Mars has a prime meridian, defined as passing through the small crater Airy-0.
When doing so, they selected a particular feature for the prime meridian of their charts.
But there was still a hope that a "natural" basis for a prime meridian existed.
As on the Earth, prime meridians must be arbitrarily defined.
French cartographers would use it as their prime meridian for more than 200 years.
Time and geographic space are measured from the prime meridian.
It lies in the northern hemisphere exactly opposite the prime meridian facing the Earth.
The axis passes through the equator at the prime meridian.
Longitude on the Moon is measured both east and west from its prime meridian.
Various other prime meridians were in use during the Age of Exploration.
