By Kang Yoon-seung
US - American researchers predict that if there really are alien civilizations, they are likely to be hostile to the Earth, the Daily Mail reported.
Viewed from a third party, Earth may be seen as being hazardous as it shows an abnormal increase in temperature and therefore aliens may conduct a preemptive attack to protect themselves, the scientists said.
The report "Would Contact with Extraterrestrials Benefit or Harm Humanity," written by NASA's Planetary Science Division, supposed several possible outcomes in case of contact with alien civilizations.
Although the newcomers may try to share their technologies to overcome domestic problems like poverty, they may also attempt destruction or spread disease to eliminate the entire population, the report read.
"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."
"These scenarios give us reason to limit our growth and reduce our impact on global ecosystems. It would particularly important for us to limit our emissions of greenhouse gases, since atmospheric composition can be observed from other planets," it added.