ocr: 59 I OT * - 1 à The last rain MARS AND EARTH: A COMPARATIVE HISTORY As we have seen, about three billion years ago. Mars's THE SEARCH se oceans, lakes, rivers, clouds, and rain vanished. What has happened since? Might there have been periods of high atmospheric pressure that once again provoked condensation and rainfall? This is not impossible. The variations in the tilt of Mars's axis as well as variations in the eccentricity of the planet's orbit can give rise to wide climatic variations. Indeed, at times the polar regions may be subjected to longer: sunlight periods. More sunlight means gre ...
