Did freshwater, and life on Earth, begin earlier than we thought?
By Itamar Kerbi, Davidson Institute, the educational arm of the Weizmann Institute of Science
The Earth was formed about 4.5 billion years ago, and went through quite a few processes before becoming the world we know today. The oceans took hundreds of millions of years to form, and the first continents appeared even later. Until recently, it was believed that the appearance of freshwater occurred even later, as the first evidence for its existence was based on the study of fossils of single-celled organisms that existed about3.5 billion yearsBut did freshwater really only appear in nature then? New research suggests it did. At least 500 million years Before.
To answer questions about the early Earth, we need to study extremely ancient and stable materials – materials that have barely changed since their formation. One of the oldest rock deposits is found in the Jack Hills in Western Australia, and it contains crystals of the mineral zircon.
Zircon is formed in the cooling magma flows of the ancient Earth, and is an extremely stable material, and therefore serves as an important source of information in the study of the Earth's ancient geology. One of its significant advantages is The possibility of dating his age, as it contains uranium – a chemical element that undergoes long-term radioactive decay at a known rate – allowing geologists Estimate the age of the crystalThe oldest zircon crystal, also found in Jack Hills, has been estimated to be 4.4-4 billion years old, making it the oldest relic of our planet ever found.
How can we learn from zircon about the water cycle in nature? When water comes into contact with zircon, it leaves its mark in the form of oxygen atoms. Contact with fresh water leaves Lighter oxygen atoms Compared to those that remain after contact with salt water. Thus, by analyzing the ratio of oxygen atoms in zircon, the research group found a sign of the existence of freshwater that is at least 4 billion years old, 500 million years earlier than the previous estimate.
Sea-land
The presence of freshwater indicates the existence of land long before what was previously thought. This discovery therefore has far-reaching implications for our understanding of the ancient Earth. The connection between freshwater and the existence of land stems from the water cycle in nature: when water evaporates, the salts dissolved in it do not remain in it, so the evaporation process turns all water into freshwater. The evaporated water can condense into clouds and fall as rain. If it falls on the oceans, it will mix again with the salts in them. On the other hand, if it falls on land, it will create a source of freshwater, such as a river or lake – until it reaches the ocean again. The water that fell as rain can evaporate again, from the lakes or oceans, and start the cycle again.
This cyclical process that occurs on Earth is called The water cycleBefore the appearance of continents, the water that evaporated always reached the ocean and merged with the salty water there. Therefore, the existence of land is a necessary condition for the appearance of freshwater in nature. According to the study, it appears that the continents on Earth were formed earlier than we thought.
The study also raises questions about the emergence of the first life on Earth – or at least on land. The oldest direct evidence of this is in a freshwater environment, and indicates Lived about 3.5 billion years ago, although there are also claims of older evidence originating from seawater, and which are still in disputeThe new study actually provides evidence that suitable conditions for the emergence of life on land existed as early as four billion years ago, and it opens the door to further research into the possible emergence of life on Earth earlier than those identified so far.
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One response
I expected from 'The Proverbs' that they wouldn't throw out exaggerated numbers of years like that without any proportions.