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Mars may have lost water due to axial tilt changes
Why did Mars, once covered with rivers and lakes, turn into a dry and cold desert? A new study conducted by scientists from the Institute of Astrophysics of Andalusia in Spain provides answers to these questions. The results are published in the journal Nature Astronomy.
Mars is now covered mostly in dry deserts, with most of its remaining water frozen in the ground and at the poles. But geological evidence from early space missions suggests that billions of years ago, the planet held significant amounts of liquid water — enough to cover the surface to a depth of about 100 meters.
One explanation for the loss of water involves the breakdown of atmospheric water vapor by ultraviolet radiation from the sun.
The hydrogen produced in this process could leave the atmosphere, taking water molecules with it. Modern measurements show that huge amounts of hydrogen are lost from the atmosphere of Mars every day.
However, calculations show that this mechanism cannot fully explain the scale of water loss over billions of years.
The authors of a new study from the Institute of Astrophysics of Andalusia in Spain hypothesized that fluctuations in the tilt of Mars’s rotation axis played a significant role.
Unlike Earth, whose tilt is maintained by the Moon, Mars experiences sharp changes in tilt angle — from 0 to 66 degrees — with an average of about 35 degrees.
According to the model, as the tilt of the axis increases, Mars’ north pole receives more sunlight, causing ice to melt and increasing the amount of water vapor in the atmosphere.
In turn, this increases the release of hydrogen into space. Computer modeling showed that at a tilt of 35 degrees, the rate of hydrogen leakage increases by about a billion atoms per year compared to current values.
Additionally, dust storms that are common on Mars increase hydrogen loss by 50 percent, depending on their intensity.
The combined effect of these factors, the researchers estimate, could have resulted in a loss of water equivalent to a layer about 80 meters thick across the entire surface of the planet. This value is close to the minimum estimates of the volume of water that once existed on Mars.
The authors note that the composition of Martian dust and other parameters could have differed from the current ones, which also influenced the processes of water loss.
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