If the growth rate is known, the maximum lichen size will give a minimum age for when this rock was deposited.

The growth rate curve, a graph of age of a lichen against the date of the substrate on which it is found has to be constructed for an area.

The North American range includes the Sierra Nevada[2] and northern Boreal forests of Canada, Greenland, Iceland, Fennoscandia and Siberia.

[10][11] Thalli of Rhizocarpon geographicum in the central Brooks Range of northern Alaska have been given a maximum possible age of 10,000–11,500 years.

The capsule was opened, exposing the lichen to space conditions for 10 days before being brought back down to Earth, where it showed minimal changes or damage.