I've just learned that the word "spacecraft" is used both for singular and plural forms. The internet even says that "spacecraft" is more common than "spacecrafts" for plural usage.

(Obviously, non-native speaker - learner)

I used to think of Mercury as a rather uninteresting hot clump of rock. It turns out Mercury is not really uniformly that hot at all. And it has water ice at the poles. And not only water, but there are organic compounds too in the polar shadows!