‘The answer to your question is yes and yes. Life is very tenacious and very adaptable,’ said Liz. ‘There are organisms, called extremophiles, that have adapted to living, even thriving, in extreme environments, environments which include total darkness and extreme cold.
‘Chemoautotrophs are creatures that live in total darkness. They’re found in deep caves and in the depths of the ocean. Unlike green plants, which utilise sunlight and photosynthesis to provide food and energy, chemoautotrophs oxidise hydrogen sulphide and methane to provide their food and energy, a process known as chemosynthesis.
‘Most creatures that live in the dark,’ continued Liz, ‘don’t have eyes – they don’t need them – and are generally white or pale-coloured. There’s no point wasting precious reserves developing eyes or pigmentation if there’s no light to see or to sense colour. Instead, they sense their surroundings by touch, developing extra long, extra sensitive limbs or hairs.’
‘So, are you saying the aliens won’t have eyes, that they’ll be blind?’ asked Zak.
‘No, I’m not,’ replied Liz. ‘I think it would be very difficult for blind creatures to develop advanced technology. And anyway, I don’t think they live in total darkness. I think they’re blocking out the sun’s light and heat to make the Earth cold. The darkness is just a by-product.
‘To answer the second part of your question,’ she continued, looking at Viv, ‘life can and does exist at very low temperatures. Cold temperatures are bad for most organisms. Freezing temperatures damage cells, both by superosmosis, which desiccates them, robs them of their water, and by the formation of ice crystals, which rupture them. Cold also increases viscosity, limiting the availability of both nutrients and waste products, which causes a build-up of waste that poisons the organism. Finally, cold temperatures cause cell proteins and enzymes to stiffen, inhibiting their function.’
‘The exact opposite of what happens with men, then,’ said Rupert, laughing, and winking at Viv, Frank and Zak. As the penny dropped, they all laughed, including Liz. Even in the darkest days, humans could still raise a smile. It was uplifting.
‘Cold loving organisms are called psychrophiles,’ continued Liz. ‘They have adapted to life at low temperature by natural selection over multiple generations, developing flexible enzymes and proteins that act like antifreeze. They’re found in glaciers, Arctic ice, snow and soil, and deep oceans.’
‘Wasn’t the meteorite you found in the ice cave near to some bacterial growth?’ asked Viv. ‘Was that a psychrophile?’
‘Yes, it was,’ replied Liz, ‘and yes, the meteorite was found lying near to the bacterial growth.’
‘Do you think the aliens landed it there deliberately?’ continued Viv. ‘Near to the bacterial growth, to study Earth life at low temperatures? Or do you think it was just fortuitous?’
‘The latter,’ said Liz. ‘I think they wanted to find out about the conditions 75 feet below the surface – things like the temperature, the atmosphere and the light level – and to see if life existed under those conditions. I don’t think they deliberately targeted that life.’
‘Liz,’ said Frank thoughtfully, ‘were extremophiles the first form of life on Earth? The conditions on the primeval Earth were pretty harsh and extremophiles are the organisms that can survive in harsh conditions.’
‘That’s very perceptive, Frank,’ replied Liz, ‘and yes, many scientists believe that extremophiles were the first forms of life, but not psychrophiles. They believe that thermophiles, the heat loving extremophiles, could have been the first form of life on Earth. High temperatures are bad news for most organisms. They degrade the green pigment chlorophyll, stopping photosynthesis, an effect seen in the kitchen when cooking green vegetables – the green colour disappears. The vegetables are blanched. Heat denatures proteins, causing them to stop working, an effect seen when eggs are fried. The change in colour from clear to white is a clear sign of denaturing, the unwinding of the proteins. Heat also decreases the amount of carbon dioxide and oxygen in water, making them less bioavailable. Over billions of years, thermophiles have evolved proteins and enzymes that work at high temperatures by successive mutations and natural selection. Thermophiles can live at temperatures above the boiling point of water (100°C), the sort of temperatures found near deep hydrothermal vents at the bottom of the ocean, and it’s here that life, protected from the harsh surface of the young Earth, is thought to have begun. The hydrothermal vents are thought by many to be the cradle of life.
‘Until the 1970s,’ continued Liz, ‘it was thought that psychrophiles and thermophiles, indeed all the extremophiles, were prokaryotic bacteria, the simplest form of life. These mainly single-celled organisms lack both a nucleus and cell membrane, in contrast to the eukaryotes, organisms whose complex cells contain both a nucleus and a cell membrane, and on which nearly all present life is based. But DNA evidence showed that the extremophiles were not really bacteria at all, but a new class of life, which they called archaea. And it’s the archaea which could well have been the earliest form of life on Earth. Indeed, DNA traces support that view, showing that prokaryotes tend to be more heat tolerant than eukaryotes. It’s thought that as time passed and the conditions on Earth became more comfortable for life, some of the archaea evolved into eukaryotes.’
‘I presume the organisms that live in hot springs and geysers are also archaea,’ said Frank.
‘Yes, they are,’ said Liz.
‘Are extremophiles a rarity? Are they just a niche form of life which only exist in a few exceptionally hot and exceptionally cold spots on Earth?’ asked Rupert.
‘That’s what most people think,’ said Liz, ‘but they’re wrong. Overall, extremophiles may constitute one third of the Earth’s biomass.’
‘Wow!’ exclaimed Rupert. ‘I thought there were just tiny pockets of such organisms. I’m amazed.’
Frank changed the topic. ‘I know the 40 nuclear bombs exploded near the asteroid didn’t do much physical damage, but what about all that radiation? It must have penetrated the asteroid. Surely that must have had some effect on the aliens?’
‘If the aliens are carbon-based life forms, which I think they are, then quite possibly,’ said Liz. ‘Ionising radiation is hazardous to life. It changes DNA. If the change is minor, caused by a low dose of radiation, the DNA can repair itself, but a large dose of radiation, a lethal dose, results in death. Intermediate or non-lethal doses result in mutations.’
‘What kind of doses are we talking about here?’ asked Rupert.
‘The radiation dose is the energy absorbed per kilogram of body mass,’ said Liz. ‘To give some examples, a medical X-ray is approximately 0.002 joules per kilogram, and the background radiation we’re exposed to on the surface of the Earth is 0.0003 joules per kilogram per year, an extremely low figure. For humans, a dose of 10 joules per kilogram is lethal, but it takes six times that amount, 60 joules per kilogram, to kill an E Coli bacterium.’
‘So a little bug is more resistant to radiation than we are? That really makes me feel good,’ said Rupert sarcastically.
‘And the radiation from the nuclear explosions…’ continued Frank.
‘That will have been very high for a very short period of time,’ said Liz.
‘But obviously not high enough to have killed them,’ said Frank.
‘Not yet, anyway,’ said Liz. ‘But it could have damaged their DNA, provided that’s what they have, and caused longer term damage.’
‘Like cancer,’ said Rupert.
‘Yeah, like cancer,’ said Liz.
‘But they could be resistant to radiation,’ continued Liz. ‘Some organisms have developed a very high resistance to radiation. For instance, some of these so-called radioresistant extremophiles can survive doses of 5,000 joules per kilogram, 500 times more than the lethal dose for humans. Some can even absorb up to 15,000 joules per kilogram with a 37 per cent viability.
In other words, 37 out of 100 would survive such a dose.
‘The reason that radioresistant extremophiles can survive such high doses of radiation,’ she continued, ‘is because they possess very efficient DNA repair mechanisms and because they carry four to ten copies of their genome, not just one like we do. So, if one, or two or even more copies are destroyed, they have several more back-up copies to replace them. They are such tough little beggars that they’ve been given the nickname Conan the Bacterium, after the tough character Conan the Barbarian played by Arnold Schwarzenegger in a film of that name. In fact, they’re so resistant to radiation they could be used to transport life through space.’
‘That’s fascinating, Liz, absolutely fascinating,’ said Rupert, intrigued by what she’d just said. ‘Do you think the aliens are radioresistant?’
‘I don’t know, but if they’ve been inveterate space travellers, they could have developed such resistance.’
‘Well, one thing’s for sure,’ said Viv. ‘If we ever wipe ourselves off the face of the Earth with a nuclear war, there’s no doubt who the survivors will be.’
‘You’re right,’ said Liz, ‘the radioresistant extremophiles and the endoliths.’
‘The what!’ exclaimed Rupert.
‘The endoliths,’ said Liz. ‘Organisms that live inside rocks and between mineral grains. They’ve been found as deep as three kilometres below ground. Not surprisingly, most are chemoautotrophs that only reproduce about once a century.’
‘And I thought my sex life was poor,’ said Rupert smiling.
Liz smiled too and carried on. ‘That’s not the only surprising fact about endoliths. Even more surprising is that the total biomass of endoliths could exceed that of all surface life!’
‘Are there any conditions on Earth where life can’t survive?’ asked Frank, amazed by the versatility and sheer tenacity of life to adapt to almost any environment.
‘In theory yes, in practice no,’ said Liz. ‘The one requirement that life definitely needs is water. We don’t know of any life that can exist without liquid water. One of the driest places on the planet is the Atacama desert in northern Chile. It’s so dry that the Viking 1 and 2 expeditions to Mars practised in the Atacama desert in 2003. As expected, they didn’t find any life in the top 10 cm of desert, but did find viable bacteria at a depth of 30 cm. So, even in the driest places, if there’s just a microscopic amount of water, as there was 30 cm below the surface in the Atacama desert, life can gain a foothold.’
‘Isn’t that what the Earth’s becoming now, a dry, barren planet?’ said Rupert.
‘Yes, it is,’ replied Liz, ‘another factor that will aid the extermination of life.’
All the talk about liquid water triggered a thought in Viv’s head. ‘Could the interior of the asteroid be full of water?’ he asked. ‘Like a giant goldfish bowl. Could the aliens be an aquatic species, an intelligent, advanced aquatic species that live in water? After all, a lot of the meteorites fell in the sea.’
‘You mean like a super intelligent dolphin or octopus?’ said Rupert.
‘I was thinking more along the lines of an aquatic humanoid, but who knows,’ replied Viv.
‘I think a lot fell in the sea because 70 per cent of the planet is covered in water,’ said Liz, ‘not because the aliens directed them there, and it’s possible they’re an aquatic species, but it wouldn’t be top of my list. However, we shouldn’t rule it out. After all, life on Earth originated in the oceans, in the salty seas, and some scientists believe that life existed in the salty seas of the early Mars, and may exist in the salty seas of present-day Europa.
‘To conclude,’ said Liz, quite enjoying her time in the spotlight, ‘extremophiles are also known that thrive in conditions of high salinity, like the Dead Sea and the Great Salt Lake in Utah, high acidity – even in conditions resembling battery acid – and high alkalinity. In fact, life can exist almost anywhere.’
‘That’s all very interesting,’ said Viv, ‘but will it help us defeat the aliens?’
‘It might,’ said Liz. ‘It just might.’
25
The Dark Freeze
If the creeping darkness wasn’t enough to chill the bones, the freezing cold certainly was. The increasing lack of sunlight caused the temperature to plummet. People struggled just to keep warm. It wasn’t just a cold snap, a short, sharp spell of exceptionally cold weather. Such events were commonplace. This was a cold snap without end. A cold snap that was getting colder by the day. Already the average temperature had plunged to minus 30°C, as cold as an Arctic winter, and it was continuing to drop. People wondered how much colder it would get. They didn’t know. But the scientists did. Not precisely, because that depended on a number of factors, but approximately. Once all the sun’s light had been blocked, the temperature would eventually drop to a mind-boggling minus 140°C, similar to the temperature on the dark side of the moon, another place untroubled by sunlight. To put that in perspective, the coldest temperature ever recorded on Earth was minus 89.2°C at Vostock, Antarctica on July 21 1983 and the coldest temperature in the Universe, the coldest temperature possible, is minus 273°C, absolute zero. It was a frightening prospect.
People panicked. They rushed to buy warm clothes. Clothes normally used for extreme weather were worn inside their homes to keep them warm. Within weeks, shops, stores and supermarkets were stripped bare, not only of warm clothing but of blankets and duvets too. Duvets with the highest TOG (derived from the Roman word toga for garment) ratings went first, followed quickly by every single item which could be used to help people keep warm. To stave off hypothermia. And death. Blankets, rugs, towels, even curtains. What they couldn’t buy, they looted. Shops everywhere were emptied. Denuded of stock. People were desperate.
As the cold and darkness bit deeper, the government rationed vital supplies. Priorities were assigned. Top of the list was energy. Energy supplies were strictly controlled. The amount of electricity, gas, oil and coal which households were allowed was reduced dramatically and diverted to places such as power stations. It was absolutely essential that power stations continued to function. Continued churning out electricity, electricity vital for producing light and heat. Light and heat that we’d come to take for granted. Oil, gas and coal earmarked for other uses was also diverted to power stations. They were the top priority.
Critics of the ‘Green Movement’ had a field day. What use were windfarms and solar panels now? No sun, no solar power. No sun, no weather. No weather, no wind. They were as useful as a snowball in hell. Why hadn’t successive governments invested more in nuclear power? Hadn’t they foreseen a scenario such as this? Probably not. The ‘Greens’ could argue all they wanted about ‘clean’ energy and protecting the environment but, at the end of the day, they ignored the facts. Ignored an inconvenient truth. The entire Universe, everything, is powered by nuclear energy. By nuclear fusion. It’s the process that powers every star in every galaxy. It is the ultimate energy source. Although we don’t yet have the technology for nuclear fusion – except in destructive hydrogen bombs – nuclear fission isn’t a bad second option.
As well as power stations, the government also prioritised hospitals – at least they didn’t abandon the sick and infirm – food production – people needed to eat – and water supplies – they needed to drink too. But it wasn’t easy. The challenges were enormous. Reservoirs had frozen over, as had most of the mountain streams and rivers that supplied them with fresh water. The government did its best trying to run the country as near to normal as possible, at least at the beginning, but it was extremely difficult. They were fighting a losing battle.
As the power cuts became more severe, people reverted to the old-fashioned ways of keeping warm. They purchased paraffin heaters and wood burning stoves, even braziers, to provide their warmth. Barbecues were brought inside. Candles became a necessity to provide light, and a little heat, for when the power w
as off. Families huddled together in a single room to conserve precious energy supplies. To eke out what little energy was left. As the supplies of paraffin, coal and wood ran out, they resorted to cannibalising their homes and gardens.
Gardens were attacked first. Garden sheds, summerhouses, gazebos and pagodas were broken up, fences torn down, decking ripped up, and the wood used as fuel to provide vital heat and light. When this supply had been exhausted, they turned to their homes. Wooden chairs and tables were broken up and burned. Wooden banisters, wardrobes, kitchen units, all broken up and burned. Even treasured pieces of furniture, precious family heirlooms, were broken up and burned just to stay alive. Nothing was spared.
The burning of all these fossil fuels exacerbated another problem: it used up oxygen, oxygen that was no longer being replenished.2 Without the photosynthesis of green plants, the world’s supply of oxygen was diminishing, being consumed by animals and the burning of fossil fuels, as well as by natural phenomenon such as volcanoes and forest fires. Due to the lack of light and rain, the dry, dead vegetation was like a tinder box, just waiting to catch fire.
Scientists monitoring the oxygen level in the atmosphere noticed a decrease, but a decrease so small that it would have no discernible effect in the short term. However, if it continued to decrease, then in the long term the oxygen level would reach a critical value. But that didn’t matter. Long before that point was reached, all life on Earth would be dead.
As the dark freeze intensified, fuel rationing became more strict. More severe. More controlled. The frozen seas – the sea ice was over three feet thick – made shipping impossible. Oil tankers couldn’t sail, couldn’t deliver their precious supplies of oil. Inland, on the large land masses of Arabia and Russia, the temperature was so low that the oil in the pipelines froze. Restocking the declining oil reserves was impossible.
Ships were stranded in mid-ocean, locked in a sea of ice. Cargo ships and luxury liners which had failed to reach port before the oceans froze over. Some of the crew and passengers were rescued by helicopter, but not many. Fuel was getting too scarce to mount repeated rescue operations and the intense cold made flying hazardous. The temperature was so low that petrol, and especially diesel, were beginning to freeze. Most of those on board were left to die a slow, painful death marooned in a sea of ice.
The Dark Freeze Page 17
