Are you in the zone? If so, why?
To start at the beginning, you do know what phlogiston is, or was, I hope?
Nowadays we accept that when something burns, it is swallowing oxygen. But before oxygen was discovered, people thought that when material burns, it is giving off something, not absorbing it. That’s why if you burn a piece of wood, the ash weighs less than the wood did to start with. That thing that it loses is phlogiston.
Today we appreciate that while this makes perfect sense, it is also untrue. So instead, let’s take aim at an even simpler target.
Like the origin of the universe, the question of life beyond the Earth is a knotty one that is now becoming a matter of experiment and evidence, not speculation. There’s just one problem. All our knowledge of life comes from one planet, the one you are sitting on. (Unless you are reading this on the International Space Station. In that case, please get in touch.)
Much of what’s written about “astrobiology” (aka exobiology) suffers badly from this drawback. It’s easy to find articles proving that (for example) life would find it tricky to get going on a planet with no Moon, or in a solar system without Jupiter or a comparable giant planet, or without a strong magnetic field, or in a multiple star system. While we are now getting to appreciate the sheer
variety of exoplanets (planets of stars other than the Sun), the literature is still crammed with anthropomorphic stuff assuming that other life will use DNA, or evolve by natural selection. Certainly there is little material on the idea of life developing elsewhere than on a planetary surface.
To be clear, I don’t know that these ideas are wrong. But I do know that today’s astrobiologists are more or less like people who have only ever spoken Danish but who are now writing books on the world’s languages. As soon as they encounter Japanese, English or Swahili, their current ideas will seem absurdly under-informed.
It may strike you that there is not much we can to clear this miasma until we find some extraterrestrial life. Not so! There is one idiotic concept in astrobiology that we can kill off right now.
This idea is the “habitable zone.” It sounds rational. It’s essentially the region round a star where you might get liquid water and balmy (but not too balmy) conditions on planetary surfaces. In other words, places like Earth. The brighter the star, the farther out this annulus of la dolce vita may be found.
What’s so terrible about this notion? Everything. First, it’s stupidly anthropomorphic, being based on the idea that liquid water is the starting point for habitability. Also, whether a specific planet is in the zone can change over time. Mars has had liquid water, but no more, because it has lost too much of its atmosphere.
But at the risk of falling into the same trap, let’s just think what we know about life on Earth. It works by passing information on building and running creatures down through generations, with slow change over time. It involves raw materials. It needs energy. The rest is detail.
In this context, it’s easy to find places that have energy and raw materials well beyond the definition of the Sun’s habitable zone. What about Io, the volcanic satellite of Jupiter? Even more obvious, how about Europa? Like Io, it’s one of the four big satellites of Jupiter discovered by Galileo Galilei in 1610. It has a shiny ice carapace below which there is probably liquid water, kept warm by tidal energy.
The Jovian system is massively beyond any possible definition of the habitable zone,
but is just one place we know of that has all the necessities for life. Indeed, another place that may match the criteria is the interior of Jupiter itself. So can we please get out of this sloppy linguistic
habit as soon as possible?
