[Many thanks to Angel Acosta-Colon for posting this on Facebook.] Here are excerpts from a fascinating article, “A Lost Sky Record: The Vanished 1910 Halley’s Comet Engraving of Cueva del Indio, Puerto Rico,” by Ángel M. Nieves-Rivera, Madeliz Gutiérrez-Ortiz, and Ángel A. Acosta-Colón, published in the August edition of NSS News: American Caving Magazine (Vol. 84: 8, 2026, 22-25).

Comet 1P/Halley is a well-documented periodic comet. Its 1910 return triggered widespread public anxiety and intense press coverage, whereas the 1986 return unfolded in a very different context, with coordinated scientific campaigns (International Halley Watch) and modern observational instrumentation (NASA/IHW 1980; Yeomans 1991). Puerto Rico offers a useful contrast between these two moments: more ephemeral, popular-material responses during the 1910 apparition and institutionalized scientific observation in 1986. Here we bring together field and archival evidence linking two cave engravings/graffiti to the 1910 apparition which left marks before the Puerto Rican scientific contributions during the 1986 return employing the late Arecibo Ionospheric Observatory. The 1910 passage of Halley’s Comet generated intense public interest and, in many places, fear. Sensationalist press and speculative commentary about “poisonous gases” in the comet’s tail provoked behaviors ranging from commercial spectacle to panic in some communities (Silva and Mirabel, 1988). Histories of the 1910 apparition emphasize the mix of scientific curiosity and popular anxiety (Hart, 1985; Yeomans, 1991; Kean, 2025).

The 1910 return of Halley’s Comet was a globally visible event documented in newspapers and memoirs; it produced both scientific observation and popular panic in many localities, including Puerto Rico. Contemporary accounts indicate that the comet was spectacularly visible in April and May 1910 and provoked strong reactions in the press and public.

[. . .] Puerto Rico’s archaeological record shows long-standing attention to celestial phenomena (for example, indigenous alignments and coastal petroglyphs). Prehistoric and historic-period material culture, instruments such as astrolabes, and manuscripts likewise document local interest in astronomy (Academia Puertorriqueña de la Historia, 1985; Oficina Estatal de Conservación Histórica, n.d.; Rodríguez Álvarez, 2010). Ana Roqué de Duprey (1853–1933), an active scientific correspondent, recorded comet observations in the late nineteenth and early twentieth centuries (Roqué de Duprey, 1923; Roqué de Duprey, n.d.). These textual sources provide a local observational context for interpreting material traces that may represent imagery of the 1910 comet.

Field recording followed standard nondestructive rock-art protocols (metric mapping, photography), and no sampling was carried out. Archival research involved reviewing digitized Puerto Rican newspapers and selected secondary sources on Halley’s apparitions. Comparative iconographic assessment relied on published site reports and photographic documentation (Acevedo-González 2006; local archival photograph from Villar-Roces 1976). Attribution rests on iconographic correspondence, documentary context, and surface weathering visible in historical photographs and during in situ inspection prior to recent covering. Ayoroa Santaliz (1990) reported the presence of the engraving in the cave in his prose work on the folkloric aspects of northern Puerto Rico. However, no date is provided, and it is unclear whether he saw it firsthand [. . .]

Measurements derived from the photograph suggest a maximum motif extent of about 1.2 meters, with incised lines forming a cometary head “coma” (about eight centimeters in diameter) and a pair of tails, tapering outward to ≈15–30 centimeters and to 24.13 centimeters in width at their widest point. The scraping is three millimeters wide and about five millimeters deep in some parts. The incision technique — shallow linear gouging with a consistent tool-striation signature — is somewhat similar to that of the pecked-out Taíno petroglyph tradition observed elsewhere in the cave (which displays percussion pitting and use-wear consistent with prehistoric styles). Stratigraphic weathering patina suggests the incision is historic. According to local oral accounts (vox populi), the bas-relief was allegedly covered with cement during the filming of a motion picture; however, no tangible evidence supporting this claim is currently available. [. . .]

Southern Puerto Rico Cave Graffiti

Interdisciplinary documentation also records a figurative graffiti element depicting a comet-like form positioned above a tomb-like motif. Iconographic features and oral-history contexts associate this image with the 1910 apparition; the motif was documented and described during recent fieldwork (Méndez & Acosta-Colón 2026). Direct dating was not possible. However, several lines of evidence support attribution to Halley’s Comet (1910): (1) strong iconographic similarity to popular 1910 representations (star-like head with extended tail and the inscribed date on the Arecibo panel); (2) contemporaneous press reports and manuscript observations indicating public concern during the 1910 apparition; and (3) surface weathering and comparative photographic evidence demonstrating that the motif was already present by the mid-twentieth century. Taken together, these elements support a working interpretation of both motifs as historic responses dating to the 1910 apparition. Puerto Rican scientific facilities participated in organized monitoring campaigns during 1985–86, including radio observations reported in the professional literature (Bajaja et al. 1987). This participation reflects a clear shift from popular or material commemoration toward coordinated, instrument-based science conducted within international frameworks (NASA/IHW 1980). Local optical observations and public outreach activities also documented the comet’s 1986 appearance in Puerto Rico. [. . .]

The irreversible alteration of the Cueva del Indio panel (cement covering) underscores significant preservation challenges for coastal karst shelters affected by vandalism, tourism, and development. [. . .]

In summary, two historic-period cave motifs in Puerto Rico — one photographed at Cueva del Indio and now cement-covered, and another documented in a southern cave — likely represent local material responses to Halley’s Comet during its 1910 apparition. These records complement documentary sources, including Roqué de Duprey’s notes, and stand in contrast to the organized scientific participation in Puerto Rico during the 1986 return. Preservation and focused archival research remain essential for recovering and interpreting similar forms of ephemeral heritage. [. . .]

For full article, go to https://caves.org/wp-content/uploads/2026/08/August_26_News-1.pdf#

[Photo of Cueva del Indio above from Puertorico.com.]