Laythe's atmosphere begins at 55,500 meters and is comparable in density to Kerbin's. It is the only satellite of Jool with an atmosphere.
With proper aerobraking near Laythe and Jool, reaching Laythe may require the least delta-V of all of Jool's moons. A periapsis of 119.5 km on a Jool approach will put your apoapsis roughly near Laythe's orbit.
Rotational/Inertial transition: 100,000? m
- Initial Release