The moon may be known for its crater-strewn surface, but they are evidence of only about half of the impacts on it, BTA reports.

Scientists from the Massachusetts Institute of Technology and Purdue and Auburn universities came to this conclusion after developing a more accurate way to track the history of impacts on the lunar surface.

It involves studying the density of rocks on and below the surface, as well as their porosity.

Millions of people around the world have enjoyed strawberry moonshine

When Earth formed 4.5 billion years ago, asteroids, comets, and space debris moved through the solar system and slammed into the young planet and its moon. This gave the Moon the highly ridged appearance seen today.

The stormy weather ends about 3.8 billion years ago.

Since then, the strikes have been weaker and less frequent.

However, the early bombardment created a fragmented porous crust with huge holes reaching well below the surface. 

Scientists are studying porosity to learn more about the moon's history.

They use measurements of surface gravity made by NASA to create a detailed map.

Their analysis reveals that the areas around the youngest craters are the most porous, while the older ones are surrounded by denser rocks. 

The study covered 77 craters ranging in age from 4.3 billion to 3.8 billion years.

The experts then modeled how porosity changes with the age of the crater. 

The experts' hypothesis is that the older craters are exposed to more impacts and they compress the surrounding rocks.

Therefore, the porosity beneath the more recent craters is more representative of the initial conditions on the Moon. 

In addition, the Moon has been bombarded so much that the surface does not show a history of all the impacts - at some point, one collision erases traces of previous ones, explained study co-author Dr. Jason Soderbloom.

What remains is the varying porosity.

According to previous research, the number of impacts is 10 times greater than the rest of the craters.

The present indicates that they were fewer, but still more than the now visible traces. 

The simulations show that at the beginning of the collisions 4.3 billion years ago, the lunar porosity was about 20 percent.

3.8 billion years ago it became 10 percent and has been stable ever since. 

An article about the research was published in the journal "Nature Geoscience". 

the moon