Should we take this seriously? The viral videos look like science fiction. But as Nasa appoints a head of UFO research, some say it is time to examine the evidence of alien life.
‘Alien corpses’ presented to Mexican congress
Fact or fiction: Ufologist Jaime Maussan has made alien claims before. Glossary
Ufologist - Somebody who investigates Unidentified Flying Objects.
Nasa - The National Aeronautics and Space Administration, responsible for the US space programme.
Astrophysicist - Scientists who try to understand the contents of the universe.
Cold War - A period of diplomatic conflict between blocs led by the USA and the USSR that lasted from 1947 until 1991, when the USSR collapsed.
Classified - Information that is labelled as top secret, only to be shared with certain people.
Conjecture - A theory or guess based on incomplete information.