When you’ve spent your career chasing the ultimate, change-everything cosmic brass ring, how do you retire without feeling disappointed? I’ve been asked that question, or some variation, dozens of times in the past month, and I’ve answered it the same way I have over my many decades as a research scientist searching for extraterrestrial intelligence.
I’m not disappointed. I understand how little searching we’ve done so far, and I’m excited about how much we will do in the future. Now it is time for me to shift from looking for extraterrestrial intelligence to looking for intelligent benefactors to help support that quest. I’ve done this before, but now I have to do it with gusto. Now I’m retired.
The existence of life beyond Earth is an ancient human concern. Over the years, however, attempts to understand humanity’s place in the cosmos through science often got hijacked by wishful thinking or fabricated tales. Of particular note, the New York Sun hoaxed its eager readers in 1835 with stories about a splendid civilization of moon-men that had supposedly been revealed by observations made with a 20-foot optical telescope in South Africa. Percival Lowell opened the 20th century with a popular, but false, interpretation of canals built by thirsty Martians to save their planet.
But things got more serious in 1959, with the publication of a paper in the journal Nature marking the beginning of the modern era of the search for extraterrestrial intelligence, or SETI. The paper’s authors, Giuseppe Cocconi and Philip Morrison, recognized that the new science of radio astronomy offered tools - radio telescopes developed from World War II-era radars - with which these old human questions could be explored.
This is what hooked me on SETI.
As I was leaving graduate school in 1974, I was recruited to join a fledgling SETI project at the Hat Creek Observatory in California, mainly because I knew how to program an ancient PDP8/S computer that had been donated to the project. I was alive at just the right time, with just the right skills.
In 1960, the pioneering astronomer Frank Drake, working at the National Radio Astronomy Observatory in Green Bank, W.Va., pointed the Tatel telescope at two nearby, sun-like stars, seeking to detect any radio signals that extraterrestrials might be transmitting, whether for their own purposes or to attract our attention. Drake’s Project Ozma failed to find any engineered signals coming from the vicinity of those stars, but it did detect unanticipated emissions coming from our own technology. To this day, telling the difference between signals that might be "theirs" and those that are ours remains a major challenge.
In his book "Is Anyone Out There?," written with Dava Sobel, Drake describes an adrenaline-charged episode when he thought he might have found what he was looking for. The SETI research community is small, but almost all of us have shared that incredible experience. As our hardware and software have evolved in sophistication, we’ve built in safeguards that filter out most human-engineered sources of interference. Most, but not all.
This happened to me in the 1990s, in the midst of a decade-long search called Project Phoenix. (It was named to commemorate rising from the ashes of congressional termination of NASA’s SETI program.) With the help of private donations, we transported a shipping container jammed with electronic gear to major observatories around the world.
We would observe simultaneously with a second, smaller telescope located hundreds of miles away. This was our main defense against confusing our signals with theirs. For any signal to be considered a valid candidate for extraterrestrial intelligence, it had to be detected at both sites and had to exhibit behavior consistent with a signal being transmitted from somewhere near the star we were targeting.
In 1997, a lightning storm in Woodbury, Ga., where our second dish was located, fried a disk drive in one of our computers and left us with only the 140-foot telescope at Green Bank for a few days. And that is when things got interesting.
Early one morning, I was preparing to end my shift babysitting the automated detection systems and pack up to head back to California when a clearly artificial signal was detected. The Phoenix system automatically did what it could without the second dish. It pointed away from the target star, and the signal disappeared, then it pointed back at the star, and there was the signal again.
I stopped thinking about packing.
I had an idea and wrote a small program to search our recent data to see if we had detected this signal before. The results revealed that we had indeed, when the telescope was pointed in other directions, and that it was our technology being picked up by the telescope’s peripheral vision. But I was so excited that I misread the numbers. My quick bit of programming, sloppy formatting and rising excitement all conspired to craft a different script.
My colleagues from the day shift arrived to join the action. I sent a quick e-mail to our administrative assistant in California asking her to help change my travel plans and to let my husband know that I would be delayed. Then the doors of the observing room at the base of the telescope swung open to admit a documentary TV crew; months earlier, we had agreed to let them film our work. Now here they were. For hours we ignored the cameras and nodded the venerable old telescope on and off the target star. The signal disappeared and reappeared as expected. We looked up the star and debated what might make it a successful host for another technological civilization.
By mid-afternoon, although the signal had never failed to show up at the right time, we reluctantly concluded that it was not, after all, evidence of a distant civilization. The way the signal’s frequency components were changing because of the Earth’s rotation was wrong. We didn’t know what it was, but we knew what it wasn’t. As I headed off to dinner, again and again I assured the TV crew that this wasn’t it after all; they were more disappointed than we were.
Remember that e-mail I sent about changing my travel plans? It turns out that innocent bit of trivial logistics was indirectly responsible for a call from The New York Times to our tired California colleagues, seeking comments on the detection. Contrary to what the screenwriters in Hollywood think, secrecy will probably not be part of any actual detection - this secret would be just too hard to keep. Conspiracy cover-up theories find no supporters among those of us who do this work.
How likely is it that someday, the signal will truly come from someone else? Nobody can answer that question. However, the original paper outlining SETI in Nature in 1959 did say something very wise in its last sentence: "The probability of success is difficult to estimate; but if we never search, the chance of success is zero."
Our 50 years of searching is equivalent to scooping a single glass of water from the Earth’s oceans to examine it for fish. It is an experiment that could work - but if it fails, the correct conclusion is that there was inadequate sampling, not that the oceans are devoid of fish.
Today, our searches are getting exponentially better. If we are looking for the right thing, it will take only a few decades to conduct a search that is comprehensive enough to be successful or to yield conclusive negative results.
Is there actually someone or something out there for us to find? This is another question without an answer, yet. In the last two decades of my career, what we’ve learned about exoplanets and extremophiles - organisms that inhabit environments once thought to be incapable of supporting life - has made the cosmos appear more friendly to living creatures.
The census of potentially habitable cosmic real estate has continued to expand. This is not the same as knowing that the real estate is inhabited, of course, though that conclusion could be part of our near future. After all, things do look good.
When I was a student, additional planets were just a good theory. Today, it’s beginning to look like almost every star hosts planets - some seem tantalizingly familiar, but some of them are unlike any in our solar system. We used to think that the limits on life were between the boiling and freezing points of water, at neutral pH values, at pressures not too different from those on the Earth’s surface. The detailed study of life in extreme environments has pushed those limits aside.
Life has evolved to thrive in environments that are extreme only by our limited human standards: in the boiling battery acid of Yellowstone hot springs, in the cracks of permanent ice sheets, in the cooling waters of nuclear reactors, miles beneath the Earth’s crust, in pure salt crystals, and inside the rocks of the dry valleys of Antarctica.
What will my granddaughter know about the limits of life before her student days are over? It’s possible that she may learn about a second genesis of life on Mars or within the ice-covered oceans of the moons of Jupiter and Saturn; possible, that is, if we continue our exploration of the bodies of our solar system. As for intelligent life - for that we need SETI.
And what SETI needs is stable funding for the long haul. For our impatient species, even a few decades is a long time, and if we haven’t yet invented the right way to search, the endeavor could take much longer. A successful retirement for me will consist of making sure that my successor, his successor and SETI researchers elsewhere do not have to ride the funding roller coaster that has characterized the first half-century of this scientific exploration.
With no guarantee of success, it is difficult to attract the best minds to a career in SETI. While many, like me, are hooked on the importance and the potential payoff of this research, few are willing to bet their family’s livelihood on it. Some university professors have been able to develop SETI programs, but only after they achieve tenure. This isn’t conducive to determined exploration. And that is precisely what the search needs right now.
After decades of confusion with UFOs and other pseudo-science, Golden Fleece awards and congressional boasts about ending funding for the "great Martian chase," the surprising exoplanet discoveries today legitimize this scientific exploration. We haven’t yet found Earth 2.0, but most of my planet-hunting colleagues say that it’s imminent. When we do, the next question is going to be: Does anybody live there?
Jill Tarter, an astronomer, retired in May as the director of the Center for SETI research at the SETI institute. She is Bernard M. Oliver chair for SETI at the institute.