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What makes a planet a nice place to live? If it’s too close to its parent star, it would end up a searing hot furnace, like Venus. Too far away, and it would end up a frozen snowball. To be habitable, or at least to host life as we know it, a planet would need to be within what is sometimes referred to as “the Goldilocks zone”. Such a planet would be the perfect distance from its star, allowing it to be temperate enough so that liquid water could exist.

But is distance to the star the only variable that makes a planet habitable? Today we talk to Dr. Ramses Ramirez, a planetary scientist at the Carl Sagan Institute at Cornell. Ramses takes a look how characteristics of a planet itself – namely, volcanism and tectonics – will affect a planet’s habitability.

Why is having a geologically active planet so important for life? Oddly enough, it has to do with the planet’s atmosphere. Greenhouse gases will escape from a planet’s atmosphere over time, lost to space. These gases would disappear over time if they are not continually replenished.

This is where volcanoes and tectonics come in. Volcanoes can replenish an atmosphere, giving the planet a chance to sustain these gases on timescales of billions of years – long enough to allow life to develop and thrive.

What does this mean for extrasolar planets? Recently, seven Earth-like planets were discovered around a star called Trappist-1. Three of these planets are in the star’s habitable zone. But what if one of these planets had volcanism? Perhaps the habitable zone would be much larger than we previously thought!
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