Many firsts of the Rosetta mission
. The first to properly orbit a comet.
. The first to watch a comet and how it changed as it approached the
Sun.
. The first to land on a comet.
. Detecting water on a comet and checking whether it could be the source of water on Earth (it turns out to be unlikely).
. The first to "smell" a comet: it found that the comet contained ammonia, hydrogen cyanide, and hydrogen sulfide, which together smell like pungent urine, almonds, and rotten eggs.