稀世

稀 = 希 + 禾 : John Hope the Educator (希) teaches Marie Curie (xi) about a very rare (稀) species of bacteria in front of the space station (Ø1). It only grows in watery (稀) cereals (禾) which are stored in the vacuum, like in outer space.

世 = 廿 + L : Mnemonic symbol: the WTO or WHO.

Sherlock Holmes (sh) is cleaning a flower pot (廿) under the shower of the space station's bathroom (Ø4) with a loofah (L) because he didn't quite understand a poster next to the shower from the WHO (世) explaining dangers arising from different germs.

In this case, L is for loofah.