Water on Mars

Today the Red Planet is dry and barren, but what about tomorrow? New data suggests that the long story of water on Mars isn't over yet.

When Orson Welles broadcast "The War of the Worlds" in 1938, many listeners were ready to believe in Martians. After all, astronomers had long debated markings on the Red Planet that might be aquaducts or fields of vegetation. Why not warlike aliens as well?

Among laypeople (and some scientists) the notion that Mars was "Earth-Like" - warm, wet and verdant - persisted for decades, until the first spacecraft visited the Red Planet. The Mariner missions of the late 1960's revealed the real Mars: heavily cratered, dotted with extinct volcanoes, colder than Antarctica and drier than the Sahara desert. There were no trees, no canals, no Martians - and very little atmosphere! "The War of the Worlds" was a fantasy after all.

Subsequent missions mostly confirmed a new paradigm: Mars was once wet, but now it is dry. Spacecraft photos of Mars reveal signs of ancient rivers, lakes and maybe even an ocean. They might have been filled with water billions of years ago, but something happened - no one knows what - and the planet became a global desert.

This image by artist Duane Hilton is a fake! It shows a standing pool of water on Mars - impossible today, but what of the future?

Wherever the moisture went, new data suggest it might not be gone for good. Indeed, water may have flowed on Mars literally as recently as "yesterday or last year," declares James Garvin, Chief Scientist for Mars exploration at NASA headquarters. Evidence is mounting that water lies beneath the Martian terrain, he says. Furthermore, every few centuries weather conditions might become clement enough for that water to "come and go" on the surface as well.