Rock carvings, or petroglyphs, discovered in a canyon in New Mexico appear to depict a total eclipse that happened over 1,000 years ago.
Experts from the University of Colorado, Boulder, say the ancient art, carved onto the face of a rock in Chaco Canyon by the early Pueblo people, may depict the total solar eclipse that happened on July 11, 1097 CE.
They suggest the carvings show the Sun’s corona – the outermost part of the Sun's atmosphere that is most easily seen during a total solar eclipse – as depicted by a circle with swirls coming out of it.
“To me it looks like a circular feature with curved tangles and structures,” said J McKim Malville of CU Boulder’s astrophysical and planetary sciences department, who led the field trip to the canyon that first discovered the petroglyphs in 1992. He published a paper on them in 2014.
“If one looks at a drawing by a German astronomer of the 1860 total solar eclipse during high solar activity, rays and loops similar to those depicted in the Chaco petroglyph are visible."
The carvings, which appear on a freestanding rock known as Piedra del Sol, also show what they think might be a coronal mass ejection, which is feasible based on data of the Sun’s activity from that time.
To test this, Malville and his team studied tree rings that contain traces of isotope carbon-14, which is created when cosmic rays hit Earth’s atmosphere. The less carbon-14 they found, the more sunspots, which indicates increased Sun activity.
They also used historical data recorded by Europeans who made observations about when the northern lights were visible, another sign of high solar activity. Finally, they looked at observations recorded in China that go back thousands of years on sunspots observed by the naked eye.
All showed there was solar activity at the time the art is dated to.
The Piedra del Sol also shows what appears to be a large spiral, meant to depict the Sun, marking the 15 sunrises counting down to the summer solstice by a triangular shadow most likely from a rock that moves across the Sun. There are also markings on the rock that match up with the Sun on the horizon during the December solstice.
“I think it is quite possible that the Chacoan people may have congregated around Piedra del Sol at certain times of the year and were watching the sun move away from the summer solstice when the eclipse occurred,” Malville said, suggesting their focus had actually been on the solstice, not the eclipse.