Surface Water On Mars...

... A very long time ago.

A University of Colorado at Boulder research team has discovered the first definitive evidence of shorelines on Mars, an indication of a deep, ancient lake there and a finding with implications for the discovery of past life on the Red Planet.

If Mars had liquid water on its surface in the past, then it had to have an atmosphere at the same time.

Planetary scientists think the oldest surfaces on Mars formed during the wet and warm Noachan epoch from about 4.1 billion to 3.7 billion years ago that featured a bombardment of large meteors and extensive flooding. The newly discovered lake is believed to have formed during the Hesperian epoch and postdates the end of the warm and wet period on Mars by 300 million years.

Does that mean there could have been an atmosphere and liquid water on Mars for those 300 million years? That's enough time to get a lot of life forms up and running.

Speaking of large meteors, look at the below rendition of Mars produced by the Mars Orbital Laser Altimeter, MOLA. The lower the elevation, the darker the color.

left click to enlarge

That big, deep blue area is a spot where a very large body impacted Mars. It is called Hellas impact basin. It is nearly six miles deep and 1,300 miles across.

It most likely blew away all of the atmosphere that allowed liquid water to remain on the surface. Once the atmosphere was gone, the surface water just evaporated away into space.

That impact would have been incredible to witness. Unfortunately, any life form that did witness this impact did not survive very long, perhaps only seconds.

Better hope nothing that size has us in it's sights.