A NASA study reviews scenarios for alien contact, and it’s not pretty

If you're scared by end-of-the-world doomsayers, look away now.

The latest theory on how the world might end has come not from a Hollywood studio or cult leader's desert hideaway, but from NASA scientists.

The space agency commissioned a group of scientists to ponder likely scenarios in the event of an alien encounter, The Guardian reported.

Their report is titled "Would Contact with Extraterrestrials Benefit or Harm Humanity? A Scenario Analysis."

Among a range of outcomes, from the benign to the terrifying (yes, the extra terrestrials could come here to enslave or eat us), is the possibility that aliens would want to destroy humanity to protect the galaxy from our destructive expansionism.

In what sounds like the plot to a B-grade sci-fi sequel to Al Gore's "An Inconvenient Truth", the scientists led by Shawn Domagal-Goldman of NASA's Planetary Science Division said human-induced climate change could be the signal aliens need to decide we're a threat to other civilizations.

At that point, it's Death Stars and Death Rays for our little blue orb.

Aliens (ETI) could attack humanity out of an "altruistic desire to protect the galaxy from us. We might be a threat to the galaxy just as we are a threat to our home planet," the report warns.

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

The report continues that such 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," it says.

The scientists also warn against sending too much information about ourselves into space as we search for alien life. We should limit our signals to mathematical formulae and definitely not biological data, which could be used to devise weapons against us.