Outer space is not a comfy place for a human to be. Direct exposure will of course kill you in minutes, although not in the way many people think: your eyeballs do not pop out, and you have a good chance of making a full recovery if your exposure does not exceed 30‒90 seconds. But even when protected by a spacesuit or the walls of a spacecraft, the body is subject to stresses such as exposure to high levels of radiation that take a toll. This, and the sheer time required to travel the huge distances of space at the speeds likely to be achievable for manned craft, mean that for the foreseeable future humans are unlikely to go much further than Mars or, at a stretch, the moons of Jupiter. Travel outside the solar system is likely to be done only by proxy in unmanned, robotic craft.
If and when humans do establish a greater and more durable presence in space we may have the Waterbear, also called the Tardigrade, to thank. In an experiment in 2007, helpfully labeled ‘Tardigrades in Space,’ numbers of this tiny animal spent ten days in orbit without any protection and lived. They withstood the almost complete vacuum and temperatures ranging from of –272.8°C (which is very close to absolute zero) up to +151°C. They survived a dose of cosmic rays one thousand times as high as would kill a human and shrugged it off. When exposed to direct solar radiation in addition to the cosmic rays, a large proportion of the test subjects bit the dust (in as far as there is any in the near vacuum of space) but, still, many survived. No other multicellular animal looks to be remotely capable of this. Perhaps, in the long term, the characteristics that enabled them to endure will be of use to humans . . . or our successors.
A typical Waterbear is about the size of the full stop at the end of this sentence. Under a microscope it looks something like a roly-poly teddy bear – if a teddy bear were to have claws, red eyes and two extra pairs of legs. The phylum has been around, little changed, since at least the Cretaceous and perhaps the Cambrian, and is more closely related to velvet worms and arthropods than anything else. (In appearance, Waterbears are more like Velvet worms; in ubiquity, more like arthropods.) There are about 750 different species of Waterbear on Earth today, living in almost every conceivable habitat from ice shelves to hot springs, from the tropics to the polar regions, and from more than 6,000 meters up in the Himalaya range to marine sediments in the abyssal zone more than 4,000 meters below sea level. In the laboratory they can withstand pressure six times as great as that felt at the bottom of the deepest ocean. This animal is what they call a polyextremophile, happy in many different extreme environments.
But even though it is a home planet extremist, the Waterbear is also, like Goldilocks, partial to inbetween places that are neither too hot nor too cold, too hard nor too soft, such as marshes, dunes, beaches and freshwater and shallow water sediments. There are about seventy species in the tepid British Isles, where their habitat ranges from rare pockets of protected fenland to moss in the gutters of bog-standard houses in the cities. This fondness for moss has earned it another name: the moss pig.
A key to the Waterbear’s success is its ability to wait out the most unfavorable times in a dormant or cryptobiotic state called a tun, in which it sheds almost all the water in its body and hardens its vital membranes with a non-reducing sugar called trehalose. On Earth it can stay this way for 120 years. When the good times do return, the Waterbear emerges from its nap – a micro, aqueous phoenix – rather as one of those Japanese paper flowers unfolds from a wad when put into a cup of water, and carries on doing whatever it was doing beforehand, which was most probably searching for algae and tiny invertebrates to eat or other Waterbears with which to mate. A well-developed ganglion, a ventral nerve cord, two simple eyes and long sensory hairs over its body, mean this animal is far from insensitive. A fortnight after Waterbears have done the wild thing, the young hatch from fertilized eggs with a full complement of body parts and exactly the same number of cells as they will have as adults, like the homunculi of medieval and Renaissance lore. All they have to do is swell up.
The success of Tardigrades in space earned the Waterbear a ticket on the Living Interplanetary Flight Experiment, or LIFE, a mission launched in November 2011 to see how Waterbears and other organisms would fare over three years of sustained exposure to space on a journey to and from Mars’s moon Phobos. To join the crew of LIFE you had to be as hard as one of the drinkers in the bar scene in Star Wars, and a lot smaller, and no member of the animal kingdom apart from the Waterbears made the grade. So there they boldly went, alongside representatives from the kingdoms archaea, bacteria, plantae and fungi, in an experiment to test, among other things, whether the ‘seeds’ of life could be transported from one planet to another and survive. Unfortunately, the Russian spacecraft carrying LIFE got stuck in Earth orbit and then burned up on re-entry, so the experiment was lost.
For now, then, the idea of surviving any distance in space remains both speculative and untested. What of life already there? Humans have a well-established and possibly irresistible tendency to fill empty places with phantasms. And ever since space flight started to look possible, we have peopled outer space with these forms just as we once saw fairies and all manner of other beings in the woods. The science indicates, however, that if there is any life elsewhere in the solar system, it will almost certainly take much less florid forms than those our imaginations can summon and be more akin to some of the obscure and sometimes surprising microorganisms living in the harshest environments on Earth. The researcher Dirk Schulze-Makuch suggests that if there is any life in the oceans on Jupiter’s moon Europa the top predator would be a fearsome creature with mass of 1 gram. If the surface lakes of Titan, one of Saturn’s moons, are home to hydrocarbon-guzzling microbes they could, conceivably, be the size of boulders – more impressive in size, but still simple life.
How will we regard such discoveries, should they actually happen? It is easy to be dismissive. These would not, after all, be life forms we could talk to. But there is, I think, another way to approach the matter. Properly understood, even relatively simple life forms are marvels of complexity. If you’re in any doubt, take a little time to look at the animations of molecular biology within a cell that can be found on the Internet.
And what of intelligent life beyond the solar system? There are between one and four hundred billion stars in our galaxy and given what we know of star and planet formation, it is almost certain that planets capable of supporting life orbit a significant proportion of those stars. Further, given the age and size of our galaxy (at least 13.2 billion years, with the hundreds of billions of stars distributed in a disc 100,000 light years across), there has been plenty of time and space for intelligent life and civilizations more advanced than ours to have evolved millions of years before we did. And from this it would seem to follow that we should be able to see evidence of them, either because they would have transmitted electromagnetic signals (which would span the galaxy in a few tens of thousands of years) or because they would be capable of deploying robotic craft able to go everywhere in the galaxy within twenty million years. Humans have already been sending signals into deep space deliberately for decades, and robots capable of interstellar travel may be only a few decades or hundreds of years away. Some argue that a civilization at least as technologically advanced as ours should, therefore, be evident across the entire galaxy. And this is before we even take into account the hundred billion or so other galaxies in the visible universe. To date, however, we have seen no signal or evidence of the existence of another intelligent civilization anywhere.
The contradiction between the idea that intelligent life elsewhere in the universe is extremely probable and the lack of evidence for it (which is known as the Fermi paradox after the physicist Enrico Fermi, who first articulated it in 1950, as the ‘Where the hell are they?’ problem) can be explained in several ways. Maybe other intelligent life is wise, content to live within limits and leave us alone. Maybe it is watching us silently and waiting until we are wise enough to be let into the club. (And maybe it will destroy us without hesitation if it sees reason to do so.) These, and other explanations, cannot be ruled out at this stage, but a better one may be that something makes the evolution of intelligence and its endurance once it has evolved much rarer than has been supposed.
The apparent absence of any intelligent life apart from us in the galaxy and to some beyond suggests that there is a ‘great filter’ or ‘improbability barrier’ that blocks the evolution of all but the very simplest organisms almost everywhere. Earth, on this reasoning, is a rare exception. We have already passed through one or more of these barriers (which may include the evolution of eukaryotic cells and of multicellular life in the first place and of having a planet free of shocks that destroy all life for enough time afterwards for intelligent life to evolve). But – more disturbingly – we have not yet run into the biggest barrier of all, which, the philosopher Nick Bostrom suggests, could be an almost invariable tendency of advanced civilizations to destroy themselves.
A great filter may be the best explanation of our apparent solitude but, as has often been said, when drawing conclusions about the probability of ‘intelligent’ life, we should not forget that when it comes to hard data we have a sample size of one. All we can say for sure is that we exist and that we are intelligent beings for at least some of the time – or at least that we have good grounds for believing ourselves so to be; the possibility that we are simulations inside some great machine cannot be ruled out completely.
In a half-joke, the cosmologist Stephen Hawking calls humans a ‘chemical scum’, so tiny and insignificant are we in the vastness of space. The physicist Paul Davies disagrees: ‘It’s very easy to denigrate human beings because we’ve made a mess of the planet and we do silly things, but. . .we have the spark of rationality and the ability to decode nature that makes us very special.’ Similarly, the physicist David Deutsch says, ‘We are a chemical scum that is different’ – notably our ability, through science, to understand and explain the cosmos as it really is.
For as long as we have been human we have looked in wonder at the stars. But for almost all that time we have had no idea what they really were. Only in the early twentieth century, following the discovery of radioactivity, did scientists begin to understand what actually makes them shine, and to develop a robust explanation of star formation, duration and dissolution.
Today we even understand quasars, the most distant and powerful phenomena in the known universe. But, according to Deutsch, even more remarkable than the quasar itself is:
the capacity of one physical system, the [human] brain, to contain an accurate working model of the other, the quasar. And not just a superficial image of it – though it contains that as well – but an explanatory model, embodying the same mathematical relationships and the same causal structure. That is knowledge! And if that wasn’t amazing enough the faithfulness with which the one structure resembles the other is increasing with time. That is the growth of knowledge.
In contrast to the vast majority of places in the universe, which are dark and cold, we live in a place that is saturated with information and energy. This has made possible creatures such as ourselves with the capacity to already ‘be’ everywhere in the universe through the use of reason and imagination in a way that nothing else we know of can be. Our ability to understand the cosmos – which is likely only to increase for as long as intelligent life continues – even has the potential to influence events at the cosmic scale.
Such grand claims and cosmic dreams may seem to be remote from our ordinary concerns in a crowded, hungry and rapidly changing world. But, Deutsch insists, they are of paramount importance. We may, for example, be able to intervene in the processes of a main sequence star such as the Sun in order to prolong conditions suitable for life in the solar system. This depends ‘on what people do: what decisions they make, what problems they solve, and on how they behave towards their children’.
Philosophers from Plato to Spinoza and Hegel have argued that those who act freely in accordance with what is revealed by reason will be loving towards others. History is a sometimes harsher master than philosophy. Science and reason have often been harnessed by political and religious systems to hugely destructive ends. The discovery of radioactivity led to the creation of nuclear weapons as well as insight into the nature of a star.
The tiny Waterbear can endure almost unbelievably harsh conditions and return to life as if nothing had happened. Further study of its remarkable abilities may lead to specific lessons in how to enhance human physical resilience in the face of challenges coming our way. We do not know whether collapse and catastrophe or something generally much more positive will result from our activities in the twenty-first century. But perhaps we can take this little bear as a talisman: a real-world, microscopic version of the ancient Egyptian scarab, representing endurance, regeneration and hope.
Excerpted from The Book of Barely Imagined Beings, Copyright © Caspar Henderson, University of Chicago Press, First published in the UK by Granta Books.