In a recent commentary, published here on the pages of Scientific American, Jason Wright, professor of astronomy at The Pennsylvania State University, outlined a clear and persuasive argument for NASA to resume funding SETI - the search for extraterrestrial intelligence.
One of the most insightful points Jason makes is that there is no a priori reason to suppose that technosignatures (from intelligent life elsewhere in the universe) should be any less detectable than biosignatures (from any kind of life elsewhere in the universe). Indeed, I think indications of this fact go back quite a way. Take for example the famous, and famously elegant, experiment performed in December 1990 when the Galileo spacecraft made a gravity assist flyby of the Earth.
Carl Sagan and his colleagues had planned ahead for exploiting this maneuver. Galileo's real purpose for the flyby was to gain a velocity tweak as part of an elaborate orbital ballet to get out to Jupiter. But at a closest distance to Earth of some 960 kilometers it was a golden opportunity to do a baseline astrobiology experiment. As the spacecraft sped by the planet it switched on its instruments - telescopes, spectrometers, radiometers - and surveyed this strange blue dot for signs of life.
The striking thing about the results, published in the journal Nature in 1993, is that while there were strong hints of biology seen in the planet's atmospheric gases and surface colors, the real kicker came from our human transmissions from the surface. Or, as the researchers put it: "…the presence of narrow-band, pulsed, amplitude-modulated radio transmission seems uniquely attributable to intelligence."
To me it's pretty remarkable that during an extreme close-up of a well-inhabited planet, using a space-probe bristling with scientific instruments, the most incontrovertible sign of life was a pure technosignature.
Of course, one study doesn't prove a general rule. But in retrospect it is a little surprising how little has been made of this point, especially since none of us can claim to know the a posteriori probability distribution for life of any kind in the universe. Rather, many astrobiology studies refer only to the biosignature results of the Galileo experiment, citing measurements of the disequilibrium of atmospheric components like oxygen and methane. All of which is absolutely solid science, and perfectly sensible. Yet it's also like leaving out one of the key punchlines in a good story.
We know that when NASA dropped funding for SETI in 1993 (a chance coincidence with the timing of the Sagan paper as far as I can see) it profoundly altered the arc for those projects. It didn't just decimate resources, it sent a message that SETI was too 'fringe', or at best too unlikely to succeed for science to take seriously.
And to be fair, SETI has always attracted more than its fair share of people whose vision is, shall we say, less clear than what is necessary for a highly challenging, high-stakes scientific endeavor. But there has also always been a cadre of excellent, committed, and entirely reasonable scientists going to bat for the mission.
Can SETI - driven by the increasing 're-discovery' of the idea of technosignatures - get back onto the menu of respected and community funded research?
Like Jason Wright, I think it should. I also think that the field would benefit from further innovation, and some increased stress-testing. This is not to say that those slogging away at radio surveys, or the search for optical signals, or peculiar phenomena that show up in current astronomical data, are doing anything wrong. But SETI could use more of the kind of adrenaline-pumping attention that we've seen with exoplanetary science in the past two decades (even more than the Breakthrough Listen project has mustered). During this time a truly remarkable array of ingenious and altogether surprising techniques and discoveries have washed across the field.
Of course, exoplanetary advances are largely driven by having actual detections of exoplanets on hand. But there are also tons of great innovations in exoplanetary theory and technique happening that, as of yet, have not been realized through astronomical observations - work on biosignatures is one good example.
A proper reintegration of SETI, helped by the scientific community actually seeing more of the much vaunted Breakthrough Listen dollars, would have to involve a major look at strategy. It would also involve some smart thinking on how to incubate a sense of opportunity for tackling a terrific intellectual and practical problem. In many ways this needs to be a grassroots movement - young (and old) researchers need to feel that their investment of time is in a good cause.
But most of all, more of us need to finally take the challenge seriously.