What really makes a planet habitable? Our assumptions may be wrong

Paul M. Sutter is an astrophysicist at SUNY Stony Brook and the Flatiron Institute, host of “Ask a Spacemanand “Space Radio,” and author of “How to Die in Space.” Sutter contributed this article to Space.com’s Expert Voices: Op-Ed & Insights.

Remember Hoth, that ice-covered world from “The Empire Strikes Back”? Though some creatures eked out an existence on the planet’s surface, it was a pretty miserable place to live — and generally considered uninhabitable, because all the water content of that world had frozen. As we continue to uncover thousands of planets orbiting other stars, and especially as we narrow down the searches for Earth-like planets, we might want to ask this: How common are these ice-covered planets, and might they be capable of hosting life?