Meteorites (also called meteoroids according to the term coined by astronomer Hubert Newton) exist everywhere in interplanetary space. These are solid elements from other stars (natural satellites, planets, planetoids, etc.) than the one on which they were found. Thus, in addition to those encountered on our planet, we have been able to observe several on Mars or on the Moon. The vast majority of those that have been observed so far are debris from asteroids. They are fragments deriving from a collision between two stars which most often come from the main belt located between Mars and Jupiter. Their sizes generally vary from a few centimetres to several metres when they enter the upper atmosphere. A meteoroid crosses space then the atmospheric envelope without disappearing at the time of the collision with the surface. However, it disintegrates during its descent and loses a large part of its mass so as to be, at the time of the shock, only a tiny fraction of the object initially entered the atmospheric medium. Thus, it ultimately represents only 1% to 1‰ of its original size. If most of the elements collected come from asteroids, it should nonetheless be mentioned that a few hundred, or less than 0.5%, come from the Moon and Mars. It also looks as though that some are from comets, such as the Orgueil meteorite (Tarn-et-Garonne).
By entering the atmospheric envelope at a speed of several tens of km/s, this rock produces a bright trail: the meteor. Visible only at night, it is a shooting star; visible also during the day, it is then called “racing car”, the latter signifying the passage of a large meteoroid. Generally, the light trail goes out about 20 km above the ground. If the object is not completely volatilised during its passage through the troposphere, it becomes a “meteorite” when it collides with the surface. It can also fragment in the sky, often due to a thermal shock, or at the time of the collision with the ground: we then observe a field of dispersion whose shape depends on the location of the fragmentation (sky or ground). These rocks from elsewhere are classified differently by meteoritologists and meteorite hunters depending on whether they are elements whose fall has been observed or elements discovered by chance. The Meteoritical Society regularly publishes a list of the meteorites analysed during the year. Around 60,000 of them were thus classified in 2018. This number is growing by around 1,500 per year.
Over the millennia, the perception of meteorites has changed. Linked first with the sacred, they have gradually become an important matter of science. In ancient times, many civilisations revered these stones fallen from the sky. The light produced during the crossing of atmospheric gases, sometimes accompanied by sound manifestations, was always an extraordinary spectacle. Exacerbating the imagination and human emotions (fear, adoration, respect), these extraterrestrial materials were sought after: they were sacred, denoting divine power or authority. They were, at that time, used during religious ceremonies, like the Omphalos of the Temple of Apollo in Delphi or the Black Stone in Mecca. Since prehistoric times, men have exploited these strange rocks whose high iron content made it possible to make weapons and jewellery. This has been observed on all continents. The Inuit would have been the first to use them, at least according to our current knowledge. Indeed, the Iron Age of these people would date from the arrival of the meteorite from Cape York (Greenland) 10,000 years ago: archaeologists have found extraterrestrial iron shards in spears of harpoons and blades of knives. In ancient Egypt, meteoric iron was also used, as evidenced by the iron dagger discovered in the sarcophagus of pharaoh Tutankhamun. Meteoric iron spears have also been found in ancient Italy.
Quite a few very ancient literatures mention the existence of these extraterrestrial rocks. In ancient China, it was customary for authors to record the descent of these rocks without mentioning their source. Around -450 BC. AD, the pre-Socratic philosopher Anaxagoras was the first to hypothesise about the extraterrestrial origin of these rocks, although his hypothesis was incorrect since he attributed them to the sun. 1500 years later in Central Asia, the polymath Avicenna claims that stone rocks and iron rocks fall from the sky; he performs fusion experiments with these elements in order to infer the metallic composition.
It only took a few decades for scientific progress to revolutionise our knowledge of the solar system. In fact, laboratories are carrying out increasingly accurate analyses and astronomical observations are becoming more and more accurate. In addition, space exploration makes it possible to visualise other stars and sometimes even to bring back samples to study them. The radiochronology used to date meteorites stones very accurately (207 Pb-206Pb) including plasma mass spectrometers and secondary ionisation (SIMS). The first successful dating took place in 1956: The American geochemist Clair Cameron Patterson estimated the age of a ferrous meteorite at 4.55 billion years, that is, the age of the solar system. Since then, the knowledge of our universe has not stopped progressing thanks to the study of these rocks. It is the assessment of the various minerals contained in a stony meteorite (primitive meteorite, also called chondrite) which enables to highlight that the minerals forming a chondrite are similar to the minerals which one finds on a terrestrial planet. This means that a chondrite is composed of particles of iron and nickel (as in a tellurian nucleus) and silicates identical to those found in the earth’s crust and mantle. Cosmochemists seek to deepen this knowledge to better explain the planetary distinction, that is, the fact that some stars of important dimensions are formed with several layers of different densities, unlike comets, satellites and asteroids small dimensions.
Chondrites are classified according to the distance between their place of formation and the sun. Some carbonaceous chondrites, which are supposed to originate from comet nuclei, have been analysed chemically: they contain amino acids, elementary links in life. This discovery supports the theory of panspermia which suggests that the living organisms present on Earth initially come from extraterrestrial places, although the “primitive soup”, experiment initiated by the American biologist Stanley Miller, tends to show that life has just as could have appeared without extraterrestrial “contamination”. Meteoritic rocks from Mars provide valuable information on Martian geology even though no sample of Martian soil has yet been announced (however, space missions are already scheduled for this purpose). Although this type of rock is very uncommon, research organisations like ANSMET have made it possible to discover a few specimens, thus enabling scientists to acquire new knowledge about the red planet.
According to estimates, the Earth sweeps 100 tonnes of interplanetary matter daily, which means that about 100 million meteorites enter our atmosphere every day. They are mainly grains of dust of less than 0.1 mg. Most of these elements are micrometeoroids, the consistency of which is similar to that of cigarette ashes, and are consumed during the passage of atmospheric gases. Thus, only six tonnes of meteoritic elements reach the ground daily. Each year, 40 tonnes of meteoric bodies from 10 g to 100 kg and 15,000 to 20,000 tonnes of micrometeorites (up to 50,000 to 100,000 tonnes with interstellar dust) pass through the atmospheric envelope each year. The most substantial specimens nevertheless lose 80% of their mass during their descent through the different gas layers. Beyond 10 − 14 kg, these dusts become micrometeorites and hit the ground in the form of grains of sand; those measuring 10 − 14 kg or less are volatilised without being totally destroyed and their minerals aggregate to fall very slowly. Most of these elements are destroyed in blocks as they descend to the surface, thus limiting the number of large impacts. The number of rocks that reach the ground the size of a tennis ball is estimated to be around 500 each year.
Fragments of very small diameters are therefore much more likely to touch the ground in the form of tiny grains: it is estimated that one falls by 1 µm in diameter every 30 µs, one by one millimetre every 30 s, one of one metre every year, one of 50 m every century, one of 100 m every 10,000 years, one of a kilometre every million years and one of 10 km every 100 million years. A meteoric element weighing more than 10 g reaches the surface every 6 to 30 minutes, which makes about 18,000 to 84,000 elements per year. If 2,000 to 5,000 meteoritic rocks of more than one kilogram strike the ground yearly, 75% vanish due to weather conditions or the place of landing (ocean, desert); among the 25% that do not disappear, few are found. On average, only 5 to 25 falls are observed annually and 2 to 5 impacts are discovered.
Rocks from space result from fragments caused by a collision between two stars or released by disintegration when a comet passes very close to the sun.
The terms to define these rocks from the sky were academically defined in 1958 by the International Astronomical Union :
The dimensions of the second were specified in 1995 by the Royal Astronomical Society: its size is between 100 µm and 10 m. Below 100 µm, we speak of interplanetary dust, because its mass is too small to generate a shooting star; beyond 10 m, we speak of near-Earth objects (minor planets or comets) whose mass is sufficient to reflect light, such as the stars visible through the telescope. The collision with a NEO could create a significant change on Earth, of winter impact type (drop in global temperature). Such a collision with a NEO with a diameter greater than 2 km could even cause a biological crisis (massive extinction resulting in the disappearance of 75% of animal and plant species). However, the limits given by the Royal Astronomical Society evolve with scientific and technological progress. Indeed, the telescopes of the GEODSS, an American optical surveillance network, are so powerful today that they make it possible to observe stars less than 10 m away. In addition, scientists have realised that particles of less than 100 µm, sometimes as small as 10 µm, are able to produce a meteor, the light trail depending on several parameters (speed, density, structure, angle of entrance). The lower and upper limits are therefore constantly reviewed.
The metallic meteorite stone is particularly appropriate for people who wish to acquire more willpower and perseverance. It has an energy of materialisation and incarnation that accompanies people in their projects. This mineral brings a precious and essential help to those who wish to carry out their projects.
This rock is also very interesting for working in the context of meditation. All of its varieties lend themselves to meditative work. It brings us closer to the birth of the universe and the Big Bang. It initiates a journey through time and space, in search of the divine. This intimate exploration is done in several stages which it is necessary to memorise well in order to return there, session after session. This allows you to gradually go deeper in this inner journey and progress at your own pace. Before starting this quest, it is, however, necessary to secure yourself by anchoring yourself at foot level; to do this, we will place black tourmalines (large schorls) at the level of the arch of the foot. This rock from space helps us to comprehend that we do not own the Earth, but that we are only passing through it. It inscribes in the wearer the need to respect it. Nowadays, meteoritic glasses are well known in lithotherapy. Formed during the collision with the ground, these stones belong to the tektite family, which also includes the beneficent Moldavite. Their journey to reach us has brought them to bear phenomenal temperatures and pressures, thus acquiring particularly fascinating and useful properties in lithotherapy.
The meteorite stone facilitates the assimilation and integration of iron by the body. Placed near the heart and the fold of the groin, ferric meteorite strengthens the immune system and protects against colds. Rich in iron and nickel, this rock acts similarly to magnetite, but in a more spectacular way. Its magnetism is very powerful, far beyond that of ferrous minerals, including magnetite.