Scientists actually agree to the opinion that in the distant past on the surface of Mars had flowing river, that there were a lake. The problem is that the then sun does not shine intensely enough to the surface of the Red Planet could have the appropriately high temperature. That’s why we formulated the theory of denser, rich in CO2 atmosphere, which, thanks to the greenhouse effect could keep the planet’s surface temperature above freezing. It is this theory stood now in question. The study of the rocks themselves, in which a probe Curiosity was once the settlement, which were explained by the presence there of an ancient lake, now showed that carbon dioxide was there not enough. Mars rover has not found there traces of carbonates, which in an atmosphere rich in CO2 would have to occur. The equipment allows him to detect even a few percent carbonate content. In any sample does not appear. It is on this basis the authors put the idea on the maximum CO2 content. In water, the carbon dioxide forms carbonate binds to the positively charged ions of magnesium and iron. Studies of other rocks lake bed indicate that the ions are available, and the environment has never been sufficiently acidic to be able to dissolve the carbonates. If there is no trace of carbonates, it must mean that carbon dioxide was not enough.