WHAT CAN WE SEE IN THE NIGHT SKY
Tens of thousands of small rock fragments enter our planet's atmosphere every day, but most of them are the size of a grain of rice and burn up before reaching Earth's surface. These extraterrestrial rocks that have "landed" on Earth provide an exceptional opportunity to piece together the history of our Solar System's birth 4.6 billion years ago and its evolution.
TERMINOLOGY
According to the American Meteoritical Society (AMS)
Meteoroids – fragments of cosmic rocks that orbit around the Sun. Their size varies from dust grains to small asteroids.
Meteor – a moving trail of light caused by a meteoroid entering Earth's atmosphere. Air friction melts the surface of the rock, causing it to glow. Even smaller extraterrestrial debris, such as dust particles from comets, can also become meteors.
Bolide – a bright meteor resembling a fireball, regardless of whether it collides with Earth's surface or burns up in the atmosphere.
Meteorite – a meteoroid that survives its passage through the atmosphere and falls to Earth.
What is the difference between a comet and an asteroid?
Asteroids consist of metals and rocks, while comets are composed of dust, rocky material, and ice.
WHAT ARE METEORITES
A meteorite is a solid piece of debris from a comet or asteroid. When it enters Earth's atmosphere, due to various factors such as friction, pressure, and chemical interactions with atmospheric gases, it heats up and emits enormous energy. As a result, it becomes a meteor and forms a fiery trail, also known as a falling star.
Meteorites are composed of minerals. Most of these minerals also make up Earth's rocks, but there are some that have not been found on Earth. According to their mineral composition, the main types of meteorites are: stony, stony-iron, and iron.
WHERE METEORITES COME FROM
The earliest theories about the origin of meteorites were made by the Roman naturalist Pliny, who observed and recorded the fall of a meteor in Thrace. Centuries later, in 1794, the German physicist Ernst Chladni collected data on several meteorite finds and falls, and published a bold idea for his time — that meteorites are rocks from space.
Meteorites are formed as a result of various processes in the Solar System that lead to the creation of solid celestial bodies capable of reaching Earth. Most of them are fragments of asteroids that broke apart long ago and now orbit the Sun in the Asteroid Belt. The first clear evidence for this was obtained in 1959, when scientists managed to photograph a falling meteorite and determine its origin. Since then, many meteorites have been traced back to the Asteroid Belt.
Only a small portion of meteorites come from Mars and our Moon. Scientists identify lunar meteorites by comparing them with samples brought back by the Apollo missions. The gases found in some meteorites match those in the Martian atmosphere, as measured by the Viking spacecraft, confirming their Martian origin.
WHAT IS THE ASTEROID BELT
The Asteroid Belt is a region in the Solar System, located between the orbits of Jupiter and Mars, which is filled with numerous irregularly shaped solid bodies of various sizes, called asteroids. It also contains some dwarf planets. The first object from the belt to be noticed was the dwarf planet Ceres, observed in 1801 by the Italian astronomer Giuseppe Piazzi.
In the following decades, many similar objects were discovered in this area, such as the asteroid Vesta. This is the second largest body in the asteroid belt, with a width of 326 miles. Similar to Earth, it has differentiated layers of crust, mantle, and core, common to rocky planets. And this may mean that Vesta is the remnant of a larger destroyed planet.
In the 1850s, astronomers began calling the ring-shaped region the "Asteroid Belt." Scientists calculate that only about 0.7% of all found meteorites originate from the Moon, 0.5% from Mars, and about 99% are fragments from asteroids.
WHERE YOU CAN FIND METEORITES
Meteorites fall everywhere on Earth, but most of them sink into the oceans. The best places to search for meteorites are glaciers, deserts, and rock-free plains. More meteorites have been discovered in Antarctica because they are relatively easy to recognize on ice. The movement and melting of glaciers leads to the concentration (accumulation) of meteorites in certain areas. The deep freezing of Antarctica helps protect them from weathering. More than 16,000 Antarctic meteorites have been collected since 1976, with 14,000 of them stored at the Smithsonian Institution in the USA.
Meteorite hunting in Morocco is widespread and attracts searchers and collectors from around the world.
WHAT METEORITES LOOK LIKE
Compared to Earth rocks of the same size, meteorites are slightly heavier. And if they are metallic, they are much heavier and ring like a bell when struck with a metal object. Some have indentations, while others have a smooth surface.
Identifying a meteorite is difficult and requires expert opinion.
By size, meteorites can range from grains of a few micrometers to large rock blocks. The largest known meteorite – "Hoba," weighs about 54 tons and fell about 80,000 years ago in Namibia.
Most meteorites are strongly or weakly magnetic, and on a broken surface, many small metal spots can be seen. Contrary to claims, meteorites are usually not more radioactive than Earth rocks, they do not glow, nor do they feel unusually warm to the touch. They are not poisonous and therefore it is not dangerous to touch them.
Meteorites that have fallen recently have a distinctive black glassy surface called a fusion crust
Older meteorites are typically weathered, covered with a dark brown coating, missing in places
WHAT IS A METEOR SHOWER
Meteor showers occur when Earth passes through debris fields left by comet tails or asteroids. Particles from them enter Earth's atmosphere, attracted by Earth's gravity. About 30 meteor showers can be observed from Earth at regular intervals annually.
Collage of 12 Perseids on the night of August 12-13, 2023, photo by Alexandra Chobanova
* The material uses photos from internet
