How old is our Earth: scientists say the answer is not as obvious as it seems

Scientists sought to find out the most accurate date for the birth of the Earth, but they were faced with the specifics of how our planet was born.

The question of how old planet Earth is may seem simple enough. It is generally accepted that our planet is about 4.5 billion years old. But the more research is done on this subject, the more erroneous the mentioned figure looks. Now scientists do not exclude that the planet may be older by as much as half a billion years.

“Given the age of the planet is easy enough, but only until the moment when the scale of research begins to increase,” says Thomas Lapen, professor of geology, head of the Department of Earth and Atmospheric Sciences at the University of Houston.

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Scientists sought to find out the most accurate date for the birth of the Earth, but they were faced with the specifics of how our planet was born.

“When people are born, it’s only a moment in time, but the formation of planets is a process that lasts millions of years,” the expert notes.

Therefore, in order to name the exact age of the Earth, astrophysicists, planetologists and geologists will first have to determine what moment in this whole process can be considered the birth of the planet.

When was the earth born

Clouds of gas and dust orbited the newborn Sun about 4.6 billion years ago. For the first million years, few major events took place around the Sun, small asteroids collided and merged here – the seeds of future planets. During the collisions, some of the rocks got bigger and bigger until they turned into planets.

But planets are not just big piles of rocks. As material accumulated, the planets differentiated into different layers: core, mantle, and crust. The process of “weight gain” and its stratification continues for tens of millions of years. Some scientists believe that this moment is the birth of the planet. But Lapin compares it rather with the “conception” of the Earth, but its birth, apparently, occurred at the time of the cataclysm that formed the Moon.

As you know, at its earliest stage of formation, the proto-Earth collided with another “embryo” of the planet, similar in size to Mars. When these two objects merged in a large collision, the Moon appeared in Earth’s orbit.

Lapin believes that it was this collision that triggered a “reboot” of the materials from which the Earth was formed. Then the surface of the proto-Earth was a magmatic ocean. But after the collision, the material of both objects mixed up, and also created the Earth-Moon system known to us. Evidence of “reboot” scientists find both in the earth’s rocks and in the moon.

“As a result of the collision, the proto-Earth was destroyed or radically changed in composition. In my opinion, that first version of the Earth cannot be considered the planet that we know,” emphasizes the professor of geology.

If this event is considered the starting point, then the age of the Earth varies between 4.4 and 4.52 billion years. But in order to finally confirm this age, it is necessary to find evidence in the past of the planet.

To do this, it is necessary to find the most ancient rocks on Earth, they should have formed immediately after the oceans of magma solidified. Such minerals are zircons, which were found in Western Australia.

To determine the exact age of these stones, scientists used radiometric dating. During the scan, the amount of uranium contained in zircons becomes known. The fact is that this element decays into lead at a well-known rate. Therefore, scientists can determine the age of a mineral from the ratio of uranium to lead in a sample. It was this method that established that the zircons found in Western Australia are about 4.4 billion years old.

Judging by the information from the rocks, the Earth-Moon system must have appeared earlier than 4.4 billion years, as the rock records would have been erased during the collision that created the Moon. So our planet is definitely not younger than 4.4 billion years. But how much older can she be?

To answer this question, scientists need to go further and study the lunar soil.

On the surface of the moon, evidence of the ancient past is much better preserved, because there are no processes such as plate tectonics that would shuffle the moon’s surface. Scientists can study the lunar soil thanks to meteorites that fall on Earth and samples taken from NASA’s Apollo mission.

Like the proto-Earth, our Moon was also once covered in an ocean of magma. The oldest samples of the lunar surface will help to understand when the magma on the moon solidified. Scientists analyzed zircons that were collected during a mission to the moon and determined that the magma on the moon solidified about 4.51 billion years ago.

But, according to Lapen, from the moment of collision, merging and cooling of bodies, as well as their differentiation, some time should have passed. And this segment can be about 50 million years.

That is why some scientists argue that calculations of the age of the Earth can be wrong by as much as 50 million years.

There is another way to narrow the time frame. Rocks from the time of the formation of the proto-Earth could be preserved in asteroids and comets.

Such time capsules sometimes fall to Earth in the form of meteorites. The most ancient at the moment is the Erg Chech 002 meteorite. Scientists believe that the space rock is a fragment of the crust of a nascent planet in the solar system. The age of Erg Chech 002 gives an idea of ​​the time when the proto-Earth was probably also at a similar stage of development.

“If we take the date of the birth of the Earth as the moment when its first core was formed, which eventually grew due to accretion, then the age of our planet is comparable to the age of Erg Chech 002,” the expert emphasizes.

According to scientists, the age of the Erg Chech 002 meteorite is approximately 4.565 billion years ago.

Is there any chance to know the exact age of the Earth

On the scale of human life, 50 million years is too long a period of time. But on a planetary scale, such an error is quite acceptable.

“This is a relatively short period of time during which many events have occurred: collision, merger and formation of cooled, hardened rocks that have become part of the core, mantle and crust of the Earth,” the scientist says.

True, Lapen does not deny that it is still possible to determine the age of the Earth thanks to additional samples from the Moon and meteorites falling to Earth.

So, moon rocks delivered to Earth by the Chinese mission Chang’e 5 are still being studied by scientists. As part of the NASA Artemis program, it is also planned to deliver lunar rocks to Earth. In addition, the US space agency is providing scientists with more and more samples from the moon, delivered to the planet as part of the Apollo mission.

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