Mars has fascinated us ever since we first looked up to the heavens. We have imagined alien civilisations, exotic life forms and even dreamed of travelling there ourselves. But after the first probes flew past the Red Planet, and with each subsequent mission that has orbited or landed on its surface, that vision has changed. We have come to realise that the planet is, most likely, dead. But that hasn't dimmed our hopes for finding evidence of past life. And our desire to travel there and colonise the Red Planet still endures.From the very beginning of this exploration, the BBC has recorded our shifting perception of Mars. Since the Sky at Night started broadcasting in 1957, there have been over 50 episodes devoted to Mars and more than ten episodes of Horizon. This programme looks back at that coverage.