Now, sub-meter-scale images from NASA’s Mars Reconnaissance Orbiter show clear, unambiguous
evidence of shorelines of a lake more than 450 meters (1,476 feet) deep that
formed about 3.4 billion years ago. 

The study indicates that conditions
favorable for flowing water and lake formation may have existed for thousands of
years on Mars during the Hesperian epoch, which has been thought to be a period
during which surface conditions did not allow significant hydrological activity.  

Evidently this is the first photographic evidence of its kind, proving once again that the boundaries of scientific knowledge continues to shift.