Although no confirmed evidence of extraterrestrial civilizations exists today, scientists and policymakers have developed post-detection protocols (PDPs) to guide institutional responses to such a discovery.
According to the SETI Institute's Search for Extra-Terrestrial Intelligence collaboration, these protocols establish rules for the "detection, analysis, and response to signals confirmed as originating from an extraterrestrial civilization." While no government has formally adopted PDPs, several UN member states have integrated key recommendations.
The scientific community has prioritized structured action plans, with the most authoritative being the "Declaration of Principles Concerning Activities Following the Detection of Extraterrestrial Intelligence." Developed by the International Academy of Astronautics (IAA)—an NGO uniting universities, labs, and tech centers—in partnership with the SETI program, the International Astronautical Federation, and the International Institute of Space Law, it was endorsed in 1992 by the International Committee for Space Research and the International Astronomical Union. This declaration was shared with all UN member states and relevant NGOs.
Other foundational PDP drafts include NASA's 1960 Brookings Institution report, "Proposed Studies on the Implications of Peaceful Space Activities for Human Affairs," which features a section on "Implications of the Discovery of Extraterrestrial Life." It outlines scenarios for governments on public disclosure.
PDPs draw from SETI, Active SETI (METI: Messaging to Extra-Terrestrial Intelligence), and CETI (Communication with Extra-Terrestrial Intelligence) research, focusing on intelligent signals like radio waves—key technosignatures of advanced civilizations—rather than microbial life, which falls under astrobiology and planetary protection.
In 1990, physicist, engineer, and sociologist Zbigniew Paprotny of the Polish Astronautical Society published "Signals from ETI Detected—What Next?" in Acta Astronautica. He identified three core pillars for PDPs still relevant today: societal acceptance of the news, public communication strategies, and message intelligibility.
Effective PDPs require evaluating signal importance to inform responses. Scientists use two validated scales for this.
The Rio Scale, developed by astronomers Iván Almár and Jill Tarter, helps assess detection claims and guide policy. Adopted by the IAA's SETI Permanent Study Group (PSG) and modeled on the Turin Scale for asteroids, it ranges from 0 to 10 to minimize false positives.
The San Marino Scale, also by Almár (2005) and adopted in 2007, evaluates risks of Earth's outgoing signals being detected and answered. It considers signal strength and content, scoring from 1 to 10.
Beyond scales, PDPs account for life form characteristics, language presence, signal origin, message content, and human societal readiness, enabling tailored communication plans.
PDPs anticipate socio-cultural impacts on media, religions, publics, governments, and scientists. Comparative studies of behaviors, histories, and beliefs inform rapid, targeted messaging.
A 1999 colloquium on astrobiology's social implications suggested religions could help absorb the shock and foster positive relations.
PDPs must address political exploitation, potential bias in framing the discovery as beneficial or threatening, and optimal disclosure timing—delaying if messages are ambiguous until clarified.
They also prepare for unilateral government discoveries sparking conflicts, especially if communication tech is exclusive.
PDPs weigh responding and response content, informed by CETI expertise.
For intelligible messages, first verify understanding, then decide transmission methods and content—ideally collective if multiple parties can respond.
Responses must be unambiguous, using universal math, algorithms, images, or symbols for non-linguistic civilizations. PDPs provide guidelines for swift international consensus.
Finally, PDPs consider tech gaps: inferior comms could distort messages, and armament disparities might risk revealing Earth's location if intentions are unclear.
