Data from the Curiosity rover helped NASA scientists figure out what the lakes of Mars looked like at different periods of its existence and prove that they were warm and suitable for the existence of life for almost a billion years. Their findings were published in the journal Science.
“The data that Curiosity obtained over 3.5 years of operation in Gale Crater indicates that approximately 3.8-3.1 billion years ago, Mars had all the necessary physical, chemical and energetic conditions for the formation of a potentially habitable environment. Write John Grotzinger of NASA's Jet Propulsion Laboratory and colleagues.
In recent years, scientists have found many hints that rivers, lakes and entire oceans existed on the surface of Mars in ancient times, containing almost as much liquid as our Arctic Ocean. At the same time, 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.
The climate history of Mars, according to Grotzinger and his colleagues, may in fact be more complex than the authors of these hypotheses imagine it, and combine elements of both theories. Scientists came to this conclusion by analyzing and combining all the geological data that their brainchild, the Curiosity rover, collected while climbing to the top of Mount Sharp in the center of Gale Crater in the first 1300 days of its work on Mars.
Gale Crater, according to scientists today, is the bottom of an ancient Martian lake, covered with sediments that formed in different eras of its existence. Moving towards the crater's highest point, NASA's rover, figuratively speaking, moved from Mars' deepest past towards its present, tracking how changes in its climate were reflected in the structure and properties of rocks on the slopes of Mount Sharp.
Using this data, scientists have compiled a kind of map of the evolution of the climate of Mars and were able to understand how the lake in Gale Crater looked like, what properties its water had and how long it lasted.
The main takeaway from all of this research is that the climate of Mars has been extremely variable in the past. For example, it turned out that in the early epochs of the existence of Gale Crater, which arose about 3.8 billion years ago, its bottom was completely dry and cold. But at the same time, in the next 800 million years, it became the bottom of a lake located in a temperate climatic zone by the standards of the earth's climate.
This lake, as scientists note, was warm and livable - as Curiosity's measurements show, it contained trace elements and even some organic molecules. Interestingly, it consisted of two rather different layers - the waters of the upper half of the lake were "acidic" and contained a lot of oxygen and metals oxidized by it, and the lower part was almost completely devoid of them.
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Many lakes on Earth have a similar structure, and the presence of two such layers today is considered by many geologists and evolutionary biologists as one of the main conditions for the origin of life and its further development. Accordingly, we can say that Mars really had all the conditions for the origin of life. On the other hand, it remains unclear what exactly gave rise to these lakes and brought their water - processes in the bowels of Mars or the impact of asteroids and comets.
