A Ray of Light on the Shroud of Turin* Paolo Di Lazzaro, Daniele Murra ENEA Research Centre of Frascati Via E. Fermi 45, 00044 Frascati (Italy) Abstract The Shroud of Turin is a linen cloth bearing the front and back body images of what appears to be a crucified man. Although it is considered one of the archaeological objects most studied in history, nobody has been able to replicate the microscopic complexity of the chemical and physical characteristics of its faint images. After countless attempts, the inability to replicate the image on the Shroud prevents formulating a reliable hypothesis on the process of the image formation. In this paper we summarize the state-of-the art of the scientific research on the Shroud, from the multidisciplinary STuRP analyses (1978) to the radiocarbon dating (1988), from biological and DNA clues to the linen irradiation experiments at the ENEA, till the illusory perception of low contrast stains on the Shroud. As detailed in this paper, despite huge scientific efforts, the Shroud is still “a challenge to our intelligence”, a remarkable object whose scientific analyses lead to many clues, but any proof. Introduction The Shroud of Turin (ST) is a centuries-old linen cloth carrying a faint but remarkable image: the front and back of a naked man with the hands crossed, corpse-like, over the abdomen. The bloodstains are consistent with a man beaten, scourged, and crucified, see figure 1. Indeed, many believe that the image was formed in the linen when wrapping Jesus’ body and so see the ST as the main proof of the accuracy of Gospel narration, with enormous religious and historical importance.

Figure 1. Photograph of the Shroud of Turin and its negative black/white obtained by Jasc Software. Except hairs, the overall image looks like a photographic negative. The two images lie head to head, as if a body had been laid on its back on the cloth, which was then folded over the front from the head downwards. The dimensions of the Shroud are 441 cm in length and 113 cm in width. From www.sindone.org

*To be published in the Proceedings of the Conference “FIAT LUX – Let there be light” held in Rome, Italy, on 3-5 June 2015, E. Fazio and R. Pascual Eds. Nova Science publisher

In this paper we summarize the main scientific information available about the ST image and cloth, harvesting among experimental results of chemical, biological and physical investigation across more than one century of scientific research. Although a single article cannot be exhaustive on a subject so vast and complex, we provide essential bibliography, which includes the main peer reviewed papers on ST scientific investigations. 1.

The images on the Shroud, a scientific enigma.

After the most recent in-depth experimental analysis of the images on the ST in 1978, the multidisciplinary team of scientists under the auspices of STuRP, the Shroud of Turin Research Project [1], affirmed [2]: “We can conclude for now that the Shroud image is that of a real human form of a scourged, crucified man. It is not the product of an artist. The blood stains are composed of hemoglobin and also give a positive test for serum albumin. The image is an ongoing mystery and until further chemical studies are made, perhaps by this group of scientists, or perhaps by some scientists in the future, the problem remains unsolved.”. The above conclusion was a consequence of the experimental results of many tests, including: X-ray fluorescence and microchemistry measurements, which exclude the possibility of paint being used as a method for creating the image. Actually, some iron oxide particles and micrometer-size vermilion (HgS) were found on the cloth [3]. However, there is a large corpus of scientific evidence [4], [5], [6] that the microscopic observations reported in [3] cannot support the ST image is a paint. It is likely the micrometer-size debris particles have been transferred by contact with artist’s painted copies of the ST that have been “sanctified” by pressing the two clothes together, as it happened on the 4th May of almost every year in Turin, across the XVII century; kinetics studies and fluorescence measurements, which support a lower than 200°C temperature process of the image formation; coloration depth: the colour is present only on a very thin coating external to each fibre (a single linen thread is made up of about 200 fibres). The coloration depth cannot be measured by using optical microscopes, implying the colour penetrates less than the shortest wavelength of visible light, namely, 0.4 micrometers; the micro-chemical analyses, suggesting the coloration of the ST image was formed by an unknown process of selective aging that caused oxidation, dehydration and conjugation of polysaccharide structure of fibres. This process produced conjugated carbonyl groups as the chromophore in a greater quantity vs. the non-image fibres; the anatomical consistency of blood and serum versus wounds, including typical fluorescence of bilirubin and exudates around the main bloodstains (invisible at the naked eye, and revealed by ultraviolet illumination), which would be consistent with a haemolytic process caused by torture. A complete list of papers published by the STuRP team can be found in [7]. Here we point out three review papers [4], [5] and [8], authored by STuRP members, which are good summaries of previously published STuRP works, in our opinion. 1.1 Attempts to create a Shroud-like image The odd physical and chemical properties of the image briefly summarized make difficult to create an image that matches its peculiar superficiality and chemistry at the microscopic level. Here we point out two most important studies made to replicate the characteristics of the ST image, namely the work of Jackson, Jumper and Ercoline in 1984 [8] and the work of Garlaschelli in 2010 [9]. In the paper [8] the authors describe in meticulous detail the creation of a gallery of images on linen fabrics made using all the techniques potentially able to create a Shroud-like image of the face of the man of the ST. The techniques tested in this work include: o Direct contact (a statue and a person covered by inks, or chemicals, or powders, then draped by a linen cloth);

o

Thermal coloration (bas reliefs heated in a furnace and placed in contact on both dry and wet linen);

o Visible light (faces covered with phosphorescent paints imaged on contoured sheets of a photographic film); o

Electrostatic field;

o

Vaporography (ammonia vapours on plaster face diffused on linen);

o Artists (professional artists, certified forensic with documented experience in realistic monotone imagery shade a Shroud-like like face on linen, first free hand, then with anchor points); o

Hybrid mechanisms (different combinations of two or more techniques among those mentioned).

Jackson, Jumper and Ercoline compared the results of the above attempts with the macroscopic and microscopic features of the ST image as detailed in [4] and [5],, and argued that, although some images appear quite similar to the face of the man on the ST when observed at naked eye, none of them can simultaneously reproduce its main features, from the 3-D 3 property to the sub-micrometer coloration depth, to the resolution of the spatial details. The conclusion was that the image on the ST is not the result of the work of an artist or forger. The “Italian Committee for Checking Claims on the Paranormal” commissioned to the chemist Garlaschelli a copy of the ST in order to investigate the possibility to reproduce the ST image by an alleged medieval forger. The results, summarized in the he paper [9], [ shows the best ever reproduction of life--size images of the ST,, obtained using materials and technique potentially available in medieval times,, namely ochre dry powder (worst results) and diluted acidic pigments (best results). After “rubbing”, the cloth was aged in an oven before being washed to remove the pigment. As a final step, pigments were added to simulate blood stains and scorches. Although the final double image is quite similar to the ST image from a macroscopic point of view, when analysing the coloration with an optical microscope at the thread level, several differences become evident [10], [11], 11], see figure 2. 2 The paper [10] and the unanswered answered Letter to the Editor [11] make clear that the Garlaschelli’s conclusion in [9] addresses only some of the ST image attributes, ignoring its microscopic complexity. In defence of his results, Garlaschelli claims claim that in general, it is impossible to reproduce all the microscopic characteristics of a very old object,, be it a coin or the image on the S ST [12].

Figure 2.. Left: microscope image of the linen threads of the image on the copy of the ST in [9, 10]. Right: microscope image of the linen threads of the image on the ST (from www.shroud.com).

The he experimental results published in [8] [8 and [9] are among the most interesting attempts to replicate the ST image. More in general, we must admit that all efforts to create a Shroud-like like image have failed to adequately reproduce the ST image characteristics as a whole. Table 1 summarises the most relevant attempts experimented to date. In some cases, scholars have obtained linen coloration and/or images that look similar at naked eye, but none ne of them match both microscopic and macroscopic features of the ST image.

Table 1. Brief summary of the main attempts to reproduce the ST image, since 1902. YEAR AND MAIN AUTHOR

TECHNIQUE

MAIN DRAWBACK

1902 Vignon

Vaporographic

Lack of spatial resolution

1939-1941 Cordiglia, Romanese

Aloe + myrrh on cadavers

Not superficial

Heated bas relief

Not superficial

1983 Nickell

Iron oxide powder rubbing on bas relief

Unlike at thread level

1993 Allen

Ante-litteram photography

Photosensitive chemicals unknown till XIX century

2010 Garlaschelli

Diluted acidic pigments rubbed on bas relief and human body

Unlike at the fibre level

Corona discharge between a metallic dummy and linen

Conductive dummy only

Ultrashort UV light pulses linen irradiation

Life-size image is beyond today-technology

1966 Ashe 1982 Pesce Delfino

2013 Fanti 2014 Di Lazzaro

1.2 Shroud-like image by ultraviolet laser pulses In the above frame, the inability to replicate the microscopic complexity of the image on the ST prevents formulating a reliable hypothesis on the process of the image formation. The answer to the question of how the image was produced or what produced the ST image is still unknown. We therefore explored a unconventional approach, by generating photochemical reactions able to produce a Shroud-like linen coloration. It is well known that the energy carried by short-wavelength electromagnetic radiation breaks the chemical bonds of the irradiated material without inducing a significant heating [13]. Moreover, linen has a molar absorptivity such that the smaller the wavelength, the thinner the material necessary to absorb all the radiation. Then, we have chosen the ultraviolet (UV) and vacuum ultraviolet (VUV) radiation to obtain at least two characteristics of the ST image, namely, a low-temperature image-formation and a thin coloration depth. Among the many laser sources available, we chose the Excimer ones because they are the most powerful and efficient lasers emitting UV and VUV pulses [14]. Since 2005, we carried out a large number of irradiations of UV and VUV radiation on linen fabrics woven in the years between 1930 and 1950 that were never used and never washed with cleansing agents, in order to avoid the presence of chemicals which might alter the optical properties of the tissue. Our main goal was to find the optimum laser conditions to activate photochemical reactions in the cellulose of linen apt to create a Shroud-like coloration. After many irradiations and with great difficulty we found the narrow combination of laser parameters (pulse duration, intensity, repetition rate and number of shots) that allows a Shroud-like linen coloration. The different coloration results obtained using different laser wavelengths allowed to recognize the photochemical reactions involved in the Shroud-like coloration, thus offering hints to plan the long-term conservation of the cloth and of the image on it [15]. We got several properties similar to those measured on the ST images by STuRP, including a proper hue of colour, a coloration limited to the crown of the threads, coloured fibres next to uncoloured fibres, a reduced fluorescence, the negativity of the image. The photos in figures 3, 4, 5 and 6 illustrate some of the results obtained. More details and other meaningful images can be found in a number of papers we published, see, e.g., [16], [17], [18]. A brief review of our results can be found in [19].

Figure 3. Linen warp thread after irradiation in the vacuum ultraviolet (193 nm). In the middle we see a region not coloured because covered by a weft thread. Individual yellow fibres are also visible.

Figure 4. High-magnification microscope view of a single linen fibre that was unintentionally damaged in the middle after irradiation in the vacuum ultraviolet. The inside of the fibre is not coloured, while the outer sheath (primary cell wall) became yellowish due to far-ultraviolet irradiation. The circles indicate yellow shreds of primary cell wall, whose thickness is 0.2 micrometer. This means we obtained a colour superficiality similar to that of the Shroud image. The diameter of the fibre is 20 micrometer. Source: [18].

Figure 5. Microscope view of the linen fabric after VUV laser irradiation. Single coloured fibres are visible next to uncoloured fibres, as observed on the Shroud image. Source: [18].

Figure 6. Image of the logo of the 2010 Shroud Exhibition Exhibiti obtained by laser scanning on a linen fabric. The yellowish, low-contrast image is almost invisible when observed in the sunlight (at ( left). In the middle, its visibility improves when observed in shadow. shad To the right, the negative of the same image is clearly visible, being a pseudo positive, as it is the ST image image, see figure 1. Source: [19].

2.

The radiocarbon dating

After fter the publication of their results in 1980-1981, 1980 scientists of the STuRP prepared a detailed list of further analyses necessary to gain a deeper insight on how the image on the ST was formed and to find the best conditions for the long term conservation of the linen cloth. An A international scientific commission was established to discuss the new STuRP proposal. In the meantime, on the 25th March, 1983 it was announced that Umberto II of Savoy bequeathed the ST to Pope John Paul II, who appointed the archbishop of Turin “pro tempore custodian” of the ST on 14th November, 1983. After long discussions, the commission finished the so-called “Turin Workshop Protocol” in 1986, concluding that: a) among the list of analyses proposed by STuRP STuRP, only the radiocarbon diocarbon dating was selected; b) seven institutions were chosen to use two dating methods, namely the “proportional counter” and the “mass spectrometry”; c) the supervision of operations was assigned to the Pontifical Academy of Science,, the Archbishop of Turin, and the British Museum; d) the control samples would be supplied by the British Museum; e) the laboratories could not communicate with each other during the measurements and would have done so only after delivering the results to the guarantors. The Protocol ruled out all the proposed analyses except radiocarbon, thus excluding STuRP from further measurements, which sounded illogical, illogical because at that time STuRP was the group of scientists with the most advanced and broad scientific knowledge of the ST. ST Later, this protocol was modified by the Archbishop of Turin Ballestrero,, perhaps with the input of his scientific advisor Gonella (Turin Polytechnic): Polytechnic) only the method of mass spectroscopy would be used and only three laboratories (Oxford Oxford University, the University of Arizona, Tucson, and the Swiss Federal Institute of Technology, Zurich)) were entrusted.. In addition, the British Museum, in the person of Tite (Research Laboratory for Archaeology and History of Art, University of Oxford), Oxford), was the only reference for the proper execution ution of the sampling and dating, dating thus ruling out the Pontifical Academy of Science as guarantor.. The details of the new protocol were given by Tite in a letter to Nature [20], [ wrriting that “Even if

the samples were shredded, it would still be possible to distinguish the shroud sample from the others. It is therefore accepted that the blind test depends ultimately on the good faith of the laboratories.” The changes in the Protocol caused further controversy. Gove, the director of the Rochester Laboratory, one of the laboratories excluded, wrote a letter to Nature [21] that criticizes in seven point the Vatican’s decision. Point one reads: “The involvement of seven laboratories has been reduced to three. This eliminates the possibility of detecting a mistake made in the measurements by one or more of the three laboratories. As Tite knows, such mistakes are not unusual.” In fact, in 1988 the accuracy and reliability of mass spectrometry were considerably worse than today. Gove ends his letter with this sharp comment: “All these unnecessary and unexplained changes unilaterally dictated by the Archbishop of Turin will produce an age for the Turin Shroud which will be vastly less credible than that which could have been obtained if the original Turin Workshop Protocol had been followed. Perhaps that is just what Turin authorities intend.” The sample was taken on the 21st April, 1988, just two weeks after the publication of the Tite’s letter [20] and it was cut in five pieces, one so-called “Riserva” and four to be dated. Two of the four (the smallest ones) were given to the Tucson laboratory, see figure 7. Each sample was then divided in 4 subsamples by the Laboratories, and separately dated.

Figure 7. Above, schematic of the sample from the ST and its partition. T: trimmed strip. R: retained part called “Riserva”. O, Z, A1, A2: subsamples given to Oxford, Zurich, and Arizona (two pieces) respectively. Below, cutting the linen strip for the 1988 radiocarbon dating. Source: [28].

During a press conference held on 13th October, 1988, Ballestrero announced the results: the radiocarbon analysis of the ST sample dated it between 1260 and 1390 A.D., with a confidence level of 95%. This dating is compatible with the first written records relating to the existence of the ST at Lirey, in France. According to the official scientific report published just four months later [22] the three dates obtained by the laboratories were: Tucson = 646 ± 31 years BP (Before Present); Zurich = 676 ± 24 years BP; Oxford = 750 ± 30 years BP. Then, applying the appropriate calibration, it came out the dating range 1262-1384 A.D. which, rounded down/up to the nearest 10 years, gives the result announced by Ballestrero.

Speculation ensued on why the ST could be so convincing in other respects and yet date Medieval. Many unsatisfactory accounts were advanced, including the possibility that the 1532 fire contaminated it, or that biological contamination (bio-plastic coatings made by fungus and bacteria) may have skewed the C14 because bacteria can digest cellulose releasing new C14 [23], or the presence of a Medieval patch possibly added by invisible mending [24]. From a strictly scientific point of view, the most significant critical remarks of the results of the radiocarbon dating were raised by the independent statistical analyses by Walsh [25] and Van Haelst [26]. In fact, their works raise four important points: 1) the error of the average of the Tucson measurements is 646 ± 17 (the value published in [22] is 646 ± 31); 2) as a consequence, the date of Tucson is out of range. Moreover, the date of Oxford is a possible outlier; 3) the claimed 95% confidence level of the age range 1260-1390 A.D. is not supported by statistical tests, including the χ2 test; 4) contrary to the assumption in [22], the measured samples are not homogeneous and the means are not equal. The conclusion of both [25] and [26] is that the dating results are not reliable and the measurement should be repeated. These important statistical studies, and in particular the point 4), could have never been confirmed because the three Laboratories refused to give the raw data, including the position of each subsample. Useless to say, this behaviour is contrary to the ethic of Science, and generated further controversy. Many scientists accepted the radiocarbon date and both support and interest in ST research declined. The situation changed 22 years later, in May 2010, after the invited talk given by Riani at the workshop IWSAI [27] which shed light on some unknown aspects of the radiocarbon dating of the ST. In short, Riani showed for the first time that robust methods of statistical analysis, in particular the combination of multiple regression analysis and the forward search algorithm, allows performing the analysis of 387,072 possible configuration of the subsamples’ position, leading to the following results [28]: i) only one of the two ST samples given to the Arizona laboratory was dated; ii) the radiocarbon data published in [22] are heterogeneous and there is a linear spatial trend of the twelve measurements of the age of the ST. As a consequence, the subsamples dating cannot be considered as repeated measurements of a single unknown quantity, thus confirming the results in [25] and [26]. According to Riani, “the statement of Damon et al. --The results provide conclusive evidence that the linen on the Shroud of Turin is mediaeval-- needs to be reconsidered” [28]. Participants attending the IWSAI were stunned after the Riani’s talk, because the Nature paper [22] did not report that one of the four pieces given to Laboratories was left undated, nor did the scientists who made the carbon dating in the many interviews and conference talks following the measurements. Everybody took it for granted that the carbon dating was the result of the C-14 and C-13 counts of 4 samples of the ST. Seven months later, in December 2010, Jull, the director of the Arizona AMS Laboratory in Tucson, published a paper which showed recent photographic images of the ST sample still in possession of his laboratory, thus confirming Riani’s discovery. In the abstract of this paper [29], Jull wrote “we present a photomicrographic investigation of a sample of the Shroud of Turin, split from one used in the radiocarbon dating study of 1988 at Arizona. In contrast to other reports on less-documented material, we find no evidence to contradict the idea that the sample studied was taken from the main part of the shroud, as reported by Damon et al. (1989). We also find no evidence for either coatings or dyes, and only minor contaminants”. An obvious question is why Jull waited twenty-two years before “contrasting” the “less documented material”. Would Jull have published this paper without Riani’s results presented at IWSAI and later published in a peer-reviewed paper [30]?

The behaviour of scientists in Tucson, coupled with the Riani’s discovery, suggest the carbon dating of the ST is still a puzzle far to be fully understood. Certainly, the linear spatial trend of the twelve measurements of the age of the ST shown in [28] and [30] suggests the presence of contamination of the linen samples, which was not removed by the standard cleaning procedure adopted before the radiocarbon measurements. 3.

Biological issues: pollen, blood, DNA

The linen cloth of the ST is plenty of biological residua, including pollens and blood. Although we do not have specific competence to comment on Biology issue, in the following we report a brief summary of published papers on pollen, blood and DNA found on the ST, referring, whenever possible, to primary sources, that is, to papers written by scholars who made in-depth measurements on the TS. 3.1 Pollen on the Shroud Despite the pollen investigation was one of the first scientific studies made on the ST in 1973, we were not able to find any peer reviewed papers on this topic. Most papers are published in conference proceedings, books, journals without peer review and websites, and only few of them are authored by scholars qualified in palynology. The botanist Frei picked up pollen on the ST by using adhesive tapes in two occasions, in 1973 and in 1978, see figure 8. One of the original papers of Frei can be found in [31].

Figure 8. Sticky tapes on microscope slides with material taken from the ST by Frei. Source: [32].

According to the review in [33], “in the 70s the Swiss botanist Max Frei Sulzer took some dust samples from the Shroud of Turin and the Sudarium of Oviedo to investigate the origin of the pollen which was on the two fabrics. He concluded that both the relics came from the Middle East and arrived in Europe through different paths. His work, which was carried out without providing sufficient methodological information and was interrupted by his death before being completed, laid itself open to some criticism. Nevertheless, the general conclusions of Frei’s research remain valid.” A cautious approach is found in the most recent review [34], which emphasizes that different studies differ on the number of pollen extracted, their identification, and the biological and geological distribution of the species discovered. However “there remain a few grains of pollen from some exclusively wind-blown Middle Eastern trees that are difficult to explain except that they fell on the Shroud while it was in Israel.” In conclusion, according to [34] “the question must remain open.” Let it be.

3.2 Blood on the Shroud The forensic doctor Baima Bollone was the only qualified expert who picked up in person and analyzed the blood from the threads of the ST. In the conclusion of the paper [35] he wrote “Sui fili di macchie di ‘sangue’ sono inoltre presenti più corposi apporti di materiale di contenuto minerale corrispondente a quello di macchie sperimentali ottenute con miscele di sangue, aloe, mirra e saponina. Le indagini di ematologia forense risultano dimostrative per la presenza di sangue”. Our translation: “On the threads of 'blood' stains a larger quantity of mineral-based material is also present, which corresponds to that of experimental stains made by mixtures of blood, aloe, myrrh and saponin. Forensic investigations of haematology are demonstrative for the presence of blood”. Other important tests were carried out by Heller and Adler [36] on threads and fibrils much smaller than those of Bollone, which confirmed the presence of blood. The most recent critical review paper on blood-related issue can be found in [37]. In this paper Kearse comments on studies by Bollone, Heller and Adler that demonstrate bloodstained fibres of the Shroud contain (human) albumin and immunoglobulin and human antibody of the IgG class, consistent with the presence of real blood. Concerning blood type AB on the Shroud, it was demonstrated using a forward typing approach only (which measures red cell antigens). In fresh blood, confirmation by additional tests known as reverse typing (which measures antibodies in serum) is necessary. Unfortunately, reverse typing tests in aged blood are somewhat problematic. They rely on antibodies both being present and maintaining a functional, working conformation over time. In aged samples of type AB, it is difficult recognising if the antibodies were never there to begin with or were once present but degraded over time. In conclusion, according to [37] human blood on the TS needs to be conclusively demonstrated, to extend the current immunological evidence beyond primate. 3.3 DNA on the Shroud An interesting paper [38] was recently published which presents the analysis of genomic DNA extracted from dust particles vacuumed from the areas of hands, glutei, feets and face of the backside of the ST in 1978 (during the STuRP measurements) and in 1988 in the region of the C-14 dated sample by Riggi di Numana. The authors write [38]: “Several plant taxa native to the Mediterranean area were identified as well as species with a primary center of origin in Asia, the Middle East or the Americas but introduced in a historical interval later than the Medieval period. Regarding human mitogenome lineages, our analyses detected sequences from multiple subjects of different ethnic origins, which clustered into a number of Western Eurasian haplogroups, including some known to be typical of Western Europe, the Near East, the Arabian Peninsula and the Indian sub-continent. Such diversity does not exclude a Medieval origin in Europe but it would be also compatible with the historic path followed by the Turin Shroud during its presumed journey from the Near East. Furthermore, the results raise the possibility of an Indian manufacture of the linen cloth.” Apart from obvious findings, like, e.g., the presence of plant fibres and pollen grains on the ST (merely confirming previously reported optical microscopy results), and that many individuals of different ethnic groups and geographic regions touched and left traces of their DNA on the linen, anything very conclusive was gained by the analysis of genomic DNA. The map diagrams showing the regions associated with plant DNA species are vast. The same holds for mitochondrial (human) DNA signals. Moreover, it is difficult making a distinction between contaminants by multiple sources across the centuries and genuine DNA signals. As a consequence, the author’s conclusions in [38] are conservative and cautious. Interestingly, the possibility of an Indian manufacture of the ST fabric mentioned in [38] might explain its non-Israeli origin as claimed in [39], though the origin of the ST fabric is still a controversial topic [40].

4.

Illusory perceptions of letters and images on the Shroud

Several works have proposed interpretations of patterns on the ST that become visible only after the use of image processing tools. These hidden patterns include presumed inscriptions, coins and flowers on the image side of the ST, as well as a face-like image perceived on the backside of the ST. We have studied the misleading effect of software techniques used to elaborate photographs of low-contrast images in general and of stains on the ST in particular. Our results suggest that the interpretation of these images cannot be considered self-consistent proofs. In particular, in [41] we have shown that image processing of recent, highresolution photographs of the ST may lead some to perceive inscriptions that do not exist on the linen cloth. This is because our brain’ ability to retrieve incomplete information acts in synergy with pareidolia to interpret false image pixels which emerge after contrast enhancement and luminosity adjustment. At the end of this brain elaboration, we perceive patterns that “make sense” but are not present in the original image. This phenomenon reflects a human predisposition to impose structure on sensory input, with the side-effect that detection of pattern can occur even when no pattern is present. Moreover, in [41] we have shown that the alleged hidden image of a face on the backside of the ST reported in [42] has a very poor spatial correlation vs. the corresponding face image on the frontal side of the ST. As a consequence, it is likely the face-like pattern we perceive on the backside after a deep image processing is an illusory image, generated by a combined effect of Gestalt, pareidolia, the brain’s ability to supply the missing contours, and reinforced by our innate propensity to interpret stimuli as faces based on minimal cues. The illusory perception of patterns is a phenomenon not limited to the stains on the ST, as similar perceptions affected by pareidolia have been observed in a number of low-contrast images, like those analyzed e.g., in radiology and forensic pattern recognition. Moreover, the objectivity of observation becomes worst when dealing with religious objects, because personal beliefs affect expectations to a great extent, influencing the perception of patterns. According to [43] “When considering the detection of inscriptions in the data-limited conditions provided by the Shroud, observers who accept the religious provenance of the artifact may be predisposed to perceive illusory inscriptions in accord with their religious expectations. By the same logic, observers who do not accept the religious provenance of the artifact may be predisposed not to perceive these inscriptions, even when the same image is viewed.” In fact, the results of the test in [43] showed that contextual information before seeing inexistent, pareidolic religious inscriptions on a linen fabric, affected the actual perceptual state of participants and did not merely affect a bias in reporting the existence of words on a piece of linen without any inscription. 5.

Conclusion

The ST is a centuries-old linen cloth that has been carbon-dated and chemically analysed; the images on the ST have been 3D-imaged, zoomed and digitally enhanced; DNA and blood analysed; pollen and invisible stains revealed. Despite today’s technologies, these studies have been inconclusive or contested, and no one has yet figured out how the image was made, no one has been able to reproduce it at the microscopic level. This is because the experimental evidences we have briefly summarized and that are detailed in the papers quoted in the References are circumstantial, to some extent. The ST is an archaeological object plenty of scientific clues, without any proof. For the above reasons, every individual’s view of the ST is ultimately based on a balance of evidence, not on anything conclusive. In this frame, Science must recognize its limits. On the one hand, the scientific knowledge of the ST will remain unfinished until a new season of in-depth measurements will be approved by custodians and finally performed. Today’s diagnostic tools are much more advanced than in 1978 and 1988. As an example, recently we have shown in [44] that specialised spectroscopy tools and data elaboration techniques allowed a contactless, non invasive analysis of a 1:1 scale copy of the ST conserved in Arquata, which has a peculiar double body image that was not made by pigments, nor by scorching. Our analyses were able to identify the techniques adopted by the artist in 1653 to achieve the body images and the other stains.

On the other hand, in our opinion, one of the main questions to focus on is the message carried out by the ST image. This message extends across scientific and non scientific disciplines. In fact, physics of light, chemistry and photochemistry, medicine, biology, psycho-perception, history, metaphysics and philosophy meet and overlap in this linen cloth, in an unprecedented attempt to solve a multifaceted enigma. The message of the ST remains, whether the ST is authentic or not.

References and bibliography [1] https://www.shroud.com/78team.htm [2] https://www.shroud.com/78conclu.htm [3] W.C. Mc Crone, C. Skirius: “Light microscopical study of the Shroud of Turin II” The Microscope 28, 105-111 (1980). [4] L.A. Schwalbe, R.N. Rogers: “Physics and chemistry of the Shroud of Turin, a summary of the 1978 investigation” Analytica Chimica Acta 135, 3-49 (1982). [5] E.J. Jumper, A.D. Adler, J.P. Jackson, S.F. Pellicori, J.H. Heller, and J.R. Druzik: “A comprehensive examination of the various stains and images on the Shroud of Turin”, Archaeological Chemistry III: ACS Advances in Chemistry 205 (American Chemical Society, Washington, 1984), pp. 447-476. [6] T. Heimburger: “A detailed critical review of the chemical studies on the Turin Shroud: facts and interpretations”. www.shroud.com/pdfs/thibault%20final%2001.pdf (2008). [7] https://www.shroud.com/78papers.htm [8] J.P. Jackson, E.J. Jumper, W.R. Ercoline: “Correlation of image intensity on the Turin Shroud with the 3-D structure of a human body shape” Appl. Opt. 23, 2244-2270 (1984). [9] L. Garlaschelli: “Life-size Reproduction of the Shroud of Turin and its Image” J. Imaging Sci. Technol. 54, 040301-040301(14) (2010). [10] T. Heimburger, G. Fanti: “A scientific comparison between the Turin Shroud and the first handmade whole copy” Proceedings IWSAI, P. Di Lazzaro ed. (ENEA 2010) pp. 19-28. ISBN 978-88-8286-232-9. http://www.acheiropoietos.info/proceedings/HeimburgerWeb.pdf [11] G. Fanti, T. Heimburger: "Letter to the Editor: Comments on -Life-Size Reproduction of the Shroud of Turin and Its Image- by L. Garlaschelli” J. Imaging Sci. Technol. 55, 020102 (2011). [12] Garlaschelli’s sentence during a public debate organised by the Chemistry Department at the University of Rome on 30th October 2014, which was open to questions from the audience, see http://www.uniroma1.it/archivionotizie/lasindone-tra-scienza-e-storia and http://www.uniroma1.it/sites/default/files/allegati_news/MANIFESTO%2030%20OTTOBRE.pdf [13] P. Atkins, J. De Paula, "Physical Chemistry" (Oxford University Press, 2006) VIII ed. ISBN 978-0-19-870072-2 [14] T. Letardi, S. Bollanti, P. Di Lazzaro, F. Flora, N. Lisi, C.E. Zheng: "Some design limitations for large-aperture high-energy per pulse excimer lasers", Il Nuovo Cimento D 14, 495-507 (1992). [15] P. Di Lazzaro, D. Murra, A. Santoni, E. Nichelatti: “The conservation of the Shroud of Turin: optical studies” EAI, special issue on Knowledge, Diagnostics and Preservation of Cultural Heritage, pp. 89-94 (2012). http://www.enea.it/it/produzione-scientifica/pdf-eai/speciale-cultural-heritage/14-the-conservation-pdf [16] G. Baldacchini, P. Di Lazzaro, D. Murra, G. Fanti, “Coloring linens with excimer lasers to simulate the body image of the Turin Shroud” Appl. Opt. 47, 1278-1283 (2008). [17] P. Di Lazzaro, D. Murra, E. Nichelatti, A Santoni, G. Baldacchini, “Deep ultraviolet radiation simulates the Turin Shroud image” J. Imaging Sci. Technol. 54, 040302-(6) (2010). [18] P. Di Lazzaro, D. Murra, E. Nichelatti, A. Santoni, G. Baldacchini: “Superficial and Shroud-like coloration of linen by short laser pulses in the vacuum ultraviolet” Appl. Opt. 51, 8567-8578 (2012).

[19] P. Di Lazzaro, D. Murra: “Shroud like coloration of linen, conservation measures and perception of patterns onto the Shroud of Turin” SHS Web of Conference vol. 15 (EDP 2015). www.shsconferences.org/articles/shsconf/pdf/2015/02/shsconf_atsi2014_00005.pdf [20] M.S. Tite: “Turin Shroud” correspondence to Nature 332, 482 (1988). [21] H.E. Gove: “Radiocarbon-dating the Shroud” correspondence to Nature 333, 110 (1988). [22] P.E. Damon et al. (21 authors): “Radiocarbon dating of the Shroud of Turin” Nature 337 611-615 (1989). [23] H.E. Gove, S.J. Mattingly, A.R. David, L.A. Garza Valdez: “A problematic source of organic contamination of linen”, Nuclear Instr. Meth. Phys, Res. B 123, 504-507 (1997). [24] R.N. Rogers: “Studies on the radiocarbon sample from the Shroud of Turin” Thermochimica Acta 425, 189194 (2005). See also a rebuttal of some of Rogers’ results by M. Bella, L. Garlaschelli, R. Samperi: “There is no mass spectrometry evidence that the C14 sample from the Shroud of Turin comes from a medieval invisible mending” Thermochimica Acta 617, 169-171 (2015). [25] B.J. Walsh: “The 1988 Shroud of Turin radiocarbon test reconsidered” Proc. of the 1999 Shroud of Turin International Research Conference, B.J. Walsh Ed., pp. 326-346 (Magistrum Press, Glen Allen, Virginia, 2000) ISBN 0-9706934-0-0. [26] See, e.g., the last paper authored by R. Van Haelst: “A critical review of the radiocarbon dating of the Shroud of Turin. ANOVA - a useful method to evaluate sets of high precision AMS radiocarbon measurements” Proc. IWSAI 2010, P. Di Lazzaro ed. (ENEA, 2010) pp. 267-273. ISBN: 978-88-8286-232-9. http://www.acheiropoietos.info/proceedings/VanHaelstWeb.pdf [27] http://www.acheiropoietos.info/proceedings/proceedings.php [28] G. Fanti, F. Crosilla, M. Riani, A. Atkinson: “A robust statistical analysis of the 1988 Turin Shroud radiocarbon dating results” Proc. IWSAI 2010, P. Di Lazzaro ed. (ENEA 2010) pp. 249-255. ISBN: 978-88-8286232-9. http://www.acheiropoietos.info/proceedings/RianiWeb.pdf [29] R. Freer-Waters, T. Jull: “Investigating a dated piece of the Shroud of Turin” Radiocarbon 52, 1521-1527 (2010). [30] M. Riani, A. Atkinson, G. Fanti, F. Crosilla: “Regression analysis with partially labelled regressors: carbon dating of the Shroud of Turin” Statistics and Computing 23, 551-561 (2013). [31] M. Frei: “Nine years of palynologycal studies on the Shroud” Shroud Spectrum International 1, 2-7 (1982). http://shroud.com/pdfs/ssi03part3.pdf [32] S.D. Shafersman: “Unraveling the Shroud” Approfondimento Sindone, 2 (1998) figure at page 32. http://llanoestacado.org/freeinquiry//skeptic/shroud/as/schafersman.html [33] E. Marinelli: “The question of pollen grains on the Shroud of Turin and the Sudarium of Oviedo” Proc. of the I Congreso Internacional sobre la Sabana Santa en España, Valencia 28-30 Abril 2012, and references therein. https://www.shroud.com/pdfs/marinelli2veng.pdf [34] H. Farey: “Problems with pollen” BSTS Newsletter 79, pp. 44-57 (2014) and references therein. https://www.shroud.com/pdfs/n79part8.pdf [35] See, e.g., P.L. Baima Bollone.: "Indagini identificative su fili della Sindone", Giornale della Accademia di Medicina di Torino, n. 1-12, 228-239 (1982). [36] J.H. Heller, A.D. Adler: “A chemical investigation of the Shroud of Turin” Can. Soc. Forens. Sci. J. 14, 81-103 (1981). See also the preliminary paper by J.H. Heller, A.D. Adler: “Blood on the Shroud of Turin” Appl. Opt. 19, 2742-2744 (1980). [37] K.P. Kearse: “A critical (re)evaluation of the Shroud of Turin blood data: strength of evidence in the characterization of the bloodstains”, Proc. of the Int. Conf. on the Shroud of Turin, St. Louis, Missouri (2014). http://www.shroud.com/pdfs/stlkearsepaper.pdf [38] G. Barcaccia, G. Galla, A. Achilli, A. Olivieri, A. Torroni: “Uncovering the sources of DNA found on the Turin Shroud” Nature Scientific Reports 5, no. 14484 (2015). [39] O. Shamir: “A burial textile from the first century CE in Jerusalem compared to roman textiles in the land of Israel and the Turin Shroud” SHS Web of Conference vol. 15 (EDP 2015). http://www.shs-

conferences.org/articles/shsconf/pdf/2015/02/shsconf_atsi2014_00010.pdf conferences.org/articles/shsconf/pdf/2015/02/shsconf_atsi2014_00011.pdf

See also the Erratum at http://www.shs-

[40] See, e.g., D. Fulbright: “Akeldama repudiation of Turin Shroud ignores evidence from the Judean Desert” Proc. IWSAI 2010, P. Di Lazzaro ed. (ENEA 2010) pp. 79-86. ISBN: 978-88-8286-232-9. http://www.acheiropoietos.info/proceedings/FulbrightAkeldamaWeb.pdf [41] P. Di Lazzaro, D. Murra, B. Schwortz, “Pattern recognition after image processing of low-contrast images, the case of the Shroud of Turin” Pattern Recognition 46, 1964-1970 (2013). https://www.researchgate.net/publication/236031482_Pattern_recognition_after_image_processing_of_lowcontrast_images_the_case_of_the_Shroud_of_Turin [42] G. Fanti, R. Maggiolo, “The double superficiality of the frontal image of the Turin Shroud” J. Opt. A: Pure Appl. Opt. 6, 491-503 (2004). [43] M. Sheen, T.R. Jordan: “Effects of contextual information on seeing pareidolic religious inscriptions on an artifact: implications for the Shroud of Turin” Perception 44 1427-1430 (2015). http://pec.sagepub.com/content/44/12/1427 [44] P. Di Lazzaro, M. Guarneri, D. Murra, V. Spizzichino, A. Danielis, A. Mencattini, V. Piraccini, M. Missori: “Non invasive analyses of low-contrast images on ancient textiles: the case of the shroud of Arquata” Journal of Cultural Heritage 17 14-19 (2016). http://www.sciencedirect.com/science/article/pii/S1296207415001247