A mission investigating whether life has ever existed on Mars has made a new discovery: “significant amounts of water” in the red planet’s grand canyon system, called Valles Marineris, according to a press release from the European Space Agency (ESA).
The water is hidden beneath the Martian surface and was discovered by the Trace Gas Orbiter, which is the first stage of the joint ESA-Roscosmos mission ExoMars. The discovery was made by the orbiter’s FREND instrument (Fine Resolution Epithermal Neutron Detector), which maps the hydrogen content of Martian soil. When the soil is struck by high-energy cosmic rays, it emits neutrons, with dry soil emitting more neutrons than wet soil. This allows scientists to get a sense of the water content of soil that lies just below the surface.
“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 percent of the near-surface material in this region appears to be water,” said lead investigator Igor Mitrofanov of the Space Research Institute of the Russian Academy of Sciences in the press release.
Water has been previously discovered on Mars, but it’s mostly concentrated on the poles in the form of ice, with only very small amounts being discovered on the surface at lower latitudes. This isn’t very useful for future human explorers, so finding an ample source of water at lower latitudes is a key focus right now.
The discovery of seemingly a lot of water in Valles Marineris is an important step in this direction. As a tweet from the ExoMars mission notes, “the reservoir is large, not too deep below ground, and could be easily exploitable for future explorers.”
There’s more work to be done, however. As the study detailing the work, published in the journal Icarus, notes, neutron detection doesn’t allow for distinguishing what form the water might take. It may be ice, or it may be water molecules in soil, and determining which it is will fall to geochemists. For a few different reasons including the morphology of the canyon, the researchers speculate it may indeed be water ice, but it may also end up being a mixture.
“We found a central part of Valles Marineris to be packed full of water–far more water than we expected,” said study co-author Alexey Malakhov in a release. “This is very much like Earth’s permafrost regions, where water ice permanently persists under dry soil because of the constant low temperatures.”