The paradox of warm and cold Mars has been solved

An international team of astronomers led by researchers from the California Institute of Technology has identified chemical mechanisms by which ancient Mars could have maintained enough heat to support liquid water and possibly life.

As reported by Space.com, the researchers started from the theory that in ancient times, Mars had a warm and humid climate, and there was a large amount of liquid water on its surface. The latter is considered one of the key conditions for supporting life. However, previous studies also revealed the paradox of a warm and cold Mars.

"For a long time, it was a real mystery why there was liquid water on Mars," says Dr Danica Adams of Harvard University. "Mars is farther from the Sun than Earth, and the Sun was weaker at the time. It was previously thought that hydrogen was the 'magic' ingredient that mixed with carbon dioxide in the atmosphere of Mars to cause greenhouse episodes. But atmospheric hydrogen has a short lifetime, so a more detailed analysis was needed."

A new study has found that temperatures on Mars in its early history may have varied widely, with periods of global warming and global cooling alternating over hundreds of millions of years before Mars eventually became a cold, dry planet.

However, scientists have found that for several billion years, Mars could indeed have had a warm and humid climate suitable for life. As part of the study, computer modeling was conducted. The mechanism used on Earth to track pollutants was taken as a basis. This made it possible to model how the hydrogen content in the Martian atmosphere changed over time.

The researchers concluded that Mars experienced periodic warming periods between 3 and 4 billion years ago. The alternation of warm and cold periods lasted for 40 million years, with each individual period lasting at least 100,000 years.

"The warm and wet periods were caused by crustal hydration, which provided enough hydrogen to accumulate in the atmosphere over millions of years," the researchers write. "During the transitions from warm to cold climates and vice versa, the chemical processes in the Martian atmosphere also fluctuated."

Carbon dioxide is constantly exposed to sunlight and converted into carbon monoxide, the scientists explain. And during warm periods, carbon monoxide can turn back into carbon dioxide, resulting in carbon dioxide and hydrogen becoming the dominant gases in the atmosphere.

It was a kind of recycling process that lasted for billions of years. Eventually, the cold periods became longer and longer, and Mars came to a point where the oxidation-reduction processes in its atmosphere changed dramatically.