Scientific interest in extraterrestrial life has grown in the past 20 years. The field of astrobiology now includes researchers from a wide variety of disciplines — microbiologists studying bacteria that survive in the most extreme conditions on Earth; astronomers who believe there may be billions of planets with conditions hospitable to life; chemists investigating how amino acids and living organisms first appeared on Earth; and scientists studying rocks from Mars are seeing convincing evidence that microbial life existed on the Red Planet.

In First Contact: Scientific Breakthroughs in the Hunt for Life Beyond Earth, Marc Kaufman, a science writer and national editor at The Washington Post, explains how microbes found in some of Earth's most inhospitable environments may hold the key to unlocking mysteries throughout the solar system.

Kaufman talks with Fresh Air's Dave Davies about the ongoing search for life in the universe — from current research, to the unknowns in the field.

"There are undoubtedly billions or trillions of planets out there and there are most likely billions in the Milky Way itself — just one of billions of galaxies," Kaufman says. "There are billions of planets in habitable zones in relation to their stars that would allow for water to be liquid and for other important conditions for life."

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