What is the approximate vertical drop depth of the South Pole-Aitken Basin floor below surrounding lunar terrain?

Approximately 13 kilometers (or about 8 miles)

The defining characteristic of the South Pole-Aitken Basin (SPA) is its profound vertical relief. Scientific analysis indicates that the floor of this massive impact structure sinks approximately 13 kilometers, which is equivalent to about 8 miles, below the level of the adjacent lunar terrain. This measurement is significant because it surpasses the depth of Earth's deepest known oceanic trench, the Challenger Deep in the Mariana Trench (around 11 km deep). Furthermore, this depth is so substantial that if Mount Everest, the Earth's highest point at roughly 8.8 km, were placed at the bottom of the basin, its peak would still be submerged by over four kilometers of lunar material above it, emphasizing the immense scale of the original impact event.