But we need Mars as an offsite backup for humanity. So my hope is that today's Mars is a barren world, ripe for future exploration and (eventually) permanent habitation. Ideally, we'd find evidence of past life on Mars, stimulating scientific research and philosophical revelation, and then we'd continue the search for life in the watery depths on the moons of outer planets. Humans could never settle on Europa or Enceladus, so let life exist there instead.

But Mars excels at denying us our most fervent wishes. From not fitting into the epicycles of Ptolemy, to lacking the canals of Lowell, to supplying no organic materials (yet) to the Curiosity rover team, the reality of Mars has consistently irritated humanity throughout history.

In Cosmos's fifth episode, Blues for a Red Planet, Sagan highlights the ways in which the Mars that is subverts the Mars we wish it to be. In this sense it's a thematic sequel to Episode 3's Harmony of the Worlds, where Mars kickstarted the development of astronomy as a science through the ceaseless taunting of Johannes Kepler to unlock the secrets of its motion across the sky.

This episode also portrays what is clearly a personal passion of Sagan's. Influenced from early childhood by the fantastic stories of Edgar Rice Burroughs, Sagan loved Mars. He deeply wished to discover life there, but Mars denied him the satisfaction of doing so, while keeping just enough hope alive by hinting at a past of liquid water and habitability.

It is perhaps this personal passion for the Red Planet that causes the episode to suffer as an hour of television. I find it the weakest episode in the series so far, lacking in forward momentum, storytelling, and the general clever "interconnectedness" that is so nicely brought to life in previous shows.

The opening sequence featuring a reading of H.G. Wells's War of the Worlds over a bucolic scene of 19th century-life is both predictable and overlong, as if they needed to fill time to reach their hour-long episode mark. I would have preferred a deeper exploration of relationship of the invasion-fantasy to the growing influence of the German empire in pre-World War I Britain and how this subverted the growing confidence of humanity's control over their destiny during the late industrial period. The martians here were defeated not by anything humans could create, but by the very diseases that had haunted our species for millions of years.

The malevolent martians of Wells's imagination evolved, for the most part, into the dying remnants of a once-thriving race as inspired by Percival Lowell's canals. In this vision, the canals are seen as a desperate engineering works project to combat global climate change. This leads to some of the most dated visual effects sequences in the series, as we fly over a artististic rendering of the ancient martian cities to the throws of Holst's Mars.

Lowell, of course, is famous for a theory that turned out to be completely wrong. The canals on Mars – mapped in detailed fashion over many years of hard work – were the projections of his dreams onto the blurry globe of this distant planet. There were no canals and no dying race of martians. Mars once again denied humanity its satisfaction.

Lowell's idea, despite being wrong, was was deeply romantic and filled with dramatic pathos. From the John Carter series to my personal childhood martian influence, Bradbury's Martian Chronicles, the story of the dying race persisted. And though most people understood that it was fantasy, the artistic concept Mars nestled itself deep into our psyche.

The latter half of the episode improves as we move focus to the actual exploration of Mars. Sagan appropriately devotes a good third of the show to the Viking landers – the most ambitious and expensive planetary exploration mission to date (there's a good argument to be made that this is still the case).