Wednesday 9 November 2016

Extraterrestrial Zoology: Mars

Since the subject of life on Mars has been well-documented, I won't linger long on the topic, but present a brief overview, as no guide of extraterrestrial life would be complete without a mention of Mars.

A brief history of life on Mars
We have long been fascinated by the idea of there being life on the Red Planet. The popularity of the concept of Martians underwent a mass explosion during the 19th century. It was theorised by scientists of the time that Mars was a dying world which was slowly becoming cooler and drier, and was the home of a civilization which was attempting to communicate with Earth. It was even suggested that a set of giant mirrors should be constructed in Texas so that we might signal to our Martian friends.
The idea of Mars being a dying planet was reinforced in novels such as H. G. Wells' The War of the Worlds, in which he depicts the Martians invading Earth.
It wasn't until more modern times that we finally recognised Mars not as a dying world inhabited by strange beings, but as a barren landscape on which life was impossible. 

. . . Or was it?


 Is it possible?
The argument for the habitability of the Red Planet was that liquid water once existed on the surface of Mars, and water is, according to our current scientific understanding, essential to life as we know it. Canyons and dried up riverbeds carved by flowing water can be seen on Mars, clear evidence that rivers once flowed across the planet. Indeed, the planet is in the habitable zone – or Goldilocks zone – along with Earth and Venus. Scientists are now fairly certain that Mars was once a watery, habitable world not unlike our own planet. There's a catch,though. New studies on Martian rocks suggest that water was most likely too acidic and salty for most life to exist there, and that only a few Earthly microbes would even have a chance of surviving these conditions. I have to say, although this piece of evidence towards the lack of life is interesting, I'm not convinced. After all, we're not talking about life on Earth, are we? We're talking about Martian life. It is feasible that a native Martian microbe could have evolved to be an extremophile – in other words, an organism adapted to survive extreme conditions. These Martian organisms could have evolved a resistance to briny and acidic conditions, making it a halophile (an organism that can surive and thrive in very salty conditions. Earthly examples of these include Halobacterium, Nitzschia, Wallemia icthyophaga, and others).

But anyway, does it really matter? Watery Mars existed more than 3.8 billion years ago, and we don't really care about microbes that could have hypothetically existed then. Well, it does matter, for 2 reasons. If we found fossil microscopic organisms on Mars, then this would still be an immense scientific breakthrough – it would prove, once and for all, that life can and does exist on other planets. But besides that, if life could have once lived on Mars, then is it possible that life could have survived the drying-up of Mars and lives on today?

Life underground
The surface of Mars is not a nice place for an organism. It's cold, and it's being showered with radiation – and no rover has yet found any solid evidence of an organism on the surface. Therefore, it seems more likely that if life does exist on Mars, then it will be present under the surface. Past volcanic activity could have feasibly created underground caverns and openings, creating aquifers, which in turn form pools of salty water, filled with essential minerals and possibly heated geothermally. If this turns out to be true, then we may well find halophilic organisms in these underground pools.
If we are to speculate a little more, then we might ask ourselves, what are the organisms down there feeding on? There's no sunlight, so there's no chance of photosynthesizing algae-like species. A clue to a possible solution lies with an odd looking organism called Acidithiobacillus thiooxidus, a form of bacteria which forms biofilms which drip from cave ceilings and resemble mucous, earning them the nickname 'snottite'. It gains energy from sulphur compounds, and its waste product is sulphuric acid. Other organisms use iron and manganese, oxidizing it, and they gain small amounts of energy from this. These microbes are using the elements in the stone around them to get energy and perform bodily functions.
It's easy to imagine Martian microbes using a similar process to use the stone around them and what's in it to gain energy.

Who knows? Maybe there is microscopic life living under the surface of Mars, in salty, acidic caves, oxidizing elements in the stone around them to survive.

Extraterrestrial Zoology: Is Anybody Out There?

In 2013, it was estimated by scientists that there could be as many as 40 billion planets orbiting red dwarves and stars like our own sun, within the Milky Way alone. These aren't any old planets though, the amount of all planets orbiting stars in our galaxy would be much greater if that were the case. No, there are 40 billion Earth-sized planets, which are in the habitable zones of their stars – the Goldilocks zone, where the planet is at just the right distance from its star to not be too hot, nor too cold. These kind of planets are ideal for life as we know it.

The Statistics
Now, let us, for a moment, imagine the universe - or try to, our brains cannot comprehend the sheer scale. Astronomers have estimated the amount of galaxies in the observable universe, and the number has come to an incredible 100 billion. Assuming that each one of these 100 billion galaxies has a similar amount of habitable planets as the Milky Way, then we can assume that there's a heck of a lot of possibly habitable worlds in the observable universe. But of course, the universe isn't limited to what we can observe. Frankly, we have no idea how big the universe is - some even believe that it could be endless. Other possibilities are that it is part of an immense multiverse, or that the universe comes to an abrupt end, and there is nothing beyond the edges. Whatever the answer, the universe is big. Really big. We can't even imagine its size. So if we take the billions of potentially habitable worlds in the observable universe, then multiply that number by millions, billions, or more, then we end up with the total amount of Earth-like worlds in the entire universe. Unless, of course, the universe is infinite or part of an infinite multiverse, in which case then the amount of Earth lookalikes and potential homes for life is also infinite.

What will aliens be like?
As you can see, there are many planets in the universe which have the potential for being home to life. But why limit ourselves to Earth-sized planets? We are blinkered by our limited knowledge of extraterrestrial life and by our imagination. Life does not necessarily have to exist on an Earth-sized world, or even on a planet at all: what about moons, or indeed even stranger places . . .? One might argue that in the immense, possibly infinite size of the universe, nothing is too far-fetched.
However, we can make educated guesses at what is likely and what isn't. We can guess that life everywhere would follow the basic laws of evolution, and therefore that certain features, such as eyes, mouths, etc, will be good things for an alien to have.

Do they even exist at all?
Of course, some might argue that there might be no aliens out there, that the universe is a lonely place, and that we are something special. Indeed, humans like to think of themselves as unique, and to a lesser extent, that Earth is to. It makes sense that humans might instinctively want for there to be no other life in the universe, because that makes humans and Earth special, and perhaps it also dulls the subconscious fear of other sapient lifeforms. Some argue that the likelyhood of molecules coming together to create lifeforms on more than one planet is simply an impossibility. To balance this out, let us think again of the sheer scale of the Milky Way, of the universe, of what may be beyond, other universes, infinity, whatever train of thought you prefer. I personally think that given the sheer scale that we are talking about here, life will have evolved on many planets. Anything else is, to me, impossible.

So, yes, I think that there is life out there, and that a more worth while train of thought is not 'are aliens real?', but questions about extraterrestrial life, assuming it is real. Where can we find it? What will it look like? What will it be made of? Will it be like us or something completely and utterly alien?

This is what I shall explore in upcoming posts.