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

Mix of:

1. All science is always “…to the best of our knowledge”. Thus, Challenge Deep is the deepest point in the ocean *to the best of our knowledge*. If we find out that we’re wrong, then we’ll have learned something new.
2. We don’t need to *explore* the ocean floor to *map* the ocean floor. For example, radar can do the work for us.