Flying saucer
"Would Contact with Extraterrestrials Benefit or Harm Humanity? A Scenario Analysis" is a report recently published by Nasa's Planetary Science Division, which puts forward the idea that the earth's rising greenhouse gases could alert alien civilisations to our presence, and if so, they might seek to destroy us to protect themselves and others.

It sounds a bit far-fetched, sure, but when news like this comes from Nasa, we tend to sit up and pay attention a bit more than if it had been scribbled on the back of a beermat and handed to us on the street by a bearded tramp.

Anyway, back to the report. In it, Nasa scientists and researchers at Pennsylvania State University also talk about beneficial and neutral possibilities -- as well as the bad stuff -- that might occur should we eventually start chatting away with E.T. and co.

But, as you might expect, most people have been paying attention to the paragraphs on "the destruction of humanity as we know it" rather than the "cute and cuddly" sections. In it, the traditional one-two-three punch of aliens eating, enslaving or attacking us are noted, as well as the possibility of infectious diseases contaminating either their species or ours.

Stephen Hawking
On a side note, it makes us think back to something our man Stephen Hawking once said on the idea of aliens possibly existing out there in spaceland.

"We only have to look at ourselves to see how intelligent life might develop into something we wouldn't want to meet. I imagine they might exist in massive ships, having used up all the resources from their home planet. Such advanced aliens would perhaps become nomads, looking to conquer and colonise whatever planets they can reach."

"If aliens ever visit us, I think the outcome would be much as when Christopher Columbus first landed in America, which didn't turn out very well for the Native Americans."

Nasa's report follows a similar idea, suggesting that the key course of action for us is to stop sending out messages into the wild black yonder that might attract attention -- including our increasingly high levels of greenhouse gases. Apparently nothing should be done "until we have a better idea of the type of ETI we are dealing with."

Little Green Men
Sounds sensible. Anyway, the report goes on to state that a pre-emptive strike from Johnny Alien definitely isn't out of the question...

"A preemptive strike would be particularly likely in the early phases of our expansion because a civilisation may become increasingly difficult to destroy as it continues to expand. Humanity may just now be entering the period in which its rapid civilisational expansion could be detected by an ETI because our expansion is changing the composition of the Earth's atmosphere, via greenhouse gas emissions."

"These scenarios give us reason to limit our growth and reduce our impact on global ecosystems. It would be particularly important for us to limit our emissions of greenhouse gases, since atmospheric composition can be observed from other planets."

So there you have it: to save yourself from marauding little green men, we all need to get a little green ourselves. Ahem. Did you see what we did there? Come on, that's funny. It so is.