On Earth could come eternal ice age.
Planets like the Earth the solar-type stars protected from global cooling is much worse than anticipated: most of them tend to eternal glaciation.
French researchers have modeled the fate of carbon dioxide on the planets, like the earth, the stars, like the Sun. It turned out that if the Earth is removed from the star 1.27 times more than now, it would be covered with eternal ice. Previously it was thought that it would be habitable even at the distance of 1.69 times greater than today.
If the terrestrial day is shorter, our planet could permanently freeze. The discovery means that the habitable zone of a yellow dwarf should be reduced by half. Red dwarfs, which are much more, in this sense, more favourable to their planets: they have such a scenario is impossible. The text of the relevant article can be found on the Preprint server at Cornell University.
The authors have modeled the fate of carbon dioxide during a major glaciation similar to that which happened on Earth 720-635 million years ago. In their model, he began to fall in the form of dry ice accumulating at the poles. Over time, due to the removal of the new carbon dioxide into the atmosphere by volcanoes in the output of the planet has decreased heat loss. She is hot, and carbon dioxide polar cap has disappeared, running rapid melting of water ice that covered the planet. Thus, modeling the Earth again became suitable for life.
However, when the researchers slightly changed the simulation parameters, the situation deteriorated sharply. On a planet with earth’s atmosphere, length of day and the inclination of the axis of the carbon dioxide polar caps can’t thaw, already 1.27 astronomical units from a star like the Sun. Moreover, their dry ice for a matter of thousands of years can be absorbed in water ice. That will block the melting of carbon dioxide and, in fact, forever will bury her. After that, carbon dioxide is cut off from the atmosphere and cannot create the greenhouse effect.
This means that the glaciation on this planet will be eternal. Defrost our planet after severe glaciations is due to carbon cycle — changes in the physical and chemical state of carbon. Ice-covered rocks can no longer bind carbon dioxide that is emitted during the eruption of volcanoes. It accumulates as long as the greenhouse effect does not cause the ice to melt. But if the main greenhouse gas itself will begin to turn into ice (at temperatures below -78 degrees Celsius), the carbon cycle ceases to work — at least if the distance from solar-type stars exceeds that of 1.27 astronomical units.
The work is important because it is still a factor in the freezing of carbon dioxide, so details were not considered. Therefore, it was assumed that the habitable zone for earth-like planets orbiting stars like the Sun extends from 0.99 astronomical units (the Earth is slightly closer, and she would be lost to the oceans) to 1.69 astronomical units. That is whether our planet, with its dense atmosphere, even on the ground of Mars, it also would be inhabited due to reduced sequestration of carbon dioxide rocks.
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