Microbes are out there: Aliens, ed. Jim Al-Khalili

I love it when Jim Al-Khalili communicates science. He’s a physicist, a BBC Radio 4 presenter of science programmes (The Life Scientific is a great podcast, btw) and he’s written, among other books, a fine work on the history of medieval Arabic science. (I have no idea about his academic publications because I can’t read the first sentence of an abstract in Nature without gibbering.) Give me his popular science books, and I am happy.

I am even more happy when science is applied to science fiction, and Aliens does this excellently. Al-Khalili took the premise that if there are aliens out there, in the vastness of space, what will they look like, and how could we detect them? He asked twenty scientists with a foot in the field to speculate – in a nicely moderated popular style – how their specialisms could illuminate what might happen. He starts with Astronomer-Royal Sir Martin Rees, and moves from astrophysics to microbiology to psychology and neuroscience. In about half the essays, the alien extremes that we already know about on Earth are explored for what they might tell us about the possibilities for life Out There. I already knew about deep-sea thermal communities of bacteria that thrive in conditions that would slaughter most other life-forms, but did you know that communities of chasmoendoliths live inside rock?

I was most struck by Rees’ remark that our first contact will not be biological, but artificial, since that’s what we are doing already. Mars already has alien visitors: our AI vehicles and exploratory equipment are already out there, dropping Earth particles into its peculiar atmosphere. The limitations of space travel (time, energy and mass) make missions operated by AIs much more likely than sending humans out in deep sleep conditions. And then there are the places we could look at: since solar winds strip atmospheres from orbiting bodies unless their gravity is strong enough, only those orbiting bodies with the right geophysical parameters are likely to hold the conditions for life. These begin with water (or another substrate fluid for nutrient exchange and solvents: several of the contributors differ about including methane in this list), and the most common chemical elements that have created life as we know it. Most of the potential life talked about is microbial, and while it’s difficult to get excited, let alone alarmed, at the thought of a mat of proteins living between silicate layers only a few cells thick, it’s that scale, and level of strangeness, that we should be open to if we’re serious about finding life Out There.

The essays are short and snappy, and include excellent round-ups of science-fiction films and novels about alien contact that should be read or seen, or avoided. There is inevitable duplication of explanation – almost everyone carefully defines how H₂O is essential – but there are also good links across chapters (evidence of a good editing hand). The consensus seems to be that Europa, Titan and Enceladus are the bodies most likely to harbour life in our own system, but my word, getting to that life will take many of our lifetimes. Even if the SETI search can detect suitable planets, identifying and contacting life on them is one of the longest-term projects we have. Assuming we’re still here on Earth when contact is made by the AIs we send out on missions lasting hundreds of years. My only complaint is that no-one, absolutely no-one, mentions the NASA press conference of a few years ago which announced with hysterical excitement that they’d found evidence of arsenic-based life on Mars. That debacle was hushed up so quickly: I really wanted to read more about the mistakes scientists make when they think they’ve found alien life, and what we learn from those mistakes.

Jim Al-Khalili (ed.) Aliens. Science Asks, Is Anyone Out There? (Profile Books, 2016), ISBN 9781781256817, £8.99