It was written by Malcolm Hulke and Eric Paice, directed by Adrian Brown and produced by Sydney Newman who later co-created Doctor Who for the BBC.
Number of episodes: 6 Professor Norman Wedgwood (David Markham) is the head of an experimental rocket group on remote Buchan Island in Scotland.
Number of episodes: 7 Professor Norman Wedgwood (now Peter Williams) and his team are planning another rocket mission to the Moon.
However, when the automatic supply ship MR2 (Moon Rocket 2) fails to launch Henderson and the children make a desperate rescue attempt with Jimmy's pet Hamlet (now a guinea pig).
However one of the crew turns out to be science writer named Harcourt Brown (George Coulouris) who has plans to divert the ship to Mars determined there is life on the planet.
Thankfully, MR4 has landed within a hundred miles of the polar ice cap so the group set off, Brown too, believing there to be life on Mars.
The crew then realise that Buchan Island has made various satellite fixes on Mercury, thus enabling MR4 to make the home journey to Earth.
As MR4 falls out of danger from the Sun's gamma rays, Brown ponders of the idea of other life on another planet and sees Venus as a possibility...
Number of episodes: 8 Returning from their unexpected trip to Mars the crew of MR4 intercept a distress signal from Captain Wilson, a U.S astronaut, and must change course for Venus to attempt a rescue in space.
Landing on Venus, the crew discover, much to Brown's delight, that the planet is capable is sustaining life and is a vast jungle.
Keeping to the left and through the desert, the Wedgwood party discover Venus is a living duplicate of Earth, with dinosaurs and prehistoric humans existing parallel to each other.
The pilot, Colonel Korolyov, explains they have extra fuel for MR4, in exchange for Wilson's secret mission - an experiment in stellar telecommunications.
Preparing to leave, Brown announces he is remaining behind since Kiki has lost her parents and aware of the responsibilities of hijacking MR4 in the first place, and that to him Venus is an unspoiled paradise.
Professor Wedgwood was retired in the first chapter leaving Conway Henderson as the lead character and Ian Murray as Buchan Island base controller.
Pathfinders to Venus included scenes of animated Dinosaurs from the Czech film Journey to the Beginning of Time.
Midway through Pathfinders to Mars at the last minute, it was decided to have the last three episodes filmed live owing to timing reasons.
The seventh episode of Pathfinders to Venus (The Valley of Monsters) was used in an academic study of children's attitudes to television viewing.
Sydney Newman later commented "The most important thing we learnt is that if anyone thinks a young audience can be fooled or won sloppily or 'on the cheap' he is sadly mistaken".
All three serials would star Flood as scientific journalist Mark Bannerman and Guidotti as his photographer Peter Blake.