The Catholic Church venerates an image of Our Lady on simple cloth, preserved in Mexico City. The legend claims that a native American, Juan Diego, experienced a vision of the Blessed Virgin. When he conveyed her requests to the local bishop, carrying out-of-season roses miraculously growing at the apparition site, the image appeared on his cloak, or tilma.
An oft-repeated claim circulating online is that the image was examined by NASA. At best, I can find indications that the image was examined by two people who had connections with NASA. A certain Philip Serna Callahan, conducted studies of the image using infra-red imaging and published his findings in a booklet in 1981. The text of this is not available online, but key findings are summarised in this 1997 article (from a believing standpoint).
Callahan was an entomologist (insect specialist), a recognised member of the Florida Entomological Society and apparently a Professor at the University of Florida – he was, at least in 1963, a faculty member at the Louisiana State University. His expertise on infrared radiation comes from studies of how insects sense the world around them. Many sources mention that Callahan was a consultant to NASA. There is one bibliography that identifies Callahan as the author of a one-page article in a NASA journal. The article itself (“Nature provides clues for solar energy conversion” on page 9) has no named author but does deal with insects being able to sense infrared radiation.
Various sources claim that Callahan recommended further studies but the only one permitted at the time was by imaging expert Don Lynn, who did work for NASA (at the Jet Propulsion Laboratory) and who also imaged the Turin Shroud and worked with art experts on other projects. I can find no independent source for Lynn having worked on the tilma, but the sources which claim he did also claim he found nothing unusual. So the only warranted headline would be “NASA scientist finds nothing unusual in image of Our Lady of Guadalupe.” Lynn was said to have performed spectrophotometry, which would mean measuring the light reflected by the image and its breakdown by colour, which contains information about its chemical composition.
In 1983, the Center for Applied Research in the Apostolate (CARA) published an interim report on studies on the tilma, noting (pages 42-43) that three remarkable features are commonly claimed: the rough cloth of Maguey fibres ‘should have’ decayed by now; the pigments and colours display unusual preservation; and the eyes of the Virgin seem to contain unusual levels of detail for such an image. Callahan – who, it should be noted, is not an art expert – offers opinions based on his infrared imaging that some features were added by a later artist (tassels and the moon under the Virgin’s feet) but admits that the nature of the pigments used might not be settled without taking physical samples.
Callahan’s work was re-examined in 1985 by two skeptics with experience in forensic art. They point out that Callahan failed to identify artist’s sketch lines not only in the parts of the image he deemed ‘original’ (and therefore divinely created) but also lacking in the areas he found to be retouched; the skeptics note that in other cases infrared imaging can fail to show sketch lines revealed by other techniques. They also suggest that features Callahan dismissed as ‘probably not’ sketch lines probably were. But the lack of certainty may say more about the biases of Callahan and the skeptics than the quality of the imaging. The skeptics also question studies of alleged reflections in the Virgin’s eyes as being wishful interpretation of blurry shapes.
The claims for the eyes are tentative at best. Dr Jose Aste-Tonsmann (whose doctorate is in computer programming) employed image enhancement techniques and applied false colour to draw out an image suggesting 13 individuals could be seen reflected in the Virgin’s eyes. But such image enhancement techniques do run the risk of creating meaningful shapes where there were none to begin with.
It appears that another scientific investigation of the tilma took place in 1982 at the initiative of its custodian, Abbot Guillermo Schulenburg. This was never officially published but was leaked by the left-wing Mexican journal, Proceso. The journal claimed that the investigation – headed by a former director of the National Center for Registration and Conservation of Movable Works – was conclusive: the fabric of the Guadalupe image is a combination of linen and hemp (not of cotton or henequen, as the legend states), that is, an ordinary canvas, normal among the painters of the 16th century. The fabric was prepared with a few strokes of white paint and the image was made with various colours obtained from the soot of ocote smoke, calcium sulfate, copper and iron oxides, a compound of sulfur and mercury, as well as from the Mexican cochineal; the expert José Sol Rosales concluded that the image was “a Byzantine-style tempera painting.” More details from Rosales are included in a paper published in 2002 (see pages 573-577) from the Academy of American Franciscan History, setting out quite comprehensively the materials used to create the image.
Abbot Schulenberg later caused controversy in 1999 by expressing the view that St Juan Diego was not a historical person, but merely a symbol, and shortly after was forced to resign from his position as custodian of the shrine. The previous year the Vatican had established a commission to consider the historicity of Diego’s existence, and this reached the conclusion that traditional native American narratives were trustworthy, leading to Pope John Paul II canonizing him in 2002.
The postulator of the cause for St Juan Diego’s canonisation has himself addressed some of the wilder claims made about the image, explicitly denying that it stays at the same temperature as a human body, or that the pupils of the eyes dilate under strong light. But he does maintain that the image shows no sign of brush strokes and was ‘imprinted’ on to the cloth.
To this day, Catholic commentators such as the Jesuit Revd Dr Robert Spitzer SJ (a noted commentator on faith-and-science issues) maintain (2022) that the tilma has numerous ‘inexplicable’ properties hinting at a miraculous origin for the part of the image which is the Virgin herself: it resists decay; appears to have no brush strokes or artist’s sketch lines; and has remarkable details in the reflections in the eyes. Other sources such as the hoax-debunking Snopes website come down hard on this stance, giving great weight to the skeptics’ suggestions that sketch lines might be present.
If Rosales’ analysis is correct in saying that the tilma is made of typical linen canvas material for its time, we should not be too surprised at its preservation. Even if this is wrong and the tilma truly is made of maguey fibre, it is not unheard of for such cloth to survive. Seven codices written on maguey cloth are listed in a paper which describes them as rare, but no miracle is invoked to account for why these artefacts from the 1500s and 1600s have survived.
As far as I can tell, then, we do know what material the Gudalupe image was created with; the evidence is inconclusive of whether there were brush-strokes, guidelines or underlying images; the reflections in the eyes are subject to the possible misinterpretation which always accompanies image enhancement; and the lack of decay is not impossible given the seven codices. There is no proof that the image was created by a human artist – but there is not particularly strong evidence that it was not.
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