A new study found that our planet was home to an amount of water almost twice the current size, which is enough to completely submerge the continents and make the Earth look like a “world of water.”
It is difficult to know what the Earth looked like in the early years before life appeared. But now geologists have obtained more evidence that the planet was somewhat different from what we live on today.
According to a new analysis of the properties of the Earth’s mantle throughout its long history, our entire world was once immersed in a vast ocean, with very few or no land masses at all. It was a very wet space rock.
The team of researchers, led by planetary scientist Junji Dong of Harvard University, suggests that minerals deep in the mantle are slowly absorbing Earth’s ancient oceans, leaving what we have today.
“We found that the storage capacity of water in a hot and early mantle was probably less than the amount of water the mantle currently carries, so the additional water in the mantle today was residing on the surface of the Earth early and forming larger oceans,” the researchers wrote in their paper.
“Our findings suggest that the long-standing assumption that the volume of surface oceans has remained roughly constant over geological time may need to be re-evaluated,” the team added.
Deep in the ground, a great deal of water is believed to be stored in the form of compounds of the hydroxyl group, made up of oxygen and hydrogen atoms. In particular, water is stored in two high-pressure forms of the volcanic mineral olivine: wadsleyite (a mineral of the silicate family) and ringwoodite (ringwoodite, a high-pressure phase of magnesium silicate).
Deep underground samples of waderslite can contain about 3% water (H2O) by weight, and ringwoodite about 1%.
Previous research conducted on the two minerals was subjected to high pressures and temperatures from the modern mantle to find out these storage capacities.
Dong and his team compiled all available mineral physics data and determined the storage capacity of water in wadslite and ringwoodite over a wider range of temperatures.
The results showed that these two metals have lower storage capacities at higher temperatures. And since the nascent Earth, which was formed 4.54 billion years ago, was warmer internally than it is today (and the internal temperature is still decreasing, and it is very slow and has absolutely nothing to do with its external climate), this means that the capacity of the mantle in storing water is now higher than it is today. It used to be before.
Moreover, as more olivine minerals crystallize from Earth’s magma over time, the water storage capacity in the mantle will increase in this way as well.
Overall, the difference in water storage capacity would be significant, although the team was conservative in its calculations.
The researchers wrote: “The storage capacity of water in the Earth’s solid mantle was greatly affected by global cooling due to the storage capabilities that depend on the temperature of its constituent minerals.”
“The water storage capacity in the mantle today is 1.86 to 4.41 times the mass of the modern ocean surface,” he added.
The researchers found that if the water stored in the mantle today was greater than its storage capacity in the ancient era, between 2.5 and 4 billion years ago, then it is possible that the world was inundated and the continents were inundated.
This result is consistent with a previous study that found, based on the abundance of some oxygen isotopes preserved in the geological record of the early oceans, that the Earth 3.2 billion years ago had less land than it is today.