Missing methane on Mars might finally have been solved

(Image credits : mars.nasa.gov)

The curiosity rover on Mars has been detecting signs of methane, however, the ExoMars Trace Gas Orbiter, would pick up significantly lesser amounts of it than the rover measured. For instance, once Curiosity measured average methane concentrations of 0.41 parts per billion inside Gale crater, a 154-meter crater at the equator of Mars and it took everyone by surprise when the European Space Agency’s ExoMars Trace Gas Orbiter flew over the crater and found no methane at all. The amount of methane in the air might have been too tiny for the orbiter to sniff it out.

Curiosity rover rounds around in the crater and in the past has indicated that there might be life on Mars because of the amount of methane present in the air. Methane is a indicator key of processes in the subsurface, such as water rock reactions decomposition of clathrates or ancient accumulated meteoritic organics, and even current or past microbial activity. Researchers collected data from the orbiter and rover and found that during the day small amounts of methane are released into the atmosphere. It gets diluted and mixed due to convection. This leads to overall low levels of methane in the atmosphere.

Convection is a heat transfer that takes place when a fluid such as air or a liquid is heated and then travels away from the heat source. It carries with the thermal energy. The fluid above a hot surface expands, becomes less dense and rises. During the night convection decreases and allows for increase of methane on the surface of Mars. This increase is what the curiosity rover is measuring. In the morning convection increase and this cycle continues.

(Image credits : nasa.gov)

John Moores head author of the study said in a statement “Our study suggests that some of the differences between measurements of methane in the martian atmosphere could be the result of methane concentrations changing over the course of each day, if a small amount of methane continuously seeps from the subsurface.” He also added  “It turns out that the fact that each spacecraft measures at a different time of the day and in different parts of the atmosphere are the keys to solving the apparent discrepancy.”

Researchers were able to calculate the amount of methane that seeps out of the crater in one martian day 2.8 kg. They have also calculated that only 27,000 square kilometres of Mars surface should emit methane at a constant rate. That is an area equivalent to 1½ Gale craters.

In an interview with Science news, Moors said, “It’s difficult to imagine that only Gale emits methane. Either Gale is even more special than we imagine, or there’s something we’re missing in the chemistry of the atmosphere.”

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