The Science of Sci-Fi: Aliens

It is probably pretty clear from the fact that I run this blog that I am something of a nerd. And what do us nerds love more than anything? No, not energy-drink-fuelled inflammatory rants on message boards, its Sci-Fi! Everyone loves a bit of cheesy, space-battling, laser shooting sci-fi action. Turns out that a lot of the ideas in science fiction have some basis in science fact. If you’ve been reading ScienceUnplugged up until now you know the routine – yup: I’m gonna ramble about a few. In this part I am going to talk about Aliens (YAY!)

Evidence – Europa and Mars

So normally when you see the word ‘Aliens’ on a blog, things go downhill rapidly. There will be none of that sort of thing here. Like how the aliens are abducting everyone and replacing people with hybrid clones… kidding. If you haven’t read my last article about extremophiles you should give it a quick read because a lot of is relevant to the alien conspiracy.

Surprisingly, the concept of alien life isn’t actually a stranger to science. I mentioned in my last article about the theories about extra-terrestrial life involved in microbiology. There are a few signs that suggest that life exists or could exist on other planets in our solar system. 

The ice moon Europa, which turns out is kinda ginger... (source)

One example of this is the ice moon Europa. Europa is one of the moons of Jupiter and is about the same size as Earth’s moon. The entire surface of the planet is covered in ice and scientists believe that a water ocean could exist beneath the ice layer. In my last article I talked a little bit about hydrothermal vents – deep sea chimneys that spout mineral-rich water heated by molten rock in volcanic regions of the sea floor. It is theoretically possible that these vents could exist on Europa and create oases of life on the ocean floor, much the same as they do here. If these places exist on Europa, they would be perfect for critters like giant tubeworms and the ultra-resilient microbe Methanopyrus kandleri.

Another interesting thing about Europa is the red marks visible on its surface. Some have speculated that these could be caused by red-pigmented microorganisms growing in characteristic patterns called blooms, similar to those that can be seen all over planet Earth. As far as theory goes, Europa is probably the most probable candidate for life outside of earth. As for actually proving it… that’s another matter altogether. The European Space Agency is planning to launch a mission to study three of Jupiter’s icy moons called the Jupiter Icy Moon Explorer (JUICE) - so maybe we will find out after 2022 when the mission is planned to take place.

The surface of mars as seen by the Viking Orbiter... do you think martians like to eat MARS-ipan...? Hahaha haha ha ...sorry (source)

Mars has also received much attention as a potential life-supporter. My thesis adviser in my undergraduate degree would always say ‘water is life’. Here on Earth, everything alive requires and is largely made up of water. If water can be identified on a planet it may represent a foundation for life. Several efforts have been made to survey the conditions on mars and several clues about the presence of water on the red planet. Mars has polar ice caps composed mainly of water which also give rise to water vapor clouds. If frozen water can be found on the planet then perhaps liquid water is a possibility also. The conditions on mars can be best described as cold and dry across most of its surface with many volcanoes and the previously mentioned ice caps. On earth, microorganisms have been found which can live in similar temperatures and conditions. 

Science hasn't proved this guy real yet - sorry (source).

I know what you are thinking – bacteria and algae don’t really measure up to the imaginative range of green, blue, purple, orange and grey skinned, tentacled and/or antennae’d creatures that show up in SciFi shows, movies and games. What is particularly interesting about the deep sea vents I mentioned is that they create the conditions for simple life forms to thrive and become the bottom rung of the food chain where they act as the food source for more complex creatures.

Probability – The Drake Equation

Another clue that extra-terrestrial life may exist is the fact that it is technically quite probable. That probably seems like a strange thing to say until you think about it: if you look into the sky on a clear night you will see a lot of stars just like our sun. We live on a single planet out of nine orbiting our sun – the only planet we know of that supports life. If even a very small portion of those stars has just one planet like Earth, then the chances of life existing elsewhere in the galaxy seem quite high.

Okay, now it gets complicated. That’s right – I’m breaking out the maths stick. It may or may not surprise you to learn that astrophysics has come up with an equation to determine the probability of extra-terrestrial life existing in our galaxy. The equation was invented by American astrophysicist Frank Drake in 1961 and goes something like this:

N = N* fp ne fl fi fc fL

Frank Drake - inventor of the euquation - he gets all the ladies now (source)

If you are anything like me, that means absolutely nothing to you. I will try and translate it a little. N is what the calculation was designed to calculate: the number of alien civilizations which could potentially exist in the Milky Way. N* is the number of stars in the Milky Way – which is currently estimated to be around 100 billion. fp is the percentage of stars that have planets around them - currently estimated to be between 20% and 50%. ne is the number of planets which have the necessary conditions to support life – the estimate on this one is between 1 and 5 – because I have only talked about Europa and Mars I’m gonna call it 3. 

The rest of the values in the equation are a little harder to answer and a little more complicated. fl is the percentage of the planets which can support life (ne) where life actually evolves. All we really have to go on for this one is Earth – while there may be some limited evidence and theories about life on other planets, we can’t actually prove whether there is life there or not just yet. It seems that life on Earth started quite early in its history, which leads astrophysicists to believe that life began on Earth as soon as it was ready to support it. Based on this fact, some scientists say that the value for Fl should be at 100%.

A baby hamster inside some kind of fruit and/or vegetable (it was kinda hard to find relevant pictures for this section (source).

That brings me on to fi – the fraction of planets where intelligent life arises. Like many of the terms in this equation, this one is pretty vague and hard to define, as is the trait of intelligence itself. Some might define this as a human-like level of intelligence – the ability to shape the world and develop technology to enhance survival and to communicate with each other. Others might define intelligence as a survival trait which allows animals to adapt to their surroundings and survive life-threatening situations. These definitions give us very different estimates for fi – on Earth only one species out of millions has evolved intelligence by the first definition which would give us an estimate for fi which is very low, whereas intelligence by the second definition is a basic requirement for a species to survive and would give an fi value between 50 and 100%.

fc is the fraction of intelligent life that has the ability and will to communicate through the development of science and technology. Again, this one is hard to define. On Earth, it took one civilisation – the ancient Greeks – to get the ball rolling on science and technology which eventually brought us to the point today where we can look beyond our planet and even beyond our solar system and galaxy. This one is pretty subjective, but it seems to me that such advancements in science and technology are vital to the survival of life on a planet, so I am going to call it 100% - you may disagree though.

On to the final value – fL. This is the fraction of a planet’s lifespan in which intelligent, communicating life lives and is probably the hardest value to answer. The predicted lifespan of Earth is about 10 billion years and we have been communicating wirelessly for less than a century and honestly, things aren’t looking great for human civilization. But let’s say we don’t nuke each other into oblivion or destroy our planet with pollution and survive and prosper for another ten thousand years, that would give us an fL value of 1 millionth.

                                                                                                                                                                                   

If I put all the values into the equation (a lot of it is personal opinion and guesswork unfortunately), I get an N value of 90 thousand estimated communicating civilizations in our galaxy. You can’t really take my word for this though – everyone filling in the equation with their best guesses will get a different answer which can range from tens to billions. 

So I guess the answer to whether there are alien civilisations like those we see on the cinema screen is… 

…probably.

You can make your own estimates and try them out in the equation here.

Stay tuned for the next article in the series – interstellar travel…

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As with every article I post here, this one has been thoroughly researched and a list of sources can be provided for anyone who is curious – just check out the contact page.