The Living Cosmos: Our Search for Life in the Universe

"The thing one should look for in a book like Chris’s is all the work being done on exoplanets. That’s a field that has exploded and should be, on principle, sustainable. Anybody with a really good telescope can go search for their own exoplanets, particularly if they’re around red dwarfs. We can expect to see more instruments and space telescopes emerge that allow us to analyse the atmospheres of these planets, especially those transiting planetary solar systems. Trappist 1, for example, a star which is just bigger than Jupiter—it’s not even a red dwarf, it’s like a brown dwarf—has seven planets around it that are, in many respects, very terrestrial. It’s more like the Galilean system around Jupiter. It’s a different class of solar system that has planets that could be habitable. Could life arise and civilisations form on those types of systems? “It will be interesting to see how this field progresses and how many years we are away from actually discovering life. ” Astrobiology has evolved from characterising simply whether or not life exists in a zone where liquid water is on the surface to searching for atmospheric biosignatures, or even spectroscopic signatures. This is described in Chris’s book. If you point a telescope towards an exoplanet that’s relatively close and see the infra-red spectroscopy of a sun bouncing off it and coming to Earth, you could see a signature that indicates whether you have chlorophyll on the surface. If the chlorophyll signature comes and goes with some kind of seasonal variation (you can see the seasons on the exoplanets come and go because you know the orbit), then you would say this has got to be a sign of life. It will be interesting to see how this field progresses and how many years we are away from actually discovering life. We may find that discovery on exoplanets long before we find it on a planet like Mars or Europa. Yes, definitely. So much space is available in terms of DNA sequences or amino acid sequences. Even if you have life restricted to using just the same four nucleotides—which is probably not the case—or even the same 20 or 21 amino acids—which we know is not the case—there’s so much variation that you can never sample that variation within the entire history of the universe on all the stars that exist in the universe. It’s just impossible. The life forms that have evolved here on this planet have followed—in the possible paths that could exist—a very, very narrow path. It’s very easy to imagine that life out there would be drastically different from anything that we’ve seen here on Earth and that it could live under different conditions to what we know of today, easily. That comes from this exploration of the subsurface and all we’re seeing is slight variations of terrestrial life. Slight variations in how the genetic code is translated into a protein. Just normal Darwinian evolution occurring under an extreme environment leads to these strange colonies of syntrophic organisms that interact in ways that we’re still trying to figure out. They’re signalling to one another using chemical processes, actually using electrons directly. If bacteria can do that, why not entire organisms? So yes, you’d expect alien life to be completely different to what we encounter here on Earth, and what we encounter here on Earth is pretty alien itself."