Airy-0 [SEP] located on astronomical body
Airy-0
Airy-0 is a crater on Mars whose location defined the position of the prime meridian of that planet. It is about across and lies within the larger crater Airy in the region Sinus Meridiani. The IAU Working Group on Cartographic Coordinates and Rotational Elements has now recommended setting the longitude of the Viking 1 lander (47°.95137 west) as the standard. This deﬁnition maintains the position of the center of Airy-0 at 0° longitude, within the tolerance of current cartographic uncertainties.
Merton Davies tied this crater into an
located at Airy-0 crater.
Tidally-locked bodies have a natural reference longitude passing through the point nearest to their parent body: 0° the center of the primary-facing hemisphere, 90° the center of the leading hemisphere, 180° the center of the anti-primary hemisphere, and 270° the center of the trailing hemisphere. However, libration due to non-circular orbits or axial tilts causes this point to move around any fixed point on the celestial body like an analemma.
See also.