It is difficult to know what Earth looked like in the early years before life appeared. Geological investigators 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 Earth’s mantle throughout its long history, our whole world was once mired in a vast ocean, with very few or no land masses at all. It was a very wet space rock.
So where did all the water go? According to a team of researchers led by planetary scientist Junjie Dong from Harvard University, minerals deep in the mantle are slowly imbibing Earth’s ancient oceans to leave what we have today.
“We calculated the water storage capacity in the Earth’s steel mantle as a function of mantle temperature.” The researchers wrote in their paper.
“We found that the storage capacity of water in a hot and early mantle was probably smaller than the amount of water currently held by the Earth’s mantle, so the additional water in the mantle today would have resided on the surface of the Earth earlier and formed larger oceans.
“Our results indicate that the long-standing assumption that the volume of surface oceans has remained roughly constant over geological time may need re-evaluation.”
Deep in the ground, it is believed that a large amount of water is stored in the form Hydroxy group Compounds – consisting of oxygen and hydrogen atoms. In particular, water is stored in two high-pressure forms of the mineral volcanic olivine, aqueous wadesslet and ringwoodite. Wadselite samples deep underground can contain about 3 percent H2O by weight; Ringwoodit is about 1%.
Previous research conducted on the two minerals subjected them to high pressures and temperatures from the modern Earth’s mantle to find out these storage capacities. Dong and his team saw another opportunity. They pooled all available mineral physics data, and determined the storage capacity of water in wadsleyite and ringwoodite over a wider range of temperatures.
The results showed that these two metals have lower storage capacities at higher temperatures. Because the Earth’s young, which formed 4.54 billion years ago, were warmer internally than they are today (and their interior temperature as well) It is still decreasing, Which is very slow and has absolutely nothing to do with its external climate), this means that the water storage capacity in the mantle is now higher than it was in the past.
Moreover, as more olivine minerals crystallize from Earth’s magma over time, the water storage capacity in the mantle would 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 storage capacity of bulk water in the Earth’s solid mantle has been greatly affected by secular cooling due to storage capabilities that depend on the temperature of its constituent minerals,” 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 in the Archean Eon, between 2.5 and 4 billion years ago, it is likely that the world would have flooded and flooded the continents.
This finding is consistent with a previous study that found, based on the abundance of some oxygen isotopes preserved in the geological record of the early ocean, that Earth existed 3.2 billion years ago. Way Less land than it is today.
If this is the case, it could help us answer pressing questions about other aspects of Earth’s history, such as where life originated about 3.5 billion years ago. There is an ongoing debate about whether or not life first formed in saltwater oceans Freshwater ponds on land; If the oceans flood the entire planet, then this mystery will be solved.
Moreover, the results could also help us search for extraterrestrial life. Evidence suggests that ocean worlds Abundant in our worldSo searching for signatures of these wet planets can help us identify hospitable worlds. It could advance the cause of the search for life in ocean worlds in our solar system, such as Europe and Enceladus.
Not the least of which is that it helps us better understand the delicate evolution of our planet, the strange, and often seemingly inhospitable, turns along the way that ultimately gave rise to humanity.
The research has been published in Predecessor AGU.