One day, perhaps in the not-too-distant future, a faraway planet could yield hints that it might host some form of life – but surrender its secrets reluctantly.

Our space telescopes might detect a mixture of gases in its atmosphere that resembles our own. Computer models would offer predictions about the planet’s life-bearing potential. Experts would debate whether the evidence made a strong case for the presence of life, or try to find still more evidence to support such a groundbreaking interpretation.

“We are in the beginning of a golden era right now,” said Ravi Kopparapu, a scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, who studies habitable planets. “For the first time in the history of civilization we might be able to answer the question: Is there life beyond Earth?”

For exoplanets – planets around other stars – that era opens with NASA’s James Webb Space Telescope. Instruments aboard the spacecraft are detecting the composition of atmospheres on exoplanets. As the power of telescopes increases in the years ahead, future advanced instruments could capture possible signs of life – “biosignatures” – from a planet light-years away.

Within our solar system, the Perseverance rover on Mars is gathering rock samples for eventual return to Earth, so scientists can probe them for signs of life. And the coming Europa Clipper mission will visit an icy moon of Jupiter. Its goal: to determine whether conditions on that moon would allow life to thrive in its global ocean, buried beneath a global ice shell.

But any hints of life beyond Earth would come with another big question: How certain could any scientific conclusions really be?

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