Credits Pixabay
In the four billion years of Mars's history, there was a time when the surface of the planet was occupied by the oceans. But they were probably less profound and formed in a more recent era than previously estimated. This is stated in a new study published in the journal "Nature" by a group of geophysicists from the University of California at Berkeley.
The most surprising fact that emerges from the study, however, is that the authors correlate the existence of large masses of liquid water on the primordial Red Planet with the intense volcanic activity of Tharsis, an eruptive complex that covers an area with a diameter of about 5000 kilometers.
The surface of Mars as we see it today is extremely arid and the possible presence of liquid water in a distant past can only be deduced by analyzing the geological characteristics of the planet.
Not all, however, agree with the hypothesis of the Martian oceans. According to the skeptics, in fact, the estimate of the amount of water present in the ancient Martian oceans is not in accordance with the estimates of the water found today in the subsoil of the permafrost, the perennially frozen surface layer of the planet and even with the amount of water that is estimated to have evaporated into space. And even the ice concentrated in the polar ice caps would not be enough to fill an ocean.
Credits Pixabay
The new model responds to these objections because it predicts that the oceans formed before or simultaneously with Tharsis, which is the largest volcanic structure on the planet.
"Our hypothesis is that Tharsis formed quickly and precariously, rather than gradually, and that the oceans came after, "explained Michael Manga, the study's lead author. "In summary, we are saying that the oceans are to be preempted and that they accompanied the lava outflow that produced Tharsis".
It is probable, the researcher added, that Tharsis has emitted an enormous amount of gas into the atmosphere. The resulting greenhouse effect produced a global warming of Mars, which created the conditions for the presence of liquid water. The same volcanic eruptions created channels that allowed the underground water to reach the surface and fill the northern plains.
Tharsis was formed about 3.7 billion years ago. At that time, it was a small relief, but later the raising of this volcanic complex came to substantially alter the surface of the planet, especially the plains that cover most of the northern hemisphere, which are probably ancient seabed. ocean.
The fact that the planetary crust was not very deformed by Tharsis implies that the seas had to be less deep than previously thought, with a reduction in the estimated water mass of about half.
The new model can also explain the irregularity of the coastline lines, with differences in height at different points of even one kilometer. This is another geological feature often used as an argument by the detractors of the hypothesis of the ancient Martian oceans, because erosion tends to determine smoother coastlines, as observed on Earth.
According to the new study, the irregularity can be explained by hypothesizing that the first ocean, called Arabia, began to form about four billion years ago, and continued to exist, for intermittent periods, for most of the first 20 percent of the arc. of time of the lifting of Tharsis. This phenomenon produced a depression of the ground and deformed over time the coastline, which could explain the differences in height of the coast line of Arabia. Similarly, the irregular coastline of a subsequent ocean called Deuteronilus could be explained if it had formed in the last 17 percent of the Tharsis growth period, about 3.6 billion years ago.
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