The middle looks like liquid, but what's all that fibrous stuff? Doesn't look like the typical dust accumulation. Mining farm animals?
The liquid is grease from the thermal paste seeping everywhere because it gets hot (and might be put in excessive amounts). This is bad long-term (2-3 years) because it dries the paste and it aerates becoming useless.
The oil also attracts urban dust, in this example some plant fragments before we installed the filters.
