Humans should reduce impact on global ecosystems and limit emissions of greenhouse gases to avoid contact with aliens, says a recent report by NASA and Pennsylvania State University.
The report titled Would Contact with Extraterrestrials Benefit or Harm Humanity? A Scenario Analysis lays down the various possibilities that humans may detect, communicate or contact aliens in the future.
The analysis organized ETI contact scenarios broadly into three different sectors; beneficial, neutral or harmful.
Although the possibilities fall along a spectrum along these lines, these three sectors represent a useful categorization scheme. While the beneficial contact would be desirable for humanity neutral contact would cause indifference for humanity and harmful contact would be undesirable.
The study mentions a large number of scenarios which fall within the harmful-to-humanity category. However, broadly categorized under two sections, the first scenario involves hostile, selfish ETI attack to maximize their own success. This scenario suggests a standard fight-to-win conflict. The second scenario involves ETI that are in no way selfish but instead follow some sort of Universalist ethical framework.
Besides this, the scientists have also pondered over the possibility of aliens trying to destroy us in order to maximize their number or diversity of civilizations. This could occur if the earth's resources could be used to more efficiently generate or retain other civilizations; though this possibility seems highly remote, given how efficiently tuned humanity is to its environment.
The authors also warn that the attack might be due to the fact that the aliens may be wary of the way that humans have altered the natural eco systems. The chemical composition of Earth's atmosphere over recent time may be a poor choice for a message because it would show a rapid accumulation of carbon dioxide from human activity.