The distinctive Golden Handle “C” shape is light skimming across Montes Jura. This is the surviving portion of the rim of the ancient impact basin, which explains why it’s so curved; it’s essentially part of a circle. The Golden Handle is visible for a few hours when the Moon is waxing, around 10 to 11 days after New Moon. The effect is caused entirely by perspective and the low angle of the rising Sun. So, like the Lunar X and V, the Golden Handle is an optical effect rather than an actual physical feature.

Inside the arc of Montes Jura lies Sinus Iridum, Latin for “Bay of Rainbows”. The bay occupies an ancient impact crater roughly 240 kilometres across. The impact formed the crater and its raised rim, of which Montes Jura is the surviving mountain arc. Later, basaltic lava flooded the interior and buried part of the rim, creating the relatively smooth plain we see today. The crater and its lava-covered floor therefore formed at different stages of lunar history.