Slowly but surely throughout the series Cox used the existence of the other bodies in our solar system as a framework on which to integrate all the latest findings in terrestrial geology, geography and biology, but in such a subtle fashion that you hardly noticed him doing it. He did plenty of whizzing around the world in helicopters, jet fighters and submarines to keep the Top Gear crowd watching, but never for the thrills alone, always to show us how thin the blue layer of our atmosphere is, the enormous gap ripped by a post-Ice Age flood into the Scablands of Washington State, or the sulphur-eating inhabitants of a deep ocean smoker. Cox had sufficient taste to let magnificent film of the real planet do the talking instead of indulging the now-obligatory expensive CGI effects.
Gradually two themes emerged: first of all a tutorial in energetics, and depending upon that a tutorial in the conditions that support life. Physics tells us that nothing can happen without a source of energy to drive it, how to identify and measure such sources of energy, and once one has grasped its principles energetic analysis wonderfully clarifies judgment about the real world - you can accept or dismiss all kinds of stories about phenomena on energetic grounds alone. It's an aspect of science that's poorly taught in schools and of which most lay people (including politicians) are almost entirely ignorant, with disastrous consequences for the quality of debate about, for example, climate change and transport policy.
Cox has a natural gift for making energetics sound so easy that it didn't even feel like a lesson, as he enthused over the sulphur volcanoes of Io, the ice-geysers of Enceladus and the way that Mars is now dead because, in effect, its battery ran out. In the last episode of the series it all came together in the most satisfying way as Cox inquired into the probability of life in other parts of the solar system, deploying a variety of extreme environments on Earth - from deep ocean to glacier to Atacama Desert - as clues. All a long way from the slightly creepy search for intelligent life performed by SETI, this was, er, down to earth biology concerning the possibility of slime bacteria living in caves under the Martian surface.
Cox showed us the way life evolved on our planet and might be doing so on others in a fully cosmic context, with no agonising about whether evolution is a fact: he took that for granted, as intelligent lifeforms were able to do back in the 1960s before evangelical cretinism threw sand in the works. In the last minutes of the program he gave the most unaffected and touching defence of a higher humanism that I've heard for years: we're likely to be the most complex lifeform that has so far emerged and that now makes us responsible toward other life-forms rather than in dominion over them as believers in Divine Providence would have it. Fitting compensation for all the dumbed-down Horizons we've suffered recently, and well worth the licence fee.