Water on Mars

Residual water ice in Vastitas Borealis Crater
14 May 2008

Even in the clearest, bluest sky on Earth, there is still water vapour in our atmosphere. If you could condense all the water vapour out of the atmosphere above you, it would form a layer of water two centimetres deep. On Mars today, there is also water vapour in the atmosphere but it would create a layer just 10 micrometres thick.

As on Earth, this water is constantly moving through a cycle of condensation and evaporation. When it condenses, it falls to the surface. When it evaporates, it re-enters the atmosphere and is blown by the winds around the planet before condensing and starting the cycle over again. Regardless of the apparent paucity, the constant movement of water through the martian atmosphere has an important effect on the martian climate.

Mars Express carries three instruments, PFS, SPICAM and OMEGA, which allow planetary scientists to study the water cycle of Mars in unprecedented detail. With their ocean of new data, scientists are building a multifaceted story of the martian water cycle. It is strikingly similar to Earth in some respects and exotically different in others.

We took the chance to question some experts on this subject while they were at the Mars water cycle workshop in Paris, France.

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