Title: What are the chances of life on another planet? | Tufts Now
Headings: What are the chances of life on another planet?
Ask the Expert
What are the chances of life on another planet?
Kenneth R. Lang, a professor in the Department of Astronomy and Astrophysics, explains
If You Like This

Content: It’s been an invaluable research tool, but has found no direct evidence that life ever existed on Mars, and has revealed that the planet’s atmosphere is too thin to protect it from the sun’s radiation. The discovery of thousands of planets orbiting nearby stars has nevertheless greatly increased speculation that there may be some kind of life on a planet outside our solar system. In the past 20 years, we have confirmed the discovery of almost 2,000 planets, called exoplanets, beyond our solar system. Four thousand other exoplanet candidates await confirmation. The ones most likely to harbor life would be smallish, rocky planets like Earth. Larger planets tend to be composed of hydrogen gas, the most abundant element in the universe, and to not have a solid surface. Good candidates for life would also occupy what scientists call the habitable zone—the zone in which a planet’s distance from the parent star makes liquid water possible. The Kepler mission —a space observatory launched by NASA in 1997 to search our galaxy for just these kinds of Earth-like planets—has found one candidate that meets both requirements, Kepler-452b. So the chances of life on another planet are high. However, we have no direct evidence yet of life anywhere other than Earth.