'Runaway Greenhouse' Stage Can Overheat Planets: It's Easier Than You Might Think

Some planets have scorched, dry surfaces, inhospitable to life. Now, scientists have discovered that it might be easier than previously thought for a planet to overheat into this uninhabitable "runaway greenhouse" stage. The findings could reveal a little more about planet formation.

When a runaway greenhouse stage occurs, the planet absorbs more solar energy than it can give off to retain equilibrium. This causes the planet to overheat, boiling oceans and filling the atmosphere with steam. This leaves the planet glowing-hot and scorched--like Venus.

So how does this situation occur? It all depends where the planet is located. There's a certain distance that a planet has to be from its star, called the habitable zone. Outside of this zone, a runaway greenhouse stage can occur. Yet in order to see the exact conditions that cause this stage, the researchers employed computer modeling. In the end, they found a lower thermal radiation threshold for the runaway greenhouse process. This means that the stage may be easier to initiate than previously expected.

"The habitable zone becomes much narrower, in the sense that you can no longer get as close to the star as we thought before going into a runaway greenhouse," said Tyler Robinson, one of the researchers, in a news release.

The new findings are crucial for searching for the potential of life on other worlds. In fact, it actually reveals that many of the planets found may have their candidacy as possible habitable planets revoked.

"These worlds on the very edge got 'pushed in,' from our perspective--they are now beyond the runaway greenhouse threshold," said Robinson.

Currently, scientists are planning to conduct more research in order to test their findings. Yet if they hold, it could mean that there may be fewer planets than we thought that meet the requirements for being habitable. In addition, it could show what might happen to our own planet in the future as the sun increases in brightness over time.

The findings are published in the journal Nature Geoscience.