A Serene Water World Once

Michelle Starr of Science Alert reports:

It's tricky to figure out what Earth might have looked like in the early years before life emerged. Geological detectives have now obtained more evidence that it was rather different to the planet we live on today.

According to a new analysis of the features of Earth's mantle over its long history, our whole world was once engulfed by a vast ocean, with very few or no land masses at all. It was an extremely soggy space rock.

So where the heck did all the water go? According to a team of researchers led by planetary scientist Junjie Dong of Harvard University, minerals deep inside the mantle slowly drunk up ancient Earth's oceans to leave what we have 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 a hot, early mantle may have been smaller than the amount of water Earth's mantle currently holds, so the additional water in the mantle today would have resided on the surface of the early Earth and formed bigger oceans.

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

Deep underground, a great deal of water is thought to be stored in the form of hydroxy group compounds - made up of oxygen and hydrogen atoms. In particular, the water is stored in two high-pressure forms 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.  READ MORE