Petroglyph suggests Puebloans recorded eclipse at Chaco Canyon

Thursday, Aug. 17, 2017 5:40 PM
Researchers believe this petroglyph, in the lower center of the image, could be a recording of a total solar eclipse that occurred July 11, 1097. The rock art, just outside the boundary of Chaco Culture National Historical Park in northwestern New Mexico, was found in 1992 by a member of a field trip of students from University of Colorado-Boulder and Fort Lewis College.
This petroglyph just outside the boundary of Chaco Canyon National Historical Park in northwestern New Mexico could be a recording of a total solar eclipse that occurred July 11, 1097. The streams coming out of the disc may resemble the sun’s outer atmosphere when it’s experiencing a “coronal mass ejection,” when clouds of solar plasma are blown away from the sun during strong solar flares.
A German astronomer drew an image of an 1860 solar eclipse showing intense solar activity. The image is similar to the petroglyph found in Chaco Canyon, which is believed to be a record of an eclipse in 1097, also depicting intense solar activity.

Get ready, because on Monday there’s going to be an onslaught of total-solar-eclipse photos posted to social media, and in all likelihood, even some selfies where your friends’ heads eclipse the eclipse itself.

The exceedingly rare occurrence is expected to draw millions of people to a 70-mile-wide swath that cuts across the country from Oregon to South Carolina to watch the sun disappear behind the moon for two minutes.

But as it turns out, our ancient ancestors may have had the same desire to record the astronomical spectacle, when a total solar eclipse lasted for four minutes on July 11, 1097. Albeit, they carved the image into a rock instead of posting to Facebook.

As hype for next week’s blackout ramps up, a mostly unknown petroglyph near Chaco Canyon in northwestern New Mexico has been gaining attention. Many believe the image is a depiction of a total eclipse almost 1,000 years ago.

“Rock art is very difficult to explain,” said J. McKim Malville, a professor emeritus at the University of Colorado-Boulder. “But nowhere else has anyone found anything that looks like it.”

In 1992, students with CU-Boulder and Fort Lewis College descended upon Chaco Culture National Historical Park for a field trip. The UNESCO World Heritage site is rich with the ruins of ancestral Puebloan civilization from 900 to 1150 A.D.

It just so happened a member of the scientific excursion stumbled upon an unmarked rock outside the park’s boundary, which featured a scattering of petroglyphs. But one stood out for its unique, unusual design, Malville said.

The petroglyph shows a circle surrounded by tangled streams that Malville says may resemble the sun’s outer atmosphere when it’s experiencing a “coronal mass ejection,” when clouds of solar plasma are blown away from the sun during strong solar flares.

Coincidentally, it looks nearly identical to a German astronomer’s drawing of the 1860 total solar eclipse, with rays and loops similar to those depicted in the Chaco petroglyph, Malville said.

However, coronal mass ejections usually don’t occur during the sun’s quiet phase of its estimated 11-year cycle. So, the astrophysical and planetary science professor had to prove the sun was extremely active during the eclipse in 1097.

In 2014, Malville, with Spanish professor José Vaquero of the University of Extremadura, published a paper in the Journal of Mediterranean Archaeology and Archaeometry in an attempt to prove the debated interpretation.

The pair of professors tracked down several sources to produce evidence that the sun was in a period of high activity during the 1097 eclipse.

For one method, the professors looked at the amount of the isotope carbon-14 (which is created by cosmic rays hitting the Earth’s atmosphere) that could be found in ancient tree rings.

The less carbon-14, Malville said, the more sunspots, which indicate higher solar activity. And that’s what they found, he said.

The two professors also dug up naked-eye observations of sunspots from accounts in China, as well as records of northern Europeans documenting the number of nights the northern lights were visible – all indicators of high sun activity.

“We did everything we could to try and disprove it, and it still seems like a reasonable suggestion,” Malville said.

The rock that has the possible eclipse petroglyph carved on it was named Piedra del Sol and features other rock art that many associate with events in the sky, including marks that lead up to the June solstice.

Former FLC professor James Judge, who helped Malville lead that field trip in 1992, says he’s not an astronomer (“I’m just an archaeologist”), but he’s pretty sold on his colleague’s interpretation of the rock art.

“In the past, people every day were tracking the movements of the sun,” Judge said. “So when something happens that shuts the sun down for a while, you can imagine what an incredible event that would be.”

Of course, there’s no way to prove conclusively whether the petroglyph at Chaco Canyon is a depiction of a total solar eclipse, as most interpretations of rock art have been lost with time.

Yet, the professors say if it is, the rock art would be the only petroglyph depicting a total solar eclipse that has ever been found, at least in the Greater Chaco region.

We’re not going to have that problem Monday.