For generations, humans have dreamed of the day when we might set foot on Mars. For many others, the dream has been one of settling on Mars and creating an outpost of human civilization there. Today, it looks as though both of these dreams are getting closer to becoming a reality, as space agencies and the commercial space industry are deep into planning regular crewed missions to the Red Planet. And when planning for long-duration missions to destinations in deep space, a vital aspect is assessing the local environment.

For example, missions to Mars will need to be as self-sufficient as possible, which means using local resources to meet the needs of the mission and astronauts – a process known as in-situ resource utilization (ISRU). According to new data from the ESA-Roscomos ExoMars Trace Gas Orbiter (TGO), the massive equatorial canyon known as Valles Marineris (Valley of Mars) contains vast deposits of ice that have remained hidden to scientists until now.

The research was conducted by Dr. Igor Mitrofanov and his colleagues at the Space Research Institute (IKI) of the Russian Academy of Sciences (RAS) in Moscow. They were joined by Håkan Svedhem of the ESA’s European Space Research and Technology Centre (ESTEC) in Noordwijk, Netherlands. The paper that describes their findings – “The evidence for unusually high hydrogen abundances in the central part of Valles Marineris on Mars” – recently appeared in the journal Icarus.

Animation of Valles Marineris based on data acquired by the Mars Express orbiter. Credit: ESA/DLR/FU Berlin (G. Neukum)

Valles Marineris has been a focal point for climatic studies on Mars for some time. Measuring 4,000 km (2,500 mi) long and up to 7 km (4 mi) deep, it is the largest canyon system in the Solar System. This depth is also why atmospheric pressure at the bottom of the canyon is believed to be higher than most places on Mars – over 1200 Pa. On average, atmospheric pressure on Mars at “sea level” is 0.636 kPa, less than 0.5% of what we experience here on Earth (101.325 kPa).

According to new evidence obtained by the orbiter element of the joint European-Russian ExoMars mission, there is plenty of water ice at the bottom of this valley. This data was obtained as part of a campaign to map the hydrogen content of Mars’ soil by detecting neutrons, a clear sign of water. The ultimate goal is to determine if Mars has water ice locked away in near-surface deposits.

For the sake of their research, the team analyzed data obtained by the TGO’s Fine Resolution Epithermal Neutron Detector (FREND) between May 2018 and February 2021. As co-author Alexey Malakhov of the IKI explained in a recent ESA press release:

“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. 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.

Artist’s impression of Condar Chasma based on Mars Express data. Credit: ESA/DLR/FU Berlin (G. Neukum)

“We found a central part of Valles Marineris to be packed full of water – far more water than we expected,” he added. “This is very much like Earth’s permafrost regions, where water ice permanently persists under dry soil because of the constant low temperatures.” This data revealed that there’s plenty of water ice in Valles Marineris, which is concentrated in the upper meter (3.3 ft) of the soil.

The water-rich area is comparable in size to the Netherlands and overlaps with Candor Chasma, a tributary valley located in the northern part of the canyon system (also considered a promising area to find near-surface water). As Mitrofanov, who is also the principal
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