Previously, experts had estimated the expiration date of the Earth: about 5 billion years ; moment in which the Sun, our star, will expand and swallow our planet. But it seems that life on Earth could have an end much earlier.
Life won’t last forever on Earth
A team of Japanese and American scientists has calculated the life expectancy of our planet’s atmospheric oxygen . How much time left? 1,000 million years. After this time, an extreme drop in oxygen levels in the atmosphere will kill most of life on Earth, as the researchers predict in their study published by the journal Nature GeoScience.
The experts aimed to investigate the long-term stability of Earth’s atmospheric oxygen. To do this, they carried out simulations of Earth’s systems, including its climate, biological and geological processes and even the brightness of the Sun, observing how oxygen levels changed as it was transported between air, water and rocks. . They found a tipping point 1 billion years from now – a time when Earth could not support most life forms.
The simulation showed that as the Sun got hotter and hotter, and releasing more energy, the levels of carbon dioxide in Earth’s atmosphere will begin to drop as the gas absorbs heat and decomposes. The ozone layer would also burn . Then, as carbon dioxide levels decrease, plant life will begin to suffer, leading to reduced oxygen production.
In fact, in just 10,000 years, CO2 levels will drop so low that plant life will become extinct. Without plant life, land and sea creatures would follow the same fateful path, due to the lack of a breathable atmosphere. Meanwhile, the simulation showed rising levels of methane entering the atmosphere, accelerating the disappearance of creatures that need oxygen to breathe. The result? A planet without life, by very small creatures, like bacteria.
The scenario will recall a primitive Earth, with deoxygenation returning the atmosphere to an inhospitable composition, as when 2.4 billion years ago, our planet carried an atmosphere full of methane, ammonia, water vapor and neon gas, without free oxygen.
The Great Oxygenation Event paved the way for multicellular life, although it is believed to have killed many anaerobic bacteria, which may have been Earth’s first mass extinction.
“Our results suggest that the planetary carbonate-silicate cycle will tend to lead to terminally CO2-limited biospheres and rapid atmospheric deoxygenation,” the authors note.
While this finding may not have a direct impact on our lives today, it may complicate the search for signs of extraterrestrial life, as it will not only be important to search for potentially habitable alien worlds, but also to find them at the right time. of its existence. The researchers calculated that oxygen could only be detected in an atmosphere for about 20-30% of the planet’s total life.
Referencia: Kazumi Ozaki et al. The future lifespan of Earth’s oxygenated atmosphere, Nature Geoscience (2021). DOI: 10.1038/s41561-021-00693-
