To the average American, the news about NASA’s Kepler spacecraft discovering evidence of potentially “billions” of Earth-like planets in “habitable” solar orbits in the universe might feel like a paradigm-shifting moment. If there are billions of Earth-like planets out there, the possibility of life existing somewhere other than Earth suddenly goes from seeming like an odds-against to an odds-on notion.
But to NASA’s scientists, that paradigm had shifted long before the headlines hit—indeed, before Kepler even launched.
While the majority of the public’s attention (and NASA’s funding) over the past decades was focused on the human spaceflight program, NASA’s astronomical science program slowly was chipping away at some of the biggest mysteries of the universe, including the origins of the elements necessary for life. By the time NASA was founded in 1958, astronomers had already figured out that all the heavier elements in the periodic table, which are necessary for life as we know it,not only could be produced, but actually were produced in the high-temperature supernova explosions of large stars. How those materials might be transported to potential planets in orbit around still-healthy stars, however, was still a mystery.
Ten years later, scientists began finding evidence of water and a variety of elements in interstellar space, which meant those elements could travel away from where they were formed. But that still didn’t account for getting enough of those elements onto a planet’s surface to spark life.
Enter the comets. By the late 1980s and early 1990s, research into the composition of comets had showed that comets contained—and released, at different points of their orbital trajectories—traces of all the elements necessary for not just life, but carbon-based life as we know it. One of the details of astronomy I find most fascinating is that every element in the periodic table produces its own unique “fingerprint” on the electromagnetic spectrum. So if you look at a cosmic object through a spectrographic instrument, you can tell, even from light years away, what elements it contains. (NASA’s Stardust mission, launched in 1999, confirmed the spectrographic notions about comets with actual material collected from the tail of the Wild 2 comet, returned to Earth in a parachute-equipped capsule.)
The existence of crucial elements in comets didn’t prove that comets provided the necessary link to delivering those materials to planets, but it made that theory more plausible. It became possible to envision a universe that not only created all the elements necessary for water, a survivable atmosphere, and carbon-based life forms, but also possessed a delivery system for getting those elements to a few perfectly-sized and composed planets, situated perfectly around perfectly-sized stars, and then occasionally combining in just the right timing and proportion to create a life-bearing planet like Earth.
But what were the chances of there being enough of those perfectly-situated, perfectly-suited planets to make life elsewhere not just possible, but plausible, or even probable?
In the fall of 1997, I interviewed a NASA astrophysicist by the name of John Mather for a book about the satellite-based scientific research conducted by NASA’s Goddard Space Flight Center. Mather had been the force behind the Cosmic Background Explorer (COBE) satellite that discovered scientific evidence supporting the Big Bang Theory of the universe’s origins. In 2006, Mather received a Nobel Prize for that research, but even in 1997 he was considered one of the most brilliant astrophysicists in the world. It’s not often you get access to a mind like that, so after I finished asking him about his research, I asked him what he thought about other big cosmic issues, including the possibility of life on other planets.
His eyes lit up. He answered that 10 years earlier, he and most of his colleagues felt that the chances of intelligent life existing elsewhere in the universe were remote. But two things, he said, had changed their views. Radically. He talked about the above-mentioned discoveries in terms of comets and the plausibility of critical elements being distributed to planets. And then, he said, came the Hubble Telescope’s first Deep Field image.
The first Deep Field image was created by assembling images taken by the Hubble Space Telescope over 10 consecutive days in December 1995. That was the same year, mind you, that the first confirmed extra-solar planet, or “exoplanet” (meaning a planet outside our solar system), was discovered. As Mather explained it to me, some Hubble researchers were curious about what they might discover if they focused the telescope for a much longer period of time than normal, to capture even the faintest light, on a tiny area of dark space roughly the size of a grain of sand held at arm’s length.
What researchers found when they focused the Hubble over those 10 days on that tiny speck of darkness, Mather said, shook their worlds. When the images were compiled, they showed not just thousands of stars, but thousands of galaxies. If a tiny speck of darkness in the night sky held that many galaxies, stars and—as scientists were beginning to realize—associated planets … the number of galaxies, stars, and planets the universe contained had to be breathtakingly larger than they’d previously imagined.
With what they were learning about the possibilities of comets and elements being seeded throughout the universe, that discovery was paradigm-shifting. The existing paradigm assumed that the chances of Earth-like, intelligent life elsewhere were remote. But if there were that many potential stars and planets, the chance of there NOT being not only life, but intelligent, carbon-based life like ours on some distant habitable planet, Mather said, was actually the possibility that was infinitesimally small.
Knowing something must theoretically exist and finding evidence of its existence are two very different things, of course. Even this new Kepler discovery reflects extrapolated data, in part because the observatory's pointing mechanism malfunctioned before it completed all of its planned observations. But Kepler, while perhaps not paradigm-changing in terms of scientists’ views on whether intelligent life exists elsewhere in the universe, is most certainly the next step forward. The Hubble Deep Field image changed astronomers’ views of how many stars and potential planets might exist. Kepler’s results have similarly recalibrated scientists’ understanding of just how many habitable planets might exist.
The Kepler results are also still game-changing, if not paradigm-changing. Gaining support for follow-on missions will be far easier with such tantalizing results arising from this one. With billions of possible alternate home planets, how can we not try to find out if any of them really are like us? And that tantalizing possibility offers NASA something the agency’s mission planners have been lacking in the past few years: a clear goal, target, and focus—one that the public might even get excited about.
But will even that goal be exciting enough for Americans to rally behind it, politically and financially? A few months after Kepler launched—an event that garnered far less attention or interest than this week’s announcement of its findings—I wrote about the difficulty of rousing enthusiasm for NASA’s non-human spaceflight research. The timelines of these projects are extremely long, even when they’re successful in the end. The COBE mission was 15 years in the making. Kepler was first conceived and proposed by its principal investigator, Bill Borucki, almost 20 years ago. And the time required to develop the technology to send even a robotic probe 12 light years across the universe will be … well, let’s just say we shouldn’t place bets on it happening in most of our lifetimes.
On the other hand, a NASA center director once told me that the biggest argument for a human space mission to Mars was that if we didn’t develop the technology to transport people to a different planet, we were doomed to remain an “SPS” (a “single planet species”) and therefore doomed to eventual extinction. So perhaps the best thing Kepler could do is provide enough of a glimmer of hope that another big blue marble exists that we are inspired to invest in the very long-term effort of finding and developing the technology to reach it.
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