Life On Jupiter

Theor climbs a mountain, hears a stream and wonders if he should try to catch a fish. In other words, when Poul Anderson wrote Three Worlds To Conquer in 1964, it was still thought possible that Jupiter was like a big Earth.

Differences:

a fall is more serious on Jupiter, even for a Jovian;

under Jovian gravity, the change of air pressure with altitude is several times greater than on Earth - a mile above sea level, Theor's spiracles get less than half the hydrogen that they need;

erosion and gravity counteract orogeny so that most mountains are low;

energies bursting out of the compressed core and mantle cause not only quakes, volcanoes and geysers but also a thirty thousand mile long permanent storm, the Red Spot.