Ghost marks appear for a short time when humidity conditions are optimal. The footprints were discovered by researchers at Cornell University while traveling through an archaeological site at the Utah Air Force training ground.
In the process of documenting the prints, the researchers conducted an archaeological survey of an area of approximately 2,000 hectares and an experimental study using non-invasive archaeological methods, including the use of a magnetometer and ground-penetrating radar.
This work revealed many more invisible prints – 88 prints have been found so far. Preliminary results indicate that these were made by a group of adults and children during the Pleistocene, a geological period that lasted from about 2,580,000 to 11,700 years ago.
The prints are most likely more than 12,000 years old, as this remote area of the Great Salt Lake Desert has not experienced marshy conditions for at least 10,000 years to produce such marks.
Source: Ferra
