The way to think of this is that very few scientific experiments or
engineering tests are done anymore using human manipulations, human
observations, or directly human-operated equipment -- EVEN ON EARTH.

I don't think this is true, end to end (which is what is required for
unmanned missions). But even if it were, it misses the point.
Interactive experimentation (as opposed to autonomous experimentation)
is limited by the speed of light. This is insignificant terrestrially,
of slight significance on the moon, but makes a lot of difference as we
go to the planets. Humans are needed close (in lightpseed distance) to
the experiment, and the only way to learn how to do this (for
experiments on Saturn's moons) is to take humans to nearby places (like
the moon and Mars).

Yes, there are some unmanned probes that do quite well out in the outer
planets, but those experiments are not all that interactive.

Jose
--
Get high on gasoline: fly an airplane.
for Email, make the obvious change in the address.