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Ancient Earth Really Was a Serene Water World, New Evidence Confirms

 

It's tricky to work out what Earth may need to appear like within the early years before life emerged. Geological detectives have now obtained more evidence that it absolutely was rather different from the earth we live to tell the tale today.

According to a brand new analysis of the features of Earth's mantle over its long history, our whole world was once engulfed by an unlimited ocean, with only a few or no landmasses in any respect. it had been a particularly soggy space rock.

So where the heck did all the water go? in line with a team of researchers led by planetary scientist Junjie Dong of the university, minerals deep inside the mantle slowly drunk up ancient Earth's oceans to go away what we've today.

"We calculated the water storage capacity in Earth's solid mantle as a function of mantle temperature," the researchers wrote in their paper.

"We find that water storage capacity in an exceedingly hot, the early mantle may are smaller than the number of water Earth's mantle currently holds, that the additional water within the mantle today would have resided on the surface of the first Earth and formed bigger oceans.

"Our results suggest that the long‐held assumption that the surface oceans' volume remained nearly constant through time may have to be reassessed."

Deep underground, a good deal of water is assumed to be stored within the sort of hydroxy group compounds - made of oxygen and hydrogen atoms. specifically, the water is stored in two high-pressure kinds of the volcanic mineral olivine, hydrous wadsleyite, and ringwoodite. Samples of wadsleyite deep underground could contain around 3 percent H2O by weight; ringwoodite around 1 percent.

Previous research on the 2 minerals subjected them to the high pressures and temperatures of the mantle of contemporary day Earth to work out these storage capacities. Dong and his team saw another opportunity. They compiled all the available mineral physics data and quantified the water storage capacity of wadsleyite and ringwoodite across a wider range of temperatures.

The results showed that the 2 minerals have lower storage capacities at higher temperatures. Because baby Earth, which formed 4.54 billion years ago, was much warmer internally than it's today (and its internal heat continues to be decreasing, which is incredibly slow and also has absolutely nothing to try to do with its external climate), it means the water storage capacity of the mantle now's on top of it once was.

Moreover, as more olivine minerals are crystallizing out of Earth's magma over time, the water storage capacity of the mantle would increase that way, too.

In all, the difference in water storage capacity would be significant, while the team was conservative with its calculations.

"The bulk water storage capacity of Earth's solid mantle was significantly suffering from secular cooling thanks to its constituent minerals' temperature‐dependent storage capacities," the researchers wrote.

"The mantle's water storage capacity today is 1.86 to 4.41 times the trendy surface ocean mass."

If the water stored within the mantle today is larger than its storage capacity within the Archean, between 2.5 and 4 billion years ago, it's possible that the globe was flooded and therefore the continents swamped, the researchers found.

This finding is in agreement with a previous study that found, supported an abundance of certain isotopes of oxygen preserved in an exceedingly geological record of the first ocean, that Earth 3.2 billion years ago had way less land than it does today.

If this is often the case, it could help us answer burning questions about other aspects of Earth's history, like where life emerged around 3.5 billion years ago. There's an ongoing debate over whether life first formed in saltwater oceans or freshwater ponds toward landmasses; if the whole planet was engulfed by oceans, that might solve that mystery.

Furthermore, the findings could also help us look for extraterrestrial life. Evidence suggests that ocean worlds are abundant in our Universe, so trying to find signatures of those soggy planets could help us identify potentially hospitable worlds. And it could strengthen the case for trying to find life on ocean worlds in our own scheme, like Europa and Enceladus.

Not least, it helps us better understand the fragile evolution of our planet, and also the strange, often seemingly inhospitable turns along the way that eventually led to the emergence of humanity.

The research has been published in AGU Advances.

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