Our efforts aimed at discovering life as we know it beyond the solar system are restricted to what’s known as the “Goldilocks zone.” This refers to the region around a star where the temperature is just right — not too hot and not too cold — for liquid water to exist.
Now, in a study published Monday in the Astrophysical Journal Letters, researchers from Cornell University have proposed that in addition to a planet’s distance from its parent star (or stars), there is another factor that affects its habitability — the presence or absence of volcanoes on its surface.
The presence of hydrogen-spewing volcanoes on rocky exoplanets, the researchers argue, can expand the Goldilocks zone around stars, potentially making them much bigger than previously thought.
“On frozen planets, any potential life would be buried under layers of ice, which would make it really hard to spot with telescopes,” lead author Ramses Ramirez, a research associate at Cornell’s Carl Sagan Institute, who, along with her colleague Lisa Kaltenegger used climate models for hypothetical planets for the purpose of the study, said in a statement. “But if the surface is warm enough – thanks to volcanic hydrogen and atmospheric warming – you could have life on the surface, generating a slew of detectable signatures.”
Hydrogen is a powerful greenhouse gas, and its presence in a planet’s atmosphere should, in theory, make the surface warm enough for life to originate. The problem is, an Earth-like planet cannot hold onto its hydrogen, which is an extremely light gas, for more than a few million years — not unless the gas is being constantly pumped into the atmosphere.
This is where the volcanoes come in.
“You get a nice big warming effect from volcanic hydrogen, which is sustainable as long as the volcanoes are intense enough,” Ramirez said.
According to the study, if we combine the warming effect from hydrogen, water and carbon dioxide on exoplanets, stars could expand their habitable zones by 30 to 60 percent. If, for instance, a planet contain hydrogen-spewing volcanoes existed in our solar system, it could orbit the sun at a distance of 2.4 astronomical units (1 AU is the average distance between Earth and the sun), and still remain habitable.
Another star system where life would benefit from the presence of planets with volcanoes is TRAPPIST-1 — a nearby star that has seven Earth-sized planets, three of which lie firmly within the habitable zone. If the findings of the study hold up, and if the system happens to have a planet whose atmospheric hydrogen is replenished by volcanoes, it could increase the number of potentially habitable planets around the star to four.
“We just increased the width of the habitable zone by about half, adding a lot more planets to our ‘search here’ target list,” Ramirez said.
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