While methane can be created through interactions between rocks and water, microbial life is an important source of methane on Earth and scientists hope that its presence on the Red Planet could point to the existence of basic lifeforms.

As it can be destroyed by solar radiation on timescales of several hundred years, any detection of the molecule in present times implies it must have been released relatively recently, even if the methane itself was produced millions or billions of years ago and remained trapped in underground reservoirs until now.

In addition, the Curiosity rover detected organic compounds on the surface of Mars last year, which offers some of the strongest evidence yet that the Red Planet may once have harboured life.

However, in April the ExoMars Trace Gas Orbiter (TGO) found little evidence of methane, despite spotting the gas on several previous occasions, putting in doubt the viability of the previous results which had only detected the gas at the edge of its detection limits.

The source of the methane plume, which the latest readings show has now ceased, is unknown as the rover does not have the ability to detect its origin.

“With our current measurements, we have no way of telling if the methane source is biology or geology, or even ancient or modern,” said Paul Mahaffy, principal investigator for SAM (Sample Analysis at Mars) at Nasa.

Around 21 parts per billion units by volume (ppbv) of methane was measured in the Gale Crater part of Mars, the highest concentration the mission has recorded.

The amount is still small compared to Earth, where it is about 1,800 ppbv – meaning for every billion molecules, 1,800 are methane.

Curiosity scientists hope they can combine observations from the surface and from orbit to help pinpoint the sources of the gas and understand how long it lasts in the Martian atmosphere. That might explain why the TGO and Curiosity have recorded such different methane observations.

While methane can be created through interactions between rocks and water, microbial life is an important source of methane on Earth and scientists hope that its presence on the Red Planet could point to the existence of basic lifeforms.

As it can be destroyed by solar radiation on timescales of several hundred years, any detection of the molecule in present times implies it must have been released relatively recently, even if the methane itself was produced millions or billions of years ago and remained trapped in underground reservoirs until now.

In addition, the Curiosity rover detected organic compounds on the surface of Mars last year, which offers some of the strongest evidence yet that the Red Planet may once have harboured life.

However, in April the ExoMars Trace Gas Orbiter (TGO) found little evidence of methane, despite spotting the gas on several previous occasions, putting in doubt the viability of the previous results which had only detected the gas at the edge of its detection limits.

The source of the methane plume, which the latest readings show has now ceased, is unknown as the rover does not have the ability to detect its origin.

“With our current measurements, we have no way of telling if the methane source is biology or geology, or even ancient or modern,” said Paul Mahaffy, principal investigator for SAM (Sample Analysis at Mars) at Nasa.

Around 21 parts per billion units by volume (ppbv) of methane was measured in the Gale Crater part of Mars, the highest concentration the mission has recorded.

The amount is still small compared to Earth, where it is about 1,800 ppbv – meaning for every billion molecules, 1,800 are methane.

Curiosity scientists hope they can combine observations from the surface and from orbit to help pinpoint the sources of the gas and understand how long it lasts in the Martian atmosphere. That might explain why the TGO and Curiosity have recorded such different methane observations.