Scientists claim that gullies on Mars were formed not only due to the evaporation of carbon dioxide, but also due to the action of water flowing over the surface. And it happened relatively recently: hundreds of thousands and millions of years ago.
Gullies on Mars
On Mars, as on Earth, there are gullies — deep elongated depressions. Recently, scientists from Brown University published a study in which they took a fresh look at their education and this could seriously affect our understanding of the global history of the red planet.
On Earth, gullies are formed by water that flows over the surface and washes away soil particles. However, until now, scientists were sure that they were not formed on Mars because of this, since there have long been no conditions under which this liquid can exist on the surface.
Instead, they believed that the reason for the formation of gullies is the evaporation of frozen carbon dioxide, which hides under the surface. However, a new study indicates that the slopes of the gullies are too steep and expand too quickly for this process. They are extremely similar to the earth, and therefore scientists think that they, too, were formed by flowing water.
When water flowed on Mars
In their study, scientists are based on a fairly proven thesis, the fact that although warm and humid conditions on Mars disappeared 3 billion years ago, liquid water could appear on it even after that. The conditions for this occurred when the angle of inclination of its axis of rotation exceeded 35 °. At such moments , the temperature on its surface could reach 32 °C.
Scientists are sure that this has happened several times over the past few million years. The last time this happened was only 630 thousand years ago. During these short periods, water flowed over the surface of Mars, which formed gullies.
However, the authors of the study do not completely abandon the theory of carbon dioxide. They believe that gullies on Mars grew slowly and between periods of warming due to this process.
The published study has become another link in the scientific debate about how the climate of Mars has changed throughout its history. There was little doubt that at its beginning it was warm, humid and had a dense atmosphere.
However, how long ago those times changed and how abruptly it happened, there are still disputes. Many of the scientists believe that a certain “transition period” lasted for hundreds of millions of years. Others disagree with them and believe that the red planet has been absolutely dead for 2-3 billion years.
According to phys.org
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