Huge supply of subterranean water discovered in Mars' Grand Canyon
A huge new deposit of water has been discovered on Mars in a formation often called the Red Planet’s Grand Canyon. The Trace Gas Orbiter (TGO) has detected an area about the size of the Netherlands where water could make up as much as 40 percent of the material near the surface.
While Mars is believed to have once held huge oceans on its surface, today it’s drier than any Earthly desert. But there likely is still water on the Red Planet – mostly around the poles as ice, or potentially in salty liquid lakes deep underground, although the evidence is mixed on the latter idea.
Closer to the equator, smaller amounts of water have been detected in the soil near the surface, in the form of either ice or hydrated minerals. But the newly discovered cache is far bigger – and far wetter – than anything else found so far.
The new water stores were found by the TGO, using an instrument called the Fine Resolution Epithermal Neutron Detector (FREND) in a series of observations between May 2018 and February 2021. This tool detects neutrons coming out of the ground, which can be a marker of the hydrogen content – and by extension the water content – of the soil.
“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,” says Alexey Malakhov, co-author of the study. “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.”
Valles Marineris is the largest canyon in the solar system, measuring 10 times longer and five times deeper than our own Grand Canyon. And that’s where FREND detected a water-rich region measuring some 41,000 km2 (15,800 square miles). Within the upper 1 m (3.3 ft) of soil, up to 40 percent of the material seems to be water, which the team says most likely exists as ice.
“We found a central part of Valles Marineris to be packed full of water – far more water than we expected,” says Malakhov. “This is very much like Earth’s permafrost regions, where water ice permanently persists under dry soil because of the constant low temperatures.”
Finding water in this part of Mars is very exciting, the team says. Future missions to the Red Planet, including human missions, tend to focus on the region near the equator, and having this much water within a meter of the surface makes it very accessible. By comparison, polar deposits seem to be several kilometers deep.
The research was published in the journal Icarus.