Water on Mars
Ice caps, subsurface ice, and ancient riverbeds show that Mars once had — and still holds — significant amounts of water.
Mars today is a cold, dry desert, yet it carries clear evidence of a wetter past and still contains water in the form of ice and possibly brines.
Evidence of Past Water
Orbital images and rover data reveal ancient river valleys, lake beds, and minerals that form in the presence of water. Billions of years ago, Mars likely had a thicker atmosphere and liquid water on its surface for extended periods.
Water Today
- Polar ice caps contain water ice mixed with frozen carbon dioxide
- Subsurface ice is widespread at mid and high latitudes
- Occasional slope features may involve briny liquid water, though this remains debated
Why It Matters
Water on Mars is central to the search for past or present life and to future human exploration. Ice could provide drinking water, oxygen, and rocket propellant for astronauts. Understanding the history of Martian water also helps scientists learn how planetary climates evolve.
Mars reminds us that water can shape a planet’s surface and then largely disappear — leaving clues for us to read billions of years later.