Saying the issue is how long, not whether, Mars had water, the Bad Astronomer himself, Phil Plait, goes on to suggest that the issue has relevance for our own planet:
It may have once been much
more Earth-like, but then something went wrong. Maybe it was the
formation of the giant volcanoes (indicated by the red arrows in the
above image), or the loss of its magnetic field that exposed its
atmosphere to erosion by the solar wind. As we study Mars more, we get
closer to figuring this out. And make no mistake: knowing where Mars
went wrong gives us great insight into our own planet. If you think
we’re wasting money on researching Mars, then I suggest you take a
cold, hard look at that cold, hard planet, then look out your window at
our own home world.
The news is here. Seas, perhaps, in the areas of this picture where red and yellow predominate.
Image credit: University of Arizona