now testing whether dust or oxygen abundance may play a role.
Some of the puzzle may have been solved, but now we have more questions. Curiosity lives up to its name.
This study was published in Astronomy and astrophysics.
–
