Orgueil meteorite

In 1864, in the southwest of France, people witnessed a fiery ball in the sky, which created a long smoky streak on its way down. Suddenly, this ball exploded at a height of 30 km in the sky and its pieces hit the ground in an area of 20 × 4 km in the village of Orgueil (Figure 1). The strong noise and the white cloud created in the path of movement led to the tracking of the impact area of the meteorite. Immediately, many reports and documents were collected from the crash site and the samples were transferred to the meteorite collection of the National Museum of Natural History in Paris and Montauban, and the Imperial Observatory research institution at the PSL University (Rozanov et al., Reference Rozanov, Hoover, Krasavin, Samylina, Ryumin and Kapralov2021).

Figure 1. A large fragment of the Orgueil meteorite in the National Museum of Natural History in France.

A preliminary chemical analysis of the Orgueil meteorite revealed that it is a chondrite rich in carbon and organic matter and contains 8–10% extraterrestrial water in its matrix, together with ammonium and magnesium salts, anhydrite, calcite, serpentine, pyrrhotite, silica and a water-insoluble polymeric carbon complex and coal. In later tests, the chemical compounds of this meteorite were determined more precisely (Table 1) (Rozanov et al., Reference Rozanov, Hoover, Krasavin, Samylina, Ryumin and Kapralov2021).

Table 1. Chemical compounds of the Orgueil meteorite (Rozanov et al., Reference Rozanov, Hoover, Krasavin, Samylina, Ryumin and Kapralov2021)

About 14% of Orgueil’s chemical compounds consist of organic substances, some of which can be produced by biological or chemical processes. However, some of them are strong biomarkers such as amino acids, nucleobases, and some molecules derived from the decomposition of chlorophyl, such as porphyrin. The reason why they are considered strong biomarkers is that these types of molecules are not produced by any of the non-biological mechanisms and at the same time their structure can be millions old, even up to billions of years. Among the amino acids identified in this meteorite, the amino acids glycine, alanine, aspartic acid, glutamic acid, leucine and proline were observed.

From the observation of life-related chemical compounds in the Orgueil meteorite, two researchers named Nagy et al. (Reference Nagy, Meinschein and Hennessy1961) decided to study this meteorite more closely from the perspective of microbiology. The initial results of these two scientists were very interesting and indicated the discovery of all kinds of particles with microscopic sizes and similar to fossil algae, which they interpreted as possible fossils of microorganisms. These two researchers put forward the following arguments and presented some explanations: (1) The high number of possible microfossil particles in the Orgueil (1,650–1,700/mg) can only exist if liquid water was in constant contact with the meteorite. Of course, in the subsequent tests, it was found that the analyzed components of the meteorite disintegrate rapidly in water. (2) The organized elements that were very similar to the microfossils mostly resembled some terrestrial microscopic organisms (especially dinoflagellates and chrysomonads), which belong to the protozoa found in aquatic environments such as seas and lakes. (3) Possible microfossils in the Orgueil meteorite were similar to another meteorite called Ivuna, which fell at different times and in another climatic region. This challenges the possibility of terrestrial origin for the found microfossils (Figures 2, 3) (Rozanov et al., Reference Rozanov, Hoover, Krasavin, Samylina, Ryumin and Kapralov2021).

Figure 2. Microscopy of the organized elements in the Orgueil meteorite (Rozanov et al., Reference Rozanov, Hoover, Krasavin, Samylina, Ryumin and Kapralov2021).

Figure 3. Microfossil with a structure resembling a magnetotactic bacterium in the Orgueil meteorite (Rozanov et al., Reference Rozanov, Hoover, Krasavin, Samylina, Ryumin and Kapralov2021). Magnetotactics are a group of bacteria that can produce nanostructures called magnetosomes, and this leads to the alignment of these microorganisms in the magnetic field. In this image, structures such as the magnetosome can be seen in the dark along the pseudo-microfossil structure.

These interpretations led to a hot debate at the time about the possible origin of these pseudo-microfossil structures. Shortly after Nagy and Hennessey claimed to have found evidence of microfossils in the Orgueil meteorite, two other researchers named Anders and Fitch (Reference Anders and Fitch1962) contradicted this claim and attributed the pseudo-microfossil structures to some factors including mineral processes or contamination with plant pollens during fell to Earth the meteorite. Until the end of the 20^th century, many other scientists also disagreed with the argument that “the similarity of morphology cannot be regarded as valid evidence for the assignment of organized elements to microfossils.” Many other researchers also rejected the possibility of contamination at the crash site or even in the museum (Rozanov et al., Reference Rozanov, Hoover, Krasavin, Samylina, Ryumin and Kapralov2021). Discussion on this topic continued into the second decade of the 21^st century until Aerts et al. (Reference Aerts and Elsaesser2016) dismissed the possibility of contamination of the Orgueil meteorite with plant pollen particles or other terrestrial contaminants, which led to the observation of forms resembling microfossils or strong biomarkers. They proved that the strong biomarkers and the organized structures are not of terrestrial origin and were generated from the Orgueil meteorite when it detached from the parent body.

The probability of extraterrestrial life in the Orgueil meteorite was strengthened by the detection of strong biomarker molecules and pseudo-microfossil structures. These findings not only strengthen evidence for the existence of pseudo-terrestrial microbial life in Earth-like celestial bodies but also largely confirm the panspermia hypothesis. From this theory, in the early stages of the Earth’s formation, the seeds of life in the form of primary single cells were brought to the ground of this planet by meteorites. After the original population multiplied and spread, these single-celled organisms spread to different parts of the Earth depending on the climatic and environmental conditions. As a result of natural selection over billions of years, they have divided into various groups of organisms. However, there is still a long way to go before the panspermia hypothesis is finally proven. Not only should more studies be carried out on similar samples, but also the discovery of organic life forms on other celestial bodies can help to prove this hypothesis.

Murchison meteorite

At the end of September 1969, a large meteorite was observed in the sky above the town of Markinson in southeastern Australia, that was broken up into various pieces by a cloud of smoke, and its pieces fell to the ground over an area of 13 square kilometers (Fuchs et al., Reference Fuchs, Olsen and Jensen1973). After collection, the largest part of this meteorite (65 kg) was sent to the Field Museum of Natural History in Chicago. Other pieces were given to the Smithsonian Institution’s National Museum of Natural History in Washington, DC (30 kg), the Museum of Australia in Sydney (about 4 kg), and the College of Melbourne in Australia (7 kg). Smaller quantities, about a few kilograms, were also given to museums, universities, research institutes, and even private individuals (Figure 4).

Figure 4. A fragment of the Murchison meteorite.

This celestial stone with a lifespan of 7 billion years is the oldest material discovered by mankind. Murchison belongs to the carbonaceous chondrite meteorites and black silicate is the most important mineral (with 77% volume and 27.22% weight). The total water content is about 12% and the carbon content is 1.6–2.2% of its weight. Table 2 lists the relative amount of chemical compounds in the Murchison meteorite (Fuchs et al., Reference Fuchs, Olsen and Jensen1973).

Table 2. Microscopy of the elements in the Murchison (Fuchs et al., Reference Fuchs, Olsen and Jensen1973)

From the 1960s, shortly after the collection of Murchison’s pieces, the search for signs of life in some of his pieces began. In the first endeavor, organic compounds such as amino acids (subunits for building proteins) were proven in this meteorite (Cronin and Moore, Reference Cronin and Moore1971). However, the extraterrestrial origin of these molecules could not be confirmed. Due to the feasibility that the meteorite was contaminated with terrestrial organic molecules after the fall, it was difficult to prove the nature of the amino acids. This confusion continued until Koga and Naraoka (Reference Koga and Naraoka2017) succeeded in identifying nine amino acids in the Murchison. By analyzing their structural features, the probability of extraterrestrial origin of these amino acids was greatly strengthened. Glycine, alanine, serine, aspartic acid, threonine, valine, glutamic acid, leucine, and isoleucine were among the most important amino acids identified in the Murchison.

The most important signs of extraterrestrial life in the Murchison were related to the research performed by Oba and colleagues (Reference Oba, Takano, Furukawa, Koga, Glavin, Dworkin and Naraoka2022). The results of this research indicated all the building blocks of nucleic acids (adenine, guanine, thymine, cytosine, and uracil) in the Murchison meteorite. It was found that these nucleobases have an extraterrestrial origin, which is a very important subject considering the longer life of this meteorite compared to the planet Earth. This discovery questions many previous hypotheses such as the bubble and fundamental soup model, which emphasize the formation of subunits that make up genetic material and proteins on the planet Earth. All evidence strongly strengthens the feasibility of an extraterrestrial origin of life.

The Murchison meteorite is significant in several respects, two of which are more important than others: The first aspect is the significance of the age of this celestial stone, which is older than the solar system and the Earth (2.5 billion years). Moreover, protosolar grains in this meteorite provide valuable information about the time before the formation of the solar system. The second important aspect of the Murchison is the presence of genetic material components in this 7.5-billion-year-old meteorite. This fact not only strengthens the possibility of the existence of extraterrestrial life in other astronomical objects but also makes the panspermia theory much more successful than in the past.

Allan Hills Meteorite 84001 (ALH 84001)

A group of researchers from the National Science Foundation discovered a meteorite named Allan Hills while traveling by snowmobile in the Allan Hills Icefield at the eastern end of the Transantarctic Mountain Range (Figure 5). In the first descriptions, the researchers described it as a non-chondritic meteorite with a strong matrix fracture, gray-green and with a surface crust consisting of 90% melt. After nine years, an oxygen isotope analysis showed that it is a Martian meteorite that is about 4.5 billion years old and formed shortly after the birth of the planet Mars. Further analysis revealed that this meteorite probably separated from the planet Mars about 17 million years ago from a crater-like area called Valles Marineris and hit the Earth about 13 thousand years ago. The 1.94 kg meteorite is a silicate-rich volcanic rock composed mainly of the following materials: Orthopyroxene (Mg,Fe)SiO₃ and with smaller amounts of chromite (FeCr₂O4₎, olivine ((MgFe)₂[SiO₄]), pyrite (FeS₂), apatite (Ca₃(PO₄)₂), and silica-rich glass (Friedmann et al., Reference Friedmann, Wierzchos, Ascaso and Winklhofer2001).

Figure 5. Allan Hills meteorite 84001 (ALH 84001).

The presence of 3.9-billion-year-old secondary carbonate (Figure 6) (which forms at the temperature of the growth range of bacteria) and magnetite in the cracks of this meteorite can be grouped as a weak biological sign (Figure 7). This weakness is because these compounds are formed in both biological and mineral processes. However, the observation of structures resembling microscopic magnetite crystals (as found in magnetotactic bacteria on Earth) in the cracks of this meteorite has made the probability of microbial life on Mars a hot topic (Friedmann et al., Reference Friedmann, Wierzchos, Ascaso and Winklhofer2001). The observation of particles resembling bacterial microfossils in this Martian rock has further strengthened the hope for life on Mars. This is because some of these particles are very similar to the structure of bacterial fossils on Earth, especially magnetotactic bacteria. This claim has always been confronted with the question that “Similarity of the appearance of the discovered particles to the microorganism fossils in the Allan Hills meteoritecannot be a convincing reason” to confirm the presence of microorganisms when this rock was separated from the parent planet. This is because many structures that resemble microfossils can form through mineral processes. The formation of such structures requires water and a temperature in the life-friendly range, suggesting the water flows and a temperature range reasonably similar to that of the Earth life during the formation of these structures (Friedmann et al., Reference Friedmann, Wierzchos, Ascaso and Winklhofer2001).

Figure 6. As a main component in the meteorite ALH 84001, carbonate formation process has been simulated by researchers.

Figure 7. Tubular, elliptical, and rope-like structures of carbonate with a diameter of 20–100 billionths of a meter, have been observed by an electron microscope in a part of the Martian meteorite ALH 84001, and are very similar to bacterial microfossils (https://www.nasa.gov).

Last point on extraterrestrial life giving the meteorite-derived information

General studies on those three meteorites (Orgueil, Murchison, Allan Hills) have revealed thought-provoking facts about life in other parts of the universe. In all three meteorites, there is evidence for microfossils, suggesting the existence of microbial life in the very distant past. Even if one accepts the uncertainty about the origin of fossil-like forms in inorganic and non-biological processes, the presence of DNA/RNA subunits in the Orgueil and Murchison meteorites is reliable evidence for the conditions needed for the formation of nucleic acids in celestial bodies other than Earth. Given the different times and places for the meteorites and the simultaneous discovery of common life features in each of them, it can be concluded that the information obtained from these meteorites is one of the most reliable documents for the high probability of extraterrestrial life. This information proves the most important subunits of biological structures can form in other parts of space. However, a quantitative and qualitative understanding of this topic will require more extensive research using advanced technologies in the future.

From Luna-1 to recent probes

Space probes are unmanned devices that leave the Earth’s gravitational field and are sent into space to explore various celestial bodies. These probes carry out a variety of missions far from Earth’s orbit. From their landing site, these kinds of devices can send valuable information to us that cannot be accurately estimated from the ground (Girija, Reference Girija2023). The first space probe was Luna-1 (Figure 8), which was launched by the Soviet Union on January 2, 1959. After this launch, there was close competition between the Eastern and Western blocks for the pioneering role in the space industry and research until the end of the 1980s. Although the Soviet Union had the upper hand at the beginning of this competition, it lost its active role at the end of the 1980s, when it was approaching collapse. Thus, the United States, as the flagship of space exploration, together with the European Space Agency, Japan, China, and India, continued on the path of exploring human civilization in deep space (Petrescu, Reference Petrescu2019). Since the beginning of space search with the help of probes, it has been possible to penetrate the atmospheres of Venus, Mars, Jupiter, and Saturn’s moon Titan over the past six decades (Girija, Reference Girija2023). In the meantime, some probe reports have contained promising information about the presence of signs of life or predisposing factors for the emergence of life in the atmospheres of these planets.

Figure 8. Luna-1 at the memorial museum of astronautics.

The below reportshave strengthened the emergence of life forms even at the microbial level: water on Mars by the Curiosity and Phoenixrovers (Petrescu, Reference Petrescu2018), liquid water streams by the Spirit and Opportunity rovers(Gargaud et al., Reference Gargaud, Irvine, Amils, Claeys, Cleaves, Gerin, Rouan, Spohn, Tirard and Viso2015) (Figure 9), frozen water on Mars by the Phoenix rover (Figure 10), huge glaciers on Saturn’s moon Enceladus by the Cassini rover (Dong et al., Reference Dong, Hill and Ye2015) (Figure 11), volcanic activity on Jupiter’s moon by the Voyager 1 rover (Davies and Hargitai, Reference Davies and Hargitai2014) (Figure 12) and frozen water at Mercury’s north pole by the Messenger rover (Johnson and Hauck, Reference Johnson and Hauck2016) (Figure 13).

Figure 9. Thick layers of sedimentary rocks on the lake bed and edge in the Gal Mars crater. Recorded by the Curiosity spacecraft (NASA/JPL).

Figure 10. Ice at a depth of 3 cm in the North Pole of Mars. Recorded by the Phoenix spacecraft (NASA/JPL).

Figure 11. The geysers of the Antarctic Enceladus, which are thrown to higher altitudes in the form of ice masses. Recorded by the Cassini rover (NASA/JPL).

Figure 12. Two simultaneous volcanic eruptions on Jupiter’s moon Io, where volcanic gray clouds rise 150 miles high. Recorded by the Voyager space probe (NASA/JPL).

Figure 13. Regions near the poles of Mercury that are constantly in shadow and are cold enough to store water as ice. Recorded by the MESSENGER rover from the NASA Applied Physics Laboratory/Johns Hopkins University, Carnegie Institution of Washington (Armytage et al., Reference Armytage, Anzures, Banerdt, Benkhoffet, Besse, Blewett, Bott, Byrne, Carli, Chabot, Chapman, Cloutis, Cremonese, Denevi, Deutsch, Dong, Doressoundiram, Dygert, Ebel, Ernst, Fassett, Genova, Grava, Hauck, Heyner, Hussmann, Iess, Imber, Izawa, Izenberg, James, Kerber, Kinczyk, King, Klima, Klimczak, Knibbe, Lawrence, Lucchetti, Mazarico, McCubbin, McNutt, Nittler, Oberst, Ostrach, Padovan, Pajola, Panning, Parman, Peplowski, Prem, Roberts, Schmude, Schorghofer, Slade, Stark, Strauss, Susorney, Thompson, Udry, Vander Kaaden, Vervack, Varatharajan, Weider, Whitten, Wilbur and Williams2018).

Last point on extraterrestrial life giving the rover-derived information

Evidence on the existence of water or environments resembling the ecosystems on Earth (such as volcanoes, ice, oceans, and water currents) in some planets has paved the way for the next steps in the search for life. Up to this point, they have not yet been confirmed as definitive proof of the life on the planets and celestial bodies studied. Apart from this problem, there are other challenges on the path of research with rovers. Even if there is life on some planets, the organisms living there might have different biochemistry to terrestrial life and use various biochemical patterns/pathways to obtain energy, reproduce, and form their structures (Hargitai and Kereszturi, Reference Hargitai and Kereszturi2015). Assuming that there are life forms whose biochemistry is similar to terrestrial organisms, proving the existence of such organisms is very difficult and requires a comprehensive study of samples taken from probes from different planets. This is because, despite the great biodiversity on Earth, more than 99% of microorganisms on this planet are still unknown. Moreover, due to the lack of knowledge about the growth requirements of these microorganisms, it is not possible to prepare the culture medium for the study of their structural and metabolic properties (Bodor et al., Reference Bodor, Bounedjoum, Vincze, Erdeiné Kis, Laczi, Bende, Szilágyi, Kovács, Perei and Rákhely2020; Pourmazaheri and Tabatabaei, Reference Pourmazaheri and Tabatabaei2013). Even if there is microbial life that has a similar biochemical pattern to terrestrial life, the possibility of identifying these organisms requires extensive research into the metabolic needs and growth conditions to create a suitable environment for their cultivation (Seyedpour Layalestani et al., Reference Seyedpour Layalestani, Shavandi, Haddadi, Amoozegar and Dastgheib2021). The knowledge obtained from the space probes will therefore enable researchers to know the basic conditions for life (Billings, Reference Billings2012).

Radio telescope for exploring organic molecules

Radio telescopes are the latest tools that have significantly contributed to the advancement of human knowledge in space science. These telescopes are huge radio antennas consisting of one or more large dishes. Unlike optical telescopes, they receive process, and record radio waves (with a lower frequency and longer wavelength than visible light) on a large scale. The processing of radio waves received from different parts of the universe provides researchers with valuable information about the quantity and quality of celestial phenomena (Song, Reference Song2023) (Figure 14).

Figure 14. Radio telescope ALMA. This radio telescope is located in the Atacama Desert of Chile and it is one of the most important human tools to prove the existence of amino acids and other precursor molecules for life. Since 2006, this device has been used to observe the formation regions of stars and planets.

Nowadays, astronomers can use radio telescopes and radio spectrometers to check the abundance of various chemical substances in cosmic phenomena, such as cosmic clouds. One of the most interesting findings discovered by modern radio astronomy is the detection of organic molecules in dust and giant clouds in interstellar space. This exploration has led to the identification of more than 100 important organic molecules that play a role in the origin of life. Among the most important of these molecules are the subunits of nucleic acids (including adenine, guanine, thymine, cytosine, uracil, niacin, and xanthine), some of the subunits of proteins (such as the amino acid glycine) (Figure 15). These organic molecules were found mainly in the regions where interstellar dust is present in greater abundance, and it seems that these regions are precisely where star formation is most likely to occur (Davies, Reference Davies2018).

Figure 15. Cloud of gas and dust in the constellation Scorpius. This region is where complex molecules can be seen using a radio telescope. In this type of region, new stars are formed from the reservoir of gas and dust in the cosmic clouds. The Scorpius OB star cluster (seen as a cluster of hot stars) is sinking into the cosmic cloud in a reddish glow.

Last point on extraterrestrial life giving the radio telescope-derived information

Although the existence of life in different parts of the universe cannot be definitively confirmed with a radio telescope, a planet or celestial body can be considered a possible candidate for life based on its atmospheric composition and orbital position. Spectroscopy of biological signs only provides information about life indicators in heavenly bodies to researchers. For example, the simultaneous presence of oxygen and methane in the atmosphere of a celestial body can be deduced as a strong indicator of biological processes (Atri et al., Reference Atri, DeMarines and Haqq-Misra2011). Various types of constituent subunits of nucleic acids and amino acids by radiotelescopes greatly strengthen the panspermia theory. Like the information received from meteorites, these results also confirm the entity of building blocks of nucleic acids and proteins in heavenly bodies. Full confirmation of this theory requires more extensive research due to the lack of sufficient documentation (Vakochand Harrison, Reference Vakoch and Harrison2022). Given different conditions on various planets, the proof of life-forming components in stellar objects in turn strengthens the possibility of extraterrestrial life.

Information about the sighting of UFOs and aliens

In general, the term UFO does not necessarily mean aliens but refers to any flying object whose nature is not easily recognizable. The initial definition of the UFOs was based on military logic. In this case, any aerial object that is unusual in terms of its aerodynamic characteristics and performance and does not resemble any type of airplane, rocket, or other man-made flying device can be grouped as a UFO. From the perspective of space science, UFOs are luminous objects in the sky or on the ground that not only lack conventional behavior and appearance for observers, but their nature and origin remain unknown after careful examination by experts (Zhang et al., Reference Zhang, Yang, Luo and Fan2023).

In many cases, UFO sightings from close distances have been reported by pilots, and these special cases are called contact experiences. Since these experiences occur suddenly and are not repeatable, they lack a methodological standard for scientific confirmation. To classify individual experiences of UFO sightings, various classification systems have been invented. One of the most common of these systems is Alan Hendry’s (Reference Hendry1979) classification. Based on this system, man-made aircraft are divided into different types such as identified flying objects, deceptive flying objects, fantasy flying objects, and exceptional flying objects. If aUFO is not among those objects, it can be placed in four groups: Close to detected flying objects; Questionable UFO (Although this group has a high level of wonder, conventional explanations about their terrestriality cannot be completely rejected); A good UFO (which has several amazing features that are at least justifiable); The best UFO (which has a very high degree of wonder and strangeness that cannot be justified by conventional explanations) (Zhang et al., Reference Zhang, Yang, Luo and Fan2023).

According to the definition and classification of UFOs, reports based on their observations can be classified into two categories: reports from individual observations and ones from scientific studies.

Moving luminous forms in the upper atmosphere

Self-illuminated plasmas are among the strangest UFOs that have been seen at altitudes 200 miles above the Earth’s surface in the form of cones, clouds, donuts, and cylindrical spheres. These objects sometimes disturb the electromagnetic activity of the satellite and sometimes they come close to the space shuttles (Figures 16 and 17). Computer analysis also indicates different speeds and even stationary states, change of direction at any angles, accumulation, engaging, “predatory hunter” behavior, and a trail of plasma dust along the movement path of these bright plasma masses (with a diameter of about one kilometer). These observations have been seen many times by astronauts and pilots. Although this phenomenon is not organic and the nature of these luminous masses remains elusive, plasma dust and plasma behave like multicellular organisms. Plasma has an inorganic nature and consists of ionized gases. The observation of the luminous plasma phenomenon in the thermosphere layer and their absorption towards electromagnetic energy sources tells the self-propagation mode that exists in the organic organisms of the Earth. These observations in the plasma dust are not only an amazing phenomenon but also strengthen the existence of inorganic life in the upper layers of the atmosphere. A sign of the extraterrestrial nature of these phenomena is not yet available, but these inorganic masses show behaviors similar to organic living organisms (self-reproduction, self-sustainability and following the laws of natural selection) (Joseph et al., Reference Joseph, Impey, Planchon, Del Gaudio, Safa, Sumanarathna, Ansbro, Duvall, Bianciardi, Gibson and Schild2024).

Figure 16. Plasma phenomenon with an approximate diameter of one kilometer in the thermosphere layer (Joseph et al., Reference Joseph, Impey, Planchon, Del Gaudio, Safa, Sumanarathna, Ansbro, Duvall, Bianciardi, Gibson and Schild2024).

Figure 17. Four luminous halo-like objects over Salem Air Force Base, Salem, Massachusetts on July 166, 1952, recorded by a member of the Coast Guard. At the time of photography, the weather was reportedly cloudy and prone to thunderstorms (Joseph et al., Reference Joseph, Impey, Planchon, Del Gaudio, Safa, Sumanarathna, Ansbro, Duvall, Bianciardi, Gibson and Schild2024).

Claims related to the sighting of extraterrestrial beings or their bodies

There were so many unsubstantiated claims about alien sightings by various people in the 20^th and 21^st centuries that. These claims not only became the main subject of many novels, films, and television shows in the contemporary era, but they also caused the creation of some sects under the influence of assumptions based on pseudo-science and Conspiracy theories. To attract more audiences, some media also created a nonscientific intellectual atmosphere and a sentimental attitude towards this issue by promoting such claims. In these cases, different appearances such as green-headed dwarfs, gray humanoid aliens, humanoid reptiles, and other types of unconventional morphologies were attributed to these alien creatures (Vakoch and Harrison, Reference Vakoch and Harrison2022). Even some conspiracy theorists like David Icke went further and claimed that some humanoid reptiles with the ability to transform into humans are controlling society and have formed some very famous political and artistic faces. The big fans of these lines of thought always accused governments and international structures of secrecy regarding foreigners. However, claims arising from pseudo-scientific thinking and conspiracy theories lack scientific validity and cannot be cited in any way (Mahl et al., Reference Mahl, Zeng and Schäfer2021).

The most important claim of alien sightings was made in September 2023 by the presentation of two different human-like corpses, 60 and 75 cm long, from Peru, a thousand years ago, to the Congress of Mexico. These corpses were exhibited by Jaime Maussan one of the famous journalists and media figures in Mexico. In this meeting, which was held in the presence of high-ranking Mexican political officials, claims were made about the genetic difference (of more than 30%) with the human species, the presence of osmium and cadmium metal chips, and the embryonated eggs in one of the corpses. The raising of such a claim in the highest political circle in one of the influential countries of Latin America was initially accompanied by a lot of media controversy (Vakoch and Harrison, Reference Vakoch and Harrison2022).

But a little later, the investigation of the Mexican prosecutor’s office denied that these bodies were extraterrestrial and stated that these corpses were artificial. Academic societies also refused to confirm the extraterrestrial nature of these bodies. They stated that evidence was not enough to confirm the extraterrestriality of those corpses. In addition to rejecting the extraterrestrial nature of these bodies, the Peruvian Ministry of Culture filed a complaint against Maussan and the people involved in this claim. Paying attention to the fact that until this moment, no valid scientific article/report has been presented regarding the authenticity of this claim, so its authenticity cannot be confirmed (Bennett, Reference Bennett2011). It seems that this event was only a demonstration to promote some nonscientific goals in the media space (Figure 18).

Figure 18. The bodies claimed to be space aliens in the Mexican Congress by Jaime Maussan, one of the prominent and controversial media figures of Euronews.

Search for extraterrestrial intelligence by attempting to send messages to the universe

Another attempt to discover extraterrestrial intelligence, which was proposed in the 1960s, is to send an electromagnetic signal to different parts of the universe so that if there is an intelligent civilization in other parts of space, alien intelligence will receive this message. In the physical method, it is used to send physical artifacts containing messages (such as Voyager’s golden records) into space. In the method of sending electromagnetic signals, radio waves or laser pulses are sent to the ends of the universe using large radio telescopes. So if there is intelligent life near the civilization of the Earth, they will find out about their intelligent neighbors on Earth (Figures 19 and 20).

Figure 19. Arecibo observatory with a width of 305 meters located in Puerto Rico. This observatory is used as the world’s largest and most sensitive radio telescope in the search for extraterrestrial intelligence (www.scientificamerican.com).

Figure 20. Voyager spacecraft and discs containing sounds and images related to Earth and terrestrial life including things like the sound of water, animals, pieces of music from different cultures, the word “hello” in different languages, and text from the politicians of the time (https://www.nasa.gov).

The question that is raised about this method is that if such civilizations exist and even if these messages are received, how can they decode the received waves? Another question is that if these messages are received by hostile civilizations, they may become aware of the location of the Earth, and thereby it has potential dangers for our civilization. Decisions about the use of these methods are made only by a few people in human society, and there is no kind of survey about this from the general public. Therefore, in terms of legitimacy, it lacks sufficient credibility and is undemocratic (Hatfield and Trueblood., Reference Hatfield and Trueblood2021). No sign of receiving the message has been obtained, so the efficiency of these methods is also questioned by many experts. Supposedly, even if radio messages are received and decoded by a possible civilization, their distance may be so great that it takes centuries, millennia, or more time to receive and react to these messages (Atri et al., Reference Atri, DeMarines and Haqq-Misra2011). It can be concluded that until this moment, the reports of the SETI using physical and radio messages have not had any results.

Historical, scientific, cultural and artistic works related to past eras

One of the hypotheses that has been somewhat popular in the contemporary era is the connection of space aliens with human ancestors in ancient times and the creation of changes in the human species. One of the first important works mentioned in this matter is Däniken’sChariots of the Gods, which was published in 1968. In this book, by relating some huge ancient structures and paintings to extraterrestrial intelligent beings, the author has claimed the connection between space aliens and ancient humans. According to the author, these communications have caused great changes in the evolution of human society. Such statements provoked criticism of his book in some scientific and ideological circles (Rayhan, Reference Rayhan2023). But Daniken’s claims were not the end of this story, and for years after the publication of this book, fans of Daniken’s line of thought and also the media attributed the discovery of every extraordinary ancient phenomenon to intelligent space aliens. Among the most important of these phenomena, the following can be mentioned: Egyptian pyramids, the Nazca lines in Peru, thepyramids/monuments of the City of Gods (Teotihuacán) located in Mexico, Saxe-Human temples, Cusco monuments in Peru, Stone structures/elevations of Stonehenge, Colossal Moai statue located on East Polynesian Easter Island, and even some petroglyphs with a design similar to ancient astronauts (Figure 21).

Figure 21. (a) Egyptian pyramids; (b) Topography of Nazca in Peru; (c) The monuments of the City of Gods (Teotihuacán) in Mexico, (d) Stonehenge rock formations in England; (e) the huge Moai statues located in East Polynesian Easter Island; (f) Paintings with a design similar to ancient astronauts in Valcomonica, Italy.

Since 2010, the media environment, especially in the United States, suddenly faced a huge wave of programs based on pseudo-scientific theories. The following topics became hot discussions among viewers and some members of society: (1) the relationship of extraterrestrials with ancient humans, (2) their effects on the development of human technology, and (3) the intervention of aliens in the affairs of human civilization. It seems that due to a kind of media competition to increase the number of audience, some media turned to producing some programs with popular titles. However, these programs lacked sufficient standards and documents to confirm the connection of extraterrestrial intelligence with human ancestors. The media tried to mix scientific and nonscientific content and to blur the line between science and pseudo-science only for audience attraction (Schiele, Reference Schiele2020).

Last point on extraterrestrial life giving the historical/scientific/cultural/artistic-derived information

Attributing some structures and ancient works to extraterrestrial intelligence is caused by a kind of unsubmissive look and ignoring many abilities of ancient people by contemporary man. One of the most impressive of these structures is the Egyptian pyramids, which consist of about 5.5 million tons of limestone, 8 thousand tons of granite, and 500 thousand mortar. In the past, it was thought that most of these materials were transferred from Aswan (located in the south of Egypt) to Giza (in the north of Egypt) from a distance of 800 km (Vakoch and Harrison, Reference Vakoch and Harrison2022).

For many believers in the theory of “the construction of the Egyptian pyramids by extraterrestrial intervention,” it is not possible to transport this volume of thick stones from long distances from the south to the north of Egypt without the use of trucks and modern machines. However, with the use of satellite images, geophysical studies, analysis of deep soil cores, subsurface structures, and sedimentology, this secret has been revealed to a large extent (Ghoneim et al., Reference Ghoneim, Ralph, Onstine, El-Behaedi, El-Qady, Fahil, Hafez, Atya, Ebrahim, Khozym and Fathy2024). Recently, it was found that during the construction of the Great Pyramid and the adjacent pyramids, a large branch of the Nile River passed through the vicinity of the construction site of the pyramids. Instead of rolling the stones or transporting them with timber, the ancient Egyptian workers and engineers took advantage of the flow of water and the use of floats to carry the necessary stones and materials along the Nile River. The pyramids are the biggest examples of amazing human structures.

Another common case regarding the connection between ancient people and intelligent spatial beings is the Nazca Geoglyph. These maps are located in an area of about 450 square kilometers in the southern desert of Peru, which depict creatures such as hummingbirds, spiders, monkeys, lizards, pelicans, trees, plants, flowers, and some geometric shapes. Distortions have often been made in the dimensions of these forms. For example, one of them is the leg of a bird, which some have claimed to be similar to the runway of an airport, while the diameter of this leg is only four meters. On the other hand, the oldest of these maps (made of piled stones) dates back to 500 BC. That is, when the Nazca people were working on an efficient system of transferring water from the depths of the earth to the surface, and had made progress in terms of engineering sciences in ancient times. Therefore, the design of these maps in the framework of ritual and cultural rituals, despite the thought they provoke, is not impossible and can be justified by the technology of the ancient inhabitants of Peru (Jarosz, Reference Jarosz2014).

From evidence obtained from the ability of ancient people to create huge structures and paintings, such as the Egyptian pyramids and the Nazca lines, it is possible to justify the construction of other cases of these ancient wonders (The Saxe-Human temples, the city of Cuzco in Peru, the temple of the Gods of Mexico, the Moai sculptures of Easter Island, and the stone ascents of Stonehenge). In the case of ancient astronauts, according to Carl Sagan (as one of the main experts and researchers in the field of extraterrestrial intelligence), there have always been various types of wrong reports, distortions, and even fraud (Sagan, Reference Sagan1986).

In general, it is impossible to go through all the claims and reports about ancient astronauts and the possible effects of alien intelligence on the human species without thinking. Their confirmation by the scientific community requires extensive verification and investigation. Despite the ambiguities about some of these phenomena, there is still no sufficient scientific evidence to confirm the connection between extraterrestrial civilizations and the ancient ancestors of modern humans. This result does not in any way mean to reject extraterrestrial intelligence, but it refuses to confirm the claims made about the establishment of alien intelligent beings with human ancestors. Unfortunately, the long-term experience of the scientific community in different periods of history indicates that the discovery of any challenging phenomenon was initially accompanied using nonscientific hypotheses by non-experts and government-affiliated intellectuals (Vakoch and Harrison, Reference Vakoch and Harrison2022). However, with the expansion and progress in many fields of technology in the coming years, many mysteries will be revealed.

Analysis of molecular biological markers from space samples

Recently, the use of AI in analyzing biological markers from meteorites has become possible. The high capacity of AI in processing data obtained from gas chromatography, electron impact ionization mass spectrometry (Pyr-GC-EI-MS), and other precise analytical methods has provided valuable information about the distribution of complex organic mixtures in carbonaceous meteorites (Cleaves et al., Reference Cleaves, Hystad, Prabhu, Wonga, Cody, Economon and Hazen2023). A 2023 study by Cleaves et al., which utilized machine learning to analyze chemical data from ancient rocks and meteorites, showed that combining AI and chemical analysis methods such as chromatography and spectroscopy enables researchers to determine the biological or abiological origin of organic compounds. Identifying whether carbon-based compounds in meteorites and other space samples are biological or non-biological has always been a primary challenge for astrobiologists, and AI appears to be the key to addressing this challenge. Additionally, the combined use of AI and chemical analysis will provide answers to many difficult questions in future samples from space probes.

With this approach, it is even possible to detect biological markers of entirely different forms of extraterrestrial life, which might not rely on DNA, amino acids, or other building blocks of life on Earth (shadow biosphere) if such life forms exist (Davies et al., Reference Davies, Benner, Cleland, Lineweaver, McKay and Wolfe-Simon2009). This is because even alternative forms of life with distinct biochemistry require at least a few compounds for storing information, providing energy, and forming structures, which AI can analyze by understanding the distribution of these compounds and identifying meaningful relationships to detect biological markers.

In this study, the composition of polycyclic aromatic hydrocarbons (PAHs) in the Martian meteorite ALH84001 was analyzed and compared with twelve terrestrial samples. These samples included four igneous rocks (Ig-1, Ig-2, Ig-3, Ig-4), four hydrothermal sedimentary and rock samples (Hyd-1, Hyd-2, Hyd-3, Hyd-4), and four samples of biological origin (Bio-1, Bio-2, Bio-3, Bio-4) (Table 4). To compare the presence or absence of polycyclic aromatic hydrocarbons (PAHs) in ALH 84001 and terrestrial analog samples, we used hierarchical clustering along with a Jaccard distance matrix in Python 3 (Figure 22). First, the analyzed parameters were classified using plus (+) and minus (−) signs, which were then converted into binary values (0 and 1). The results revealed significant variations in PAH composition between the evaluated samples. To validate the hierarchical clustering results, we also generated a heatmap representation of the PAH data, which confirmed similar patterns between ALH 84001 and the terrestrial analog samples (Figure 23). Based on hierarchical clustering method 11 diverse clusters were found in compared PAHs for ALH84001 and terrestrial analog samples. This showed that the evaluated samples showed a significant differences in the analyzed.

Table 4. Presence or absence of Polycyclic Aromatic Hydrocarbons (PAHs) in ALH 84001 and terrestrial analog samples

The presence (+) or absence (–) of polycyclic aromatic hydrocarbons (PAHs) in ALH 84001 and 12 terrestrial analog samples. Data is based on qualitative analysis, without quantitative PAH concentration measurements.

Samples include biogenic rock and sediment (Bio-1–Bio-4), igneous rocks (Ig1–Ig4) and hydrothermal deposits (Hyd-1–Hyd-4):

Bio-1: Stromatolite near Zeerust, South Africa (Sklarew* and Bartholomew 1981).

Bio-2: Organic matter in Jurassic carbonates Orbagnoux, French Southern Jura (Thlaijeh et al., Reference Thlaijeh, Lepot, Carpentier, Riboulleau, Duca, Vojkovic, Tewari, Sarazin, Bon, Nuns, Tribovillard and Focsa2024).

Bio-3: Preserved organic matter in a fossil ocean continent transition in the Alps (Mateeva et al., Reference Mateeva, Wolff, Manatschal, Picazo, Kusznir and Wheeler2017).

Bio-4: Jurassic small sedimentary basins exposed in the northwest onshore area of Sri Lanka (Ratnayake and Sampei, Reference Ratnayake and Sampei2015).

Ig-1: Migmatites from Siljan crater, Sweden (Pikovskya et al., Reference Pikovskya, Khlyninaa and Kutcherovb2021).

Ig-2: Granites from Siljan crater, Sweden (Pikovskya et al., Reference Pikovskya, Khlyninaa and Kutcherovb2021).

Ig-3: Pyroxene obtained from the Geological Museum of the University of Hong Kong (Tian et al., Reference Tian, Liu, Hammonds, Wang, Sarre and Cheung2013).

Ig-4: olivine-type silicates obtained from the Geological Museum of the University of Hong Kong (Tian et al., Reference Tian, Liu, Hammonds, Wang, Sarre and Cheung2013).

Hyd-1: Hydrothermal sediments of the South Mid-Atlantic Ridge (Xin et al., Reference Xin, Zhigang, Shuai, Xuebo, Xiaoyuan, Yao, Baoju, Kunbo, Yunchao and Jiang2014).

Hyd-2: Hydrothermal sediments collected from the Logatchev hydrothermal field on the Mid Atlantic Ridge (Li et al., Reference Li, Peng, Zhou, Li, Chen, Wu and Yao2012).

Hyd-3: Hydrothermal sediments collected from the Kairei hydrothermal field on the Central Indian Ridge (Li et al., Reference Li, Peng, Zhou, Li, Chen, Wu and Yao2012).

Hyd-4: Hydrothermal sediments and rocks from South Mid-Atlantic Ridge (Xin et al., Reference Xin, Zhigang, Shuai, Xuebo, Xiaoyuan, Yao, Baoju, Kunbo, Yunchao and Jiang2014).

Figure 22. The variation of PAHs among the evaluated samples. Hierarchical clustering.

Figure 23. The variation of PAHs among the evaluated samples. Heatmap visualization of the investigated data.

The results of this study indicate that the polycyclic aromatic hydrocarbons (PAHs) detected in the ALH84001 meteorite exhibit the greatest similarity to igneous samples (Ig-1–Ig-4), while showing significant differences from both biogenic (Bio-1–Bio-4) and hydrothermal (Hyd-1 to Hyd-4) samples. These findings, supported by Jaccard similarity analysis and hierarchical clustering, strongly suggest that the PAHs in ALH84001 are most likely of abiotic origin.

In 1996, McKay et al. hypothesized that the PAHs in ALH84001 could be remnants of past biological activity on Mars. This claim, one of the most controversial in the field of astrobiology, was based on the structural resemblance of these compounds to biogenic PAHs. However, the findings of this study contradict McKay’s hypothesis, as the PAH composition in ALH84001 aligns more closely with igneous rocks rather than biogenic materials.

Since PAHs can form through non-biological processes, such as thermal and magmatic reactions, these results suggest that the PAHs in ALH84001 are likely products of geochemical abiotic processes rather than biological activity. This study underscores the importance of understanding abiotic mechanisms in the formation of organic compounds on Mars and highlights that the mere presence of PAHs cannot be considered definitive evidence of past life. Further structural, isotopic, and geochemical analyses will be essential for a more comprehensive evaluation.

Decoding complex signals in case of receiving messages from extraterrestrial civilizations

The SETI has so far failed to find evidence of this type of intelligence (Gundu and Charanarur, Reference Gundu and Charanarur2024). This search involves analyzing a vast array of data, primarily in the form of radio signals or other forms of electromagnetic radiation, looking for patterns in the received waves that could be considered signals from extraterrestrial intelligence. However, the immense size of space, the potential diversity of signals, and the limitations in detecting and analyzing these signals make this approach extremely challenging. One of the biggest challenges is filtering out cosmic noise, which can obscure extraterrestrial life signals, if they exist. AI algorithms, with their ability to process large data sets and model complex behaviors, are capable of identifying and eliminating extraneous noise. Furthermore, AI can discover algorithms previously unnoticed by humans, such as identifying complex patterns or signals that might seem random (Durrani, Reference Durrani2024). The most innovative contribution of AI in this field is the improved accuracy in identifying cosmic signals that might have been undetectable in the past.

Analyzing UFO data and examining the possibility of extraterrestrial origins

One of the main challenges in analyzing UFO data is distinguishing between natural phenomena, artificial objects, and the potential existence of extraterrestrial life. AI, using advanced deep learning algorithms, can simulate models of normal and anomalous behaviors of aerial objects in the sky and differentiate these patterns from the received data. One of the most innovative applications of AI in this context is the use of complex neural networks (CNNs) to analyze images and videos of UFOs. These networks can detect even the smallest differences in structure and movement of objects, so that if an object behaves anomalously, it can be automatically flagged (Ayeni, Reference Ayeni2022). This method significantly increases the speed and accuracy of data analysis and ultimately helps identify unusual cases that may indicate extraterrestrial life.

AI also plays a crucial role in filtering and analyzing radar and acoustic data from UFOs. One of the biggest problems in signal analysis is severe interference and noisy data. In this context, AI algorithms, particularly reinforcement learning methods, can train systems to distinguish valid signals from environmental noise (Thornton et al., Reference Thornton, Kozy, Buehrer, Martone and Sherbondy2020). By combining these algorithms with data on the behavior and characteristics of UFO movement, AI can automatically simulate specific behavioral patterns that are more indicative of extraterrestrial nature. This technique helps researchers gain a better understanding of the nature of observed phenomena and ultimately make more informed decisions on whether these phenomena are extraterrestrial or natural.

Assessing the habitability of other planets using available data

AI, due to its high analytical capabilities, can bring revolutionary changes to how we assess the habitability of planets within our solar system and exoplanets. Machine processing algorithms, by analyzing data from space telescopes, can identify the composition of a planet’s atmosphere and detect essential life elements such as oxygen, methane, and water vapor. Furthermore, deep neural networks can analyze temperature, atmospheric pressure, and distance from the parent star, uncovering habitability patterns that were previously hidden from researchers (Charbonneau, Reference Charbonneau2024). With the development of AI models, humanity can now examine the likelihood of life existing in distant corners of the universe with unprecedented accuracy, potentially marking the first steps toward discovering alien ecosystems.