The quest to find habitable — and perhaps inhabited — planets and moons beyond Earth focuses largely on their location in a solar system and the nature of its host star, the eccentricity of its orbit, its size and rockiness, and the chemical composition of its atmosphere, assuming that it has one.
Astronomy, astrophysics, cosmochemistry and many other disciplines have made significant progress in characterizing at least some of the billions of exoplanets out there, although measuring the chemical makeup of atmospheres remains a immature field.
But what if these basic characteristics aren’t sufficient to answer necessary questions about whether a planet is habitable? What if more information — and even more difficult to collect information — is needed?
That’s the position of many planetary scientists who argue that the dynamics of a planet’s interior are essential to understand its habitability.
With our existing capabilities, observing an exoplanet’s atmospheric composition will clearly be the first way to search for signatures of life elsewhere. But four scientists at the Carnegie Institution of Science — Anat Shahar, Peter Driscoll, Alycia Weinberger, and George Cody — argued in a recent perspective article in Science that a true picture of planetary habitability must consider how a planet’s atmosphere is linked to and shaped by what’s happening in its interior.
They argue that on Earth, for instance, plate tectonics are crucial for maintaining a surface climate where life can fill every niche. And without the cycling of material between the planet’s surface and interior, the convection that drives the Earth’s magnetic field would not be possible and without a magnetic field, we would be bombarded by cosmic radiation.
“We need a better understanding of how a planet’s composition and interior influence its habitability, starting with Earth,” said lead author Shahar, who is trained in geological sciences.
“This can be used to guide the search for exoplanets and star systems where life could thrive, signatures of which could be detected by telescopes.”
It all starts with the formation process.