Mercury and the moon are shrinking, but what about the earth? Understand the phenomenon

As a natural part of the geological evolution of the celestial bodies, All of them shrink . This is mainly due to the gradual cooling of its nuclei, and can lead to its characteristics, up to billions of years.

This process is universal for all celestial bodies that have a solid or semi -solid structure and that have sufficient internal heat to generate significant changes in their structure over time.

At “birth”, planets and moons are extremely hot due to the heat of accretion (formation) and the decay of their radioactive elements. But over time, this internal heat is being lost to space, and when the materials cool, its tendency is to contract.

Of course, the nature of the constituent materials of the celestial body influences this process. And that is why planets with large metal nuclei, such as mercury, are more susceptible to this shrinkage, For when it cools, the metal contracts more than the rocks.

There are other examples of volumetric reductions in the solar system, such as our moon, as well as satellites of gaseous planets, and even dead stars, such as some white dwarfs, shrink as they cool.

But what about the earth? The answer is yes: Our planet is cooling and although smaller than mercury, also has a solid nucleus with 85% iron. However, some characteristics make their cooling, and consequently their shrinking, slightly slower. Check it out.

How is Mercury shrinking?

For over 50 years, scientists have found that Mercury has been shrinking. The first evidence was detected by NASA’s Mariner 10 mission, which flew over the planet in 1974 and 1975, and discovered “Lobadas Escarpuses.”

These relief forms are cliffs similar to cliffs, up to three kilometers high and hundreds of kilometers long. Its shape is curved and irregular as if they were lobes or winding ripples.

In an article for the Conversation platform, Open University Professor David Rother Rother explains that as Mercury interior shrinks, its surface has less and less area to cover.

“This is like wrinkles that form on an apple as it gets old, except that an apple shrinks because it is drying, while Mercury shrinks because of the thermal contraction of its interior,” compares the planetary geoscientist.

Although the heat of its surface reaches 430 ° C during the day, the fact that it has a large nucleus, which occupies 80% of the planet’s volume makes your rock layer (cloak and crust) relatively thin can not adjust to the shrinkage of the metallic nucleus.

NASA’s Messenger spacecraft, which orbited the closest planet in the 2011 sun until 2015, revealed that Mercury had contracted around seven kilometers since its formation 4.5 billion years ago.

The moon is also shrinking

The realization that the moon is shrinking was announced in 2010, by astronomers of the National Museum of Air and Space (NASM), from Smithsonian Institution, also through the observation of images of looked cloths taken by cameras aboard the apollos 15, 16 and 17.

They were compared to 14 new cliffs detected by the Cameras of NASA’s Lunar Recognition orbit, 2019. The new formations showed that the structures were not restricted to the Lunar Ecuador, as shown in the Apollos photos.

In a statement at the time, Planetary Scientist Tom Watters of NASM stressed that “one of the remarkable aspects of Lunar cliffs is their apparent little age.”

The so -called “thrust failures”, geological structures that form when one part of the rock is pushed violently over another, caused a global contraction on the estimated lunar surface of about 100 meters in the recent past, says Watters.

He also analyzed eight lumnamotos that occurred in 2019, and concluded that they were produced by still active geological failures, which may be “producing lunar earthquakes today, As the moon continues to cool and shrink “.

And the earth? How are we shrinking? ‘

Unlike Mercury, which has an extremely thin atmosphere, and the moon, which has virtually no atmosphere, the earth has a thicker gas layer. It helps to retain material that falls from space and contains the escape of light gases such as hydrogen and helium

Although many large meteors burn upon entering the atmosphere, it is estimated that about 40,000 tons of dust and spatial particles enter the earth annually.

However, this volume is considered insignificant when compared to the amount of gas that escapes from the atmosphere to space over time. That is, despite the gain of external material, the earth also loses mass continuously.

According to the scientific communicator, Chris Smith, “physicists have shown that the earth is losing about three pounds of hydrogen gas every second. There are about 95,000 tons of hydrogen that the planet is losing each year,” the microbiologist BBC explains.

In his analysis of the factors that actually affect the mass of the earth, Smith ponders that, on the one hand, the earth’s nucleus loses energy by cooling, on the other, it accumulates heat from the greenhouse effect and climate change.

The balance of all this results in an annual loss of 50 thousand tons of mass. It may seem a lot, but it is very little compared to the mass of the planet, representing only 0.00000000000000001% of the total.

In terms of size, the calculation was performed by NASA scientists using a series of techniques that included the reach of the milemmetric satellite laser.

The results estimated an average change in the radius of the earth equivalent to 0.1 millimeter per year, something like the thickness of a human hair, What is considered practically insignificant in practical terms.

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This content was originally published in Mercury and the moon are shrinking, but what about the earth? Understand the phenomenon on the CNN Brazil website.

Source: CNN Brasil