Seeds of Life?

I thought this extract from my old book Companion to the Cosmos might be of interest in the light of the news about the system TRAPPIST-1

 

interstellar chemistry Many molecules (more than 80 by the mid- 1990s) have been discovered in clouds of gas and dust between the stars. Although the nuclei of different elements are built up inside stars by the processes of nuclear fusion, under the conditions of heat and pressure inside a star atoms cannot combine together to make molecules. So all of the variety of molecules seen in interstellar space must have been produced by chemical reactions going on in the clouds of gas and dust where we detect those molecules today. The complexity of the reactions involved in this interstellar chemistry is indicated by the complexity of some of the molecules identified — several contain 10 or more atoms, and one is the amino acid glycine (NH2CH2COOH), an essential building block of life on Earth.

Many of the molecules found in interstellar space are made up from carbon, oxygen and nitrogen (the most abundant elements manufactured from hydrogen and helium inside stars), together with hydrogen itself (see CHON). Simple compounds made up of carbon and hydrogen (CH) and carbon and nitrogen (CN) were discovered at the end of the 1930s, using optical spectroscopy. But the first real progress towards an understanding of interstellar chemistry came in the 1960s, when suitable radio astronomy techniques were developed to identify the characteristic radiation of polyatomic molecules in space. The hydroxyl compound (OH), water (H2O), ammonia (NH3) and formaldehyde (H2CO) were soon identified.

In the 1970s, astronomers were surprised by the variety and complexity of organic molecules (that is, molecules that contain carbon atoms) found in space. These included ethyl alcohol (C2H5OH), which is present in one large complex of molecular clouds (known as Sgr B2) in sufficient quantities to make 1027 litres of vodka. As well as these complex molecules, interstellar clouds must also contain simple compounds such as oxygen (O2), nitrogen (N2), carbon dioxide (CO2) and hydrogen (H2), which are stable and form very easily from the basic atomic ingredients that are known to be present.

The key to interstellar chemistry is the presence of a large amount of carbon in the form of grains of graphite in these interstellar clouds. These show up from the way in which they absorb visible light from more distant stars, which can be explained by the presence of elongated grains about 0.1 millionths of a metre long, mostly made of carbon but with water ice and silicates present as well. It may seem odd to think of interstellar clouds as being laced with soot, but carbon is one of the most common products of nucleosynthesis inside stars, and there is a family of stars (known as carbon stars) which are shown by their spectra to have atmospheres relatively rich in carbon, and which vary regularly, puffing in and out with periods of a year or so, and ejecting material into interstellar space as they do so. The evidence suggests that many (if not all) stars go through a phase of such activity.

Most of the complex molecules are found in unusually dense clouds in space, where there is enough of the sooty dust to act as a shield, protecting the molecules from the strong ultraviolet radiation from nearby young stars, which would tend to break the molecules apart. These are exactly the clouds in which new young stars, and their associated planets, are forming. The molecules are probably built up by reactions that take place on th surfaces of dust grains, where atoms can “stick” and have a chance to interact with one another. The molecules later evaporate from the surfaces of the grains. All of this makes it extremely likely that new planets are “seeded” by quite complex molecules early in their existence; any molecules present in the interstellar clouds from which stars and planets form could easily be deposited on a planet by, for example, the impact of a large comet.

Interstellar chemistry involves not only interactions between material in gaseous form and the solid grains of dust in molecular clouds, but also interactions with the stars themselves. It is harder than you might think for such a cloud to collapse and fragment to form stars. When it starts to do so, gravitational energy is released in the form of heat, making the molecules in the cloud move faster and generating a pressure which resists further collapse. The cloud can only collapse further if this excess heat can be disposed of, in the form of electromagnetic radiation. This is produced by the molecules of compounds such as carbon dioxide and water vapour in the cloud. Then, when a young star begins to form, it produces copious amounts of ultraviolet radiation, which would tend to blow the cloud apart. Fortunately, though, the grains of carbon dust (or soot) in the cloud absorb the ultraviolet radiation and re-radiate it in the infrared part of the spectrum, at wavelengths which can escape much more easily into space. Carbon dust grains, and molecules produced by interstellar chemistry, are essential in the cooling processes without which the stars which edge the spiral arms of a galaxy like our own Milky Way would not form in such abundance.

In the early 1990s, astronomers found evidence of a complex molecule in the form of a ring in interstellar clouds. The evidence came from the NASA Ames Research Center, and concerned the detection of features interpreted as those of the spectrum of pyrene (C12H10), in which a dozen carbon atoms are joined together in a ring, with ten hydrogen atoms attached to it around the outside. This provided the first independent support for controversial claims made by Fred Hoyle and his colleague Chandra Wickramasinghe in the 1970s and 1980s.

Hoyle and Wickramasinghe have gone further than any other astronomers in claiming that some of the features seen in the radiation from molecular clouds can be explained in terms of very large organic molecules called polymers. These form chains of repeating units. The basic component of a polysaccharide chain, for example, is the so-called pyran ring, a hexagon made up of five carbon atoms and one oxygen atom (C5O). These rings link together to make a chain when one of the carbon atoms joins on to another oxygen atom, which itself joins on to the next pyran ring in the chain, and so on. Once formed, a pyran ring shows one of the fundamental properties of life — it acts as a template, encouraging the formation of more identical rings which join up in a growing polysaccharide chain.

Hoyle and Wickramasinghe have suggested that even more complex polymers such as cellulose may already have been directly revealed by their spectral signatures in radiation from these clouds (other astronomers dispute this interpretation of the data), and that molecules of life itself may be present in the clouds but not yet detected. Once, these ideas were derided as so heretical that just voicing them may have cost Hoyle the Nobel Prize he deserved for his work on nucleosynthesis. In fact, the team has an impressive track record (they were, for example, the originators of the idea that interstellar clouds contain grains of soot, an idea established now beyond reasonable doubt), and their ideas look far less extreme now that glycine and pyrene have both been identified in space.

At the very least, it is now difficult to escape the conclusion that when a planet like the Earth forms its atmosphere and oceans are soon laced with complex organic molecules. Since interstellar chemistry seems to be the same in molecular clouds across the Milky Way, this suggests that the complex chemistry of other planets would be similar to that of the Earth, and that where life has evolved from that complex chemistry it should be based on the same sort of compounds (including amino acids) that we are.

 

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A Science Fiction Taster

I am putting together a collection of my science fiction short stories, to be published by Elsewhen Press.  This is one that will not be in the collection, because it was a collaboration with the well-known science writer Marcus Chown.  So I thought I would offer it here as a taste of things to come, with thanks to Marcus for permission to share it with you.

Survival of the Fittest

By John Gribbin and Marcus Chown

 

 

When Darwin coined his famous theory concerning evolution by natural selection, he had in mind a different kind of fitness from the benefits we gain from physical exertion.

 

 

“Don’t go too far, Jan.” Frances Reese’s warning was still ringing in Du Toit’s ears as he cut the jet pack and attempted a landfall a kilometre from the cluster of spacecraft. The terrain a hundred metres below was largely hidden, cloaked in mottled shadow, but it was unlikely, in such low gravity, that he would come to grief by dropping blind. Still, there was no sense in taking chances. He peered down into the gloom, trying to make out something as he fell in a long, leisurely arc towards the surface.

He had had to get away, get some precious solitude, and even mother-hen Reese had relented, grudgingly, when he’d told her, in all seriousness, that he was set to explode. It was true; make no mistake. He might have been the most even-tempered and phlegmatic spacer on the long flight out to the Dragon, but intolerable pressure had built up inside him like a head of steam, until he didn’t like to think what he might do to any of his crew-mates if he didn’t crack a release valve, and soon.

Of course, he had known exactly what to expect when he had volunteered for this crazy mission. But, somehow, recognising intellectually the pitfalls of overcrowding on a long interplanetary flight had not prepared him for the nerve-jangling click of Wenzel’s jaw as he munched each and every mouthful, or Finnegan’s deathly bleak depressions which infected the rest of the crew like an emotional cancer, or even the innocuous but endless chess games between Xu and Bertorelli – the board with its magnetic pieces always cluttering up the rec room table (why couldn’t they play on the computer, for God’s sake?) and never leaving enough room for a food tray.

Irritating habits, idiosyncrasies, petty selfishness magnified to enormous proportion: the old, old story. No doubt he, Du Toit, irritated the hell out of half the crew with a dozen microscopic mannerisms. He knew for sure that most of his colleagues took exception to his keep-fit routines. “Training for the Olympics, Jan?” Every time he tried to work out in the limited space available he’d get the same crack from Xu, usually followed by a remark about how humankind had reached the top of the evolutionary tree by intellectual superiority, not brute force. Maybe that was a comfort to someone who stood little more than 150 centimetres high and weighed well under sixty kilos back on Earth. But he’d never seen why being intellectually gifted gave you a license to let your body run to seed, and he didn’t care who knew his views.

Perhaps, in a myriad of small ways, he was continually getting his own back. That sadistic thought had helped him to keep sane and maintain his outward cool through all these difficult months. At least he hadn’t hit anyone, which was more than could be said for Jackson. Who would have believed they’d have to transfer meek and mild Jackson from the Hoyle to Aries II in mid-flight, with all the risks of that manoeuvre, just to get him away from Saha and prevent the first interplanetary murder?

He felt the metal claws on his boots snag the surface, and flexed his legs to take up the momentum. The Sun was directly overhead, forever at zenith now that the comet was no longer spinning, but it was still too distant and dim to illuminate the surface properly. But some detail was visible close by. Where the ice wasn’t streaked with dust it seemed to glow eerily as if from an internal light source, deep down inside. He’d seen the same ghostly effect on Earth, walking across freshly fallen snow on a starry night.

Du Toit turned off his helmet light and felt himself poised between the stars and the faint Sun and the glowing surface of the comet. He seemed to be in a valley, or at least a depression of some kind, cupped in a giant hand carrying him through space. He had to remind himself that this really was a world, with a substantial surface area, with hills and cliffs, mountains and crevasses. It was difficult to reconcile this reality with the image of a tiny speck – for that was all it had been – that he had watched for three months in the Hoyle’s 50-centimetre finder.

When he clicked the full beam of his light back on, the cone of illumination lit up a wide cleft in the ice with sheer ice walls towering on both sides of him. The wall to his right must be 50 metres away, but the left-hand wall was just a few strides from him. His gentle landing, floating down almost parallel to the ice face, could so easily have become a tumble down the nearly vertical face. Back home they’d call the feature a kloof. Du Toit’s Kloof! How about that? He would talk to Reese on his return to the ships and request that they name it after its discoverer. He had no idea how long the feature would persist in the heat of the Sun once the ice started buckling and boiling off into the vacuum, but it was the nearest he would ever get to immortality.

He began walking parallel with the ice walls – long, looping, comical strides, each of which ended in an awkward manoeuvre he had yet to perfect, in which he corkscrewed the claws of one boot into the ice to gain purchase for the next stride and to ensure he didn’t bounce off into space. All this was unnecessary. He had a jet pack and, if he floated away in the minuscule gravity of the comet, all he had to do was orient the nozzle and trigger a short burn to nudge himself back down to the surface. But that would be cheating. He wanted to walk, or at least practice what laughably passed for walking on this oversized snowball. He had spent too much time these past few months floating inside a spaceship or tethered to one or another of the vehicles, directing the burns that cancelled the angular momentum of the comet. He wanted at least the pretence of normality, and that was why he was out here, doing silly walks on a chunk of primordial ice between the planets.

In two days time Reese would order the big burn that would change the course of this ponderous iceberg of the vacuum. Only a couple of hours before, they had finished orienting the fusion engines. So Reese had given them all a much-needed forty-eight-hour break from their daily toil. And he had taken a walk in the dark rather than oblivion in his bunk. Sleep wasn’t what he needed. No, he needed a breath of fresh air. Metaphorically, of course.

The kloof had tributaries, narrow fissures which swallowed up the light of his helmet beam. Du Toit stopped and peered into one. He could see at least a hundred metres into the crack, which stretched downward into the comet, maybe to its rocky core. He would never know, since a sharp bend interrupted his line of sight. Better watch out for crevasses, he reminded himself. His quest for solitude had taken him out of radio touch with the ships. That, perhaps, was unwise. But he would be careful.

What the scientists of a century ago would have given for an opportunity like this! A human expedition to a comet, an opportunity to test out theories of the origin of the Solar System. But nobody on this expedition was interested in the scientific possibilities, whatever nonsense the Reunited Nations seemed to be feeding the news media as a cover. Wouldn’t they be getting a surprise soon! To the astronauts, the Dragon was just a missile which had to be steered in a certain direction. A ready-made, deep-frozen atmosphere, to be dumped on Earth’s Moon. But a vestige of scientific curiosity remained. We ought to make some sort of effort to send back some data on the comet, thought Du Toit, idly. After all, there won’t be another opportunity like this.

He swung his helmet out of the crack and began examining closely the wall of the kloof. It had a curious texture, looking like fabric; narrow, sinuous runnels were crisscrossed by dust veins. He pressed the palm of his glove against the wall and convinced himself that he could feel the roughness. He had a good imagination.

Thoughts of scientific investigation slid from his mind as he imagined the great bulk of the comet, a sleeping Dragon waiting to be warmed into life as it neared the Sun. This was a landscape that no other eyes would ever see, let alone investigate scientifically. He moved on, trying now to think of nothing at all, to blank out all the tedious events of the past months, using the walk to recharge his mental batteries. Breathing deeply, and leaping along rhythmically as he learned the trick of the twist in each step, he began to fall into a meditative, trance-like state, and felt fatigue seeping out of his bones. He glided to a halt, cupped in the bowl of ice, and turned slowly to see how far he had come. It was then that he felt the first, faint rumble beneath his feet.

Du Toit froze. His pulse rate and a dozen other physiological signs somersaulted off scale. What was that? Movement where there should be no movement, deep down inside the comet. The Dragon was coming to life – but much too early; it shouldn’t stir for weeks yet. For an age he stood motionless, with only the flutter of a muscle and the beating of his heart preventing the complete fusion of his awareness with the structure of the comet. He felt himself fusing with the ice, imagining layers upon layers of icy crystal plane stretching down into the cryogenic core. He felt that he could detect any microscopic slippage of these crystal planes. Poised on the knife-edge between comet and space, he felt for the heartbeat of the vacuum – but the rumble had stopped. With sudden relief, the answer came to him. The fusion engines! Reese must be testing the main drive. Of course!

Then the world fell apart. Literally. He was thrown loose from the ice and found himself floating in a shower of splinters as the comet convulsed beneath him and a great gaping canyon opened up before him, barely ten metres away along the floor of the kloof. A rising berg of ice, tens of metres across, nudged him to one side as it moved ponderously upward and out into space. Du Toit saw that he was heading for the nearest ice wall, and fast. A spacer’s instinct made him lunge at his tool belt, activate the emergency grapple line. There was no time to see whether the explosive harpoon buried itself in solid ice or powdered snow. The stars were obliterated, eclipsed by a moving mountain of ice. Then he hit, and darkness closed in.

When he awoke, he was floating. But the grapple line had held. Thank God. His head was fuzzy and his left elbow bruised and stiff. The suit had not been pierced. But when he triggered his jet pack, nothing happened. He was alive, but his principal means of propulsion was useless. He hauled in the grapple line, hand over hand, until once again he could hook his boots into the surface and ‘stand’ on ‘solid’ ice. How long had he been out? The needle on the gauge showed thirty minutes of oxygen used; given that he’d been unconscious and breathing shallowly, that meant maybe an hour had passed.

What had happened? The massive quake couldn’t have been anything to do with Reese. The Dragon, dormant since the birth of the Solar System, had hiccupped. They knew it would happen when the heat of the Sun got stronger – but not this soon. They were still out near Mars, and the Sun was too feeble to melt off even a film of surface ice. No, it had to be the fault of the expedition, somehow, with heat from the engines and the change in stresses caused by halting the comet’s spin combining to release an old pressure along a line of weakness that had been there since the dawn of time. But that was no excuse.

He began to pay out the grapple line, crawling now, not leaping, over the kloof floor. Something else was wrong. What was it? His fuddled brain tried to take stock of the surroundings. The Sun! Where had the Sun gone? It should be directly overhead; it had been before the quake. Where was the Sun? Scrabbling frantically onward, slipping and sliding on the ice, digging his toe claws into the ice to stop himself, Du Toit reached the canyon he had seen open up in the kloof floor. But it was no longer a canyon. There was nothing on the other side.

Trying hard to swallow panic, he craned over the edge, and found the Sun. It was down a sheer face of glistening ice. How could that be? How – then his brain finally understood, and Du Toit felt a cold hand seize him in its grip. Surely it couldn’t be. He closed his eyes for a moment, but when he opened them the scene was still the same.

In the light of the distant Sun he saw rubble and ice, great blocks of the stuff, occluding the stars: a flotilla of calved icebergs setting sail upon the sea of the vacuum. With him riding on one of them. Hoping against hope that it wasn’t too late, he tripped the Mayday transmitter.

 

What in God’s name was that?” Reese supported herself against the rec room wall as the groggy sleepers assembled. While they slept, she had been on watch, working, as always, at her desk console. Blood seeped from her nose where she had hit a support stanchion when the first big shock had struck. She pawed at the leaking droplets, but it did no good, only staining the sleeve of her tunic. As the myriad tiny droplets slowly settled and were dispersed by the air currents, she spoke through an incongruous pink haze.

Bertorelli proffered the tiny vacuum cleaner they used to clear up such messes, but she waved him aside, turning from one crew member to another as she sought an explanation of what had happened. Nobody had one. Then Finnegan, white from shock, blurted out “DuToit!” and Reese felt a sickness inside. He was out there, somewhere, a human needle in a landscape they hardly knew in the first place and which had now been twisted out of all recognition by – something. By forces they had failed to recognise or anticipate. By the unexpected – and the unexpected could mean the end for the whole mission, not just Du Toit.

“Mary, get an all-around scan working, at once. Bertorelli, see if Aries can be ready to fly. We may have to go out and find him.”

 

As Du Toit gazed down the seemingly endless cliff, his brain suddenly adjusted the perspective. The ‘cliff’ became a flat floor, and it no longer seemed endless. In fact, it was only a few metres across. He stood once again and ‘walked’ across to the other side. Looking over the edge, he saw the same scene repeated. He was on a small chunk of ice, a faceted, irregular lump. Secured by his clawed boots, he could roam at will over the surface, but there was virtually no gravity at all to hold him in place or give a sense of direction. In that case, he told his brain firmly, anywhere I am standing the ground is straight down beneath my feet. And don’t you forget it.

A sudden flash of light caught his eye, and he turned (slowly! carefully! this lump of ice might not be very big, but he preferred to stay on it rather than float off on his own) to look. What was it? Then another flash, slightly to one side, and he realised what was happening. The icebergs surrounding him were rotating, and like faceted jewels they were catching the light of the Sun as they did so. It was beautiful. But admiring the beauty of his surroundings wasn’t going to get him back to the safety of Dragon base. There was no reply to his Mayday, which meant that either his transmitter or his receiver were useless. Or both. He’d soon know; if Reese had heard the electronic cry for help she’d have the Aries off and running after him in a matter of minutes. After all, he couldn’t walk home.

Du Toit continued to stand quietly, watching the shifting display of glinting icebergs around him, conserving energy and oxygen. His own miniature world was also rotating, he noticed, so that the Sun had now ‘risen’ completely to the zenith and was dropping away behind him. Think! he commanded his still dazed brain. There’s no reply to my signal, and no sign of Aries, They haven’t heard me. He took a small drink of water from the tube next to his mouth and chinned the bar to release a stimtab. He’d have to pay the price of increased heart rate and higher oxygen consumption in order to clear his head. Maybe Xu was right after all. He wouldn’t get out of this hole by physical effort. What he needed was a bright idea, some intelligent scheme to signal his whereabouts to the others. C’mon, Jan, he subvocalised, show Mary you’re not just a big physical ape.

He began to feel better, physically and mentally, as the stimulants got to work. The Sun set behind him, and Du Toit saw the comet itself, the Dragon, rising high in the sky of his tiny world. So near, and yet so far. He felt colder in the dark, and, although his brain was clearing and he knew this was purely a psychological reaction, began to walk towards the horizon so that he could see the Sun again. Dig one boot in, and thrust backwards; unhook without pulling yourself to a halt; dig the other boot in, and twist; repeat indefinitely. The rhythm flowed back. And then he had an idea.

 

“He must be out of oxygen by now.” Bertorelli and Xu were together in the Aries II, floating free amongst the debris of the cometary convulsion. There was little doubt that Du Toit was out there somewhere, but where? Hopefully, they’d nosed among the fragments looking for a spacesuited figure, but to no avail. It was far worse than the proverbial needle in a haystack. He might be no more than a hundred metres away, but with no means of signalling his presence they’d never know, unless they struck very lucky indeed.

Xu thumbed the talkback button and spoke to Reese at Dragon base. “We’ll stay out here until we run out of air if you like. But I’d rather be carrying out an intelligent search pattern than just drifting at random.”

“There is no intelligent search pattern, Mary. He could be anywhere in the shoal of ice. It’s up to him to signal us, any way he can, and then I want you out there ready to grab him. I’ll give it another hour, then we’ll admit defeat.”

Reese turned away from the console wearily. Things could have been worse. Their main work was done; the fusion engines were mounted to shift the orbit of the comet as required, and the installation had only suffered minor damage in the quake. They could complete the mission without Du Toit. And they’d all known someone might get killed along the way. But somehow the idea of losing him on a sightseeing trip, on his day off, seemed much worse than if he had suffered an accident while working on the engine installation.

Wenzel’s head came through the hatch, followed by the rest of his long, thin body. Politely, he adjusted his attitude to match the ‘up’ of his commander.

“Boss, I’ve got something weird. I don’t know what it is, but it doesn’t make sense, and you said to watch out for anything unusual at all.”

“What is it, Chuck?” Wenzel had been monitoring the search program set upon by Xu. It was their last hope of detecting any signal Du Toit might try to make.

“Well, it’s like this. All these chunks of ice out there are rotating, and I’ve had the computer work out all their rotation rates and velocities. It’s easy to monitor them from the way they flash in the sunlight. I had a half-baked idea that I could extrapolate back to the ground zero of the breakup, and work out a search based on the probability of an object with Du Toit’s mass moving at a typical velocity having travelled a certain distance by now. But it’s no use – the search volume is still far too big.”

“So what have you found?”

“It’s one of those icebergs. Its rotation is speeding up. At first I thought it might be Du Toit, using his jetpack to increase the spin of the thing, or trying to steer it back to us. But there’s no trace of his exhaust plume in the spectrum of the thing, and anyway if he had a working jetpack he could fly right in the front door. Besides, the change is tiny – I’d never have noticed if the computer hadn’t flagged it as an anomaly. But it just isn’t natural. How can a lump of ice in space start to rotate faster all on its own?”

“I’ve no idea, Chuck, but we’re sure gonna find out. In this universe, if something doesn’t seem to be obeying the laws of physics, chances are there’s intelligence at work. I only hope it’s Du Toit.”

She turned back to the board, and flipped the toggle for Aries II.

 

When Xu pulled the fogged helmet off Du Toit’s shoulders, he was nearly unconscious. The suit’s air conditioning, damaged during the quake, hadn’t been able to cope adequately with his recent exertions, and his face was running with sweat. He breathed deeply, opened his eyes and smiled weakly.

“Hi, Mary. I’m glad it’s you. But I could’ve done with you getting the message sooner.”

“You big ox, Jan. You had us all worried to death, you know. But we should have guessed that superman was indestructible.”

“Indestructible, but crazy.” Bertorelli, his smile equally broad, interjected. “Who else would have tried to walk home on a piece of ice floating in space, like some demented logger floating on a Canadian river? When Reese told us that iceberg was spinning up and we drifted over to take a look, I don’t know what I expected to see. But it sure wasn’t the sight of you running over the horizon like the Seventh Cavalry charging to the rescue.”

“Just took a little intellectual effort to work it out.” Du Toit, though exhausted, was recovering fast in the oxygen-rich atmosphere of the Aries II. “Action and reaction, equal and opposite. Law of conservation of angular momentum. If I push one way to walk around the ice, the ice has to spin the other way to compensate. Faster I walk, more the ice spins. Knew you big brains would understand icebergs don’t spin faster by magic, and the shiny surface made a great mirror to signal with. Mary’s right – intelligence is the key to survival.”

“But not just intelligence,” she acknowledged. “If I’d been in your shoes I might have had the idea, but that lump of ice would never have noticed my body mass trying to make it spin up. Survival of the fittest needs brain and, brawn, and I’m glad it was you out there, not me.

“C’mon, Jan, we’re taking you home.”

 

© 1990 John Gribbin and Marcus Chown

First published in Aboriginal Science Fiction, Sept.-Oct. 1990