It is difficult to imagine what the Earth might have looked like in the early years before the appearance of life. Geological detectives have now obtained more evidence that it was quite different from the planet we live on today.
According to a new analysis of the features of the Earth’s mantle throughout its long history, our entire world was once encompassed by a vast ocean with very few or no masses of earth. It was an extremely soaked space rock.
So where the hell did all the water go? According to a team of researchers led by planetary scientist Junjie Dong from Harvard University, the minerals deep inside the mantle slowly drank the ancient oceans of the Earth to leave what we have today.
“We calculated the water storage capacity in the Earth’s solid mantle based on the mantle temperature,” the researchers wrote in their paper.
“We found that the storage capacity of water in a hot, early mantle could have been less than the amount of water that the Earth’s mantle currently has, so that the extra water in today’s mantle would have resided on the surface of the Earth early.” and would have formed larger oceans.
Our results suggest that the long-standing assumption that the volume of surface oceans has remained almost constant over geological time should be reassessed.
In the depths of the ground, it is believed that a large amount of water is stored in the form of compounds from the hydroxy group – made up of oxygen and hydrogen atoms. In particular, water is stored in two high-pressure forms of the volcanic mineral olivine, wadsleyite hydrate and ringwoodite. Underground wadsleyite samples could contain about 3% H2O by weight; ringwoodit about 1 percent.
Previous research on the two minerals has subjected them to the high pressures and temperatures of the mantle of modern Earth to find out these storage capacities. Dong and his team saw another opportunity. They compiled all available data on mineral physics and quantified the water storage capacity of wadsleyite and ringwoodite over a wider temperature range.
The results showed that the two minerals have lower storage capacities at higher temperatures. Because the baby Earth, which formed 4.54 billion years ago, was much warmer internally than it is today (and its internal heat is still declining, which is very slow and also has absolutely nothing to do with it). dealing with its external climate), means water storage the capacity of the mantle is now greater than it once was.
Moreover, as more olivine minerals crystallize from the Earth’s magma over time, the mantle’s water storage capacity would increase in this way as well.
Overall, the difference in water storage capacity would be significant, even if the team was conservative with its calculations.
“The bulk storage capacity of the Earth’s solid mantle has been significantly affected by secular cooling due to the storage capacity of its temperature-dependent constituent minerals,” the researchers wrote.
“The mantle’s storage capacity is currently 1.86 to 4.41 times larger than the modern mass of the surface ocean.”
If the water stored in the mantle today is larger than its storage capacity in the Archaic Aeon, 2.5 and 4 billion years ago, it is possible that the world was flooded and the continents swirled, the researchers found.
This finding is in line with a previous study that found, based on the abundance of certain oxygen isotopes conserved in an early ocean geological record, that the Earth had 3.2 billion years ago. way less ground than today.
If so, it could help us answer burning questions about other aspects of Earth’s history, such as where life first appeared about 3.5 billion years ago. There is an ongoing debate as to whether life first formed in the oceans of salt water or in freshwater ponds on land; if the entire planet were covered in oceans, that would solve that mystery.
Moreover, the discoveries could also help us in our search for extraterrestrial life. Evidence suggests that oceanic worlds are abundant in our universe, so searching for the signatures of these soaked planets could help us identify potentially hospitable worlds. And it could strengthen the argument for searching for life on the oceanic worlds of our own solar system, such as Europe and Enceladus.
Last but not least, it helps us better understand the delicate evolution of our planet and the strange, often seemingly inhospitable along the way, which eventually led to the emergence of humanity.
The research was published in AGU Advances.