What Happened When Two Scientists Came Across an Exposed Water Crust?
What if the early Earth was fully covered in water?
New evidence from the water crust indicates that around three billion years ago, Earth was a water- world. If this study gains traction, it can revolutionize the way scientists study exoplanets and habitability. They might also have to re-evaluate how life originated on Earth.
These findings part of a recent paper—co-authored by Benjamin Johnson from Iowa State University and Boswell Wing from the University of Colorado. The project began when Johnson found out from Wing that there was a well-preserved water crust in Western Australia that could help them to determine a lot of things about the Earth’s history.
Their work was mainly targeted to the Panorama District, belonging to the Australia Outback. This Australian region is home to a unique oceanic slab that is 3.2 billion years old. Some portion of the water crust carries chemical hints regarding the seawater of the ancient Earth.
Johnson clarified in a press release that they did not find any watery samples from the ancient water, but they got their hands on some useful rocks. These rocks had come into contact with water from those times and provided information regarding those interactions.
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The authors were fuelled by a desire to restart the debate on the origins of the ancient Earth, especially how it looked. The introductory part of their paper gave some interesting insights. They explained that the chemical and physical histories of the ocean played a major role in the origin and evolution of Earth’s biosphere. Altered water crust and marine chemical sediments were pivotal in preserving a geochemical record of these histories.
Examining The Ancient Water Crust
Marine sediment is an area that has been well-researched for some time. However, the authors went for an innovative approach by examining the ancient water crust instead. It is believed that the ancient oceans consisted of oxygen in different forms; these were collected by the water crust.
The scientists succeeded in gathering around 100 samples belonging to the ancient rock and performed analysis against two oxygen isotopes: oxygen-18 and oxygen-16. The idea was to take out the relevant quantity of each isotope from the ancient crust and then test it with the amounts of the sediment.
The results suggested that since the formation of the water crust more than 3 billion years ago, it contained oxygen-18 in greater amounts. Both scientists have come to the conclusion that these results indicate that there were no continents during the formation of this crust. They went on to explain that during the continental formation period, they were comprised of clays that would have absorbed the oxygen-18, due to its heavier weight. Therefore, if any continent existed 3.2 billion years ago, it would have likely to contain oxygen-18.
The overlying crux of this work shows that the oceans of the Earth passed through two separate states on either side of the formation of continents—one before they were formed and one after they were formed.
Did the Paper Break a Common Misconception?
A great deal of studies has revolved around marine chemical sediments to find out how continents formed in ancient history. The study tells that those sediments consisted of microcrystalline silica, phosphates, iron oxides, and carbonates. Since all these materials are made of aqueous species, they might mirror ?18O of the water that coexists with them.
These sediments are more or less an archival record from the ancient Earth. The older deposits reflect that the levels of oxygen-18 have increased throughout the history of Earth. However, this latest work argues that, in fact, the seawater oxygen-18 decreased over time.
Both scientists also built an ancient Earth model, representing the starting point of continent weathering during the late Archaean period and how the ocean evolved over the times in terms of oxygen-18. Hence, it was the formation of continents that caused changes in the oxygen-18 data.
Does the Study Completely Reject the Idea of Any Land Form?
Despite the study’s hints towards the likelihood of an Earth bearing the form of a water-world, it is still possible that land existed in some form. For example, areas of land boasting the size of an island, or micro-continents may have been present in those times. They might have been too rocky and volcanic in nature.
However, it is unlikely that the large land-form of modern Earth, containing tall mountain ranges and richer soil, existed back then. This was only possible if the oxygen-18 levels from those times were similar to the modern amounts of the isotope. The wing included this reasoning in the press release and denied the possibility of the modern formation of continent soils in the ancient Earth.
The authors have been vocal in claiming that their work cannot be seen as a non-refutable piece of evidence regarding the overarching debate surrounding the early Earth. They are open to other possibilities that might have influenced their results.
For instance, if the formation of ancient continents was slower than the later continental formation, this may point out to the variation in oxygen-18 results. Moreover, it is also not beyond the realms of possibility that the clays swallowing oxygen-18 were formed in the ocean, not on the continents.
This directs us back to an engrossing mystery of the science: when were the continents formed?
Some evidence seems to back up the theory that the continental formation was only made possible when the Earth’s core released heat and became cooler. Regardless, it was not until the Jurassic period that the modern continents came into existence. Before that, Gondwana was the solitary continent. It covered around one-fifth of the surface of the Earth. The wing has expressed a desire to study the younger regions of the Earth’s crust to figure out more about the formation of continents.
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