A wet planet before Earth

A wet planet before Earth

If current Martian conditions do not allow the establishment of oceans on its surface, it was quite different when the planet formed. A new study suggests that the Red Planet’s primordial atmosphere was particularly dense and rich in water vapor and dihydrogen. A very rapid appearance of vast amounts of liquid water and possibly favorable conditions for the origin of life.

There is no doubt today that the surface of Mars was, in the distant past, shaped by liquid water. Traces of ancient rivers feeding ancient lakes are clearly visible from the orbit. In addition, the Curiosity and Perseverance rovers have provided irrefutable evidence for this, thanks to rock analysis and accurate photographs of typical lake sediment units. Today, however, Liquid water has completely disappeared from the surface of the planet.

The Martian atmosphere played a major role in this major environmental change that occurred about 3 billion years ago.

Steamy primitive atmosphere

Analysis of the atmosphere shows that the Red Planet is currently unable to maintain liquid water on its surface. But flow traces and lake sediments tell us that the situation was quite different 3 billion years ago. However, it is difficult to define what the atmospheric conditions were at that distant time.

Therefore, scientists have decided to create the first numerical model of the evolution of the Martian atmosphere from the formation of the planet to the establishment of oceans and lakes.

This model suggests that, like Earth’s, the Martian atmosphere was originally rich in water vapor, concentrated in clouds in the lower layers of the atmosphere. Upper parts, outer parts are very dry. Conversely, molecules of dihydrogen (H2), very easy to maintain, would soon have escaped into space.

A dense, H2-rich atmosphere allows oceans and lakes to form quickly

The results were published in the journal Earth and Planetary Science Letters, allows us to define the atmospheric conditions that prevailed on Mars shortly after its formation. From to scientists Chetty Company, this primordial atmosphere must have been very dense, about 1,000 times denser than the current Martian atmosphere. Only a huge ocean of magma occupied the planet’s surface, and like the primitive Earth, the atmosphere was composed mainly of dihydrogen. However, under high stress conditions, H2 is a powerful greenhouse gas.

Unlike the current thin atmosphere, Mars’ ancient atmosphere would have been a veritable blanket of lead. Rapid formation of oceans of liquid water on the surface of the planet. These warm oceans would have been stable for millions of years before H2 is gradually lost in space and the Martian atmosphere gradually loses its density. So Mars would have been “wet” soon after its formation, long before the same conditions appeared on Earth.

A favorable environment for the emergence of life, but it did not last long

The data used to develop the model came from analyzes of Martian rocks by the Curiosity rover and from studies of some Martian meteorites. Through analysis of deuterium and hydrogen (D/H) isotope ratios, scientists were able to show that Earth and Mars began life under relatively similar atmospheric conditions. However, the two planetary environments would have diverged 3 billion years ago as Mars began to lose its light hydrogen isotopes to space.

These results are very important from the point of view of the search for extraterrestrial life. It has been shown that prebiotic molecules at the base of life can readily form in H-rich environments.2 Like the early Martian atmosphere. Mars would have been so All material available to see life growing on its surface in its youth.

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