Extreme Deoxygenation, Elevated Methane Could End Humans, Most Life Relying on Oxygen

Humans, animals, and plants need oxygen to survive. However, according to researchers, there's an extreme drop of this chemical element on Earth, and those relying on it could perish due to suffocation.

Deoxygenation on Earth

Life flourishes on Earth due to oxygen. However, it's not always the case, and scientists have projected that the atmosphere will eventually return to being low in oxygen and high in methane.

The researchers conclude in a new study that atmospheric oxygen is not likely to remain a constant feature of habitable planets, which has consequences for our quest for evidence of extraterrestrial life. With this change, the Earth will return to a condition similar to before the Great Oxidation Event (GOE), which occurred around 2.4 billion years ago.

According to the model, deoxygenation of the atmosphere will most likely occur before the onset of moist greenhouse conditions in Earth's climate system and before there is a significant loss of surface water from the atmosphere, with atmospheric O2 plummeting to levels reminiscent of the Archaean Earth.

"The drop in oxygen is very, very extreme," Earth scientist Chris Reinhard from the Georgia Institute of Technology said. "We're talking around a million times less oxygen than there is today."

This will end the road for most other living creatures, including humans, who depend on oxygen to survive. Hopefully, during the next billion years, we will find a way to leave the planet.

To arrive at their findings, the scientists performed in-depth simulations of Earth's biosphere, accounting for variations in Sun brightness and the consequent decrease in carbon dioxide concentrations as rising temperatures break down the gas. Reduced carbon dioxide levels lead to a reduction of photosynthesizing organisms, such as plants, which in turn produce less oxygen.

Previously, scientists had estimated that rising solar radiation would evaporate Earth's oceans in roughly 2 billion years. However, based on an average of less than 400,000 simulations, this model predicts that life will end first due to a decrease in oxygen.

The finding is especially pertinent today because of our ongoing quest to find habitable planets outside our solar system. According to the researchers, it's feasible that we should be searching for biosignatures other than oxygen to have the highest chance of finding life.

The study is a component of the NASA NExSS (Nexus for Exoplanet System Science) project, which looks into whether planets other than Earth are habitable.

ALSO READ: Extraterrestrial Intelligence Would Discover Earth More Readily During Jurassic Era Than Today [Study]

What Is Archean Earth?

The Archean Earth, or Archean Eon, is a period that spanned 4 to 2.5 billion years ago. It was followed by the Proterozoic Era, which lasted 2.5 to 0.54 billion years ago. During this period, the Earth's crust cooled down just enough for rocks and other continental plates to form.

Since they historically left a minimal trace of themselves in the rock record and because there were no notable extinction events features that distinguished the divisions of the geologic record, eons are long. Although it is absent from the geologic record, the "boring" has dominated Earth's history nonetheless.

According to Koch (1998), archaea or their progenitors were probably among the first species to emerge and continue to exist now. One of them is found in contemporary conditions that are oxygen-free, which is poisonous and causes it to create methane as part of its metabolism. However, many other primitive species, including bacteria, have survived, and their metabolisms have fueled numerous worldwide chemical and biological cycles.

The gas oxygen is the most critical metabolic byproduct of early organisms. It is vital for the Earth's climate and geologic development and essential for humans and every other animal that has ever existed, all of which depend on free oxygen for survival. Although other primitive creatures produced oxygen, archaea do not.