How much Water is on Mars?

The question of water on Mars is one of considerable interest to scientists, as water is essential for life as we know it and would also be a vital resource for any future human missions to the Red Planet.  Mars does have water, but it exists in markedly different forms and quantities than what we find on Earth.

Current State of Water on Mars

• Polar Ice Caps:  Mars has polar ice caps made of water and dry ice (frozen carbon dioxide) that expand and contract with the changing seasons.  The water ice in the caps is estimated to be equivalent to a global layer about 21 meters (69 feet) deep, if spread uniformly across the surface.
• Subsurface Ice:  The Mars Reconnaissance Orbiter and other missions have provided evidence for large deposits of water ice just below the surface, especially at higher latitudes.  These subsurface ice deposits can be tens of meters thick.
• Frozen Soil:  Mars has a layer of permafrost that extends from the poles to latitudes of about 60 degrees in both hemispheres.  This permafrost contains water, but the exact amount varies.
• Atmospheric Water Vapor:  Mars’ atmosphere contains trace amounts of water vapor.  Although the Martian atmosphere is very thin, the water vapor content can vary with altitude, time of day, and geographical location.
• Transient Liquid Water:  Some evidence suggests that liquid water may flow on the surface in very small amounts for short periods under certain conditions, although this is a subject of active research and debate.

Past Water Reservoirs

Several Mars missions have found compelling evidence that liquid water once existed on Mars in significant amounts.  These include:

• River Valleys:  Extensive networks of dried-up river valleys suggest that liquid water once flowed on the surface.
• Lake Beds:  Features like Gale Crater, where the Curiosity rover is exploring, are believed to have once contained lakes.
• Ocean Hypothesis:  Some scientists hypothesize that Mars may have had a large ocean covering much of its northern hemisphere in the distant past, although this is still a matter of debate.

Challenges and Implications

• Salinity and Acidity:  Even if liquid water exists or existed, the salinity and acidity levels might be too high to support Earth-like life.
• Resource for Future Missions:  The presence of water in any form is essential for future human exploration and colonization, as it can be used for drinking, growing food, and producing oxygen and fuel.
• Search for Life:  Water is considered a prerequisite for life as we know it, so its presence on Mars is central to the question of past or present life on the planet.

Check out our 3D Mars Learning Center for more information on Mars.   You can also learn more at: NASA Mars Exploration.