Once upon a time it was the dark side of the Moon that was facing Earth, according to scientists who publish a study showing that our satellite changed its axis a long time ago, and that its current poles are not the same as then.
In a study published this Wednesday, March 23 in the journal Nature, American scientists from the Institute of Planetary Sciences in Tucson (Arizona) reveal that several billion years ago, the Moon changed its axis and its poles were placed in different places from today. It has thus pivoted to show us its current face, whereas before these changes, it is the current hidden face which was turned towards the Earth.
To reach these conclusions, these scientists observed that the hydrogen deposits of the ice sheets are today in incongruous places with respect to the thermal environment of the Moon, namely offset from the current North and South poles. , and out of the shadow of the Sun. They calculated that these hydrogen deposits were located opposite each other and equidistant from their respective poles, but in opposite directions. A proof according to these scientists that the axis of rotation of the Moon has tilted by about 6 degrees, thus moving the position of the poles.
To explain such a change, Matthew Siegler’s team highlights the mass of elements that make up the Moon. Indeed if the mass of the elements of a planet evolves, the latter can change orientation, tilting. On the Moon, the Procellarum region, the largest of the lunar seas, located west of the visible face of our satellite, was once geologically more active and very volcanic. This region was therefore, at the time, warm and less dense. Over billions of years, as it solidified, the Procellarum region changed mass and may have influenced the moon’s axis of rotation.