Apollo 11

Mare Tranquillitatis. The first crewed landing: 21.5 kg of samples, a laser retroreflector still used today.

Lunar laser ranging to Apollo retroreflectors tests gravity to high precision, the same physics that predicts where a Planet Nine would have to be. Marker position is to scale on the Moon; the Moon itself is enlarged.

Sources

1. NASA: Apollo landing sites (LRO)
2. LPI: Apollo landing site coordinates

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