Essential Background
Whether you are engaging fully with the “Petroglyph Inquiry” (recommended) or just browsing the set of seven images, we strongly recommend that you begin by reading the 2-page section provided below.
This will support an enjoyable learning experience with the descriptions of the images and their corresponding tactile-art graphics. In particular, it will increase your familiarity with:
- Chaco Canyon and the Ancestral Puebloan people
- Solar Eclipses and the Sun’s Corona
- The NASA PUNCH Mission, Solar Storms, and the Sun’s 11-Year Sunspot Cycle
1. Chaco Canyon and the Ancestral Puebloan People
Chaco Canyon is the focus of the “Ancient” dimension of the Ancient and Modern Sun-Watching outreach theme for the NASA PUNCH mission. Chaco is home to a World Heritage site in the remote high desert of what is now called northwestern New Mexico. There is archaeological evidence that Chaco flourished with human activity for a few centuries about a thousand years ago.
The journey to Chaco Canyon requires a sturdy vehicle that can handle several miles of a seriously rough ride over the rocks and ruts of a backcountry road. Chaco’s landscape is wide open with sparse vegetation and long views to the horizons, interrupted gently by the features of 100-foot Canyon walls and mesas composed mostly of great chunks of gritty sandstone.
The deep silence in Chaco can be wonderfully pierced by cackling ravens or howling coyotes. And after a blustery summer thunderstorm, unseen spadefoot frogs may bring a chorus of distinctive croaking to life. These monsoon rains also release the scents of sage and other herbaceous plants. In the autumn, bugling elk join the soundscape and the golden abundance of rabbitbrush lines the roads and paths.
In Chaco, the night sky is not only overhead, but all around you in every direction, as if you were wrapped up in a blanket of stars. Chaco is world-famous for its monumental, sandstone architecture and its abundant evidence of ancient sky-watching. Most of the buildings are aligned to the cardinal directions and/or other celestial events in ways that make them ongoing testaments to the astronomical knowledge of their builders.
The masonry of a Chaco building helps reveal the timing of its construction. The differences in masonry style can be felt as well as seen. Earlier masonry used irregular sizes of sandstone bricks resulting in walls with uneven surfaces. The masonry evolved with time to become more artful and intricate. The sandstone bricks became of a more standard size, resulting in walls with more even surfaces and greater load-bearing capacity that could support taller structures, perhaps as high as four stories!
The descendants of the people who built the Chaco buildings a thousand years ago still live in the Chaco region and still practice age-old sky-watching traditions as well as contribute to NASA projects like PUNCH. These descendants include the people of Acoma, Hopi, Zuni, and many other modern Pueblos in the Southwestern United States.
Our Puebloan colleagues say that whatever the meaning of a carefully rendered petroglyph (rock carving) or pictograph (rock painting), it was important to their ancestors and remains important today. Chaco rock art demonstrates the full spectrum of techniques (painting, pecking, abrading, incising, and drilling). One of the most well-known rock carvings is the Sun Dagger spiral petroglyph. Perhaps the most famous rock painting is the red “Supernova” pictograph (a trio of crescent, star, and human hand).
2. Solar Eclipses and the Sun’s Corona
The Sun and Moon are 3-dimensional spheres in space that, by coincidence, appear to be disks of the same size in Earth’s sky. The Sun is a star that is 400 times wider than the Earth-orbiting Moon. But the Sun is also 400 times farther away than the Moon. With just the width of your thumb when your arm is outstretched toward the sky, you could cover a full Moon or the bright light of the Sun’s inner disk.
When a solar eclipse occurs, the Moon is passing in front of the Sun, blocking the light of its disk. A total solar eclipse occurs when the Moon totally blocks the light of the Sun’s disk. These few minutes are called totality, during which time human eyes can perceive the white glow of the Sun’s outer layers called the solar corona. It took centuries and the advent of solar photography in the late 1800’s before we knew for sure that this glow was a part of the Sun instead of being a part of the Moon or a phenomenon of Earth’s atmosphere.
Also, during totality it becomes dark enough for bright stars and planets to appear in the sky. If the “curlicue” petroglyph represents an eclipse, might there also be some representation of this in evidence nearby? It turns out that that the bright planet Venus, which normally only shows itself to Earth observers near the horizons, would have been visible higher in the sky during the 1097 total solar eclipse. Could the small, pecked circle located up and to the left of the main curlicue petroglyph indicate that the Ancestral Puebloan people saw the bright light of Venus in the sky during the eclipse?
Today, many NASA missions, including PUNCH, observe with a special instrument called a coronagraph that uses an occulting disk to block out the light of the Sun’s disk and reveal the fainter light of the solar corona. This allows scientists to study this still-mysterious region of the Sun at any time, not only during total solar eclipses. The outward flow of material from the Sun that forms the solar corona becomes both hotter and faster with increasing distance from the Sun – a puzzling fact that remains a topic of leading-edge scientific research to explain.
3. The NASA PUNCH Mission, Solar Storms, and the Sun’s 11-Year Sunspot Cycle
The NASA PUNCH mission is designed to help us learn more about how the Sun’s corona expands to become the “solar wind” – the fast flow of charged particles that engulfs everything in the Solar System. PUNCH is also designed to study solar storms called Coronal Mass Ejections, or C-M-Es [see-em-eez]. A CME is an explosive release of material from the Sun’s corona that disrupts the continuous flow of the solar wind and races through the interplanetary space between Sun and Earth.
CMEs are more frequent during times of maximum sunspot activity in the Sun’s 11-year cycle. About every 11 years the Sun displays a greater abundance of sunspots and thus there is a greater likelihood of solar storms erupting from those magnetically active regions. On average during the few years of solar maximum there are about three CMEs per day. After each solar maximum there is a period of solar minimum when solar storms are less likely to occur. CMEs can still occur during solar minimum but on average occur only once every 5 days. CMEs can imperil spacecraft and astronauts as well as enhance the beauty of Earth’s Northern and Southern Lights. Just as our Sun-watching ancestors learned to predict and live well with the Sun’s seasonal cycles, PUNCH, Parker Solar Probe, and other NASA Sun-watching missions are helping our technological society learn to live well with the solar magnetic activity cycle.
We did not know about CMEs until the 1970’s when NASA spacecraft first started observing the corona in a more focused way. Our awareness of such solar storms today and when they are more likely to occur plays an important role in the Petroglyph Inquiry.
Thank you for reading this essential background information! You can always return here using the second link in the Navigation Bar at the top of the page. If you have also read the Petroglyph Inquiry introduction (the first link in the Navigation Bar), then you are ready to begin the Petroglyph Inquiry.
Click the NEXT button below to proceed to the description for Tactile Graphic 1: Sandstone Petroglyph in Chaco Canyon