You'll have seen that I gave Larry O'Hanlon some words on this one.

Tom Stepinski's work is good in that it tries to quantify vague statements such as "Earth-like". It also helps us get a handle on erosion rates.

These valleys were formed on early Mars (Late Noachian to Hesperian) and do not relate to the modern climate. The modern climate is WAY drier than the old one, and even the old climate is WAY drier than the driest deserts on Earth.

There are some interesting issues about rates in different places that suggest intermittent conditions rather than steady.

Still trying to get Tom a submarine dataset for him to work with and take the arguments one step further...