Final answer:
Finn and Philby noticed a lack of water clouds and low water vapor abundance while descending into Jupiter's atmosphere.
Step-by-step explanation:
Finn and Philby finally noticed a lack of water clouds and a surprisingly low abundance of water vapor while descending into the atmosphere. The scientists expected the probe to pass through frozen water clouds and then clouds of liquid water droplets, but it descended through an unusually dry, cloud-free region. This discovery was surprising to the Galileo scientists and provided valuable information about Jupiter's atmosphere.