In Not of this World, I use the Drake Equation to argue UFOs are probably not extraterrestrial spacecraft. Frank Drake’s simple equation is often used to explain the search for extraterrestrial intelligence (SETI). Although the details of the equation are not important here, replacing one term in the equation Lc, the lifetime of communicating civilizations with a different term Ls, the lifetime of spacefaring civilizations, produces two versions of the equation – one estimates the number of communicating civilizations, Nc, and the other the number of spacefaring civilizations, Ns. Doing some simple math, we end up with the following relationship:

Nc/Ns = Lc/Ls

If UFOs are real and extraterrestrial, then Ns > 0. After more than six decades, SETI has not yet detected an extraterrestrial signal of intelligent origin, that is, from another technological civilization within the galaxy. Thus, one might conclude that Nc = 0. So if Nc < Ns, then Ls > Lc, which implies that is it easier to build an interstellar spacecraft than say a cellphone.

I use the example of a cellphone as they are the epitomy of our advanced information-based civilization. SpaceX is developing a fleet of rockets to take us to Mars. But we are a long way away from going to the stars. Still, If ETs had a civilization like our own we’d know about them from their radio emissions. Why? Because if, according to the principle of mediocrity, our technology is not exceptional, and the galaxy is teaming with intelligence as SETI advocates claim, then some civilizations are like ours, others are more or less advanced. Some use radio, others don’t.

So why has SETI not detected a signal after all these years?

Technosignatures

Perhaps realizing that they have not found what they set out to find, SETI has updated its strategy. A recent proposal considers the possibility of detecting evidence of previous technological civilizations, also known as “technosignatures,” within our solar system:

If technosignatures were discovered in the solar system, it would be worth considering whether their origin might not be interstellar. Specifically, since the Earth is home to the only known species capable of interstellar communication and planetary travel (although both technologies remain in their early development), the Earth remains the only known planet fecund enough to promote technological life, and so it or an early, habitable Mars or Venus could even be the origin of such technology… previous episodes of widespread, planet-altering technology on the Earth by putative, now-extinct species (that existed long before humans did) might be identified through paleoclimate investigations using isotopic proxies, land-use analysis, transuranic elements (or fission byproducts), or by searching for artifacts in the geologic record.

Jason Wright. 2019. NASA and the Search for Technosignatures: A Report from the NASA Technosignatures Workshop. https://arxiv.org/abs/1812.08681

Framing their proposal as a search for evidence of previous technological civilizations that originate within the solar system is convenient in that it sidesteps the problem of extraterrestrial civilizations (aka UFOs). Additionally, the discovery of a “long-extinct species (that existed long before humans did)” avoids the risk of societal disintegration resulting from contact with extraterrestrials discussed in the 1961 Brookings Institute Report.

The Silurian Hypothesis

Admiring shades of lava which imperceptibly passed from reddish brown to bright yellow, their way lit by crystals appearing as lighted globes, they continued through the lava gallery, which gently sloped until they reached the inter section of two roads. Without hesitation Professor Lidenbrook chose the eastern tunnel. And the journey continued through a succession of arches, appearing before them as if they were the aisles of a gothic cathedral; the walls were enhanced with impressions of rock weeds and mosses from The Silurian epoch.

Journey to the Center of the Earth, Jules Verne/Rick Wakeman

Gavin Schmidt and Adam Frank’s 2018 paper The Silurian hypothesis: would it be possible to detect an industrial civilization in the geological record? is a thought experiment to help imagine what possible technosignatures might look like. The authors nimbly skip over alternative archaeology, theories of past civilizations, Atlantis, and other controversial ideas, and jump back hundred of millions of years to the Silurian Epoch.

The Silurian Epoch is the period 443 to 416 million years ago following the massive Cambrian Exposition in which practically all major animal phyla started appearing in the fossil record. What was happening on Mars at this time? There was probably no water there and hadn’t been for billions of years.

Where Schmidt and Frank’s theory gets interesting is how it might apply to what we’ve found on Mars. Simple life, microbes, not yet. Evidence of material culture, possibly.

The possibility of extraterrestrial artifacts or evidence of recent technological civilizations other than our own within our solar system is anathema to most planetary scientists. A case in point is a collection of unusual surface features in the Cydonia region of Mars discovered by a Viking orbiter spacecraft in 1976 that resemble archaeological ruins. The planetary science community has to believe these features are natural geological formations. If they don’t, then someone had to build them. But who? They couldn’t have been built by indigenous Martians because current theories hold that conditions on Mars were not suitable long enough for advanced life to have developed. That they can’t be extraterrestrial in origin is rejected for the same reason the SETI community rejects UFOs – they can’t be here, so they’re not. This then leaves only one possible explanation…

I have to admit that when I first considered the possibility of ancient aliens from earth three decades ago, it seemed far-fetched. But given the facts to date, what better way for an ancient human technological civilization from earth to tell future generations that they are not the first, but just the latest technological civilization than by constructing an enormous humanoid face staring up into space from the surface of Mars?

Crazy, perhaps. But any crazier than NASA’s latest technosignatures proposal?