Planet -okeany - 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 familiar continents 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?
3 billion years ago, our planet was completely covered in water
Earth was an ocean planet
When a series of powerful collisions between dust and space rocks marked the birth of our planet 4.5 billion years ago, 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, they were discovered by scientists from Northwest Australiawho decided to analyze the rock found deep in 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.
According to the theory presented by scientists, the continents appeared much later: at the moment when plate tectonics pushed the huge rocky masses of land 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.
Comet bombardment could start life on Earth
When the Earth was a hot ocean of magma, water vapor 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, assistant professor of geology and atmospheric science at Iowa State University.
In their new study, Johnson and his colleague Boswell 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.
Could life have arisen on an ocean planet?
After analyzing more than 100 samples of sedimentary rocks, scientists found that about 3.2 billion years ago, the oceans contained more oxygen-18 than oxygen-16, which is currently the most common 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 inclined to believe 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. Be that as it may, if the theory of scientists is confirmed, finding life on oceans already discovered by man, such as GJ 1214b or Kepler-22b, will be possible only if the above-mentioned exoplanets follow the path that our blue planet once passed. Otherwise, water may be important, but just an ingredient for the emergence of life on an organic basis, which without the participation of additional factors will not be able to provide a comfortable environment for the emergence of the first microorganisms
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