Many ancient asteroids have by now gotten gravitationally pulled to crash into planets, (like what triggered killing 2/3 of Earth life, followed by the extinction of dinosaurs). Recently one got observed pulled into Jupiter. Later another, pulled into Russia, broke apart (without killing anyone).
Over billions [1,000,000,000s] of years, many also crashed into moons. Luna's backside should be expected to look much more cluttered than its front, messed up by past crashed in asteroid junk. This is because when some past asteroid had gotten pulled in from its path by the gravity of Earth and Luna, if Luna was in the way, it would've crashed there, thus on Luna's backside, rather than soon being able to strike Earth. (Luna is .27 as wide as Earth.)
But if an asteroid got pulled in by Earth & Luna when Luna's front somewhat faced it, thus then being somewhat behind Earth, then the much bigger Earth gravity would have likely first captured the asteroid. That would have thus left Luna's front side smoother facing Earth, more clean than the backside from past asteroid strikes.
Such a rare unusual difference between two faces of a moon should only gradually develop if a planet had that moon having a very slow rotation day, locked identical to its orbit period around its planet, thus having a permanent back side kept forever facing out away, thus once each orbit effectively protectively in front of its planet.
Astronomers had sent satellites around Luna to view its backside. They saw a more messed up asteroids struck backside. (Such satellites had been looking down at Luna's surface, thus never for any goofy reason viewing up toward Luna's high L2 Lagrangian point well behind Luna, if anything had been at least briefly visible up there. Also L2 was much higher out from Luna than the orbit radius of a normal satellite sent around Luna.) And if some future satellites would be sent around behind Luna, they would surely be sent to view down at Luna again. (To view space out beyond Luna, astronomers instead had good telescopes elsewhere.)
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