Every day dozens of tons of meteorites reach Earth, most of them are tiny, but some are large enough to change the course of life on Earth. What is the source of these stones?
And how to find it?
Why do scientists care about studying it?
Here are 10 facts about her:
What are meteorites?
A meteorite is a debris of rocks that float in space within the solar system, and its size ranges between a small grain of sand and a large rock with a diameter of one meter.
Objects with a diameter greater than that are called asteroids, according to the definitions of the International Astronomical Union.
When the meteor penetrates the atmosphere of the planet, drawing a path of light in the sky, it is called a meteor or a fireball, and if it reaches the surface of the earth, it is known in this case as a meteorite.
The source of most meteorites is the asteroid belt between Jupiter and Mars (European Space Agency)
What is the source of meteorites?
Most meteorites on Earth come from the asteroid belt between Jupiter and Mars, but some also come from Mars or the Moon and from the remnants of comets.
In theory, small pieces of Mercury or Venus could have reached Earth as well, but none have been conclusively determined.
According to NASA, more than 50,000 meteorites have been found so far on Earth, and the proportion of them from asteroids represents the absolute majority by about 99.8%, and the remaining percentage (0.2%) is distributed almost equally between Martian and lunar meteorites.
How many blocks of stones that reach the ground daily?
Most meteorites are very small like a grain of sand, so they decay in the atmosphere because of their very high speed of 48,280 kilometers per hour, and generate heat of more than 1600 degrees Celsius.
But larger stones - and fortunately few in number - survive their journey through the atmosphere and reach the Earth's surface.
Scientists estimate that approximately 48.5 tons of meteorite material reaches the Earth's surface every day, according to Space.com.
Meteoritic rocks from Mars have pockets of trapped gas (Steve Jurvetson-Flickr)
How to identify the sources of meteorites?
Scientists can learn the source of a meteorite based on a range of evidence, such as analyzing photographic data of its fall that is useful in calculating its path and determining its source, or comparing the structural properties of meteorites with different classes of asteroids, or by determining its age.
For example, meteorites from Mars have pockets of trapped gas that match what Mars satellites and rovers have found.
As for those that come from the moon, their composition is usually similar to the composition of the rocks that astronauts brought from the moon during the Apollo missions.
What are meteorites made of?
Scientists classify meteorites into 3 types according to their composition:
Stone meteorites: They are the most common type, and represent 95% of the total stones falling on Earth, and they consist mostly of silicate materials, and contain small scattered grains of iron.
Rocky iron meteorites: They contain equal proportions of minerals such as iron, nickel, and silicate materials. They are rare and represent less than 2% of all known meteorites.
Iron meteorites: Very dense and composed of iron and nickel, scientists believe that they formed inside the cores of asteroids early in the history of the solar system, when the dense minerals sank to form a core very similar to the core of the Earth.
Although this type is rare among the meteorites that have been seen falling to Earth, it is among the most common types of meteorites that scientists have found because it is easy to identify them even after a long period of their fall, and because it differs greatly from the rocks of the earth, and its resistance to weather factors.
The most common meteorites consist of silicates with small grains of iron (James St. John-Flickr)
Where can meteorites be found easily?
Meteorites land randomly above Earth, although most fall into waters that cover more than 70 percent of our planet's surface, and can never be found.
But it is easy to find meteorites in geologically stable desert regions such as the Sahara or in Antarctica, where the low rate of precipitation in these areas maintains them, allowing them to accumulate over time, and the lack of vegetation makes these stones easier to find.
According to a report published on the Arizona State University website, scientists estimate that desert and polar regions may contain dozens of different meteorites per square kilometer, although they are difficult to distinguish from ordinary terrestrial rocks.
For example, a team of researchers found 425 meteorites in Antarctica in 2013 in just 40 days.
How can we distinguish between terrestrial rocks and meteorites?
It can sometimes be difficult to distinguish a meteorite from an ordinary terrestrial rock just by appearance alone, although in certain regions of the world they are easier to distinguish in terms of distinctions.
For example, meteorite rocks are distinguished from the rocks found in most desert areas by their dark color, which also helps to identify them easily in snow-covered areas.
Some other characteristics, such as the large density of the mass of iron meteorites, help to find them, as these rocks appear to be more heavy than usual, even if their size is relatively small.
Meteoritic rocks are distinguished from the rocks found in most desert regions by their dark color (Bcquerel).
What is the largest meteorite known so far?
The Hoba stone, which was found by chance in Namibia in 1920, is the largest meteorite that has been found so far. It is about 3 meters long, about a meter thick, and weighs 66 tons. Trace amounts of cobalt and other minerals.
Scientists estimated that it fell to the ground about 80,000 years ago, but the irony is that no crater occurred, contrary to what was expected. Such an object must have penetrated the atmosphere at a very high speed, and hit the ground hard enough to make a great crater.
Scientists believe that the absence of the crater may indicate that the "Hoba" stone fell to the ground at a lower speed than expected due to its flat shape, which slowed its speed upon impact.
What are the most famous events of the fall of meteorites in history?
There is no doubt that the meteorite that caused the extinction of the dinosaurs 65 million years ago was the most important of these known events.
Scientists believe that this object left a hole with a diameter of 180 kilometers in the Gulf of Mexico, according to a report published by the Nine Planets.org website (nineplanets.org).
The Barringer Crater crater in Arizona, with a diameter of 1200 meters and a depth of 200 meters, is one of the most famous effects of the fall of these bodies on Earth, and scientists estimate that it was formed about 50,000 years ago by an iron meteorite with a diameter ranging between 30 and 50 meters.
As for recently, the fall of an object over a remote uninhabited area in western Siberia known as Tunguska in 1908 is the most famous of these events.
Scientists believe that this orb was about 60 meters in diameter, and its fragmentation before hitting the ground led to no crater being formed. However, the event caused all the trees to be flattened on the ground over an area of 50 km long, and the sound of the explosion was heard in London, thousands of kilometers from the area.
The "Hoba" meteorite found in Namibia is the largest meteorite known so far (Bexhere).
What is the benefit of searching for meteorites?
Scientists believe that meteorite rocks contain an important record of the history of our solar system over a period of about 4.6 billion years, and searching for them allows us to learn details about how the solar system evolved and how meteorites could affect our future. Some of these stones coming from space contain grains of dust that they produced stars before our solar system formed, and studying these grains will enable our understanding of star formation and evolution.
Also, the fact that some "primitive" meteorites contain the first solid material formed in our solar system made researchers use its age, which is 4.568 billion years, to accurately determine the age of our solar system, and to know the conditions that prevailed in the early solar system.
The study of meteorites also helps scientists understand their role in the emergence of life on Earth, and how they affect the course of life on Earth by causing the major extinctions, for example.