The moon slowly moved away from the icy Earth

Researchers from the University of Colorado in Boulder, USA, have received new information about the equatorial bulge of the Moon, a geological feature that formed when the Moon solidified from the melt, as it gradually moved away from the Earth.

In this study, the parameters of the removal of the Moon from our planet are calculated and it is assumed that the hydrosphere of the newly formed planet at that time either did not exist at all or existed in the frozen state – which indirectly supports the hypothesis that the dim Sun at that time radiated by about 30 percent less energy, compared with the present time.

The moon in our days is moving away from the Earth at a rate of about 4 centimeters per year. It is believed that this movement occurs as a result of gravitational, or tidal interactions between the Earth and the Moon. The same process leads to a slowing down of the Earth’s rotation and an increase in the duration of the day.

Scientists believe that tidal and rotational forces formed the Moon after its separation from the Earth. The influence of these forces led to the “flattening” of the Moon at the poles and the formation of the equatorial bulge. About 200 years ago, the French mathematician and physicist Pierre Simon Laplace determined that if the moon rotated at a speed of one revolution per month, the bulge size should be about 20 times larger than in reality.

In their new work, the researchers determined by computer simulation that the process of forming a bulge of the Moon did not occur suddenly, but rather slowly – for some several hundred million years, during which the Moon slowly moved away from the Earth. It happened about 4 billion years ago.

However, for such a slow removal of the moon to take place, it is necessary that the dissipation of energy by the terrestrial oceans in response to the tidal perturbation from the side of the Moon be significantly reduced. This, in turn, can be explained by the fact that the water of the terrestrial oceans was in a frozen state, the cause of which could be a dull sun, the intensity of radiation of which at that time was significantly reduced, the authors of the work believe.