Porosity of the moon’s crust told the story of its bombardment

(ORDO NEWS) — Approximately 4.4 billion years ago, the early solar system experienced a huge number of collisions – the Moon and other celestial bodies were intensely bombarded by massive asteroids, comets, and, later, smaller space rocks and debris.

This period began approximately 3.8 billion years ago. On the Moon, this turbulent time left traces in the form of a surface abundantly dotted with craters, as well as a fissured and porous crust.

Now, researchers at the Massachusetts Institute of Technology, USA, have found that the porosity of the Moon’s crust, which extends quite deep below the surface, can provide a lot of information about the history of the bombardment of our planet’s natural satellite.

This study shows, using computer simulations, that during the early period of the bombardment, the Moon had a high porosity of about 20% (for comparison, the porosity of pumice is only three times greater, about 60%). Such high porosity was explained by early collisions with large bodies, the authors believe.

Previously, scientists believed that the constant bombardment of the lunar surface led to a gradual increase in porosity.

But, to their surprise, by running simulations of the bombardment processes, the team found that almost all of the original porosity of the Moon was reached in a relatively short period of time, as a result of collision with large bodies – while subsequent multiple impacts with smaller bodies, on the contrary, led to the compaction of the crust and a decrease in porosity.

This was also pointed out to the authors by the fact that, according to observations made using the Gravity Recovery and Interior Laboratory (GRAIL) satellite, the crust around young lunar craters has a looser, more porous structure than around older craters. When modeling with porous crust as initial conditions, the neighborhoods of ancient craters,

This new look at the bombardment of the lunar crust has overestimated the number of impacts with small bodies – about twice the number of small craters corresponding to such impacts that can currently be seen on the lunar surface, the authors show.

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