Nasa

The Earth might be more special than we previously thought. A new scientific study has found that if we were just a fraction further from the Sun, our planet would be locked in a never ending Ice Age.

The findings, published in the journal Earth and Planetary Science Letters, will help us understand what criteria to look for in Earth-like exoplanets.


For years, scientists have discovered a huge amount of evidence that shows the Earth is the perfect place for life.

“It has a magnetic field that protects us from the solar wind,” says Martin Turbet, from Sorbonne Universitésin Paris. “It has an ozone layer that shields us from UV light, it has the right amount of water on the surface for both lands and oceans to exist.”

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Turbet and his colleagues have found another factor to Earth’s list of exceptional qualities. The study looked at the effect of carbon dioxide condensation on cold planets during an Ice Age.

On planets slightly colder than Earth, they found CO2 would condense at the poles preventing it from escaping as a gas and warming up the planet through the greenhouse effect.

“We show in fact that the Earth is just at the right distance from the Sun to be able to escape from episodes of complete glaciation, that - we know - must have occurred 2.4Gy and 700My ago,” he explains. Move the Earth away from the Sun by only 15 per cent, the team found, and it would be permanently frozen.

“We had some clues that CO2 condensation could occur on cold planets, and that it could affect the ability of Earth-like planets to escape from episodes of complete glaciation,” Turbet says, “but no-one has ever been able to quantify it.”


The results give us further clues as to where the habitable zone, the region in which it may be able to host liquid water, of an Earth-like planet lies, including discoveries in our backyard.

The past two years have been extremely successful when it comes to discoveries of potentially habitable exoplanets. The biggest discoveries include Proxima Centauri b, the closest exoplanet to Earth, and the seven planets of the TRAPPIST-1 system.

“It is widely believed that these Earth-size planets could be in synchronous rotation around their star, with one side permanently locked in the dark,” Turbet says. “The nightside surface temperature of such planet can be so low that the CO2 would condense on it. And such process is of high relevance to assess the habitability of these newly discovered worlds.”