Mars and Earth
The week NASA released a video to the public that summarizes the climatic history of Mars it is worth dedicating a few lines to the evolution of the neighboring "red" planet. We know from the studies carried out, the images captured and the samples taken by the different space expeditions that its climatic evolution has been the most similar to Earth in the entire solar system.
From the Martian characteristics observable from Earth through a telescope we can highlight an atmosphere with white clouds although not as extensive as on Earth, seasonal changes very similar to those on Earth, 24-hour days, the generation of sand storms and the existence of ice caps at the poles that grow in winter. Looks familiar, right?
Due to its very low pressure and temperature conditions, the existence of liquid water on its surface would be almost impossible, which shows Mars as a desert planet with a thin atmosphere of CO2. In counterpoint, the Martian geology with a large number of craters, volcanoes and canyons among others has shown us as one of the most complete in the solar system.
Through the rocky and geomorphological formations found, a reconstruction of its evolution can be made. Runoff channels have been observed in some craters, quite similar to those observed on earth as a result of erosion produced by rivers and streams, which indicates the continuous circulation of a fluid on the surface that produced this erosion, almost certainly water. liquid.
Most of these channels appear related to ancient craters, which makes us think that the climate that allowed the existence of liquid water on the surface developed at the beginning of the planet's history. A logical explanation would be the existence of an ancient atmosphere denser than the current one, with a greater greenhouse effect that would raise the temperature.
Martian Geomorphology
This atmosphere could not be composed solely of CO2 since calculations determine that when the amount of this gas in the atmosphere generates a pressure greater than 2,5 bars, it condenses. An atmosphere of these characteristics would not achieve that the surface temperature exceeded 220ºK, well below 273ºC, the stability temperature of water. And therefore there was no liquid water.
In the younger terrains we see the overflow channels, which are large structures tens of kilometers wide and hundreds of kilometers long, beginning in collapsed zones of the terrain. It is related to catastrophic and instantaneous flows of water stored in the subsoil and that comes to the surface. Much of all this water on the surface would pass into the atmosphere by evaporation, increasing the pressure and temperature due to the greenhouse effect of water vapor, also releasing the frozen water and CO2 that exist in the Martian soil.
This would accelerate global climate change that could lead to the formation of an ocean in the lowlands of the Northern Hemisphere, along with extensive polar ice caps. The oceans would later be lost perhaps by infiltration into the subsoil, and the planet would return to a climate "similar" to the current one.
These overflow channels of which we spoke appear in several episodes throughout the history of the planet, but all later to the ancient craters produced in what is known as Great Weather Bombardment. Therefore we deduce that stages of a cold and desert climate like the current one, interspersed with abrupt episodes of warmer weather and the existence of large bodies of water in the northern hemisphere have been repeated cyclically throughout the history of the planet.
More information: Life on Mars, more evidence that shows this possibility, Comet 'Siding Spring' is heading towards Mars