Contamination of Earth by Extraterrestrial Plague – Space Pox – Viral Video (Literally) One of the biggest threats to humanity is probably just around the corner. Commercial organisations are working on projects to develop space travel and explore, colonise or mine other planets, moons and asteroids. The risk of these developments introducing Alien Microbes to Earth is discussed in this article.
Regular visitors to my website will be familiar with articles describing developments in medicine and molecular biology. Another area that interests me is the search for life in outer space. I would particularly like to discover how alien biology differs from earth biology especially in terms of its biochemicals. Will it make use of DNA, RNA, Protein, and Carbohydrate molecules as we do? Will it have adapted versions of these, or perhaps be built around a totally different biochemistry to anything we have on Earth?
It is believed that many (perhaps billions) of planets or their moons will have evolved some form of life although we still have to find proof. As is the case here on earth the most abundant life forms in space will certainly be microbial. Microbes were the first life forms to evolve on earth and we will probably find such microscopic life forms in space before we come across more complex organisms like ourselves. In fact only recently in the history of planet Earth have more complex organisms evolved. For the vast majority of our planet’s history it was only inhabited by microbes.
If another asteroid hits the earth like the one that wiped out the dinosaurs it might destroy all the animals and plants on Earth but the microbes would almost certainly survive. This is because they are versatile, hugely diverse, can be highly robust and resistant to destructive forces. They are also able to evolve and adapt very rapidly. Our microbial ancestors may even have originated on other worlds and were then brought here on asteroids during the Earth’s early history.
As a former medical microbiologist I am very much aware of the variety of microbes on our own planet – these bugs are able to live in some of the most inhospitable places on earth – at the poles, next to volcanic vents in the ocean or deep in the ground where no atmospheric oxygen is present. They can make energy out of some of the most unusual substrates – such as sulphur, hydrogen, iron or hydrogen sulphide (the ‘rotten eggs’ gas found near volcanoes). On the ocean beds they even digest oil playing an important role in clearing up the mess from oil spills and leaks.
Microbes can dramatically change their environment. They even change whole planets. We believe that originally the Earth did not have any atmospheric oxygen – it had an anaerobic (oxygen free) atmosphere – and the bugs that first grew here would have actually been killed by the presence of any oxygen.
In the very early days of evolution on Earth these ‘oxygen hating’ microbes learned how to harness sunlight to make energy and store it in chemicals like sugars. One of the byproducts of this process was the conversion of water (and carbon dioxide) into oxygen. With time large quantities of oxygen appeared on the earth. Yes the oxygen we breath was originally created by microbes (We also believe the water was brought here by asteroids – but that is another story). These bugs were able to use nitrogen and carbon dioxide in the atmosphere to enable the creation of proteins. By putting lots of oxygen (and ozone) into the Earth’s atmosphere microbes helped to protect all future life forms from harmful radiation from space (including from the sun). They also converted unusable inorganic elements like carbon, nitrogen and sulphur into organic forms that more complex living organisms (like us) can use as food and energy. Without all this preparation by microbes the Earth would not today be suitable for the evolution and survival of humans.
By the way those oxygen hating bugs are still with us – but they now live in parts of the Earth where they do not come into contact with oxygen – like at the bottom of the ocean, deep in the ground or hiding in the middle of the poo in your gut (plenty of nice methane there!). They are so sensitive to the presence of oxygen we have to use special air free methods and containers to try and grow them – if the earth ever loses its atmosphere these guys would still be here.
So we should not underestimate the power of microbes to change a whole planet and to influence the evolution of living systems. We are all familiar with some of the obvious harmful effects of a few microbes – they can cause disease in both people and crops. In fact microbes can even make other microbes sick – bacteriophages are special viruses that attack bacteria and can kill them. We use these bacteriophages in genetic engineering to inject new genes into bacteria to make them manufacture special proteins for us.
What many of us don’t appreciate is that our bodies are actually complex partnerships between our own cells and the many billions of microbes that live with us – on our skin, in our guts and even inside our cells. Many people are surprised to learn that a few percent of the DNA (the stuff genes are made of) in all of our cells actually came from viruses. During our evolution these viruses have infected our cells and injected new genetic material (together with their own genes) into our DNA. So our own genes appear to be based, at least in part, from exchanges we have made in the past with microbes. This genetic exchange actually allowed us to evolve more quickly and develop more sophisticated biochemical processes. Every cell in your body has several energy generating units called mitochondria – they are unusual because they actually have their own genes – this is because they were originally bacteria that the predecessors of our own cells formed a partnership with. Yes bacteria came inside our cells and now help them to generate energy more efficiently.
I feel very strongly that we need to be very careful to protect the cooperation between our own bodies and the microbes that live on and inside us. Not only do they protect us from disease (nasty germs find it harder to get to our bodies because the path is blocked by our ‘friendly’ bugs) but they also help us to digest some kinds of foods and produce vitamins in our gut. This is our microbiome and we need to be careful whenever we use antibiotics or even detergents, soaps and preservatives in our foods. These products, although designed to kill disease-causing bugs, can also harm the friendly microbes upon which our health and well-being depend. Our body is not our own – it is a symbiotic partnership with microbes.
Although the scientist in me is interested to learn what forms of microbial life exist in space I am also very concerned that we will need to be very careful. My biggest fear is that we could contaminate our own planet with ‘alien’ microbes that are much better at using the available resources than the life that already exists here. Our own history is littered with stories of explorers who returned to their homelands carrying terrible new diseases like the plague or syphilis. In our early attempts to colonise new countries we almost wiped out populations of natives by giving them small-pox, influenza or even the common cold. When you bring new microbes into ‘virgin’ territory the population will not have had a chance to develop any natural immunity. After ‘white explorers’ arrived in the Americas 80-90% of the unprotected Native Americans are estimated to have died of small-pox.
This lack of natural protection will certainly hold true for any foreign microbes that we bring to Earth from other planets, moons or asteroids. If we have not had contact with them before we will not have evolved any natural resistance. Most forms of protection like antibodies, antibiotics and other drugs depend upon the precise chemical structure and processes used by the target microbe. But if these microbes use a totally different chemistry our bodies and our scientists will not know where to start. Even the antibiotics we use to-day were originally invented by Earth microbes (they used them to kill off their microbial competitors). We simply stole and copied them and they almost certainly will not work on alien bacteria.
The Earth is surrounded by a vacuum that is constantly bombarded by radiation (we are protected from this by the oxygen and ozone in our atmosphere). Any bugs floating through space on, for example, an asteroid would probably be destroyed long before they reach the Earth by the radiation. And if this is not enough the huge temperatures generated as an asteroid falls through our atmosphere would finish off the sterilisation process. For this reason it is probably quite unlikely that microbes from other parts of space could reach us on their own (Although the products of microbial disintegration, like amino acids – the building blocks of proteins, might survive this thorough cleansing process. If these building blocks are found on asteroids they could be a sign that bugs do exist in space).
Mankind is starting to penetrate this protective shell around our own planet as we start to explore other worlds. As we send space vehicles to visit planets and other bodies in space and carry out tests we will soon learn about the life forms that have evolved elsewhere in the universe. I worry about what might happen if we try to bring back samples to test on earth (like the moon rocks we collected in the past) or if we send humans to carry out scientific missions (and bring them again home afterwards). We will risk bringing microbial ‘contamination’ back to Earth. We could be unleashing a Pandora’s box of problems – it is believed that upon their return the explorers who first visited the Americas with Columbus brought syphilis back to Europe (prior to this time the disease was not known in Europe – this ‘Great Pox’ killed over 5 million people).
Therefore we need to be vigilant. In our thirst for knowledge we must design our testing processes and projects very carefully. If information can be gleamed using automated equipment that does not need to return to Earth this would be preferable to the risk of contaminating ourselves with any microbes we find. However we should also be careful to ensure the equipment we send is absolutely sterile – we do not want to risk contaminating virgin worlds with Earth bugs. I am sure the scientists at established governmental space bodies like NASA and the ESA understand these issues but many commercial enterprises are starting to get very interested in space exploration. We need to make sure the proper controls are in place and that these projects are frequently being independently tested.
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