Ocean planets are not uncommon in our galaxy. Being completely covered by water, these distant celestial objects can be a real storehouse of life. However, did you know that 3.2 billion years ago the Earth was also covered by a vast ocean and had no continents at all? According to an article published on livescience.com, the continents we knew appeared much later than we previously thought. So what influenced the course of development of the blue planet and turned it into a place where there are not only oceans, but also land?
Earth was an ocean planet
When 4.5 billion years ago a series of powerfulcollisions between dust and space rocks laid the foundation for the birth of our planet, the very young Earth was a bubbling, molten sphere of magma thousands of kilometers deep. Cooling gradually as it rotates, several million years after its birth, cooling magma formed the first mineral crystals in the earth's crust. After 4 billion years, it was precisely them who were discovered by scientists from Northwest Australia, who decided to analyze the breed found in the depths of the smallest continent of the planet. In the course of the study, it turned out that the crystals were the remains of an ancient ocean floor, indicating that once a very long time ago there was no land on Earth in the sense that we are all used to.
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According to the theory presented by scientists,continents appeared much later: at the moment when plate tectonics pushed huge rocky land masses up to break through the sea surface. Meanwhile, the first water of the Earth may have been brought here by ice-rich comets from outside our solar system. An alternative version claims that moisture could come in the form of dust from a cloud of particles that gave rise to the Sun and objects rotating around it.
When the Earth was a hot ocean of magma, a waterysteam and gases escaped from the surface of a hot ball into its atmosphere. “Then heavy rain fell from the earth’s gas envelope, caused by a sharp cooling,” said lead author Benjamin Johnson, associate professor of the Department of Geological and Atmospheric Sciences at Iowa State University.
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In his new study, Johnson and his colleagueBoswell Wing, Assistant Professor of Geological Sciences at the University of Colorado, turned to a unique find they made in the Australian outback. The piece of material they discovered is a rocky structure that covered the ocean floor 3.2 billion years ago. A piece of rock has preserved oxygen isotopes that can help researchers decipher changes in the temperatures of the planet’s ancient ocean, as well as in its global climate.
Having analyzed over 100 sedimentary samplesrocks, scientists found that about 3.2 billion years ago, the oceans contained more oxygen-18 than oxygen-16, which is currently the most abundant in the ocean. Thus, by leaching oxygen-18 from the oceans, the mainland land masses indicate that in ancient times continents simply did not exist. In this case, could any life have arisen under conditions so different from modern ones?
Benjamin Johnson and his colleague are addictedadhere to the opinion that life on Earth could appear only in two places: in hydrothermal springs and ponds on land. Both those and others are able to provide gradually evolving living beings with enough organic substances for growth and development. Anyway, if the theory of scientists is confirmed, finding life on already discovered human ocean planets, such as GJ 1214b or Kepler-22b, will be possible only if the above-mentioned exoplanets follow the path that our blue once passed. planet. Otherwise, water may be important, but only an ingredient for the emergence of life on an organic basis, which without the participation of additional factors cannot provide a comfortable environment for the emergence of the first microorganisms.