Ancient Earth was truly a calm aquatic world, and new evidence confirms this

It is difficult to understand what the Earth might have looked like in the early years before life appeared. Geological researchers have now obtained more evidence that it was somewhat different from the planet we live on today.

According to a new analysis of the properties of the Earth’s mantle throughout its long history, our entire world has been inundated by a vast ocean, with little or no land mass. It was a very humid space rock.

So where the hell has all the water gone? According to a team of researchers led by planetary scientist Junjie Dong of Harvard University, minerals deep in the mantle are slowly absorbing Earth’s ancient oceans, leaving what we have today.

“We calculated the water storage capacity in the Earth’s steel mantle based on the mantle temperature,” the researchers wrote in their paper.

“We found that the water storage capacity in the first warm mantle was likely less than the amount of water currently carried by the Earth’s mantle, so the extra water in the mantle today would have resided more early on the Earth’s surface and formed oceans.

“Our results indicate that the long-held assumption that the volume of surface oceans has remained roughly constant over geologic time may require re-evaluation.”

Deep in the earth, it is believed that a large amount of water is stored as a group of hydroxy compounds – made up of oxygen and hydrogen atoms. In particular, water is stored in two high pressure forms of the volcanic mineral olivine, aqueous wadselite and ringwoodite. Deep underground wadselite samples may contain about 3% H2O by weight; Ringwoodit is around 1%.

Previous mineral research has subjected the high pressures and temperatures of modern earthen mats to determine these storage capacities. Dong and his team saw another opportunity. They pooled all available data on mineral physics and measured the water storage capacity of wadsleyite and ringwoodite over a wider range of temperatures.

The results showed that both minerals have a lower storage capacity at higher temperatures. Because the tiny Earth, which formed 4.54 billion years ago, was much warmer inside than it is today (and its internal temperature is also still dropping , which is very slow and has absolutely nothing to do with its outdoor climate), which means that the water storage capacity in the mantle is now higher than before.

In addition, as more and more olivine minerals crystallize from the earth’s magma over time, the water storage capacity in the mantle will also increase in this way.

Overall, the difference in water storage capacity will be significant, although the team is careful in their calculations.

“The bulk water storage capacity of the Earth’s solid mantle has been greatly affected by the secular cooling due to the temperature-dependent storage capacities of its constituent minerals.” The researchers wrote.

“The water storage capacity in the mantle today is 1.86 to 4.41 times the mass of the modern ocean surface.”

Researchers found that if the water stored in the mantle today was greater than its storage capacity at Archean Aeon 2.5 to 4 billion years ago, then the world would likely have been submerged and the continents submerged. .

This finding is consistent with a previous study which found, based on the abundance of certain oxygen isotopes kept in early ocean geological records, that Earth there are 3.2 billion years. Path Less than Earth today.

If so, it could help us answer pressing questions about other aspects of Earth’s history, such as where life first appeared around 3.5 billion ago. years. There is an ongoing debate as to whether life first formed in saltwater oceans or freshwater pools on Earth; If the ocean engulfs the entire planet, then this mystery will be solved.

Moreover, the results could also help us search for extraterrestrial life. Evidence suggests that oceanic worlds are also abundant in our world, so looking for signatures from these humid planets can help us identify hospitable worlds. This could advance the cause of the search for life in the oceanic worlds of our solar system, such as Europe and Enceladus.

Notably, it helps us better understand the delicate evolution of our planet and the strange, often seemingly inhospitable, turns on the path that ultimately led to the emergence of humanity.

The research was published in Predecessor AGU.