There's Water In Them Thar Hills!

It's hard to spot, dust-covered and otherwise unremarkable. But the ESA's 3-D imaging system orbiting Mars has found what looks like a vast ocean just below the surface of Mars.

It's the largest body of water discovered on Mars outside of the polar regions and, in an upcoming edition of the science journal Nature, scientists will estimate this frozen lake at about 900 km by 800 km (540 by 480 miles).

"It's been predicted for a long time that you should find water close to the surface of Mars near the equator," Jan-Peter Muller, from University College London, UK, told the BBC.

How did it get there? Early theories suggest some catastrophic event -- they're not sure what -- triggered formation of the lake eons ago. The discovery still must be confirmed by a follow-up observation. But it would make sense to scientists who tout the existence of riverbeds near the Martian equator. They've long held that there could be a large body of water somewhere around the planet's midsection.

"This is an area where there are a lot of river features but no-one has ever seen a sea before, and certainly no-one has ever seen pack ice before," Muller told the BBC News website.

The body of water is covered with a thin layer of dust deposited over millions of years, according to initial observations. "The story runs that water flowed in some kind of massive catastrophic event; pack ice formed on top of that water and broke up, and then the whole thing froze rigid," Professor Muller said.

Michael Carr, a Martian water expert at the US Geological Survey in Menlo Park, CA, agrees with the idea that the water originally came from underneath the Martian surface… perhaps somewhere north of a formation called the Elysian Plates.

"We know where the water came from... You can trace the valleys carved by water down to this area," Carr said in an interview with New Scientist Magazine.

"The fact that there have been warm and wet places beneath the surface of Mars since before life began on Earth, and that some are probably still there, means that there is a possibility that primitive micro-organisms survive on Mars today," Muller said.

Now, Muller and other scientists want to see an ESA lander target the area for further research. Below the ice, they think it's possible water -- and perhaps primitive life -- may exist.

FMI: www.esa.int