Sometimes you can hear: the Earth owes its habitability to its satellite, the gravity of which holds the axis of our rotation, and that, in turn, is responsible for seasonal temperature fluctuations. Remove Selene and everything will go haywire, we are told. New research casts doubt on this thesis.
Yes, yes, we have already informed you that the thesis about the usefulness of a constant tilt of the earth's axis raises doubts! But Jack Lissauer, the discoverer of Uranus's two moons, of NASA's Ames Research Center, USA, went even further. Together with his colleagues, he asked this question: how exactly would the absence of the Moon destabilize this very axis?
Does the megaloon (above) really need this palm to survive?
Photo Mike Neal / nealstudios.net
“If the Earth did not have the Moon, the tilt of its axis of rotation - and thus the climate - would vary much more than it is now, this is true, - the scientist admits. "But nothing so bad that the previous models showed us would have happened."
The thesis about the importance of the Moon for the stability of terrestrial conditions is very important. The diameter of our satellite is 0.27 Earth's - that is, its comparative dimensions are colossal. And if the moons in other systems massively reached this size (in comparison with their planets, of course), we would have already detected at least one of them in the data of the Kepler telescope. But this does not happen, and the modern theory of the formation of the Moon even explains why: Selena is simply not a satellite, but a part cut off from the once existing Earth Moon, which arose as a body only as a result of the collision of this very Earth Moon with a large planet. Consequently, such cases are not very frequent, and so is the powerful stabilizer of the axis of rotation of the Earth-like planets of other systems.
According to previous calculations, without the Moon, the planet's axis of rotation would not vary in the range of 22.0–24.6 °, but would fluctuate in a pantagruel manner - from 0 to 85 °, that is, right up to lying on its side! In the latter case, the polar night and polar day would become a reality for almost the entire planet, which is why the climate would hardly improve. At 0 °, the northern regions would be poorly populated, others argue, and the equator is always overheated.
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Mr. Lissauer and colleagues created their own model of axis oscillation, limiting its operation to 4 billion years. And - you will laugh - it turned out that for all this time (equal to the history of the Earth today) the inclination of the Earth's axis did not exceed 40 ° and did not fall below 10 °.
“If we take the time required for the development of a complex life, then during such a period the changes can be, say, ten degrees in both directions,” the researcher is stunned. At the same time, if the Earth had retrograde rotation (the Sun would rise in the west), which should sometimes occur among rocky exoplanets of other systems, the oscillations of the tilt axis would be even less, because the rotation of the planet around its axis would go in the direction opposite to that along which she travels around the star.
If the satellites of the giant planets of the Solar were correlated with the host planets, like the Moon and the Earth, there would be a lot of "super-earths" around Jupiter
Art by Mary Anne Peters
Long-term climate fluctuations associated with such processes would indeed take place, but they cannot be described as catastrophic, the scientist argues. To this should be added the thesis already put forward that a too strong tilt of the axis ("spreading" of the polar night and day) simultaneously with the cooling effect due to an increase in albedo (a lot of ice would form in the unlit hemisphere during the night) would increase the efficiency of solar absorption by the planet. light, which in theory should give a heating effect. This means that the range of fluctuations would hardly be excessive - and in general, the climate situation would not be as dramatic as it was thought. It makes no sense to limit the detailed study of Earth-like exoplanets to those that have relatively large satellites, the scientist believes: life can do without them.
The results of the study were presented at the convention of the American Geophysical Union in San Francisco.