Only one researcher could have figured out how Mars was able to support rivers and seas even after the planet began to cool and its atmosphere thinned, and it’s all because of a cycle of water and carbon dioxide.

We know from geological and mineralogical evidence that about four billion years ago, Mars it was warm and humid enough to have extensive liquid water on its surface, from rivers and lakes to a large northern sea. This period covers two geologic eras: the Noahian, which lasted from 4.1 to 3.7 billion years ago, and the Hesperian, which lasted from 3.7 to about 3 billion years ago. The Noahian is characterized by warmer conditions, but in the latter stages Mars should have started to grow cold as he steadily lost his atmosphere to space. However, there is still evidence of river channels and seas dating back to the Late Noachian and Hesperian eras. Planetary scientists have been puzzled as to how Mars could still be wet at this time, and one theory is that the Red Planet experienced an unexplained period of global warming.