Justification
It is arguably the case that, due to the immense distances between stars, any evidence we discover of extraterrestrial intelligence, whether it be an artifact or an electromagnetic signal, may come from a long-vanished civilization. Thus the entire SETI project can be seen as a form of archaeology. Additionally, due to the extreme age of the universe, there may be a reasonable expectation for astrobiology research to produce evidence of extinct alien life prior to the discovery of alien life itself.
The study of alien cultures might offer us glimpses into our own species' past or future development.
Vicky Walsh argued for the existence of "exo-artifacts" using the principle of mediocrity and the Drake equation. She proposed that a theoretical and speculative field of archaeology be established in order to test outlandish claims, and to prepare for a time when undeniably extraterrestrial artifacts needed to be analysed.
"If it is possible to construct an abstract archaeology that can be tested and refined on earth and then applied to areas beyond our planet, then the claims for ETI remains on the moon and Mars may really be evaluated in light of established archaeological theory and analysis".
Ben McGee similarly proposed the creation of a set of interdisciplinary, proactive xenoarchaeological guidelines, arguing that identifying suspected artifacts of Astrobiology is all that is required to justify establishing a methodology for xenoarchaeology. He emphasized the necessity of proactive xenoarchaeological work in order to avoid future bias, mischaracterization, and information mismanagement, and he cites three scenarios under which such a methodology or set of guidelines would be useful, those being "Remote sensing" of a potential xenoarchaeologial artifact, encountering an artifact during "human exploration," and "terrestrial interception" of an artifact.
Greg Fewer has argued that archaeological techniques should be used to evaluate alleged UFO landing or crash sites, such as Roswell.
Read more about this topic: Xenoarchaeology