There’s an apocryphal story about the time an eminent scientist was asked to write 500 words for a leading magazine on whether alien life might exist. The resulting article consisted of the words ‘nobody knows’, repeated 250 times.
That point’s still true today. There are plenty of clues that point towards the idea that life might well exist elsewhere, but absolutely no empirical proof of any outside our own planet. What’s more, it’ll be some time before any is available. It will become possible, shortly, to determine the atmospheric chemistry and other features of exoplanets – basically when the new mega-telescopes, including the Webb, come online during the 2020s. The technique is fairly cool; when an exoplanet transits the face of its star, we can pick up the way starlight is affected by the atmosphere – which tells us the chemistry of the atmosphere.
With a big enough telescope we can also directly image a planet and possibly determine other details from direct photography. Only a handful of exoplanets have been directly imaged so far – as you can imagine, picking up a planet against the glare of a parent star at the sort of distances involved is tricky.
At the distances involved all this still means picking up data from a handful of photons, which is why it needs more sensitive instruments than currently available.
But I figure that most of the time, that’ll still only provide indirect evidence – I suspect we won’t see a chlorophyll line in the spectrum and instead have to deduce the possibility from the chemistry of the atmosphere. The thing is that some of the chemistry that points to life ‘as we know it’, such as methane, could also be produced by non-life mechanisms. And so could the chemistry associated with life ‘as we don’t know it’.
Direct hard evidence, short of picking up the alien version of ‘I Love Lucy’ via such projects as ‘Breakthrough Listen’, is going to have to wait on some other developments.
By that I mean the probe being planned right now to investigate Europa – which, it turns out, doesn’t mean drilling through a kilometres-thick ice-cap to find its internal ocean. Apparently Europa has geysers, some of which spew vapour huge distances into space. All a probe need do is fly through the plume and take some measurements.
Of course, that also means having the right instruments on board. That was the problem with the Viking missions of the 1970s, which had a complex robot lab to check for microscopic life because even then nobody expected Martian life to be obvious. Unfortunately the results were ambiguous, it turns out because of the nature of Martian soils. However, nobody knew that when the experiments were being designed.
Lack of the right instruments was also the problem with the Cassini probe which was flown through geysers on Saturn’s moon Enceladus – Cassini hadn’t been designed for that purpose and didn’t have the instruments to do a full chemical analysis.
The problem with the planned Europa probe of the 2030s is that there will be only one of them, and it’ll be made to a budget. You get the picture.
Still, it would be very cool if something were picked up – even microscopic life – because it would mean that our sample size – currently ‘one planet only’ – would double. And that, I think, would change all sorts of things.
Though, to me, at least, it still wouldn’t mean that all the stories of ‘oofoes’ and alien abductions are true. That’s another matter altogether. Thoughts?
Copyright © Matthew Wright 2018