For decades many researchers have tended to view astrobiology as the underdog of space science. The field—which focuses on the investigation of life beyond Earth—has often been criticized as more philosophical than scientific, because it lacks in tangible samples to study.
Now that is all changing. Whereas astronomers once knew of no planets outside our solar system, today they have thousands of examples. And although organisms were previously thought to need the relatively mild surface conditions of our world to survive, new findings about life’s ability to persist in the face of extreme darkness, heat, salinity and cold have expanded researchers’ acceptance that it might be found anywhere from Martian deserts to the ice-covered oceans of Saturn’s moon Enceladus.
Highlighting astrobiology’s increasing maturity and clout, a new Congressionally mandated report from the National Academy of Sciences (NAS) urges NASA to make the search for life on other worlds an integral, central part of its exploration efforts. The field is now well set to be a major motivator for the agency’s future portfolio of missions, which could one day let humanity know whether or not we are alone in the universe. “The opportunity to really address this question is at a critically important juncture,” says Barbara Sherwood Lollar, a geologist at the University of Toronto and chair of the committee that wrote the report.
The astronomy and planetary science communities are currently gearing up to each perform their decadal surveys—once-every-10-year efforts that identify a field’s most significant open questions—and present a wish list of projects to help answer them. Congress and government agencies such as NASA look to the decadal surveys to plan research strategies; the decadals, in turn, look to documents such as the new NAS report for authoritative recommendations on which to base their findings. Astrobiology’s reception of such full-throated encouragement now may boost its odds of becoming a decadal priority.
Another NAS study released last month could be considered a second vote in astrobiology’s favor. This “Exoplanet Science Strategy” report recommended NASA lead the effort on a new space telescope that could directly gather light from Earth-like planets around other stars. Two concepts, the Large Ultraviolet/Optical/Infrared (LUVOIR) telescope and the Habitable Exoplanet Observatory (HabEx), are current contenders for a multibillion-dollar NASA flagship mission that would fly as early as the 2030s. Either observatory could use a coronagraph, or “starshade”—objects that selectively block starlight but allow planetary light through—to search for signs of habitability and of life in distant atmospheres. But either would need massive and sustained support from outside astrobiology to succeed in the decadal process and beyond.
There have been previous efforts to back large, astrobiologically focused missions such as NASA’s Terrestrial Planet Finder concepts—ambitious space telescope proposals in the mid-2000s that would have spotted Earth-size exoplanets and characterized their atmospheres (if these projects had ever made it off the drawing board). Instead, they suffered ignominious cancellations that taught astrobiologists several hard lessons. There was still too little information at the time about the number of planets around other stars, says Caleb Scharf, an astrobiologist at Columbia University, meaning advocates could not properly estimate such a mission’s odds of success. His community had yet to realize that in order to do large projects it needed to band together and show how its goals aligned with those of astronomers less professionally interested in finding alien life, he adds. “If we want big toys,” he says. “We need to play better with others.”
There has also been tension in the past between the astrobiological goals of solar system exploration and the more geophysics-steeped goals that traditionally underpin such efforts, says Jonathan Lunine, a planetary scientist at Cornell University. Missions to other planets or moons have limited capacity for instruments, and those specialized for different tasks often end up in ferocious competitions for a slot onboard. Historically, because the search for life was so open-ended and difficult to define, associated instrumentation lost out to hardware with clearer, more constrained geophysical research priorities. Now, Lunine says, a growing understanding of all the ways biological and geologic evolution are interlinked is helping to show that such objectives do not have to be at odds. “I hope that astrobiology will be embedded as a part of the overall scientific exploration of the solar system,” he says. “Not as an add-on, but as one of the essential disciplines.”
Above and beyond the recent NAS reports, NASA is arguably already demonstrating more interest in looking for life in our cosmic backyard than it has for decades. This year the agency released a request for experiments that could be carried to another world in our solar system to directly hunt for evidence of living organisms—the first such solicitation since the 1976 Viking missions that looked for life on Mars. “The Ladder of Life Detection,” a paper written by NASA scientists and published in Astrobiology in June, outlined ways to clearly determine if a sample contains extraterrestrial creatures—a goal mentioned in the NAS report. The document also suggests NASA partner with other agencies and organizations working on astrobiological projects, as the space agency did last month when it hosted a workshop with the nonprofit SETI Institute on the search for “techno-signatures,” potential indicators of intelligent aliens. “I think astrobiology has gone from being something that seemed fringy or distracting to something that seems to be embraced at NASA as a major touchstone for why we’re doing space exploration and why the public cares,” says Ariel Anbar, a geochemist at Arizona State University in Tempe.
All this means is astrobiology’s growing influence is helping bring what once were considered outlandish ideas into reality. Anbar recalls attending a conference in the early 1990s, when then–NASA Administrator Dan Goldin displayed an Apollo-era image of Earth from space and suggested the agency try to do the same thing for a planet around another star.
“That was pretty out there 25 years ago,” he says. “Now it’s not out there at all.”