Meteors bring messages from other worlds and it is necessary to protect them

Its extraterrestrial origin captivates us. Most of us humans will never reach space and no one will ever be able to visit all the worlds from which meteorites arrive.

The carbonaceous chondrite ALH77307 in transmitted light makes it possible to identify the vitreous spherules known as chondrules. It is representative of a pristine carbonaceous asteroid. JM Trigo CSIC/IEEC , Author provided

Josep M. Trigo Rodríguez , Institute of Space Sciences (ICE – CSIC)

Every day in some corner of the Earth free samples of the stars that surround us fall. And they arrive by cosmic messenger, the result of multiple processes that launch these rocks from asteroids and planetary bodies in orbits around the Sun through which they move for tens of millions of years until, after a carom, they finally find our planet. Meteor falls, heralded by brilliant balls of fire , gift us with fascinating rocks that carry a message in a bottle from remote parts of the Solar System.

Its extraterrestrial origin captivates us. Most of us humans will never reach space and no one will ever be able to visit all the worlds from which meteorites arrive.

Your messages

In expert hands, its minerals provide scientific information capable of delving into the past. They tell stories about the formation processes of asteroids and planets in the beginnings of our planetary system, long before the Earth was formed.

Thanks to the dating of the minerals produced by aqueous alteration, we know that carbonaceous chondrites were the first hydrated bodies in the Solar System, before the Earth existed . Even the tiny components inside, formed before the Sun, speak to us, telling us the story of our galaxy. By containing presolar grains and certain isotopes that are the product of the decay of radioactive elements formed in other stars, we know, for example, that the Sun was born in an association of stars more massive than itself .

Thus, we can extract from them fascinating stories waiting to be told. For this reason, a branch of space sciences turns to its study and cataloging, also as representative samples of the bodies from which they come.

Rocks that survive their abrupt encounter with Earth

They don’t have it easy at all in their abrupt and tortuous encounter with our planet. The rocks that cross the interplanetary medium reach the roof of the atmosphere at hypersonic speeds (between 11 and 72 km/s) for which they suffer friction with the atmosphere and the process called ablation. This is how the luminous phase that we call a fireball or ball of fire is generated , in which more than 95% of the initial mass is usually lost, and the rock tends to fragment, crumble and evaporate.

It is good news that the Earth’s atmosphere provides a shield for these projectiles to fragment effectively without posing a danger. In fact, meteorites have such a low thermal conductivity that they cool down during the fall: it is a myth that they reach the ground incandescent.

We could agree that these fascinating rocks, arrived from far corners of our planetary system , should be the heritage of all. Any country that is passionate and respectful of science takes steps to preserve this legacy offered by Mother Nature. Spain included them in the Geological Heritage Law and since then the meteorites fallen in Spain are protected by law, they must be made known, preserved, and it is illegal to sell them.

we know where they come from

At the CSIC we have made technological advances applicable to the digital detection of these luminous phenomena to identify and catalog the fireballs that sometimes produce meteorites. Some become as bright as the Moon and we monitor them from the CSIC’s Fireball and Meteorite Research Network (SPMN), which, for more than 25 years, has maintained an updated list as a result of a citizen science project.

By reconstructing their trajectories, we measure their degree of depth and survival, and we calculate the places of possible fall. In addition, we reconstruct their orbits in the Solar System to understand the dynamic routes that transport them to Earth.

For example, seventeen years ago we managed, for the first time in Spain and ninth in the world, to reconstruct the orbit of a meteorite, the Villalbeto de la Peña ordinary chondrite . Since then we have obtained the orbits of other meteorites and we have been increasing our knowledge about the origin of these rocks. The last four meteorite falls that we have recovered and identified in Spain so far: Ardón (1931), Villalbeto de la Peña (2004), Puerto Lápice (2007) and, recently, Traspena (2022 ) .

Most meteorites reach Earth by circuitous routes from when they break away from their parent body, in an asteroid-plagued region called the main belt , located between the orbits of Mars and Jupiter. This is what happened to the metric-sized rock itself that caused the fall of Villalbeto de la Peña. By measuring its age from exposure to cosmic rays, we deduced that it took about 48 million years to reach our planet since it was launched previously by another impact on the surface of its parent asteroid. An authentic play of cosmic billiards.

Where and how to find meteorites

It is not easy to find meteorites. They are not common and erode quickly when they are on the earth’s surface. The reason is that they contain reactive minerals to the action of water and atmospheric oxygen. For this reason they oxidize easily, weakening the consistency of the rock, which ends up disintegrating.

Only in desert regions are these processes minimized by environmental dryness and survive longer, as Phil Bland’s studies have revealed . But, as if the challenge posed were not enough, recognizing a meteorite will also depend on knowing how to distinguish them from certain terrestrial rocks and minerals that, when altered by the action of the elements, adopt shapes and shades reminiscent of a meteorite (in the world Anglo-Saxon are known as meteorwrongs ).


Meteorites partially or totally possess a thin fusion crust produced on their entry into the atmosphere. This layer is less than a millimeter thick, is usually dark or black, and changes over time. They also have generally flat faces and edges, rounded by the friction they are subjected to during their course through the atmosphere at hypervelocity. Due to the overpressure they suffer when penetrating the deepest and densest layers of the atmosphere, they fragment and some show their interior, where shiny metallic grains are usually found. If they have just fallen, their fusion crusts are dark and the ores are bright, making them easier to find.

Meteors are also usually heavier than terrestrial rocks. If in doubt, we do not recommend any type of test that destroys or alters the sample, not even subjecting it to a magnet so as not to alter its primary magnetic field.

The experts will give a quick response and inform you of the procedure to follow to be recognized as discoverers, in the event that it was indeed a meteorite. As an anecdote I remember that meteorite to which we gave our name in 2014, Ardón, a small chondrite that fell in 1931 in front of a girl who wonderfully preserved it for 80 years 

Where should the meteorites end up?

In any case, they must reach expert hands and an official center that makes them available to the scientific community and, for the most part, on public display. The meteorites must be in museums and research centers that preserve them and where they are in charge of showing them to the public.

Our specialization in the Institute of Space Sciences of the CSIC has allowed us to be the only Spanish international repository center for NASA Antarctic meteorites. In addition, as members of the Meteorite Society , we have given many meteorites an official name, which is why we have a unique collection that is available to young researchers so that they can acquire training in those materials that make up the bodies of the Solar System.

A rigorous classification requires time, chemical and mineralogical analyzes that begin in our White Room for Meteoritics and Return of Space Samples of the ICE-CSIC . In the event of identifying a new meteorite, we dedicate ourselves to its study and characterization to give it a name at no cost to those who provide us with the sample and returning most of it to its owner, advising him on the steps to follow.

Sadly, too often, public interest in meteorites centers on their economic value, even though the most common are far less valuable than precious metals. This bias diverts us from the most relevant aspect: scientifically they are unique, as they have sculpted in their materials the evolutionary processes suffered by the asteroids or planetary bodies from which they come. Incredible stories of cosmic resilience waiting to be told if they fall into expert hands.The Conversation

Josep M. Trigo Rodríguez , Principal Investigator of the Meteorites, Minor Bodies and Planetary Sciences Group, Institute of Space Sciences (ICE – CSIC)