A link to the audio is available on the site. Be sure to check out the pictures that are referenced in the interview.
A geoglyph is a large design or motif (generally longer than 4 meters) produced on the ground and typically formed by rocks or similarly durable elements of the landscape, such as stones, stone fragments, live trees, gravel, or earth.
Geoglyphs on Mars mirror those found on Earth. Here’s another interview with these authors of Cydonia Codex: Reflections from Mars.