NASA has identified a gas on Mars that is produced by living things on Earth, leaving scientists baffled as to what could be hiding in the Red Planet.
The Curiosity Rover detected a steady stream of methane coming from Gale Crater, appearing at different times of the day and fluctuating seasonally – sometimes as much as 40 times higher than normal.
Although NASA has not yet found life on the Martian world, scientists believe the source comes from deep within the ground.
The team has suggested that methane could be encased in solidified salt and only seep out when temperatures on Mars rise – or when Curiosity rolls over the crust and cracks it.
On Earth, this simple molecule, made up of one carbon atom and four hydrogen atoms, is usually a sign of life: gas passed by animals as they digest food.
NASA’s Curiosity Mars Rover detected methane coming from near Gale Crater – but not always. Scientists wanted to know why.
Scientists used this sample of Martian soil to conduct an experiment on how it forms a crust, trapping methane beneath the planet’s surface during the day.
NASA’s Curiosity Mars Rover has been roaming the surface of Mars since 2012, and in all that time, the most mind-boggling thing it discovered was a steady stream of methane coming from Gale Crater.
The spot in Gale Crater where methane was emitted was the only place on Earth where Curiosity detected the gas.
But Curiosity didn’t see any cows on Mars, nor did it find any people who just ate a large portion of cabbage.
In laboratory experiments that mimic conditions on the Martian soil, scientists were able to simulate what might be going on.
Over a long period of time, salts bubble up from deep beneath the planet’s rocky, dusty surface, a substance known as ‘regolith’.
These salts are called perchlorates and are abundant on Mars.
The perchlorates, which are toxic, are abundant in the ice trapped beneath the Earth’s surface.
As ice does when there is too little atmosphere, this ice gradually evaporates. And as this salty vapor filters through the regolith, it leaves a piece of itself behind.
The perchlorate salts trapped in Martian permafrost evaporate and become trapped in the ground. There it forms a crust that traps methane beneath the surface during the day.
When the team bubbled salty vapor up through the simulated Martian regolith, it created a crust that could trap gas.
When enough of these salts accumulate in the regolith, they form a kind of shell – like sand on the beach when it dries into a brittle crust, or like the puck of coffee grounds left behind after pulling a shot of espresso.
“On Mars, such a process could occur naturally over a long period of time in the shallow permafrost regions, and it may be possible for enough salt to accumulate in the top layer to form a seal,” wrote the scientists behind the new research. studythat was published in the magazine JGR planets.
As the salty vapor bubbles up, methane also bubbles up.
Its source remains a mystery.
It could come from some kind of living beings, or from geological processes beneath the Earth’s surface, which are still invisible to human scientists.
Wherever it comes from, it gets stuck under the salt crust.
By pumping different concentrations of perchlorates through the simulated Martian regolith, scientists found that three to thirteen days was long enough for this impermeable crust to form.
The rocky bottom surface of Gale Crater traps methane, but Curiosity could release it if it tears the crust.
Curiosity is the only NASA craft to detect methane on the planet. It has not yet been observed in the Martian atmosphere.
A perchlorate concentration of 5 to 10 percent was also needed to create a solid salt crust.
They pumped neon gas up beneath the crust, replacing methane, confirming that the layer was robust enough to hold gas beneath.
But when the planet’s temperature rises at certain times of day or certain seasons, this crust breaks, releasing the methane.
And that’s when Curiosity would detect methane in the air.
However, it’s not just the temperature that can crack the crust.
The crust is probably about two inches thick, just under an inch. And Curiosity is heavy enough to break through if it rolls over, the team behind the study wrote.
“To test this hypothesis, it would be useful to take methane measurements when the rover first arrives at a location with abundant high-salinity features (such as salt veins),” they wrote. “Another test would be to try to get Martian air while drilling into the salt-rich surface.”
NASA has not yet attempted such an experiment.