We have known for a long time that water ice exists in comets, but this is the first evidence of water ice on comets.
Understanding a comet's water cycle and supply is critical to understanding these bodies as a system and as a possible source that delivered water to Earth.
It's not uniformly distributed ... it's not like it's hiding in the dirt and we just didn't see it.
The common expectation was that water would be all over the surface. But what we found was that it was in small, discrete areas.