The first oceans appeared on Mars about four billion years ago, almost immediately after its formation, 200-300 million years earlier than was commonly believed
“Our colleagues have always believed that the Tharsis Plateau, the largest volcanic landform on Mars, originated before the oceans of Mars were born, about 3.7 billion years ago. We found out that the oceans arose either with it, or appeared even earlier,”- said Michael Manga, a geologist at the University of California at Berkeley (USA).
In recent years, scientists have found many hints that rivers, lakes and entire oceans of water existed on the surface of Mars in ancient times, which contained almost as much liquid as our Arctic Ocean. On the other hand, some planetary scientists believe that even in ancient times, Mars could be too cold for the permanent existence of the oceans, and its water could be in a liquid state only during volcanic eruptions.
Recent observations of Mars with ground-based telescopes have shown that over the past 3.7 billion years, Mars has lost an entire ocean of water, which would be enough to cover the entire surface of the red planet with an ocean 140 meters thick. Where this water disappeared, scientists today are trying to figure out by studying ancient Martian meteorites.
Manga and his colleagues found that the oceans of Mars were born 200-300 million years earlier than scientists believed by studying the structure of the coastline of the supposed ocean of the red planet, which covered most of the northern hemisphere in the distant past.
Many planetary scientists, according to Mang, doubt the very existence of this structure, since parts of the bottom of this ocean are located in “wrong” places where water would have to flow from bottom to top to cover its entire area. In addition, its other regions were too deep, while others, on the contrary, were too shallow in order to create a single reservoir with a common water level.
Californian geologists found an explanation for this by analyzing how the formation of the Tarsis volcanic plateau could have influenced the birth and evolution of the Martian oceans, as well as drawing attention to one recently discovered fact associated with this largest geological structure of Mars.
Studying this plateau and the adjacent northern plains, where the ocean of Mars was once located, scientists noticed that many of the relief features associated with its coastline looked earlier than Tharsis itself and the volcanoes associated with it. This prompted them to think that this structure was born not before, but after the formation of the oceans of Mars.
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Guided by this idea, scientists compared how the coastline of these reservoirs changed with how quickly Tharsis grew during about half a billion years after its formation. This comparison showed, in a surprising way, that virtually all of the distortions and changes in the coastline were due to how the ocean floor was deformed by the growing volcanoes.
Removing all these distortions, scientists discovered that the Arabian Plain of Mars, which is the oldest part of the bottom of its oceans, arose even before the formation of Tarsis, hundreds of millions of years before the supposed time of the appearance of the oceans of the red planet.
This Arabian Ocean, as their calculations show, contained about 3% of the total volume of water than its modern "relative" on Earth. In other words, it was about twice as large as the modern Arctic Ocean and contained more water than the Earth's polar caps. According to scientists, it became liquid thanks to the heat and greenhouse gases that volcanoes produced, including the future Tharsis.
In subsequent eras, the area and volume of this reservoir constantly changed as Tarsis grew, which gave rise to strange features in the coastline of the northern ocean of Mars, and made it much deeper than it was at first. Planetary scientists hope that the seismographs of the Insight lander, which will go to Mars in May, will help test their theory.