The ever-expanding universe has countless planets. There are more than 20 billion Earth-like planets estimated to be in the Milky Way alone. But how many of them can nurture life? And how do we find them out? Unless these worlds directly contact us, the only way to discover other habitable planets is to look into their atmospheres.
Scientists have already detected atmospheres on large exoplanets, and when the James Webb Telescope becomes functional, they should be able to study the atmosphere of Earth-like exoplanets. But what astronomers need to look for to confirm life on the exoplanet?
One of the top contenders is oxygen. On our planet, oxygen accounts for 21% of the atmosphere and can be easily detected by its spiral signature. So if we find oxygen and water on an Earth-sized exoplanet, is that a sign of extraterrestrial life? Well, a new study says finding oxygen isn’t enough to confirm that.
The study suggests that relying on Earth’s model for a planet’s atmospheric evolution can be wrong. Early Earth didn’t have oxygen in abundance, and it was only created as a waste product by early life forms. Only after the photosynthesis evolution, oxygen became so useful.
While hydrogen is the most easily found element in the universe, oxygen is expected to be common on rocky planets, accompanied by nitrogen and carbon. So, water (H2O), carbon dioxide (CO2), and nitrogen (N2) will likely be present on every potentially habitable planet. However, researchers found that free oxygen appears geologically.
The team examined planets orbiting red dwarf stars that make up for 75% of stars in our Milky Way galaxy. It also means that the most potentially habitable planet could be orbiting a red dwarf.
However, red dwarf stars are different from the Sun. They emit large solar flares that can destroy the atmosphere of a close-orbiting planet. Besides, their ultraviolet light emission is low due to which molecules break apart, and atoms get ionized. This process drastically changes the evolution of a planet’s atmosphere. It means that oxygen on red dwarfs can be a false alarm.
