Can planetary science contribute to the search for extraterrestrial intelligence (SETI)?

The search for extraterrestrial intelligence (SETI) is a legitimate scientific field, which engineers, astronomers and other scientists have been engaged in at least since the 1950s when the field was founded by the Frank Drake. Institutions famous for their involvement in SETI research include the SETI Institute in Mountain View, California. Most SETI work involves observing electromagnetic signals from interstellar sources and uses the tools of astrophysics rather than planetary science. Essentially, planetary science involves the solar system, astrophysics involves what is beyond the solar system. Despite this fact, could there be a role for planetary science in SETI? In other words, is there a reason to search for signs of extraterrestrial intelligence in our own solar system?

SETI in the solar system, or planetary SETI, is fraught with pseudoscientific claims (remember the face on Mars?), making it too risky for most SETI scientists to touch. Nonetheless, there is growing interest in planetary SETI in the scientific community. The main proponents of planetary SETI include Jason Wright at the Penn State Extraterrestrial Intelligence Center at Penn State University and Paul Davies at Arizona State University.

Wright, for example, argues that although there is currently no evidence for extraterrestrial intelligence (ETI) in our solar system, we may be more likely to encounter ETI native to our own solar system than an interstellar ETI given the difficulty in crossing interstellar distances with known physics.

Whereas conventional SETI involves looking for electromagnetic signals, SETI in the solar system also involves the search for extraterrestrial artifacts and thus can be considered a form of exo-archaeology. One way to search for extraterrestrial artifacts is to survey image data from planetary surfaces like the Moon and Mars to search for anything unusual. This could be done by using machine algorithms to comb planetary image data for features that have characteristics that look plausibly artificial (i.e., more Euclidian than fractal, etc.). This could also be used to look for objects of scientific interest, like boulders and volcanic features, and thus would not only be of interest to SETI.

Considering the hostile surface conditions on even the most Earthlike solar system planet beside Earth itself, Mars, and the difficulty a civilization that evolved in a subsurface ocean on an icy moon would have in breaching the ice shell to reach for the stars (a good premise for a science fiction story though), it is highly unlikely that we will actually find alien monoliths on Europa or lost alien cities on Mars. The significance of such a discovery, however, does make a search worth the effort given the low costs involved. No new missions or data would need to be created in order to carry out the the investigation since planetary image data, machine learning, and AI already exist. Furthermore, we can philosophize as much as we want, but we will never truly know if we do not actually go out and search.

Unlike the targets of conventional SETI searches, which reside in solar systems so distant we likely will never actually encounter them beyond distant messages and signals, planetary SETI searches involve entities we might actually encounter in the near future. This makes the topic of Unidentified Aerial Phenomena (UAPs), previously Unidentified Flying Objects or UFOs, more relevant to planetary SETI than to conventional SETI.

UAPs are another topic which serious scientists typically have avoided because of its connection to the fringe, but there is growing scientific interest in UAPs and there have been recent efforts by NASA to investigate their nature. To be clear, no one is setting out to prove that UAPs are in fact extraterrestrial spacecraft (what I will call the extraterrestrial hypothesis for UAPs) and no evidence for the extraterrestrial hypothesis of UAPs has was found by the most recent independent panel formed to investigate the topic.

Nonetheless, while there is currently no reason to consider the extraterrestrial hypothesis for UAPs likely, it an engaging hypothesis that is relevant to planetary SETI. Could planetary SETI efforts be used to evaluate the extraterrestrial hypothesis for the identity of UAPs?

One way to incorporate the study of UAPs into planetary SETI would be to search for UAPs in both terrestrial (Earth) data and in planetary data along with the search for structures. The detection of similar UAPs in other planetary atmospheres would not by itself prove that these were alien spacecraft of course, it would just show that UAPs are also present on other planetary bodies and not solely an Earth phenomenon.

Discovery that UAPs are not unique to Earth might even be evidence against a technological explanation since we currently have no reason to believe that technological civilizations are present on other planets in the solar system. Discovery of UAPs in other planetary atmospheres besides Earth might suggest that it is an atmospheric phenomenon rather than a technological one, whereas the presence of UAPs only in Earth’s atmosphere could be evidence that they are the result of technology since we know at least one technological species exists on Earth.

In what case then would the discovery of UAPs, say on Mars or the Moon, be evidence in support the extraterrestrial hypothesis for UAPs? One scenario which would support UAPs being technological is if planetary SETI efforts reveal that possible artificial structures and UAPs occur together in planetary environments. If UAPs are only found in significant frequency on planets which also have evidence of possible artificial structures, based on planetary SETI surveys, this could be considered support of the hypothesis that UAPs are the result of non-terrestrial technology. This would not by itself prove that UAPs are extraterrestrial spacecraft, but possible artificial structures and UAPs co-occurring would be a compelling reason to investigate the extraterrestrial hypothesis of UAPs further.

I am of course describing a hypothetical scenario. No evidence has been found that UAPs are anything other than unidentified aerial phenomena in Earth’s atmosphere, but if we are to seriously investigate the extraterrestrial hypothesis of UAPs and not just endlessly argue and speculate, planetary SETI provides a way to investigate the possibility. It would require a rigorous scientific investigation of UAPs on Earth, search for similar phenomena in data from other planetary bodies, and a search for possible artificial structures on other planetary surfaces. This search is unlikely to result in evidence of extraterrestrial intelligence, but it can be done with existing datasets and technology, and would have profound implications if we did actually find something that unambiguously supported non-terrestrial technological intelligence in the solar system. I say it is at least worth a try.

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