Red rain from space! Bat's blood and meteors! Alien landings! Cells without DNA! But come out from behind the sofa – although it sounds like Doctor Who, in fact it’s fictional science – all to be found in another thrilling episode of BBC2’s science documentary programme Horizon. What are the origins of life on earth? It’s a continuing mystery that has perplexed and intrigued both scientists and science fiction writers for years. Panspermia, in case you hadn’t heard, is not an awful culinary experiment by drunken students, but rather the "theory" developed by the late Sir Fred Hoyle (and others such as Professor Chandra Wickramasinghe, Chair of Astrobiology in Cardiff) to explain the beginnings of life on this planet. Essentially, Panspermia claims that early life was alien, having fallen to earth from space many moons ago and seeding the evolution of everything on earth today.

Wild, you may think. Interesting even. Is there any evidence for this hypothesis? Not really. But that doesn't stop the cranks from cranking the pseudo-science handle, and Horizon producers from listening to them blindly.

The focus of a recent Horizon programme on Panspermia was the ‘Red Rain of Kerala’. Five years ago, a localized region of Southern India suddenly experienced lots of red rain falling from the sky, allegedly coinciding with a meteor burst. Enter the astrobiologist (although I’d prefer to call him an ‘astrobiotheoretician’) Dr Godfrey Louis. Instead of running some simple tests to determine basic composition – the sort of thing a local food analyst might do – they put samples of the red rain straight into a scanning electron microscope. (Apparently the scanning electron microscope is a tool beloved of astrobiologists, despite its well-known – that is, if you’re a real biologist – propensity to throw up artifacts). Low and behold, they looked like red blood cells. That's where the meteor-hitting-a-flock-of-bats idea came from. I shall not expand, it’s far too silly. But it seems they are tough beasts, too tough for red blood cells. The thick plottens.

So what are these mystery objects: so small, yet so hard? Maybe they are alien spores, the cry goes up. Yes, of course. Hence the next most logical step: to try to extract DNA from them because, and I quote, "all living things on the planet have DNA in them". Analysed they duly are, and no evidence of DNA is found. Now I quote the eminent astrobiologist: "They didn't have DNA in them. Therefore they must be alien". Yes, he really said that. Amusing. Except this is on respectable TV; this is the BBC. No matter that down a fairly cheap light microscope they look suspiciously like red algae. That apparently doesn’t make good telly.

So this shoot-from-the-hip speculation (pun intended) continues unchallenged, and interviews with other cranks ensue. Perhaps you remember that controversial research paper which purported to 'prove' the presence of bacteria in meteor rock samples (now thought by most to be a little more basalt that bacillus) – well, there was a whole section on that. Bacteria do live in places where mere humans cannot. It is impressive and amazing, and definitely true. They are bloody tough bastards, bacteria. But this in no way proves they can exist in outer space.

Viewers were then treated to a tremendously exciting experiment where a guy fires a bit of rock impregnated with, one assumes, millions of bacteria, at a water-bag in front of a metal target, meant to simulates an asteroid hitting the sea and the seabed below. Dramatic indeed, except that the little bit of rock missed the target and shattered to smithereens, so the experiment was a blow-out. The thesis was that if you throw stuff really hard at something solid, then most of the living things in the stuff die, but a few can survive. This also apparently also proves that earth originated from space. The programme, rather alarmingly, also used as evidence the fact that the surviving remnants of experimental equipment from the Space Shuttle disaster had live bacteria in it. Therefore bacteria are from space. End of story.

Professor Chandra Wickramasinghe and his "team", presumably succumbing to peer pressure, are then filmed as they reanalyse the red rain particles to once again try to get DNA out. This time they succeed: we see some poor lowly researcher showing the eminent astrobiologist the ethidium bromide stained agarose gel scattered with PCR generated bands. With this evidence, at face value, most scientists would have concluded that the red rain particles were of biological origin, and the most likely explanation would be that they came from earth. But this is not what Wickramasinghe concludes. And then, instead of the Horizon producers asking the pertinent, tough questions: what species-specific primers did you use to get those bands? Have you sequenced the PCR products to find out which species of 'red rain' algae has been mislabeled as ‘alien matter’? – we get nothing.

We are left with the Professor saying something like "oh…so…some of the samples have DNA…". Swiftly cut to same Professor punting in Cambridge, uttering the immortal words "... on reflection and after talking to Godfrey, I think I would now fairly firmly believe that it did represent an invasion of microbes from space." The only person interviewed with any common sense was a fairly level-headed NASA scientist who basically said when it come to understanding life, trust the biologists, not the astronomers.

It vexes me to see a whole ‘science’ programme riddled with errors, weird logic, misjudgments and confusion – and at the end, not going for the kill. One minute they are pretending to be sceptical of the theory, the next gushing with enthusiasm for it. I think I remember when Horizon used to be cutting-edge, analytical and – dare I say – even scientific.

Maybe it’s not important to get distressed about these things. Maybe these programmes are good for titillating the public, perhaps stimulating some to research the area to find out more. But it’s not okay to provide biased, illogical content under the science banner, using tax-payers money to do so. The fact that not so many people really watch these things, and those that do might care two hoots, is irrelevant because it enters into the mainstream without challenge, shamelessly propagating the idea that a lack of intellectual rigor is normal.

More worrying to me was an article by Andrew Thompson on the BBC online website entitled 'Searching for "our alien origins"', peddling the whole Panspermia line with even less critical analysis than Horizon and no doubt slated to be enshrined for all eternity in the highly reputable BBC archives. Contrast this with the more critical arguments in an earlier 2001 BBC article entitled “Scepticism greets 'space bugs' claim” which was very balanced and pretty much discounted the claims supporting Panspermia.

It may well turn out that some organic part of our world originated in space – given that the universe is a jolly large place with lots of stuff whizzing about, this seems even probable. That’s not the point, though. We need rigour, balance, sharper analysis and less crazy sexed-up science that serves only to blur the boundary between Dr. Who and Dr. Why.

Related links

Visit Paul's website to learn more about his science communication activities and to see some of his gorgeous microscopic images.

You can hear a former BBC Horizon editor defend his tactics in an interview with LabLit.com here.