In 1993, Sen. Richard Bryan (D–Nev.) introduced a last-minute amendment that ended funding for Project HRMS, the last major Search for Extraterrestrial Intelligence (SETI) program funded by NASA. "This hopefully," he quipped, "will be the end of Martian hunting season at the taxpayer's expense." Today, NASA does not have any SETI programs, and does not solicit proposals for SETI projects from astronomers. As a result, the field has atrophied, with only a handful of practitioners left and virtually no pipeline to train more.
Some of us are hopeful change may be around the corner. Congress currently seems not hostile but downright receptive to SETI, and there is no actual statutory prohibition on NASA supporting a SETI program. NASA recently chartered the National Academies of Sciences, Engineering, and Medicine to form the ad hoc Committee on Astrobiology Science Strategy for Life in the Universe to evaluate its astrobiology portfolio, and this committee should recommend that NASA embrace SETI as part of its mission.
Since the late 1950s, astronomers have realized that our technology is sufficient to send and receive signals of sufficient strength to be detected at interstellar distances. If there are other technological species in the galaxy, a simple radio or laser signal would be an unambiguous sign of their existence. Finding such intelligent life is the goal of SETI.
Since then, finding alien life has become a major priority for NASA. Supporting the field of astrobiology is a major part of NASA's research portfolio, and finding signs of microbial life in the solar system or in the atmospheres of distant planets is one if its top priorities.
And yet, “traditional SETI is not part of astrobiology” declares the “NASA Astrobiology Strategy 2015” document. But as many members of the field will tell you, this is incorrect. According to NASA, astrobiology is defined as the study of the "origin, evolution, distribution, and future in the universe" of life.
And indeed, NASA has ambitions to identify biosignatures—the results of interactions between life and its environment—that would reveal the existence of primitive life on other worlds. NASA uses studies of the origin and evolution of past life on Earth as a guide to identify these biosignatures.
But some of the most obvious ways in which Earth is inhabited today are its technosignatures such as radio transmissions, alterations of its atmosphere by industrial pollutants, and probes throughout the Solar System. It seems clear that the future of life on Earth includes the development of ever more obvious technosignatures.
And there is no a priori reason to believe that biosignatures should be easier to detect than these technosignatures. Indeed, intelligent, spacefaring life might spread throughout the galaxy, and therefore be far more ubiquitous than planets that have only microbes. Life might be much easier to find than the NASA strategy assumes.
Indeed, it has been noted cynically, but not untruthfully, that NASA eagerly spends billions of dollars to search for “stupid” life passively waiting to be found, but will spend almost nothing to look for the intelligent life that might, after all, be trying to get our attention. This is especially strange since the discovery of intelligent life would be a much more profound and important scientific discovery than even, say, signs of photosynthesis on the nearest exoplanet to the solar system, Proxima b.
While it is not completely clear why NASA does not include SETI in its astrobiology portfolio, there are several factors that seem likely to be at play.
The first is that SETI sometimes suffers from a “giggle factor” that leads some to conflate it with UFOs or campy science fiction, and indeed Sen. Bryan's grandstanding shows how this "giggle factor" harms science. But NASA should fight against this sort of small-minded attitude; indeed Carl Sagan successfully persuaded another SETI opponent in the Senate, William Proxmire, that his opposition to this important field was a mistake.
The second is the erroneous perception that SETI is an all-or-nothing proposition that yields no scientific progress unless and until it succeeds. On the contrary, the demands of radio SETI have led to major breakthroughs in radio instrumentation, and many SETI false positives have proven to be exciting new astrophysical phenomena, including active galactic nuclei (CTA-21 and CTA-102), pulsars (originally, if somewhat facetiously, dubbed “LGM” for “Little Green Men”) and perhaps the still-not-fully-understood “Tabby’s star.”
Third, there is the erroneous perception that, since radio SETI has been active for decades, its failure to date means there is nothing to find. On the contrary, the lack of SETI funding means that only a tiny fraction of the search space open to radio SETI has been explored. The truth is, we only begun to seriously survey the sky even for radio beacons, and other search methods have even less completeness.
Finally, there is the erroneous perception that SETI will proceed on its own without NASA support. While it is true that the Breakthrough Listen initiative has pledged to spend up to $100 million over 10 years, in truth its spending has been far below that level, and it is focused on a small number of mature search technologies. Beyond this initiative, private benefactors have supported the SETI Institute’s Allen Telescope Array, but not at the level necessary to complete the array or fund its operations.
To be sure, many people feel that SETI is unlikely to succeed, too risky to spend a lot of resources on. Others are sure, based on the fact that "they" have not visited us recently, that they must not be out there, or must not want to be found. But the question of our place in the universe is too important not to spend at least some of our resources on, and whatever merit one subjectively assigns SETI, it is clear that its optimum share of NASA's research portfolio is not zero. As Giuseppe Cocconi and Philip Morrison wrote in their seminal 1959 paper on SETI: "The probability of success is difficult to estimate; but if we never search, the chance of success is zero."
And so, NASA should support a major SETI initiative or, at the very least, expressly encourage SETI practitioners to compete on a level playing field with practitioners of other subfields for NASA astrobiology resources in the quest to discover life elsewhere in the universe.
This will uncork pent-up SETI efforts that will allow SETI practitioners to develop new search strategies, discover new astrophysical phenomena and, critically, train a new generation of SETI researchers to guide NASA’s astrobiology portfolio to vigorously pursue the discovery of all kinds of life in the universe—both “stupid” and intelligent.
And if, as many suspect, technosignatures prove to be closer to our grasp than biosignatures, this will ultimately lead to one of the most profound discoveries in human history, and a reinvigoration of and relevance for NASA not seen since the Apollo era.
In retrospect, we will wonder why we were so reluctant to succeed.