Mars may be hiding a vast stash of water beneath the Medusae Fossae Formation (MFF) near its equator.
This ice-rich deposit could be the largest known water reservoir in this part of Mars, with an estimated volume comparable to Earth’s Red Sea.
If melted, it has the potential to flood the entire planet in nine feet of water, scientists say.
Fresh data from the Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) suggests the underground water reservoir extends up to 2.2 miles (3.7 km) deep—far more than previously thought.
“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,” said Thomas Watters, lead author of the study and a scientist at the Smithsonian Institution.
“Excitingly, the radar signals match what we’d expect from layered ice, similar to Mars’ known polar ice caps.”
A geological mystery deepens
The MFF has long intrigued scientists due to its size and unusual composition.
Stretching for hundreds of miles and rising over a mile high in places, it marks the transition between Mars’ northern lowlands and southern highlands.
The formation has been a focal point of scientific debate, with theories ranging from it being a massive accumulation of windblown dust to layers of volcanic ash or sediment.
Early observations suggested the MFF contained ice, as radar scans revealed a structure both transparent to signals and unusually low in density. But alternative explanations persisted—until now.
Researchers believe that the MFF plays a crucial role in shaping the Martian environment.
Its dust-rich deposits, which have been sculpted by wind into striking ridges, have been influencing the planet’s atmosphere for millions of years.
Scientists suspect that underneath this layer lies a vast store of ice.
“This latest analysis challenges our understanding of the Medusae Fossae Formation and raises as many questions as answers,” said Colin Wilson, ESA project scientist for Mars Express and the ExoMars Trace Gas Orbiter.
“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.”
What it means for future Mars missions
Mars’ poles contain vast ice reserves, but their harsh terrain and energy challenges make them unsuitable for human landings.
As scientists prefer landing crewed missions near the equator, the discovery of equatorial ice could offer a strategic advantage to scientists and engineers.
Water on Mars could be used for drinking, oxygen generation, and even fuel production, reducing reliance on Earth-based supplies.
“The MFF deposits, buried under extensive dust layers, remain out of reach for the time being,” said Colin Wilson, ESA project scientist for Mars Express and the ExoMars Trace Gas Orbiter.
“Yet, each discovery of Martian ice enriches our understanding of the planet’s hydrological history and current water distribution.”
Beyond its role in exploration, the discovery offers new insights into Mars‘ past climate. The presence of deep equatorial ice suggests a drastically different environment in the planet’s history
Scientists believe the MFF’s ice, protected by layers of dust or ash, could reveal clues about Mars’ ancient, water-rich past.