Making a Splash on Mars

On a planet that's colder than Antarctica and where water boils at ten degrees above freezing, how could liquid water ever exist? Scientists say a dash of salt might help.

When scientists revealed dramatic new pictures of flood-like gullies on Mars, the big surprise wasn't that the Red Planet might harbour water. Researchers have known for years that water exists there. There are trace quantities of water vapour in Mars' atmosphere and substantial amounts of water ice at the martian poles. There may even be enough frozen water beneath Mars' surface to fill a large ocean if melted. What was amazing is that water may be present as a liquid very near the planet's surface and occasionally on top of the surface when underground deposits burst forth for a brief flash flood.

"We have conditions on Mars that seem to forbid liquid water very close to the surface," said Michael Carr of the US Geological Survey (USGS) at a press conference in June 2000. "At high latitudes, where the gullies are located, the temperatures are 70 to 100 degrees centigrade below freezing. It's incredibly cold. We expect the ground to be frozen 3 to 6 km deep."

The low temperature of Mars conspires with the planet's thin atmosphere (it is 100 times thinner than Earth's) to make water possible in only two forms: solid ice and gaseous vapour. A cup of liquid water transported Star Trek-style to the surface of Mars would instantly freeze or boil (depending on the local combination of temperature and pressure). Researchers think that the water which carved the martian gullies probably boiled explosively soon after it erupted from underground.

more from GSFC Martian gullies in Newton Crater. Scientists hypothesize that liquid water burst out from underground, eroded the gullies, and pooled at the bottom of this crater as it froze and evaporated. If so, life-sustaining ice and water might exist even today below the Martian surface - water that could potentially support a human mission to Mars.

"The air pressure is so low on Mars that even in the most favourable spots, where the pressure is higher than average, liquid water is restricted to the range 0 to +10 °C," says Bob Haberle of the NASA/Ames Research Centre."Fresh water on Mars begins to boil at 10 °C. Here on Earth we can have water anywhere between 0 and 100 °C - that range is reduced by a factor of ten on Mars."