A possible link between the ancient oceans and the huge volcanoes of Tharsis on Mars

The possible ancient oceans of Mars (Image courtesy Robert Citron images, UC Berkeley. All rights reserved)
The possible ancient oceans of Mars (Image courtesy Robert Citron images, UC Berkeley. All rights reserved)

An article published in the journal “Nature” describes a research on the oceans that formed on Mars when the planet was young. A team of geophysicists from the University of California at Berkeley provided what are believed to be evidence of a connection between those oceans’ formation and the volcanic system of the Tharsis region, the largest of the solar system, which might have warmed the surface enough to keep water liquid for a long time.

The work carried out for years by space probes and rovers allowed to find abundant evidence that in ancient times there was liquid water on the planet Mars but the reconstruction is still far from complete. In many ways the young Mars was similar to the Earth but even having a much denser atmosphere than today it’s difficult to understand how there could be enough warmth to have oceans. Estimates of the amount of water present in the subsoil today also make it difficult to think about oceans.

This new research sees in the volcanoes that were very active when Mars was young the key to understanding the climatic conditions that used to exist on the planet. If the Tharsis volcanic system formed quickly and early in Mars history, it may have transported heat to the surface to keep the water in a liquid state and may have released greenhouse gases into the atmosphere that helped keep the climate suitable to have oceans.

Another argument used by skeptics concerns the shoreline of the hypothesized oceans, which are very irregular with considerable variations in height, very different from those of the Earth’s oceans. According to the researchers, the first ocean of Mars, called Arabia, formed from about 4 billion years ago and existed, perhaps intermittently, in a period that could reach the first 20% of Tharsis’ growth. The volcanoes’ growth would have caused a ground depression deforming the shoreline, an explanation for its characteristics.

According to this theory, the second ocean of Mars, called Deuteronilus, formed during a period equal to about 17% of Tharsis’ final growth, about 3.6 billion years ago. It could be responsible for those shorelines if it had existed before and during the period of growth of the Tharsis system. The huge size of that volcanic system and its influence on the Martian geology can also explain the problems with the estimates of water existing in the northern plains.

The image shows an artistic representation of two phases of the evolution of the Martian oceans. On the left in blue there’s the possible extension of the Arabia Ocean about 4 billion years ago. On the left in blue there’s the possible extension of the Deuteronilus Ocean about 3.6 billion years ago, smaller than the previous one.

The problem in verifying this theory lies among other things in being able to accurately date the evolution of Tharsis and the shorelines. NASA’s InSight mission with a lander that is scheduled to be launched in a few weeks will help. The instruments on board InSight were designed to record seismic activity on Mars and through the vibrations it will be possible to better understand what’s underground, including the amount of water.

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