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Billions of years ago, freezing carbon dioxide warmed the polar ice caps, melting about half the total water on Mars.
Illustration of an ice-covered river on an ancient Mars. (Image Credit: Peter Buhler/PSI).
New Delhi: New research indicates that 3.6 billion years ago, the climate on Mars was cold enough to freeze the carbon dioxide in the atmosphere, that was deposited on top of the water ice caps at the poles. This carbon dioxide ice acted as insulation, preventing the escape of heat welling up from the deep interior of a young Mars, just a billion years after the Sun was born. The insulation was sufficient to melt about half of all the water available on Mars, that flowed across the surface without a period of climate warming. The research is based on modeling of the carbon dioxide on Mars today.
The researchers expanded the model to probe the exchange of carbon dioxide between the reddish Martian soil, or regolith, with the atmosphere, and then applied the model to a pivotal period in the history of Mars. The researchers discovered that the carbon cycle is controlled by the degree of the rotational tilt of Mars, which wobbles over the course of 100,000 Martian years. When the spin is straight, the poles do not receive much heat from the Sun, with the carbon dioxide escaping from the equatorial regions and getting deposited at the poles. However, when Mars tilts, the carbon dioxide ice sublimates, or turns directly into gas from ice, allowing the cooler regolith to soak it back up like a sponge.
Subglacial rivers flowed on an ancient Mars
The conditions would have resulted in massive amounts of water melting from the polar ice caps. The meltwater would then saturate the Martian crust, with underground water freezing as permafrost. The meltwater forms rivers beneath the ice sheets, with the subglacial rivers leaving behind long gravel striations called eskers. Eskers observed near the south pole of Mars are consistent with the subglacial rivers predicted by the new model. A paper describing the findings has been published in the Journal of Geophysical Research: Planets.
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