Water vapour has been detected escaping from Mars’s atmosphere, offering scientists a fresh clue as to whether the Red Planet was once home to life.

The Red Planet features several ancient dried out valleys and river channels which have long pointed towards the possibility of liquid water once flowing there, though most of it is now locked up in the ice caps or buried underground.

Now, a team of researchers, including two from the Open University, have discovered traces of hydrogen, one of the two components of water along with oxygen, leaking out of the Martian atmosphere.

The team made the discovery using the Nadir and Occultation for Mars Discovery (NOMAD) – an instrument on board the ExoMars Trace Gas Orbiter (TGO), a spacecraft operated jointly by the European Space Agency (ESA) and Russia’s Roscosmos that is currently in orbit around Mars.

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“The NOMAD instrument is fundamentally changing our understanding of the evolution of water on Mars,” said Dr Manish Patel, co-principal investigator of NOMAD.

“This fantastic instrument is giving us a never-before-seen view of water isotopes (water variants with different molecular masses) in the atmosphere of Mars as a function of both time and location on Mars.

“Measuring water isotopes is a crucial element of understanding how Mars as a planet has lost its water over time, and therefore how the habitability of Mars has changed throughout its history.”

The finding comes amidst a burst of other spacecraft entering orbit the Red Planet.

In the past seven days both China’s Tianwen-1 probe and the United Arab Emirates’ Hope probe successfully entered orbit around Mars.

And on 18 February NASA’s Perseverance rover is scheduled to touch down on the Red Planet’s surface.

Reader Q&A: How did Mars lose its atmosphere?

Asked by: Asser Awsaf

Mars today has a thin atmosphere: the volume of gases (mostly carbon dioxide) in its atmosphere is less than 1 per cent that of Earth’s. However, evidence from the surface of Mars indicates that the planet was once much warmer and wetter than today. This suggests that the Martian atmosphere must once have been much thicker, creating a strong greenhouse effect that trapped the Sun’s light.

Thanks to numerous missions to the Red Planet, we now know that in its early infancy, up until around four billion years ago, Mars had a strong magnetic field, created, just like Earth’s, by convection currents of molten metals in the planet’s core. But, unlike Earth, Mars cooled enough internally to switch off this mechanism, and the planet ended up with no global magnetic field. Without this magnetic field, the planet was less protected from the solar wind – the stream of energetic charged particles flowing from the Sun.

The solar wind stripped away most of the Martian atmosphere in only a few hundred million years after the planet lost its magnetic field. This process was quick because the Sun rotated much faster in its youth, which made the solar wind more energetic. The loss of a large fraction of its atmosphere to space was a major cause of Mars’s transition from a warm, wet climate to today’s cold, dry one.

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Jason Goodyer
Jason GoodyerCommissioning editor, BBC Science Focus

Jason is the commissioning editor for BBC Science Focus. He holds an MSc in physics and was named Section Editor of the Year by the British Society of Magazine Editors in 2019. He has been reporting on science and technology for more than a decade. During this time, he's walked the tunnels of the Large Hadron Collider, watched Stephen Hawking deliver his Reith Lecture on Black Holes and reported on everything from simulation universes to dancing cockatoos. He looks after the magazine’s and website’s news sections and makes regular appearances on the Instant Genius Podcast.