Researchers have detected a big mass/gravity anomaly basically under the moons largest observable point of impact. This was found within data from the (holy) GRAIL (Gravity Recovery and Interior Laboratory) NASA mission. Maybe some nice metallic depostits from some huge AF asteroid crashing into the moon many billions of years ago? Maybe the base from Iron Sky?
I quite recently listened to a (German) podcast on geological ages determination methods. Mindboggling, that such a crater (the moon’s South Pole-Aitken Basin)would still be visible after 4 billion-ish years.