Space

ExoMars Discovers Hidden Water in Mars’ Grand Canyon – The Largest Canyon in the Solar System

Valles Marineris, Mars

Valles Marineris, seen at an angle of 45 degrees to the surface in near-true color and with four times vertical exaggeration. The image covers an area of 630,000 sq km. The digital terrain model was created from 20 individual HRSC orbits, and the color data were generated from 12 orbit swaths. The largest portion of the canyon, which spans right across the image, is known as Melas Chasma. Candor Chasma is the connecting trough immediately to the north, with the small trough Ophir Chasma beyond. Hebes Chasma can be seen in the far top left of the image. Credit: ESA/DLR/FU Berlin (G. Neukum)

The ESA-Roscosmos ExoMars Trace Gas Orbiter has spotted significant amounts of water at the heart of Mars’ dramatic canyon system, Valles Marineris.

The water, which is hidden beneath Mars’ surface, was found by the Trace Gas Orbiter (TGO)’s FREND instrument, which is mapping the hydrogen – a measure of water content – in the uppermost meter of Mars’ soil.

While water is known to exist on Mars, most is found in the planet’s cold polar regions as ice. Water ice is not found exposed at the surface near the equator, as temperatures here are not cold enough for exposed water ice to be stable.

Missions including ESA’s Mars Express have hunted for near-surface water – as ice covering dust grains in the soil, or locked up in minerals – at lower latitudes of Mars, and found small amounts. However, such studies have only explored the very surface of the planet; deeper water stores could exist, covered by dust.

Artist’s impression of the ExoMars 2016 Trace Gas Orbiter at Mars. Credit: ESA/ATG medialab

“With TGO we can look down to one meter below this dusty layer and see what’s really going on below Mars’ surface – and, crucially, locate water-rich ‘oases’ that couldn’t be detected with previous instruments,” says Igor Mitrofanov of the Space Research Institute of the Russian Academy of Sciences in Moscow, Russia; lead author of the new study; and principal investigator of the FREND (Fine Resolution Epithermal Neutron Detector) neutron telescope.

“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.”

The water-rich area is about the size of the Netherlands and overlaps with the deep valleys of Candor Chaos, part of the canyon system considered promising in our hunt for water on Mars.

Tracking neutrons

Igor and colleagues analyzed FREND observations ranging from May 2018 to February 2021, which mapped the hydrogen content of Mars’ 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,” adds co-author Alexey Malakhov, also 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.

ESA’s ExoMars Trace Gas Orbiter (TGO) has discovered large amounts of water locked up within Mars’ extensive canyon system, Valles Marineris. Credit: From I. Mitrofanov et al. (2021)

“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.”

This water could be in the form of ice, or water that is chemically bound to other minerals in the soil. However, other observations tell us that minerals seen in this part of Mars typically contain only a few percent water, much less than is evidenced by these new observations. “Overall, we think this water more likely exists in the form of ice,” says Alexey.

Water ice usually evaporates in this region of Mars due to the temperature and pressure conditions near the equator. The same applies to chemically bound water: the right combination of temperature, pressure and hydration must be there to keep minerals from losing water. This suggests that some special, as-yet-unclear mix of conditions must be present in Valles Marineris to preserve the water – or that it is somehow being replenished.

Artist’s impression of Mars Express. The background is based on an actual image of Mars taken by the spacecraft’s high resolution stereo camera. Credit: Spacecraft image: ESA/ATG medialab; Mars: ESA/DLR/FU Berlin

“This finding is an amazing first step, but we need more observations to know for sure what form of water we’re dealing with,” adds study co-author Håkan Svedhem of ESA’s ESTEC in the Netherlands, and former ESA project scientist for the ExoMars Trace Gas Orbiter.

“Regardless of the outcome, the finding demonstrates the unrivaled abilities of TGO’s instruments in enabling us to ‘see’ below Mars’ surface – and reveals a large, not-too-deep, easily exploitable reservoir of water in this region of Mars.”

Future exploration

As most future missions to Mars plan to land at lower latitudes, locating such a reservoir of water here is an exciting prospect for future exploration.

While Mars Express has found hints of water deeper underground in Mars’ mid-latitudes, alongside deep pools of liquid water under Mars’ south pole, these potential stores lie up to a few kilometers below ground, making them less exploitable and accessible to exploration than any found just below the surface.

Perspective view of Candor Chasma. Mars Express took snapshots of Candor Chasma, a valley in the northern part of Valles Marineris, as it was in orbit above the region on July 6, 2006. Credit: ESA/DLR/FU Berlin (G. Neukum)

The finding also makes Valles Marineris an even more promising target for future human exploration missions to the planet. The largest canyon in the Solar System, Valles Marineris is arguably Mars’ most dramatic landscape, and a feature that is often compared to Earth’s Grand Canyon – despite being some ten times longer and five times deeper.

“This result really demonstrates the success of the joint ESA-Roscosmos ExoMars program,” says Colin Wilson, ESA’s ExoMars Trace Gas Orbiter project scientist.

“Knowing more about how and where water exists on present-day Mars is essential to understand what happened to Mars’ once-abundant water, and helps our search for habitable environments, possible signs of past life, and organic materials from Mars’ earliest days.”

TGO launched in 2016 as the first of two launches under the ExoMars program. The orbiter will be joined in 2022 by a European rover, Rosalind Franklin, and a Russian surface platform, Kazachok, and all will work together to understand whether life has ever existed on Mars.

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  • "...assuming the hydrogen we see is bound into water molecules."
    Big assumption. Hard to drink hydrogen. Even harder for any Martian microbes to live. The ones they have been looking for in a dried up lake. These Martian explorers are getting desperate?

    • It's the smaller assumption, considering that water is the most abundant form of hydrogen in rocky bodies, whether as ice or as crystal water. That is why they suggest it.

  • Back in 2006, our lab observed outflows of water at crater wall outflow sites. adjacent to these outflows, we observed rapid sinking of the Martian surface, strongly suggestive of subterranean liquid - probably water - building up and flowing during warm conditions. We reported this to NASA.https://microphonium.blogspot.com/2006/12/possible-source-of-martian-outflow.html. In addition, we captured stereo pairs of Martian Orbiter images that allow you to see the sinking in three dimensions. Other researchers have found series of sinkholes - dozens of them in a row, suggesting subsurface rivers of water.

    • No, your microphone laboratory did not scientifically observe and report anything - there are no references - and it is a thinly pseudoscience veiled ad for a commercial product.

      I would not by your product, even if I was interested in that and not the science article here, since you can't honestly declare what you present.

  • @Ken Towe, patience eager beaver. You can't just drive around the corner to the Martian market and get Martian Aquafina. You have to identify promising locations first, then send additional probes to confirm.

  • Am I the only one that is surprised about how little shock about the discovery of water that this story is getting? Scientists and astronomers have been wondering for 1000's of years. Now thats its confirmed, its like we always knew. Old news. Where is the surprise at? Instead of talking about of how much, where are the point of views about what we can do with the "new" knowledge and is it true. Its gone directly to "old news" instead of how true it is. It is teh formation of a discussion of possible earth like life on another planet. Its not just the possibility of a swimming pool there, its the fundamental question of if there is life on other planets. We are treating this as a multibillion dollar possibility of drilling a drinking well on another planet. Its more than that. Where did the fundamental questions go?

    • Water in the form of ice has been suspected and found across the outer solar system for decades, and as water clouds on exoplanets for several years. On Mars specifically Opportunity and Spirit found evidence for historical water in the early 00s, and Phoenix verified polar ices later that decade.

      It isn't shocking, but still mildly exciting. Perhaps more so for future exploration purposes than for massive changes in current understanding of Mars water cycle. That relates to the possibility of subsurface water resources, where earlier evolved life now may be surviving. That is the question that the Rosalind Franklin 2 m drill set may start to explore.

  • Looks like a good place for that fracking equipment investment money NFT ?? It getting ever more clear that only robots can survive on Mars and the trip to Mars (and not get cancer(s) ..
    So I'm happy to see this kind of machine exploration... maybe something useful back on Earth will come of it?

    • Yes, only robots can't get cancers - humans get cancers with or without going to Mars.

      But really, the estimate of 5 % decreased average lifetime compares to the current 10 % decrease of living in the average polluted city (a situation rapidly improving), which already 50+ % of humanity has shown willing to risk. I'd rather go to Mars, for the excitement.

      • "Excitement"... Yes the excitement of drinking your own piss while living in a truck stop toilet as your muscles and organs degenerate, eaten by cancer from deep space radiation.. (and thats just the trip getting there)..
        As for "5% estimate".... WOW.. look at the condition of these astronauts spending just a few weeks/months in low earth orbit, sheilded by the earth.. they have massive medical issues, failing eyesight, muscle loss, cardio issues.... now put them in deep space and watch the body decay even faster... that "5%" is probably the life expectancy of living 3 years on Mars....
        Humans are biological creatures that evolved on Earth with gravity, fresh air, clean water and real food. We are totally unsuited for outer space. the sooner we ditch the fantasy of going to live on Mars, the sooner we can fix the problems on space ship earth. Send the robots, they can do it cheaper and safer and better..

        • It is solving the enormously complex challenges presented by space travel that results in technological advances which ultimately help us in solving more earth-bound troubles. Besides, our problems here are mostly due to over-consumption of resources and over-population; we know how to solve those, we just lack the will.

        • One of the big problems is primary cosmic rays. They hit the shielding and make showers of secondary cosmic rays. The more the shielding for other radiation. The more shielding to hit making more, ionizing, secondary cosmic rays.

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European Space Agency (ESA)

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