Nor any drop to drink
So, if Mars was “wet”, where did the water go? (And it may have been as much as 1/2 of the volume of Earth’s oceans.) Ryan Mandelbaum on Gizmodo reports on a recent model of Martian hydrology published in Nature by a group of Oxford geophysicists (or areophysicists, perhaps). In short, Mars has a higher percentage of iron in its interior than Earth does, and iron really likes to lock up water, or at least the oxygen component in water (see the phenomenon of rust, which accounts for much of the color of the “red” planet).
The key comes from Mars having a denser crust and a cooler under-crust (the mantle) that would transfer more water to the interior and allow it to react with the iron, capturing the oxygen and moving it away from the surface. This model needs to be tested against competing theories (like loss of water to space due to lower gravity and lack of a magnetic field to prevent atmospheric scouring by the Sun’s solar wind, or water locked up as sub-surface ice due to cooling from atmospheric changes). The article quotes Tomohiro Usui of Tokyo Institute of Technology from his commentary in Nature: “Subsurface exploration will be required to test both the hydrated-crust and ground-ice theories, and therefore shed light on the evolution of Martian water inventory.”
Which is a very sophisticated way of saying, “Let’s go to Mars!”