Hi All
Robert you're right on with the fallacies of extrapolating one area of Mars to the whole BUT the Sahara was wet in recent times. A dry patch that has been dry for a billion years is unusual to say the least. From olivine we can say humidity and ground water has been very low over a big patch of Mars because Mars' seasons and geology don't stand still.
We know tectonics is dead on Mars, hence it's not going to be subducted, yet there is some vulcanism. But inclination is far from constant and so we expect signs of change for Martian seasons and cycles over the kiloyear range like Earth - especially since the poles have shifted around even more dramatically on Mars than Earth. But bare olivine means no rain for a very LONG time. Fog maybe, maybe snow during high-pressure excursions, but never warmth and rain.
Adam
Space/Science » in reply to Old news, but FALSE.
Good point... but...