A 1968 report concluded that "there seems to be no reason to attribute [the unexplained sightings] to an extraterrestrial source without much more convincing evidence."

The scientific team found the sample containing the quasicrystals looked like it had an extraterrestrial source.

This latter ratio is known from extraterrestrial sources, such as some moon rocks and meteorites, which are relatively free of parental sources for helium-3 and helium-4.

Sarah Halifax is an astronomer who long ago translated the first transmission received from an extraterrestrial source: Sigma Draconis.

In Futurama, a language exists called Alienese, which originates from an unspecified extraterrestrial source.

This confirmed an extraterrestrial source.

But some scientists remain skeptical of all theories of extraterrestrial sources of the attributes of life.

The unnatural advance in technology was attributed to extraterrestrial sources by some publications, and managed to fuel a new generation of conspiracy theorists.

He prefers human-centered explanations to events and phenomena where some try to find extraterrestrial sources.

Unexpected excesses in energy or excesses from a given spatial direction indicate an extraterrestrial source.