How are we sure Challenger Deep is the deepest point when we have barely fully explored our ocean?

Question

Basically the title, but I always wondered if the Mariana Trench was the actual deepest point on our planet

In: 56

Answer 1

The oceans aren’t *that* much of a mystery. We’ve mapped them in sufficient detail to know there aren’t any super-deep trenches that could rival Marianas. If there were a deeper point in the ocean somewhere, it would have to be freakishly narrow, but such a deep, narrow crevice is unlikely to form and stay that way for long.