Tuesday, October 26

Earth’s atmosphere is not eternal


Earth's atmosphere is not eternal

Earth’s atmosphere is not eternal

A new study by scientists at the University of Toho and the Georgia Institute of Technology has determined that Earth’s oxygen-rich atmosphere will not last forever. In approximately one billion years, oxygen levels will drop steeply as the Sun gradually warms, bringing our planet to conditions similar to what it was during its formation, 2.4 billion years ago.

The release of a greater amount of energy from an aging and overheated Sun will be fatal for the Earth’s atmosphere: the decrease in oxygen levels will be compounded by the absence of ozone layer, a situation that will expose the Earth to high levels of ultraviolet light and heat from the sun. According to a Press release, this will completely eliminate terrestrial and aquatic life.

Consequently, the survival of microbial life forms can only be expected at that time. Primitive bacteria that are hidden today will reign again on a planet that is already uninhabitable for man and for almost all the vital expressions that we know today. What’s more: according to the new research, published in the journal Nature Geoscience, the extinction of plants will be fundamental in this process.

Plant death and oxygen depletion

Along with solar heating, carbon dioxide levels will reach minimum values, creating a scenario in which organisms that depend on the photosynthesis process, such as plants, will inevitably perish. This massive plant death will become the main cause of the sharp drop in oxygen values, because plant species will stop producing it.

Although oxygen currently makes up about 21% of the Earth’s atmosphere, creating a perfect environment for the development of large and complex organisms such as humans, these characteristics did not exist in the initial stages of the planet’s formation and will not be observed within of a billion years. Scientists estimate that an oxygen-rich atmosphere will only be possible for 20 to 30 percent of Earth’s entire history as an inhabited planet.

To carry out their study, the researchers built a model of the Earth system that simulates climatic and biogeochemical processes. After running the model more than 400 thousand times, varying its parameter and focus, the specialists obtained exact data on the cycles that will lead to the emergence of a atmosphere poor in oxygen, in the distant future of the Earth that is now possible to define with precision.

Extraterrestrial life: beyond oxygen

Taking into account that the presence of oxygen in the atmosphere is one of the most sought after biosignatures to determine the habitability of planets and exoplanets, the scientists in charge of the new study believe that their findings may also be useful in the search for extraterrestrial life.

However, they stressed that additional biological signatures should also be considered in this type of scientific endeavor, applicable to weakly oxygenated worlds. According to the opinion of these experts, hydrocarbon mists in a planet’s atmosphere could become a consistent biosignature when searching for extraterrestrial life.

Consequently, this research confirms, on the one hand, that an oxygen-rich atmosphere is a condition that the Earth will enjoy for a specific period of time and, at the same time, shows us that the search for life forms outside our planet must also focus on the presence of biological signatures that do not depend on oxygen as its primary element.

Reference

The future lifespan of Earth’s oxygenated atmosphere. Ozaki, K., Reinhard, C.T. Nature Geoscience (2021).DOI:https://doi.org/10.1038/s41561-021-00693-5

Photo: NASA and Unsplash.


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