NASA asks: Will we know life when we see it?

In the last decade, we have discovered thousands of planets outside our solar system and have learned that rocky, temperate worlds are numerous in our galaxy. The next step will involve asking even bigger questions. Could some of these planets host life? And if so, will we be able to recognize life elsewhere if we see it?

A group of leading researchers in astronomy, biology and geology has come together under NASA's Nexus for Exoplanet System Science, or NExSS, to take stock of our knowledge in the search for life on distant planets and to lay the groundwork for moving the related sciences forward.

"We're moving from theorizing about life elsewhere in our galaxy to a robust science that will eventually give us the answer we seek to that profound question: Are we alone?" said Martin Still, an exoplanet scientist at NASA Headquarters, Washington.

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Credit: NASA

This image is an artist's conception of what life could look like on the surface of a distant planet.

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Credit: NASA/Aaron Gronstal

Life can leave "fingerprints" of its presence in the atmosphere and on the surface of a planet. These potential signs of life, or biosignatures, can be detected with telescopes.

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Credit: NASA/Aaron Gronstal

Abiotic processes can fool us into thinking a barren planet is alive. Rather than measuring a single characteristic of a planet, we should consider a suite of traits to build the case for life.

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Credit: NASA/Aaron

Since the data we collect from planets will be limited, scientists will quantify how likely a planet has life based on all the available evidence. Follow-up observations are required for confirmation.

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NASA: We could find alien life in 20 years.