A poll conducted by NASA and the Science and Entertainment Exchange compiled a list of the ‘least plausible’ science fiction movies of all time‘.

Gattaca, (1997)

Unsurprisingly, 2012 got the gong for the worst offender whilst Gattaca, according to Space Agency boffins, ticked the most boxes with regard to science textbook accuracy.

As a screenwriter and author of YA fantasy novels requiring the creation of plausible fictional monsters, it got me thinking: what about the plausibility of the weird and wonderful aliens that inhabit moviedom? How do they fare against a quick science reality check? What are the chances of some of the more, er, shall we say, ‘exotic’ movie ETs actually evolving on some distant planet in the first place?

And how likely is it they would go on to traverse the impossible distances between stars in an improbable array of spacecraft only to hover over remote deserts and cornfields in front of less-than-credible witnesses no one is going to believe anyway? (And that’s a ‘best-case’ movie alien scenario: see War of the Worlds below.)

The big, unanswered (at least not satisfyingly, anyway) question in most alien movie scenarios is: why would aliens bother coming all this way in the first place? After all, surely there’s a few hundred million other planets they might have more reasonably contacted/invaded/destroyed/fleeced of water along the way.

In moviedom the reasons put forward are as varied, manic and mad-capped as a filmmaker’s imagination; none of them especially plausible. They range from colonising Earth to steal our natural resources (Skyline), to imparting wisdom and knowledge (Contact), to taking over our minds and bodies in order to ensure the survival of their species (Midwich Cuckoos), usually to nefarious ends.

But mostly aliens turn up in moviedom in a desperate attempt to enhance an otherwise lacklustre script. Desperate directors panic: “My movie is already stuffed full of implausible chase scenes and unlikely gun fights, with cardboard characters dropping clanging clichés in scene after anachronistic scene.” (Cowboys & Aliens, anyone? Me neither, but check out the trailer‏.) No problem! There’s always room for an improbable alien abduction or two to keep things moving at a clip.

So, bearing in mind the popularity of movie aliens is largely due to the fact they represent to the movie going public aspects of ourselves, and thus give an insight into how we see others, including our own governments and those of foreign powers, let’s assess the plausibility of some of the weird other-worldly beings committed to celluloid.

Plan 9 From Outer Space (1959)

Oh, and for the purposes of this list, I’m not concerned with obviously fake, aluminium-foil-suited-with-TV-aerials-on-their-heads aliens a-la 1950’s B-movies when both science and movie making were not as advanced as today.

With that caveat in mind, my top three movie aliens in descending order of implausibility are:

3) The alien in Alien. For some sci-fi fans, I admit, this will be an unpopular choice on a list like this. But hear me out: I admit this screen alien is a very, very nasty species indeed. As a depiction of sheer other-worldly alien-ness it has never been bettered on celluloid.

Unlike your typical Star Trek school of prosthetic-heavy aliens – all of which merely represent different evolutionary strands of actual Earth-based species (that handily speak fluent RP English), Ridley Scott’s creature, influenced by the work of Swiss surrealist, HR Giger is the real deal.

The Alien creature is an essay in nightmarish terror (as well as technical and artistic brilliance), however without actually ever having observed this creature on its home world (Ridley Scott, take note: that is the Alien prequel we all wanted to see!) it’s hard to comment on just how likely its famously weird gestation cycle is.

Presumably whatever environment allowed it to evolve into an unfeeling, emotionless and largely unintelligent predator would not be a nice place, implying all sorts of potential biological horrors and mutations. (Read:  face-huggers and chest-bursters.) Moreover, there are actually varieties of parasitic insects, such as the Scabies mite, that implant eggs in humans – so not that far-fetched then.

However it’s debatable whether in a hostile environment a large-scale creature that required its young to gestate in a living host would climb to the top of the evolutionary ladder. Why not? Think about it: its gruesome reproductive cycle would make it exclusively reliant on other species for survival – species it’s hell-bent on wiping out!

Oh, and acid for blood? Nice touch, but it was implied in the films that this was a defence mechanism. Hmm. A defence mechanism that requires the opening of the defender’s veins is not that likely due to the (ahem) minor evolutionary drawback that the ‘success’ of the defence mechanism kills the organism deploying it.

2) Predator. Scary in a (sort of) human-like way, the towering alien predator with the Milli Vanilli dreadlocks hunting Arnold Schwarzenegger’s ‘Dutch’ in the 1980 blockbuster represents a particularly nasty aspect of human nature; namely, our predilection to destroy ourselves and each other for little more than ‘sport’.

Having somehow simultaneously evolved to be both viciously unpleasant and technologically advanced these aliens decided intergalactic space travel was the perfect opportunity to boldly go where no alien had gone before, hunting down other alien species they come into contact with along the way in brutal and bloody planetary safaris. (‘Why’ was never explained – presumably to make them feel a little bit better about themselves.)

Oh, and based on their track record in two sequels of varying quality these chain-mail-vested aliens have a penchant to pick on species that are physically and technologically inferior; so they’re bad sports then, but even worse losers. They tend to blow themselves and their quarry up – like a petulant child overturning a chess board – by way of exploding suicide bomber-like, er, bracelets when cornered.

You’ve been warned: it’s lose-lose with these spider-mouthed alien sporting cheats.

War of the Worlds (2005)

1) The Martians from War of the Worlds. Ugly. Inhuman. Driven to maniacal interplanetary missions with no other agenda than death and destruction in the name of colonisation on their tentacled minds.

Oh, and they’re prone to lethal bouts of, er, flu. (Ok, ‘terrestrial microbes’ – same difference: ‘flu’ to you and me.)

Yeah. You read that right. The combined global military couldn’t dent their plans for planetary domination – no way! However sneeze in their direction and … Gesundheit! They never stood a chance.

Hey, it’s plausible: an alien civilisation packing off to destroy Earth in a bout of interplanetary homicidal mania with giant, spider-like ground craft and destructive death rays could be forgiven for forgetting to pack the Kleenex and Tamiflu!