US scientists have laid out a plan to search for life in the universe


The discovery of many potentially habitable planets beyond the solar system and a growing understanding of the variety of life on Earth provides NASA an opportunity to advance the field of astrobiology, according to a new National Academy of Sciences report.

A blue-ribbon panel of researchers chaired by the University of Toronto’s Barbara Sherwood Lollar assembled the report at the behest of the US Congress, which asked in a 2017 law that a “strategy for astrobiology” be developed to prioritize “the search for life’s origin, evolution, distribution, and future in the universe.”

The 196-page report does not offer easy access to ET, but the steady drumbeat of scientific advancement it documents suggests an increasingly sophisticated understanding of what we know—and don’t know—about biology on our planet and beyond.

Indeed, the recently gained knowledge it highlights is the front end of a wave: Only the Viking mission in the 1970s hunted rigorously for signs of life on other planets, and now the first new NASA mission to do so, the Europa lander, is being designed. In the past four years alone, scientists using data gathered by space probes on Mars discovered evidence of past surface water, the presence of nutrients and organic molecules, and methane gas in the atmosphere that varies by season.

This doesn’t mean life exists now on Mars, but it is helping contribute to an understanding of astrobiology as a discipline that looks at physical and chemical processes over time to determine if the conditions for life once existed or may do so in the future.

Much work on astrobiology is Earth-focused; it is the only place we know life exists and thus is our guinea pig for detecting life from a distance. The Galileo space probe found signs of life on our planet in 1990.

The report stressed that recent discoveries of life on Earth that exists without the sun’s energy, deep under the ocean or the ground, should inform what we look for on other worlds. Scientists are expanding their understanding of habitability beyond a binary and into a spectrum, which may sound trite, but previous research relied on blunt instruments and blunter assumptions about alien life—starting with the idea that it would appear on the surface.

Still, a key problem is that scientists still don’t understand precisely how life came about on Earth, making it difficult to know what to look for on other worlds. Missions like Japan’s Hayabusa 2 and NASA’s OSIRIS-REx are planning to return samples from carbon-rich asteroids to Earth in the next five years, giving more insight into the early solar system and our own planet’s development.

By far the largest development stressed by the scientists were the Kepler spacecraft’s advances in identifying planets beyond the solar system. The number of identified exoplanets has doubled since 2015, “enough to warrant taking the next steps toward the discovery of life on exoplanets.” That entails—no surprise here—following through on NASA’s planned James Webb Space Telescope, which will be able to learn important characteristics about distant planets spotted by NASA’s latest observatory, TESS.

Technology, too, plays a hand. There are prosaic problems to solve, like the difficulty of creating drills that work well in low-gravity to penetrate beneath the surface of distant planets, or the tools to identify faint biosignatures in extreme conditions without generating false positives. But there are promising developments, like tinier, more powerful satellites and data-science techniques to plow through the huge amounts of data gathered by NASA observatories. The report, like most space-related enterprises, makes much of the potential of public-private partnerships to expand data collection.

Some thinkers relying on the Fermi paradox believe the probability of life beyond Earth is vanishingly low. But this report is a reminder that the assumptions we make about life beyond our own world are rapidly changing—and that investigating them empirically can reveal truths about ourselves as well.

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