|The martian surface may have once been flowing with liquid water, under an atmosphere contaminated by volcanoes on Mars. Image: Ittiz|
Volcanoes may have once been active on Mars, possibly warming the planet enough for liquid water to exist on the Martian surface for a short period of time.
Mars currently exhibits lake beds, dry river channels, and lake basins that provide evidence liquid water likely once flowed across the surface of the Red Planet. Investigation of the role of vulcanism on Martian geology may provide additional evidence for ancient water on Mars.
Sulfur dioxide gas, released by volcanoes, may have created conditions warm enough for liquid water to flow during several points in the history of the planet. These eras of warmth each lasted just a few tens of thousands of years before the planet cooled once more.
Billions of years ago, the Sun was cooler than today, further cooling the planet.
The atmosphere of Mars is too thin to currently support liquid water on the surface. Astronomers believe most of the liquid water on Mars flowed across the surface around 3.7 billion years ago, when volcanoes were far more active on the planet than they are in the modern day.