Since its birth around a half century ago, SETI has largely focused on looking for alien civilisations beyond our own solar system, searching for radio signals from prominent or nearby stars. But what if there were earlier technological civilisations in our own solar system, or even here on Earth?
SETI typically focuses on interstellar radio signals or other studies of objects beyond the Solar System, however an alternative search avenue has been appreciated for nearly as long: the search for alien artifacts within the Solar System. This has not only been a topic for science fiction (e.g. 2001: A Space Odyssey) but in the SETI literature. Indeed, the apparent lack of such artifacts has been used as evidence that humanity must be the only spacefaring civilization in the Galaxy (Hart, 1975). Despite Hart’s claim, we can hardly rule out such artifacts in the Solar System, as demonstrated by Freitas (1983a) and Haqq-Misra & Kopparapu (2012).
In these discussions it is assumed, implicitly or explicitly, that the origin of such artifacts would be not just extraterrestrial (Haqq-Misra & Kopparapu, 2012, refer to them as “Non-Terrestrial Artifacts” (NTAs)) but extrasolar. But if such technology were to be discovered, we should consider the possibility that its origin lies within the Solar System, and potentially on Earth.
After all, given that the bodies in the Solar System are at least five orders of magnitude closer than the nearest star system, and given that we know that not only are the ingredients of and conditions for life common in the Solar System, but that one of its planets is known to host complex life, it is perhaps more likely that their origin be local, than that an extraterrestrial species crossed interstellar space and deposited it here. At the very least, the relative probabilities of the two options is unclear.
In this paper, I discuss the possibility for such prior indigenous technological species; by this I mean species that are indigenous to the Solar System, produce technosignatures and/or were spacefaring, and are currently extinct or otherwise absent.
Wright notes that one of the great difficulties in finding evidence for previous technological civilisations in our solar system is simply the passage of time – old stuff disappears. “The Earth is quite efficient, on cosmic timescales, at destroying evidence of technology on its surface,” he notes. “Biodegredation can destroy organic material in a matter of weeks, and weathering and other forms of erosion will destroy most exposed rock and metals on a timescale of centuries to millennia, if human activity does not erase it faster.
Wright points out that, at the very longest, some “large and durable structures, in the right environments” – such as the Giza pyramids – might last for ‘just’ tens of thousands of years. Given complex life has existed on Earth for over 400 million years (40,000 sequential periods of 10,000 years), you see the problem in searching for ‘ancient aliens’. Not least, because, on timescales of hundreds of millions of years “plate tectonics will subduct almost all evidence for technology with the crust it sits upon, erasing it from the surface entirely.
Regardless of those difficulties, where should we look? Wright suggests that Venus – with a thinner atmosphere in the past – and Mars, once covered in water, would be good candidates. And he reminds us that search should also include Earth (though he disavows the topic of ‘ancient aliens’ on his blog). Furthermore, he notes, “while all geological records of prior indigenous technological species might be long destroyed, if the species were spacefaring there may be technological artifacts to be found throughout the Solar system.”
It’s a fascinating hypothetical topic, though it is worth pointing out that Jason Wright is not particularly happy about “all the wrong kind of attention” the paper has received “from the yellow press and the ufologists….it is mortifying…Now excuse me while I answer all these emails from Coast to Coast and ufologists sending me pictures of clouds.”
No doubt his frustration has arisen from the “astronomer says ancient aliens existed in our own solar system” headlines that the paper has generated, with many mis-judging what the words “may” and “is possible” mean, in terms of likelihood of ancient alien civilisations. As Wright says on his blog, he put his paper together…
…not because I think they exist, but because we’re at the point where it should be possible to say for sure that certain types of them didn’t. The end of the paper is all about the things we can do to start drawing some conclusions.
I recommend – as I have to SETI people before – that it might be worth engaging with the ufologists and Forteans, rather than dissing them, as they could be some of your staunchest advocates, even if there is some disagreement over assumptions and conclusions.