(ORDO NEWS) — Earth is the only planet on which we know life exists. But the conditions for life may not be limited to Earth-like planets, and scientists have now identified one type of exoplanet that could have habitable conditions for billions of years.
It’s all about liquid water, which stays for a long time. On Earth, the presence of liquid water was vital to the origin of life. More broadly, exoplanets that can store liquid water may have a better chance of developing life.
A new study by astronomer Marit Mollus of the University of Zurich in Switzerland has shown that a nice, dense atmosphere of hydrogen and helium can maintain temperatures and conditions suitable for life for a very long time.
“One of the reasons why water on Earth can be liquid is its atmosphere,” says astrophysicist Ravit Helled of the University of Zurich in Switzerland.
“Due to its natural greenhouse effect, it retains just the right amount of heat to create the right conditions for oceans, rivers and rainfall.”
However, the Earth’s atmosphere did not always look like it does today. Now it is mostly nitrogen, followed by oxygen, and only minor amounts of hydrogen and helium.
When the planet formed, it had what is called a primordial atmosphere made up mostly of hydrogen and helium: the main constituents of the cloud of dust and gas from which the sun and solar system formed.
The Earth lost its original atmosphere quite early, probably through several processes, including exposure from a very hot young Sun and meteorite bombardment.
But it’s entirely possible that a Super-Earth-like exoplanet – more massive than Earth but less massive than Neptune – could retain its original atmosphere for much longer than Earth.
“Such massive primordial atmospheres can also cause a greenhouse effect – very similar to Earth’s atmosphere today,” Helled explains.
“So we wanted to find out if these atmospheres could help create the necessary conditions for liquid water.”
Research has shown that exoplanets with dense primary atmospheres may indeed be warm enough to support the presence of liquid water for 10 billion years.
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