Water reservoir on Mars is two miles deep, would cover planet with nine feet of water

Mars holds many curious features, and one of the most intriguing is the Medusae Fossae Formation (MFF). This enormous stretch of terrain sits near the planet’s equator, exactly where smooth northern plains meet rugged southern highlands.

Scientists have puzzled over this place for years because it seems to hide something that might change our understanding of the Red Planet’s past.

A radar tool called the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) has provided new clues by bouncing signals beneath the MFF.

The echoes reveal underground layers that hint at an astounding discovery, and one that is of particular importance to future human settlers on Mars.

Deep water on Mars’ MFF

Thomas Watters, from the Smithsonian Institution, and lead author of both the original and recent studies, sheds light on these recent findings.

“We’ve explored the MFF again using newer data from Mars Express’s MARSIS radar, and found the deposits to be even thicker than we thought: up to 2.2 miles (3.7 km) thick,” says Watters.

“Excitingly, the radar signals match what we’d expect to see from layered ice, and are similar to the signals we see from Mars’s polar caps, which we know to be very ice rich.”

Enough water to cover Mars 9 feet deep

The implications of this discovery are profound. The ice within the Medusae Fossae Formation, if melted, could envelop the entire planet of Mars in a water layer measuring between 5 and 9 feet deep (1.5 to 2.7 meters).

This represents the largest water reservoir discovered in this region of Mars, holding enough water to rival the volume of Earth’s Red Sea.

The MFF is a geological marvel, covering hundreds of miles and can tower over a mile high. It sits at the intersection of Mars’s highlands and lowlands, a potential major source of Martian dust and one of the planet’s most expansive deposits.

Wind-sculpted ridges, along with a blanket of dust or ash, appear to protect layers of ice from the harsh conditions on modern Mars.

Experts believe these vast dust deposits might be the biggest single source of Martian dust, which could mean they shaped the planet’s atmosphere over long periods.

Earlier studies of the MFF

The initial observations by Mars Express hinted at the icy nature of the Medusae Fossae Formation due to its radar transparency and low density.

However, alternative theories proposed that the formation could be a colossal accumulation of windblown dust, volcanic ash, or sediment.

“Here’s where the new radar data comes in! Given how deep it is, if the MFF was simply a giant pile of dust, we’d expect it to become compacted under its own weight,” says co-author Andrea Cicchetti of the National Institute for Astrophysics, Italy.

“This would create something far denser than what we actually see with MARSIS. And when we modelled how different ice-free materials would behave, nothing reproduced the properties of the MFF – we need ice,” Cicchetti concluded.

Rewriting Martian history

The current understanding of the MFF region suggests a composition of dust and ice layers, topped by a protective layer of dry dust or ash, hundreds of meters thick.

Mars, though appearing arid now, shows signs of a water-rich past, including remnants of river channels, ancient ocean beds, and water-carved valleys.

This discovery of significant ice near Mars’s equator, like that suspected beneath the MFF’s surface, points to a radically different climatic era in the planet’s history.

“This latest analysis challenges our understanding of the Medusae Fossae Formation, and raises as many questions as answers,” says Colin Wilson, ESA project scientist for Mars Express and the ESA ExoMars Trace Gas Orbiter (TGO).

“How long ago did these ice deposits form, and what was Mars like at that time? If confirmed to be water ice, these massive deposits would change our understanding of Mars climate history. Any reservoir of ancient water would be a fascinating target for human or robotic exploration.”

Why does any of this matter?

For future Mars missions, the discovery of ice at equatorial locations like the Medusae Fossae Formation is invaluable.

Missions require landing near the equator, away from the polar caps or high-latitude glaciers, and water is a critical resource.

However, Wilson cautions, “The MFF deposits, buried under extensive dust layers, remain out of reach for the time being.

Yet, each discovery of Martian ice enriches our understanding of the planet’s hydrological history and current water distribution.”

While MARSIS looks deep underground, the ExoMars Trace Gas Orbiter (TGO) offers a shallower view. TGO’s FREND instrument tracks hydrogen in the topmost three feet of soil.

Not long ago, FREND discovered a hydrogen-rich patch the size of the Netherlands inside Mars’s Valles Marineris.

Such findings show how valuable orbiters can be when searching for water in places that may support future landings.

Colin Wilson concludes, “Our collective Mars exploration efforts are progressively unveiling the mysteries of our planetary neighbor, offering glimpses into its past and potential for future exploration.”

Mars continues to surprise

To sum it all up, the Mars Express’ exploration of the Medusae Fossae Formation (MFF) mark a significant milestone in our understanding of Mars and its climatic history.

Mars researchers say there are still many questions about how and when these mysterious formations accumulated their icy layers.

The significance is clear, though: abundant ice so far from the poles could reflect a period in Mars’s past when the climate supported large-scale water deposits at different latitudes.

Detecting and mapping these resources will be helpful for both science and practical planning.

“Together, our Mars explorers are revealing more and more about our planetary neighbor,” adds Colin.

The full study was published in the journal Geophysical Research Letters.

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