How Fast Is Radio Signal?

Radio signals travel at light speed — 299,792,458 m/s. A signal to Mars takes anywhere from 3 to 22 minutes one-way, depending on the planets' relative positions. This time delay is why every Mars rover move is pre-planned hours in advance.

Mars rovers are pre-programmed because radio commands take up to 22 minutes one-way — real-time control is physically impossible.

• Mars round trip: 6 to 44 minutes
• Voyager 1 round-trip: about 45 hours