“Stones cannot fall from the sky”: physicist Dmitry Wiebe debunks popular myths about meteorites

The most ancient meteorite, the fall of which was observed by people, flew to Japan on May 19, 861. And since then, mankind has come up with many legends about these celestial bodies.

Physicist Dmitry Wiebe at the forum "Scientists against myths" toldhow to separate myths about celestial aliens from the truth. The video of the lecture appeared on YouTube channel forum organizers ANTROPOGENESIS.RU, and Lifehacker made an outline of it.

Myth 1. Meteor is a small meteorite

This, rather, is not a myth, but a confusion in the names. “The expanse is stitched with meteorites” is a famous line from a song in which most of us do not see anything strange. But in fact, meteorites and meteors are not the same thing at all. And in order not to get confused in these concepts, it is worth referring to the official terminology.

April 30, 2017 The International Astronomical Union adopted document, in which he clarified how to correctly name flying space bodies and the atmospheric effects associated with them.

• Meteor - this is light and other physical phenomena that occur when a solid body enters the atmosphere. For example, a bright flash, a shock wave, heating and ionization of air. Meteors can be observed not only on Earth, but also on any planet that has a sufficiently dense atmosphere. That is, it is not an object, but various signals that it has entered the atmosphere.
• Bolide. This is the name of a meteor that has a brightness of more than -4 magnitude units. This figure roughly corresponds to the brightness of Venus.
• Superbolide - a meteor with a brightness greater than -17 magnitude units. This value is approximately in the middle between the brightness of the full moon and the sun.
• meteoroids - those very solid bodies that enter the atmosphere if their size is from 30 microns to one meter in diameter.
• Shards of asteroids - anything over a metre.
• Interplanetary dust - particles smaller than 30 microns. They don't create meteors. These dust particles are slowed down by the atmosphere, cool down and quietly descend to Earth.
• Meteorite - this is a body that has already cooled down and slowed down its movement in the atmosphere. It does not create light and other effects and falls to the surface only under the influence of gravity. Or it has already fallen and lies quietly on the ground.

There is a rule according to which heavenly guests receive names.

So, for example, the meteorites Sterlitamak, Krasnoyarsk and Enzisheim appeared. Meteor meteorite crater in Arizona. But this is not confusion: that was the name of the post office closest to the place where the celestial body fell.

Myth 2. Official science did not recognize the existence of meteorites

As proof of this myth, a phrase is sometimes cited that appeared in the conclusion of the commission of the Paris Academy of Sciences. This commission, on the instructions of the academy, studied a meteorite that fell in France.

The phrase from the verdict of scientists sounded like this: "Stones from the sky cannot fall." Many believe that such a conclusion of researchers is evidence of the inertia of official science, which does not want to notice obvious facts.

In fact, everything was different. In 1768, a meteorite actually fell in France. The Paris Academy of Sciences sent an expedition to the crash site to check how real the rumors about the mysterious stone, which came from nowhere. It also included the famous chemist Lavoisier.

The commission found a meteorite and indeed made a statement about rocks falling from the sky. But scientists only said that such bodies cannot arise in the Earth's atmosphere. "From the sky" - in this case, means "from the atmosphere."

Later, a whole science of space aliens arose - meteoritics.

In the 18th century, information about fallen celestial bodies became more and more. In 1850, scientists discovered one such object that landed about 200 kilometers from Krasnoyarsk. It was a huge piece of rock, consisting of stone and iron. But where iron came from, it was not clear. Indeed, in the Siberian taiga there were definitely no secret metallurgical plants where such an amount of steel could be smelted.

This metal was called "pallas iron" after the scientist who studied it. The physicist Ernst Chladni in 1794 wrote the work "On the origin of the iron masses found by Pallas and other similar ones." In it, he made two assumptions. First: such pieces of rock flew to Earth from outer space. And second: meteors and fireballs, which the inhabitants of our planet often observe, appear due to the fall of such stones.

The appearance of this work can be considered the beginning of meteoritics. So scientists back in the 18th century not only did not deny the facts, but also tried to study them carefully.

Myth 3. Meteorites can threaten human health

Many people are worried about whether cosmic bodies are harmful to our health. And they do not mean the danger of being hit by a heavenly stone on the head. They are interested in whether meteorites will cause chemical burns or radiation exposure.

Our ancestors did not think about such a danger. They gladly used meteoric iron to make weapons or tools. So, the Ensisheim meteorite, which fell in Germany, became like a ball in 500 years, because pieces of rock were beaten off from it all the time. They were used for both medical and witchcraft purposes.

The benefits of cosmic bodies were for sure: it was thanks to an unknown large meteorite that water appeared on Earth 65 million years ago.

But today people are afraid of harm from aliens. They think: if the stone came from outer space, then it was exposed to radiation. Therefore, it can be dangerous.

Scientists have carefully studied the content of radioactive isotopes in heavenly stones. For example, in the Glatton meteorite, which fell in 1991 and was studied a week after the fall. It turned out that the activity of its isotopes is only a few becquerels per kilogram - this is a unit of measurement of radioactivity. For comparison, the same indicator for an ordinary banana is 130 Bq/kg.

Another concern: whether meteorites will bring an unknown infection to Earth. And here scientists unequivocally say that this is impossible. That is, meteorites are not dangerous.

Myth 4. The composition of the meteorite may contain unknown chemical elements

Back in the 19th century, scientists repeatedly made attempts to find some unusual substances in space rocks, and maybe even new elements.

Today, physicists know that in the early stages of the existence of the young solar system, its substance was radioactive. For example, there was a lot of aluminum-26 and iron-60 here. The decay of radioactive isotopes heated the matter. Therefore, cosmic bodies several tens of kilometers in size differentiated. This means that they were divided into an iron core and a silicate, that is, stone, mantle.

Then these celestial bodies collided and crushed. Today we find fragments of these differentiated asteroids. It was these meteorites that once introduced our ancestors to iron. But nothing new, which would not have been on Earth at all, was not found in their composition.

There were also undifferentiated bodies, fragments of which also fall to the surface of the planet. This is the most primitive type of meteorites - chondrites. There is no sensation either: in their chemical composition, they are very similar to the Sun, which consists of elements well known to us.

Myth 5. Meteorites only come from the asteroid belt

A significant part of space guests arrive from the space between the orbits of Mars and Jupiter - that is, really from the asteroid belt. Sometimes we can even specify from which celestial body the meteorite broke off.

For example, Vestoids, meteorites from the asteroid Vesta, often fly to us. We know this for sure because they have the same spectral properties and chemical composition. Sometime in the past there was a powerful collision of this asteroid with a massive object. As a result, a lot of debris was formed, which are still flying to Earth.

But not only guests from the asteroid belt get to us. For example, some very interesting meteorites turned out to be from Mars.

Scientists determined the place of their appearance as follows. These meteorites are composed of volcanic rocks much younger than those of the solar system. This means that they must have formed on a planet where volcanoes erupted recently - for example, 150 million years ago.

When scientists had already concluded that some of the asteroids were coming to us from the Red Planet, they found another interesting meteorite. Inside it, small glass inclusions-droplets were found. They turned out to be hollow, and air from the atmosphere of the celestial body on which they arose was conserved in them. It turned out that its chemical composition is the same as that of the atmosphere of Mars. That is, the hypothesis was confirmed: "Martians" regularly fly to Earth.

In addition, scientists also find lunar meteorites. Determining that they were part of our satellite is not difficult, because scientists have samples of lunar rocks. Those that were brought to Earth by American astronauts and Soviet automatic stations.

We can expect that among the meteorites there will be guests from distant star systems. For example, from Fomalhaut.

Myth 6. Meteorites always arrive unexpectedly

This is exactly a myth. In past centuries, people really could not predict where and when the next heavenly stone would arrive. But today we have enough observing facilities to see in advance a small asteroid approaching the Earth. While very rare, but scientists are still able to do it. And then - to calculate exactly where the new meteorite will fall.

This first happened in 2008. Astronomers, a few hours before entering the earth's atmosphere, noticed a celestial body and even managed to name it - this is asteroid 2008 TC3. They calculated its trajectory and knew exactly where it would land. Indeed, fragments of a meteorite were found at the calculated point. They named him Almahata Sitta.

Scientists recorded another asteroid flying towards us in February 2023. Then they determined the place and time where he would fall. Exactly in this place, in France, they later found him.