Before “Voyager” meant “a flyby probe of the Outer Solar System,” it meant “an orbiter and lander for Mars.” It was, essentially, a bigger, more ambitious version of what became the Viking missions. big enough that the Saturn V was the launcher, sending two craft at a time.
A number of companies put in bids to design and build the spacecraft. Below are images of the TRW concept. The conical section is the capsule holding the lander; the propulsion section is derived from the Lunar Module descent stage.