Today was a very big day in 1969, as it was the day on which, at 17 minutes past 8 in the evening, Neil Armstrong and Buzz Aldrin (but not Michael Collins) landed their lunar module in the Sea of Tranquility, becoming the first humans to land on the surface of the Moon.
There has been a great deal written and said about this event, with which I won’t attempt to compete. I will just say that although the intrepid moon men brought back 21.5 kg of lunar material, the main impact of their visit from the Moon’s perspective was to leave behind several tonnes of extremely expensive scrap metal.
The Sea of Tranquility (Mare Tranquillitatis), once thought to be an ocean on the Moon, is a large basalt basin, probably produced by a lava flow following the impact of something quite large, at the time of the Pre-Nectarian epoch, meaning it was formed before the Mare Nectaris. The Pre-Nectarian doesn’t really have an equivalent epoch on Earth, because any rocks of a similar age down here would long ago have been sucked back below the surface to be recycled.