Orbiter discovers hidden water in Mars's Grand Canyon

The ExoMars Trace Gas Orbiter, operated by the European Space Agency and Russian space agency Roscosmos, has detected "significant amounts of water" in Mars's Grand Canyon, Valles Marineris.

The water, which is hidden beneath Mars’s surface, was found by the orbiter’s FREND instrument, which is mapping hydrogen in the uppermost metre of Mars’s soil, the ESA said.

The water-rich area is about the size of the Netherlands, and overlaps with valleys of Candor Chaos, the ESA said.

The ESA said that while water is found in the planet's polar regions, it is not found exposed at the surface near the equator as the temperatures there are not cold enough for exposed water ice to be stable.

Multiple past missions, including the ESA's Mars Express, have sought water near the surface of the planet, in the form of ice, locked in soil or in mineral. However, the studies have only explored the planet's surface, and water could exist deeper in the planet, covered by dust, the agency said.

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“With TGO we can look down to one metre below this dusty layer and see what’s really going on below Mars’s surface – and, crucially, locate water-rich ‘oases’ that couldn’t be detected with previous instruments,” said Igor Mitrofanov of the Space Research Institute of the Russian Academy of Sciences in Moscow.

“FREND revealed an area with an unusually large amount of hydrogen in the colossal Valles Marineris canyon system: assuming the hydrogen we see is bound into water molecules, as much as 40% of the near-surface material in this region appears to be water,” he said in a statement.

The team analysed FREND observations from May 2018 to February 2021, which mapped the hydrogen content of Mars’s soil by detecting neutrons rather than light.

“Neutrons are produced when highly energetic particles known as ‘galactic cosmic rays’ strike Mars; drier soils emit more neutrons than wetter ones, and so we can deduce how much water is in a soil by looking at the neutrons it emits,” said Alexey Malakhov of the Space Research Institute of the Russian Academy of Sciences. “FREND’s unique observing technique brings far higher spatial resolution than previous measurements of this type, enabling us to now see water features that weren’t spotted before".

“We found a central part of Valles Marineris to be packed full of water – far more water than we expected. This is very much like Earth’s permafrost regions, where water ice permanently persists under dry soil because of the constant low temperatures,” he said, adding that they think the water on Mars likely exists in the form of ice.

“This finding is an amazing first step, but we need more observations to know for sure what form of water we’re dealing with,” said ESA's Håkan Svedhem.

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