Earth-like planets probably water-logged

I agree. My own work on planets suggests this too. Earth may actually be a rather dry planet!

Mars is a frozen planet - the best analogues would be Jupiter's icy Moons Gannymede and Callisto. These are even colder, and have a huge H2O content, but it is largely frozen and the rock and ice have not seperated into layers. The regolith remains a frozen permafrost cementing grains together. Clathrates may exist as well as normal water ice.

Mars may still have a greater % of water than Earth, but it has NEVER been melted to any appreciable degree. The % of ice in the near surface, IF continued to depths of 10 km, would result in an inventory equivalent to a 3-5 km ocean on Mars. Clearly Mars has never had such an ocean (witness the intact southern highland craters) ergo, Mars has NEVER melted.

White Mars doesn't say that Mars is dry, except at the surface. It says Mars is Frozen, and always has been.

SURFACE WATER POSSIBLE UNDER MARS-LIKE CONDITIONS

The trick is not maintaining the water, once it appears at surface. Carr, Baker, and recently Hecht all demonstrated that liquid water would survive long enough to do whatever was asked of it.

The problem is how do you get water to the surface?

3 ways:-

1) generate water directly from atmospheric vapour ("rain")

2) melt ice at the surface during a diurnal or annual freeze-thaw cycle, under high pressure (e.g. Hellas)

3) geothermal heat from below melting permafrost and allowing it to flood to the surface

problems:-

1) is a low rate mechanism and requires H2O saturated air at high pressure and relatively high temperature. Problem is, that same air cools every night and freezes out its H2O. Next day, when warmed again, it is at low saturation, so can't form rain.

2) In general, areas that get warm enough to melt ice are dessicated, since they remove ice from the surface and immediate subsurface through sublimation (and possible melting) when it's warm. Thus, the uppermost few decametres of permafrost on Mars is dry dust, not ice, due to diurnal and annual warming.

3) The crust of Mars is frozen on average to a depth of 10 km. Imagine the power and grandeur of a hot-water system that can punch through this. What will it look like? Try Yellowstone as an example - boiling springs, geysers, the works.

Now imagine this on Mars. Remember that even more so than on Earth, whenever water is liquid, it is close to boiling. Vapor phase transport will tend to dominate, and the hot springs will boil to geysers at subsurface depths of 1 km or more, steam will rise to the surface, and clusters of Ice Towers will result, not rivers...