Exoplanets with volcanic hydrogen may harbour extraterrestrial life, say scientists!

Image courtesy: NASA/JPL-Caltech

New Delhi: Recently, NASA scientists revealed their discovery of seven Earth-like planets orbiting the same star, called TRAPPIST-1, that lies 40 lights years away in a distant galaxy.

The whole new 'solar system' beyond our own, is the first known system of seven Earth-sized planets around a single star.

Of seven planets, three are located in the habitable zone, the area around the parent star where a rocky planet is most likely to have liquid water.

Thanks to this discovery, scientists feel that hunting for habitable worlds now may be easier than before.

Suggesting that exoplanets with hydrogen pouring from volcanic sources may have a warmer atmosphere and provide a better target to find alien life in the universe, scientists feel that such a habitable zone may mean that TRAPPIST-1 – the recently discovered system of seven planets – contains four habitable zone worlds, instead of three.

"On frozen planets, any potential life would be buried under layers of ice, which would make it really hard to spot with telescopes," said lead author Ramses Ramirez from Cornell University in the US.

"But if the surface is warm enough – courtesy volcanic hydrogen and atmospheric warming – you could have life on the surface, generating a slew of detectable signatures," Ramirez said.

Combining the greenhouse warming effect from hydrogen, water and carbon dioxide on planets sprinkled throughout the cosmos, distant stars could expand their habitable zones by 30 to 60 percent, researchers said.

Planets located great distances from stars freeze over, researchers said.

"Where we thought you would only find icy wastelands, planets can be nice and warm - as long as volcanoes are in view," said Lisa Kaltenegger, professor at Cornell.

The idea that hydrogen can warm a planet is not new, but an Earth-like planet cannot hold onto its hydrogen for more than a few million years. Volcanoes change the concept.

"You get a nice big warming effect from volcanic hydrogen, which is sustainable as long as the volcanoes are intense enough," said Ramirez, who suggested the possibility that these planets may sustain detectable life on their surface.

A very light gas, hydrogen also "puffs up" planetary atmospheres, which will likely help scientists detect signs of life.

"Adding hydrogen to the air of an exoplanet is a good thing if you're an astronomer trying to observe potential life from a telescope or a space mission. It increases your signal, making it easier to spot the makeup of the atmosphere as compared to planets without hydrogen," Ramirez said.

In our solar system, the habitable zone extends to 1.67 times the Earth-sun distance, just beyond the orbit of Mars.

With volcanically sourced hydrogen on planets, this could extend the solar system's habitable zone reach to 2.4 times the Earth-sun distance – about where the asteroid belt is located between Mars and Jupiter.

This research places a lot of planets that scientists previously thought to be too cold to support detectable life back into play.

"We just increased the width of the habitable zone by about half, adding a lot more planets to our 'search here' target list," said Ramirez.

(With Agency inputs)