Mars Express Found a Sea of Water Ice Buried Under 300 Meters of Dust at the Equator

ESA’s (European Space Agency) Mars Express has found layers of water ice stretching several kilometers below ground – the most water ever found in this part of the planet. f melted, the ice locked up in the MFF would cover the entire planet in a layer of water 1.5 to 2.7 m deep: the most water ever found in this part of Mars, and enough to fill Earth’s Red Sea. The Red Sea has about 233,000 cubic kilometers of water. The Red Sea covers almost half a million square kilometers to an average depth of 490 meters.

“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 3.7 km thick,” says Thomas Watters of the Smithsonian Institution, USA, lead author of both the new research and the initial 2007 study.

Although Mars now appears to be an arid world, the planet’s surface is full of signs that water was once abundant, including dried-up river channels, ancient ocean and lake beds, and water-carved valleys. We’ve also found significant stores of water ice on Mars, such as the enormous polar caps, buried glaciers nearer the equator, and near-surface ice laced through martian soil.

Massive stores of ice near the equator – such as those suspected to lurk below the dry surface of the MFF – couldn’t have formed in the planet’s present climate. They must have formed in a previous climate epoch.

The extent and location of these icy MFF deposits would also make them potentially very valuable for our future exploration of Mars. Missions to Mars will need to land near the planet’s equator, far from the ice-rich polar caps or high-latitude glaciers. And they’ll need water as a resource – so finding ice in this region is almost a necessity for human missions to the planet.

The deposits are covered by hundreds of meters of dust. It is usually about 300-600 meters of dust.

Geophysical Research Letters – Evidence of Ice-Rich Layered Deposits in the Medusae Fossae Formation of Mars

Abstract
Subsurface reflectors in radar sounder data from the Mars Advanced Radar for Subsurface and Ionospheric Sounding instrument aboard the Mars Express spacecraft indicate significant dielectric contrasts between layers in the Martian Medusae Fossae Formation (MFF). Large density changes that create dielectric contrasts are less likely in deposits of volcanic ash, eolian sediments, and dust, and compaction models show that homogeneous fine-grained material cannot readily account for the inferred density and dielectric constant where the deposits are more than a kilometer thick. The presence of subsurface reflectors is consistent with a multi-layer structure of an ice-poor cap above an ice-rich unit analogous to the Martian Polar Layered Deposits. The volume of an ice-rich component across the entire MFF below a 300–600 m dry cover corresponds to a global equivalent layer of water of ∼1.5 to ∼2.7 m or ∼30%–50% of the total estimated in the North Polar cap.

Key Points
Mars Advanced Radar for Subsurface and Ionospheric Sounding radar sounder data reveals layering in the Medusae Fossae Formation (MFF) deposits

Layers are likely due to transitions between mixtures of ice-rich and ice-poor dust, analogous to those in Polar Layered Deposits

An ice-rich portion of the MFF deposit may contain the largest volume of water in the equatorial region of Mars

Plain Language Summary
The Medusae Fossae Formation (MFF), located near the equator of Mars along the dichotomy boundary between the lowlands of the northern hemisphere and the cratered highlands of the southern hemisphere, is one of the largest and least understood deposits on Mars. The Mars Advanced Radar for Subsurface and Ionospheric Sounding radar sounder detects echoes in MFF deposits that occur between the surface and the base which are interpreted as layers within the deposit like those found in Polar Layered Deposits of the North and South Poles. The subsurface reflectors suggest transitions between mixtures of ice-rich and ice-poor dust analogous to the multi-layered, ice-rich polar deposits. An ice-rich part of the MFF deposit corresponds to the largest volume of water outside the polar caps, or a global equivalent layer of water of ∼1.5 to ∼2.7 m.