Anna Sofaer was a young artist and photographer visiting New Mexico when she discovered the dagger of light bisecting a rock art spiral at Chaco Canyon. Decades of subsequent research have revealed the rocks placed by ancient Chacoans over a thousand years ago mark solstice, equinox and lunar events.   We talk to Anna and her colleagues, Rob Weiner and Rich Friedman, about the history, archaeology and mysteries of these monuments — and the threats from extractive industries.

The three guests from today’s show will be giving a presentation Thursday January 24 at 6:30 p.m. at the James A. Little Theater at the School for the Deaf, sponsored by the School for Advanced Research.