Its mountains always seem to catch the light in a different way, and in good lighting conditions, the contrast mixing brightness and darkness on both sides makes this place something magical. The low sun in this region is something to be treasured, so each small crater stands out like a ring of light. This low lighting also emphasizes the ridges present in the sea (peculiar low sinuous ridges) making them very prominent and easily visible on the flat floor of the bay.
Sinus Iridium is called a bay, but it is actually a crater whose southeastern wall has been practically destroyed, only a few very low disconnected fragments can be traced. On the other hand, the hills to the northwest are continuous and quite high, thus superbly highlighting the Montes Jura, whose outer rim is disturbed by the prominent Bianchini crater. The continuous section of these mounds is bounded at both ends by the Promontorium Heraclides and Laplace.
One thing that should be very clear is that the Iridium floor slopes downwards towards the southeast, thus penetrating Mare Imbrium, so that the opposite side is about 61 meters below sea level, that is, completely buried. There is nothing like it anywhere else on the moon. The sequence of events that took place appears to be quite simple. The sea itself was formed about 3 billion years ago, probably after the Great Bombardment. Since the impact that formed Sinus Iridum must have occurred earlier, this leads us to believe that at least 4 large floods of lava that formed the sea were responsible for burying the entire southeast edge of this magnificent crater.
Sinus Iridum is one of the moon's most enchanting features, but to do so, you must observe it at the right time. As the sun rises over it, the mountain tops are illuminated by sunlight, while the floor is still in darkness. The result is that the wall appears to be floating above the moon, beyond the terminator. Lunar observers refer to this as Rainbow Bay.
This occurs once every lunation (lunar cycle), but it doesn't last long, and as the sun creeps into the lower floor, the floating arc effect soon wears off. It is fascinating to follow the changes that occur with the increase of the sun's altitude, even a small telescope will show it very well.
Take a closer look at the exact location of Laplace Promontory and its intriguing geology. Imagine yourself at the top at 2,600 meters high, observing all this immense plain around you! Did you feel a chill?
Text: Avani Soares
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