Or so David Shiga tells us in "Evidence for Mars floods all dried up?" (New Scientist, 22 August 2011):
Kelin Whipple of Arizona State University (ASU) in Tempe agrees that lava probably carved the huge channels, such as Kasei Valles (shown). He says the study calls into question the case for huge volumes of water – and possibly an ocean – on ancient Mars.
But Phil Christensen, also at ASU, says clays and fans of sediment still point to the existence of smaller Martian lakes and rivers. These would be better places to search for life, he says, because they would have held water for longer periods than the giant channels, where floods – if there ever were any – would have been fleeting. "Lakes and deltas are probably the places people are going to look for life," he says.
But just use your imagination, and you will discover that lava too can host life.
See also: The Shroud of Turin makes way more sense than water on Mars