The deposition of ice that formed in the craters on opposite sides of the moon three billion years ago indicates that it has already changed its axis of rotation.
The volcanic activity of the satellite of the Earth, manifested billions of years ago, may have moved the poles to their present position. This was stated by a team of scientists from the Planetary Scientific Institute in Tucson, Arizona.
They said that their calculations, published in the journal Nature, open the way to understanding how water reached the inner part of the solar system. According to one of the leading specialists of the institution, Matthew Ziegler, the axis of the moon has shifted by 6 degrees to its present position since the time of high volcanic activity.
"Such activity causes huge changes in the mass of the moon, as in the formation of a giant crater of a volcano or a whole volcanic system," said Ziegler.
The team found the source of the change in rotation to the center of the Procelllarum region. This is the dark part of the lunar surface, which is also the center of almost all volcanism on it. “Looking at how the poles move, we can see how Procellarum has evolved and the appearance of the moon has changed throughout its existence,” said Ziegler.
Since this region was the most geologically active in the early history of the Moon, Ziegler said that this change in the axis of rotation occurred several billion years ago.
The scientific team used simulations to determine which density changes were to occur in the depths of the moon in order to cause a change in satellite orientation by 6 degrees.
When analyzing indicators of hydrogen from the moon collected almost ten years ago, Ziegler's team noticed that at each pole there were deposits of hydrogen, which was slightly shifted away from their current position.
These hydrogen deposits are directly opposite each other, so that the conditional line drawn from one to another will pass through the center of the moon, but both sides will go in different directions relative to the present poles.
Since hydrogen was most concentrated in the extremely cold regions of the moon, it was possible to assume that it was water. "In the shaded craters near the lunar poles it is really cold. In most areas, the temperature never rises above minus 170 degrees Celsius," said Ziegler.
"At such temperatures, ice manifests itself like any other material - it does not melt and does not evaporate, so it can remain there forever. It has been on the Earth’s satellite since the change of its poles has just begun, which probably occurred about three billion years ago. This means that the moon can give us information about how water reached the inner part of the solar system, which, as is commonly believed, did not have a water component. "
Future ice sampling missions will help determine where the water came from on the moon: from comets and asteroids, or from volcanoes on the satellite itself.
NASA already has plans for a lunar rover in the 2020s, which is supposed to drill the soil to a depth of one meter and get ice samples, but their transportation is still a technical problem.
“There is hope that the new results will affect NASA’s plans,” said Ziegler.