Alien Chemistry: A scientific look at the possibility of Extraterrestrials

Do Aliens exist? What would they look like if they did? Is it possible that there might just be a planet capable of sustaining life near our solar system?

Late last year, a planet was found to be orbiting one of the Sun’s nearest neighbours, Alpha Centauri B.

This star is just four light years away, practically on the doorstep as far as the universe is concerned, so the fact that the planet is also around the same mass as Earth must initially have seemed exciting. A second home, not now, but for the future? A planet that could support humanity? The possibility of intelligent, alien life?

Thing is, there’s just one problem with that – the planet orbits the star far closer than Mercury orbits our own. This means that liquid water is unlikely to exist on the planet, certainly not on the surface, and probably not inside the planet either. And without liquid water, there cannot be life.

Or can there? You see, somewhat understandably, planet hunters such as those that found this small world only

Cold Planet
An impression of a cold planet (Credit: Nigel Soederhuysen)

really concentrate on planets that could hold water in its liquid form – those in the ‘Goldilocks’ zone. They don’t have the resources to look at everything properly, so they have to focus their small amount of funding. They look, find a planet that is highly unlikely to have ‘habitable’ conditions, and move on.

But this does not necessarily mean that these conditions are inhospitable to everything. Ask any biologist who researches so-called ‘extremophiles’ and they’ll tell you that life can be found just about anywhere on Earth. Even the European Space Agency sent little creatures called Tardigrades to space, exposing them to vacuum, starving them of oxygen and water, and all in temperatures of around -273°C. They brought them back, gave them water, warmed them up… and they were fine.

So creatures can survive, even thrive, in seemingly inhospitable conditions. So if conditions are different to what humans can stand, what could live there? Certainly microbes, such as the hardy tardigrade, could just about manage it. But, exciting as this would be, it isn’t quite what most people ask about. So what about intelligent life?

Now, the various factors that go into the production of planets affect what elements, and in what amounts, end up on the planet. Earth, for example, has a lot of silicon, phosphorous, iron; and of course the hydrogen and oxygen that combine to make the water that we’re all dependent on. Every living thing here is carbon-based.  But other planets may be different.

For example, reduce the temperature, to around -200°C, and water is no longer liquid – but nitrogen is. Cold worlds such as these may have oceans, lakes and streams of liquid nitrogen. Although the molecule is different, any intelligent life would probably look a little familiar – it’s a liquid, so fins would most likely be preferable. Eyes may also look similar, if the light levels are around the same there as they are here.

The large amount of carbon contained within our bodies could also be replaced, this time with silicon. It also is able to bond four times, like carbon, although it does have slightly different properties. Calcium may still work just as well in the bones of alien creatures, although perhaps in varying amounts – dependent on the mass, and therefore the strength of gravity, of the planet.

The physical appearance may differ, for example on a high-mass planet, a ‘Super Earth’, more legs may be needed, to spread the weight. Or perhaps a highly furry creature may have evolved, to deal with extreme cold. Maybe, just maybe, there are creatures made of gas, living off the energy of the lightning storms which are frequently found on gas giants.

Lack of oxygen is not necessarily disastrous, either. It’s thought that Earth’s atmosphere used to contain not oxygen, but another well-known gas – methane. Primitive life may have breathed the methane, and expelled oxygen, producing the atmosphere we have today, so it is possible that life on other planets may breathe methane. Neptune’s blue colour is produced by the methane in its upper atmosphere, so it isn’t a giant leap to a small, rocky planet with methane in the atmosphere – it just has to be cold enough.

I can understand that, with the limits in funding and other resources, those looking for planets are more focused on worlds that could hold life as we know it. But, as they point their telescopes to the sky, I ask one question:

What about life as we don’t know it?

All pictures from Flickr, used under the Creative Commons license found at


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