The Aliens Are Coming!

by Ben Miller

  A CLOCKWORK ORANGE

  Let’s start with what physics can tell us about a larger-than-life Earth planet. No prizes for guessing that a bigger Earth means stronger gravity, but what effect will that have on the land, oceans, and atmosphere? Interestingly, quite a lot. Calculations show that plate tectonics kicks off when planets are roughly Earth-sized, and switches off when they reach around five times Earth mass. At the lower bound, you get deep oceans and large continents; by the time you reach twice the Earth’s mass, stronger gravity produces shallow oceans with island archipelagos.

  That’s exciting, because shallow oceans and islands, as we know, are great for biodiversity. Even today, we find the interiors of large continents and the depths of our deepest oceans more sparsely populated, while islands and lagoons teem with life. But we are getting ahead of ourselves. Would we expect life on a super-Earth to follow the same path it did here on Earth, with single-celled life emerging in the oceans, evolving complexity, then invading the land?

  Again, in my view, the path may be different, but the destination remains the same. According to our pet hypothesis, single-celled life started in the vent at least twice: once as bacteria and a second time as archaea. Anything that happened more than once is a prime candidate for convergence, so we can assume that single-celled life is a given. Both bacteria and archaea then navigated the next step; namely, they weaned themselves off the electrical energy of the vent, and learned to harness light energy, also known as photosynthesis.

  Of course, this early photosynthesis involved using light energy to rip electrons from chemicals that surrounded the vent: Hydrogen sulfide, for example, was a favorite; iron was another. Those electrons were then forced on to molecules of carbon dioxide, creating sugars. Eventually, in one type of cell only, the cyanobacteria, it gave way to a much more complicated, but altogether more successful process: oxygenic photosynthesis. Here, light energy was used to rip electrons from water, also creating sugars, but this time releasing oxygen as a waste product.

  Primitive photosynthesis, in other words, emerged several times; oxygenic photosynthesis only once. To my mind, that means we have to surrender to the possibility that other Earths and super-Earths will not be flooded with highly combustible oxygen. But that needn’t cramp our style. After all, free oxygen was a huge problem for primitive life. Not only was it toxic, but it oxidized atmospheric methane, removing a vital greenhouse gas from the atmosphere and triggering a Snowball Earth in the form of the Huronian glaciation.

  Eventually, of course, life adapted, and eukaryotes which could burn oxygen in their mitochondria came to rule the Earth. But couldn’t eukaryotes have evolved anyway, without the oxygen problem? Endosymbiosis, which created the eukaryotic cell, has happened more than once; to take a notable example, just as we think an archaeon engulfed and enslaved a bacterium to produce the eukaryotic cell, so we believe that a eukaryotic cell engulfed a cyanobacterium to produce the plant cell.

  The eukaryotic cell is the McLaren P1 supercar to the prokaryote’s Mazda MX-5; once it appears on the scene, the brakes to complex multicellularity are well and truly off. Here on Earth, complexity has arisen in animals, fungi, plants, and algae, and it’s a fair bet it will emerge on our super-Earth, too.24 Which complex forms will first populate the oceans, however, is anyone’s guess. The strange creatures of the Ediacaran are probably our best rule of thumb, but who knows how things will progress from there?

  All we can rely on, really, is the same extraordinary adaptive power that we find here on Earth. If some single-celled organism does manage to crack oxygenic photosynthesis, no doubt plant-like forms will invade the land just as they did here. They might not be green, of course. No one is entirely sure why chlorophyll absorbs mostly blue and red light: It may just have been the nearest pigment at hand, or it may be optimized in some way to the kinds of light photons that make it through the atmosphere. Whatever the answer, there’s no reason that alien chlorophylls would have to be green. To our eyes, the plants on an orange dwarf planet could just as easily appear yellow, or even black.

  And if oxygenic photosynthesis fails to emerge, well, no doubt life will find another way. Complex multicellular organisms that use sunlight to synthesize sugars—a weird cross between a plant and a fungus, perhaps, or a bioluminescent slime mold—will eventually populate the oceans and then the land. Once they do, other complex creatures that are capable of eating them will follow.

  Again, none of their body plans would necessarily be recognizable, but weapons, armor, jointed limbs, eyes, mouths, and brains have evolved so many times here on Earth it’s reasonable to assume they will put in a regular appearance. Maybe the thicker atmosphere will encourage flight, and the air will swarm with all manner of airborne creatures; maybe the many island habitats will produce a greater diversity of terrestrial life than here on Earth. We can’t be sure. Eventually, however, one or more intelligent species will develop civilization, and that’s when the real fun will start.

  BACK TO THE FUTURE

  The possibility that super-Earths are even more habitable than our own planet brings one thing into sharp focus: any alien civilizations we do find are likely to be much older than our own. That makes it hard to know what to look for. It’s hard enough to imagine where human civilization will be in five years, let alone an alien civilization in 500 million. How would such planets show up in our telescopes?

  Kepler 62 is a perfect example. Discovered on April 18, 2013, it’s an orange dwarf star roughly 1,200 light-years away in the constellation of Lyra. Not only might it be as much as eleven billion years old, but it also has two super-Earths in its habitable zone. Assuming that the Earth is average, and it takes four billion years to raise a technological civilization, that means intelligent communicable alien life could have existed on either or both of those planets for a billion years.25 Where do we start? What do we look for?

  We certainly have no way of predicting what one-billion-year-old technology would look like. But given what we know about life here on Earth, we can still make a shopping list of things to look out for. From the Second Law of Thermodynamics we know that all life, no matter how intelligent, dissipates energy as heat. Heat, as you know, is essentially infrared light. So all we have to do is point one of our infrared space telescopes at a nearby orange dwarf with super-Earths in its habitable zone and see if they are giving off a splurge of infrared light, right?

  Sadly not. Even though orange dwarves are far dimmer than our own Sun, they are still way too bright for even the next generation of infrared telescopes such as the James Webb to be able to pick out the heat signature of a civilization. We might have more luck picking out what’s known as a Dyson sphere—a civilization which has blacked out its home star with light-absorbing satellites—but there are lots of darkish things in the sky which emit in the infrared, such as protostars surrounded by dust, making their existence very hard to prove.26

  As I hinted earlier, however, it might be within the capabilities of the James Webb, and indeed the forthcoming ground-based European Extremely Large Telescope (E-ELT)27 to pick up enough infrared from transiting super-Earths to be able to work out what they have in their atmospheres. We could look for the distinctive spectra of oxygen and methane, for example, both of which we know are produced by life here on Earth, or pollutants such as chlorofluorocarbons (CFCs). But to really examine the infrared given off by nearby super-Earths we are going to need something game-changing.

  And that something might just be NASA’s New Worlds mission. Currently at the drawing-board stage, New Worlds is an ingenious way to solve the problem of life-bearing planets being very dim compared to their home stars. Essentially, a space telescope is launched together with an occulter, a colossal starshade which can be maneuvered to block out the light of the home star so that the planets show up. That way we can get a clear look at both the infrared and the visible light that such planets give off, and maybe even resolve surface features like oceans and land masses. Imagine the exci
tement if the images show networks of light, just as you might see on the dark side of Earth.

  CLOSER TO HOME

  So much for Earths and super-Earths. What other types of planet might harbor life? The first place to look, obviously, is our own solar system, where currently there are two leading candidates: Europa and Titan. Europa, you’ll remember, is one of the four moons of Jupiter picked out by Galileo in 1610, photographed by the Pioneer and Voyager probes in the 1970s, and last visited by NASA’s Galileo spacecraft in 2003.28

  Crucially, the Galileo mission discovered that Europa is an icehouse world, with a warm saltwater ocean contained within a crust of ice. There are clays sitting on top of the ice, suggesting a recent collision with an asteroid or comet; as we know, comets and asteroids also carry organic materials, so there’s a real chance Europa’s ocean is seeded with long-chain carbon molecules. Not only that, but the Hubble Space Telescope has recently spotted plumes of water vapor billowing out from Europa’s south pole, suggesting that we might not have to dig through the ice to sample its ocean.

  There are two missions slated to launch to Europa in the early 2020s. The ESA’s Jupiter Icy Moon Explorer (JUICE) will arrive around 2030, though NASA’s as-yet-untitled Europa mission might get there first if it manages to piggy-back their new Space Launch System. As the name suggests, JUICE will also fly by Ganymede and Callisto; the NASA mission, on the other hand, will focus specifically on Europa. By the time they’re done, we’ll know exactly what temperature the ocean is, how deep, and how salty. Even more excitingly, the NASA mission may yet attempt to fly through one of Europa’s water plumes with its mouth open to look for interesting chemistry.

  If it’s looking positive, no doubt a landing mission will soon follow; anything from a probe that touches down near the south pole to sample surface water from the plume, to a submarine capable of burrowing down through the ice into Europa’s ocean. What might the life-forms down there look like? The short answer is we have no idea. Assuming we don’t come face to face with the Europan equivalent of the Kraken, the smart money would be on some form of microbial life. Beyond that, we would be looking for complex carbon molecules—things like amino acids and sugars—but, of course, Europan life might use a completely different suite of carbon molecules from the ones we find here on Earth. Even if we find it, we might not immediately recognize it.

  Titan is another enticing prospect, although a new mission to follow up on the ESA’s Huygens probe is still several decades away. Titan, you’ll remember, is truly an alien world. Its climate and terrain are remarkably similar to our own, except methane takes the place of water, and water ice takes the place of rock. Methane clouds float through its thick nitrogen atmosphere, showering methane rain into lakes and dumping methane snow in its mountains.

  Here, the most exciting mission would be one where a submersible is landed on one of Titan’s methane oceans, and explores the depths for signs of life. Could its methane lakes provide the perfect solvent for silicon chemistry? Silicon belongs to the same chemical group as carbon, and is also capable of forming long-chain molecules. Might it be possible that complex life could evolve on Titan, only based on silicon rather than carbon?

  The astronomer Maggie Aderin-Pocock thinks so; in a 2014 article she proposed that such aliens might take the form of enormous floating jellyfish, buoyed by enormous bladders, sucking in atmospheric nutrients through giant mouths, and communicating with one another via pulses of light. Oh yes—and their bottoms would be orange to camouflage them in the hazy Titanian skies. But if you think that’s weird, you need to know about Vadim Tsytovich and his living clouds of dust.

  SEARCHING FOR THE CORKSCREW

  Might clouds of interstellar dust be alive and have seeded the first life on Earth? That’s the intriguing proposition of the veteran Russian plasma physicist Vadim N. Tsytovich. In 2007 he published a speculative paper in the New Journal of Physics in which he described how plasmas—that’s clouds of charged particles to you and me—might actually organize dust grains into self-replicating helical structures that tick every box for living things.

  Plasma, as you may know, is the fourth state of matter after solid, liquid, and gas; essentially, it’s what you get when gas molecules break down to form charged particles, or ions. A classic example would be a neon sign, a glass tube of neon gas that becomes a light-emitting plasma when it has electricity passed through it. Another would be an electric spark, where free electrons from cosmic rays or background radiation are accelerated by an electric field, and collide with air molecules causing them to form a plasma. Electricity then flows through the plasma, producing light, heat, and sound.

  Although we don’t tend to come across them that often on Earth, plasmas are actually one of the most abundant forms of matter in the universe. Not only are there vast filaments of plasma out in intergalactic space, but we also find them in interstellar molecular clouds, in the proto-planetary disks that surround young stars and the upper atmosphere. In all these cases they are mixed with dust, which they organize into fascinating structures known as “plasma crystals.”

  In modeling such crystals, Tsytovich discovered that they have some remarkably lifelike properties. Essentially, under the right conditions they are capable of forming double-helical structures that are highly reminiscent of DNA. Not only does the width and length of the helices change, providing a way of encoding information, but in some simulations they would divide into two, effectively reproducing themselves.

  We have yet to create such structures in the laboratory, but Tsytovich is convinced that the helical dust structures within plasmas exhibit all the properties of living matter. After all, they feed on the energy of the plasma, they reproduce, and they evolve into permanent complex structures. Could they in some sense be alive? And, for that matter, where exactly is the boundary between living and non-living things? As Fred Hoyle suggested in his 1957 novel The Black Cloud, could there be intelligent beings made up of nothing more than electrically charged dust?

  COOKING UP SOME ANSWERS

  Last night I was preparing some pasta for my middle son. I took a small pan of boiling water, gave it a glug of olive oil, and chucked in a handful of pasta tubes. Ten minutes later I lifted the lid to check on it. All the tubes were standing up on end, crowded cheek-by-jowl on one side of the pan, surrounded by boiling water. From a jumbled mess in the bottom of the pan, they had been jostled into a highly ordered state.29 Why should that be?

  We see this sort of thing all the time in nature, but as yet we don’t quite have the physics to describe it. Our thermodynamics—our theory of how energy and information are related—has really only been figured out for systems that are in balance, or, as a physicist would say, equilibrium. But most systems in the real world aren’t like that. Supply a thing with energy, and more often than not it organizes itself. Thump a tank of water with a regular beat and you will produce a pattern of ripples. They may look pretty, but their deeper purpose is to dissipate the energy of your thumps as quickly as possible. In the same way, when I heat the bottom of the pan, the pasta organizes itself because that way it can dissipate the heat more rapidly into the room than if it were jumbled up.

  There is some very interesting work being done in this area,30 and it indicates that something very similar is going on with living systems. The gravitational energy of the Sun needs dissipating. The Sun becomes layered, and initiates nuclear fusion, radiating highly organized light. That light then enters the biosphere, where carbon molecules become ordered into life in order to dissipate the energy of that light. Life exists to speed the heat death of the universe.

  Our problem as organisms, of course, is that we don’t see the bigger picture. We see our existence as a battle, an attempt to maintain order in a world that demands chaos. But we are missing the point. In our struggle to stay alive, we are serving the universe because we are dissipating energy. The universe doesn’t want those fossil fuels in the ground, it wants them burned. What better way to d
o that than to throw up an intelligent civilization with an insatiable thirst for energy?

  Following that logic, intelligent life should truly be everywhere. Wherever there is an energy source we should expect to find that matter organizes around it, helping it to dissipate its energy as fast as possible. In the case of a star, one way is to form a solar system. Within the gas, dust, and planets of that solar system, matter will organize itself into spheres, weather patterns and life. The reason we developed intelligence and technology is the same one that caused bacteria to develop photosynthesis: It’s a great way to dissipate the energy of the solar system.

  There is nothing fundamental that separates life from non-life. It is all just matter. We are ripples. Seen this way, the aliens are everywhere. Some are no more than the smooth regular pebbles on the beach, or the bubbles of carbon dioxide in your fizzy drink. Still others are molds and fungi. Others are quantity surveyors. And others are helical crystals in clouds of dust.

  CHAPTER EIGHT

  MESSAGES

  In which the author quarries for a Rosetta Stone, and blasts the skies with Big Data.

  With what meditations did Bloom accompany his demonstration to his companion of various constellations?

  Meditations of evolution increasingly vaster: of the moon invisible in incipient lunation, approaching perigee: of the infinite lattiginous scintillating uncondensed milky way, discernible by daylight by an observer placed at the lower end of a cylindrical vertical shaft 5000 ft deep sunk from the surface toward the center of the earth: of Sirius (alpha in Canis Major) 10 lightyears (57,000,000,000,000 miles) distant and in volume 900 times the dimension of our planet: of Arcturus: of the precession of equinoxes: of Orion with belt and sextuple sun theta and nebula in which 100 of our solar systems could be contained: of moribund and of nascent new stars such as Nova in 1901: of our system plunging toward the constellation of Hercules: of the parallax or parallactic drift of socalled fixed stars, in reality evermoving wanderers from immeasurably remote eons to infinitely remote futures in comparison with which the years, threescore and ten, of allotted human life formed a parenthesis of infinitesimal brevity.—James Joyce, Ulysses