But not so fast, says highly respected veteran Mars researcher Victor Baker, of the University of Arizona's Lunar and Planetary Laboratory in Tucson, Ariz. Just because there are some problems with the water hypothesis is no reason to throw it out entirely, he said. What's more, you have to be careful not only when you compare Martian features to Earth's, but also to other planets.
"He's reasoning on the features of Moon and Venus when we don't know the causes of those features either," said Baker.
So while there might be similarities, it's not at all clear that erosive, low viscosity lavas are the common cause. "It's very obvious that immense flows of water and lava have been involved," said Baker.
Baker also warns against falling wholeheartedly for the lava hypothesis just because it seems simpler. "To say something is better because it's simpler is how physicists think," said Baker. That reasoning is less successful in the more complicated world of geology. "Simplicity is a human artifact," he said.
This might sound rather philosophical, but it comes from Baker's decades of watching and participating in many Mars water controversies.
"Mars is great because it has a character of familiarity and strangeness," said Baker.
That, at least, is something on which he and Leverington agree.
"Previously I had a very terrestrial view of the Martian surface," said Leverington. On Earth, water is the great molder of landscapes, after all. But after staring at enough images of strange channels on the moon and Venus, his perspective changed. "Now I try to get away from the provincialism that we have as inhabitants of this water world."