Many observers of this year’s total solar eclipse will undoubtedly want to capture this extraordinary event by photographing or sketching it. Evidence at an archaeological site in New Mexico suggests that a witness to a similar event nearly a millennium ago did the same thing. The medium was rock, and that observer created a rock carving called a petroglyph by chipping away rock with a stone chisel.
The petroglyph is on the south side of a free-standing rock in Chaco Canyon, just a few hundred yards from the Chaco Culture National Historical Park visitor center (this is some 102 miles northwest of Albuquerque, as the crow flies.) Scholars have referred to the rock as Piedra del Sol (“Sunstone”) because it contains several Sun-related features typically found in archaeological remains, including a spiral petroglyph apparently used to mark the location of the Sun on the summer solstice. But the alleged solar eclipse petroglyph is especially compelling because total solar eclipses are rare for any given location.
The petroglyph consists of a filled-in circle with curlicues shooting out from its perimeter. While other petroglyphs are nearby, a smaller, filled-in circle to its upper left has been
interpreted by some scientists as representing the planet Venus, which would have been visible once the Sun darkened during eclipse.
The curlicues may represent the Sun’s corona and, perhaps, coronal mass ejections (CMEs), which are abnormally large concentrations of plasma released from the corona. These CMEs are more common during times of peak solar activity, which generally follows an 11-year cycle.
So, do the observations and inferences match the astronomical facts? Determining the time and location of past and present eclipses is fairly straightforward, and we know that a total solar eclipse was visible from Chaco Canyon on July 11, 1097, during the height of the Chaco culture. Research has also shown that this eclipse happened during peak solar activity. Finally, astronomers can easily ascertain the relative position of the planets and other celestial bodies in past years, and this circle is indeed in the proper position for Venus, relative to the Sun, for July 11, 1097.
We will likely never know for sure whether this petroglyph really does represent a total solar eclipse, but there is sufficient evidence to keep our curiosity alive.
By Kevin Schindler, Lowell Observatory Public Information Officer and Historian