Sigh,

More sad, tired "science" about water on Mars.

A couple of obvious omissions/errors:-

The authors have used daily maximum temperature as the measure for water stability, ignoring the diurnal cycle at each location. Therefore their statement that water may be stable in some locations for 34% of the orbit (year) is incorrect. Water may be stable at some time on 34% of days, during the year, but typically for short periods of time on each such day, so the overally stability is much less than 34% of the entire year.

The authors duck the issue of seasonality of water vapour distribution, and its source. (they mention that there is an issue but ignore it because there is "not enough data". In fact there is plenty enough to show that the author's analysis is incorrect). The full Viking dataset shows clearly that the northern hemisphere high of water vapour is a seasonal product from sublimation of the water ice in the northern polecap, once all the seasonal CO2 ice has gone. This therefore occurs in late northern spring/summer.

It is obvious that this corresponds to southern hemisphere late autumn/winter, when the atmospheric pressure is at a minimum due to sequestering in the polecaps, so the timing of the pressure and water vapour peaks are out of phase.

This means that water is very unlikely to precipitate out of the atmosphere.

This is made even less likely if you consider the behaviour of a single air packet. It gains moisture over the north pole in summer, perhaps becoming saturated. It is still too cold for liquid water to form, though. When it moves south, it warms and becomes relatively LESS saturated, and therefore less likely to form a condensate at all.

In order to get H2O to condense, one must return the air packet to the temperature at which it was originally saturated - i.e. polar chill, in equilibrium with ice.

So there is NO evidence in this paper for liquid water stability on Mars.

Same old drum, same old tune, same old bandwagon...