Henry triggers the return signal to bring home Tiny, and the return is only a matter of seconds. Titan is approximately 80 light minutes away from Earth, and while they have developed FTL travel for a specialized craft, there's no indication they were able to do so for radio signals. It should have been necessary to send the return signal and then have to wait approximately 80 minutes (give or take some, depending on the distance between Earth and Titan due to orbits at that time of year).
Henry tells Carter the orange fog was Ethane , however Ethane is colorless and odorless.
However he says it is primarily composed of Ethane, he doesn't say what other components might be in it.