  Airy-0 Crater fromMRO; also, from A to C,Mariner 9,Viking 1 andMars Global Surveyor (Airy-0 is the larger crater in top center of each frame). | |
| Planet | Mars |
|---|---|
| Region | InsideAiry Crater |
| Coordinates | 5°06′S0°00′E / 5.1°S 0°E /-5.1; 0 |
| Quadrangle | Sinus Sabaeus |
| Diameter | 0.5 kilometres (0.31 mi) |
| Eponym | SirGeorge Biddell Airy |
Airy-0 is a crater inside the largerAiry Crater onMars, whose location historically defined the Martianprime meridian. It is about 0.5 km (0.3 mile) across and lies within the dark regionSinus Meridiani, one of the earlyalbedo features to be identified on Mars. In 2018, theIAU Working Group on Cartographic Coordinates and Rotational Elements recommended setting the longitude of theViking 1 lander (47.95137° west) as the reference line.[a] This definition maintains the position of the center of Airy-0 at 0° longitude, within the tolerance of current cartographic uncertainties.[1]
Merton Davies tied this crater into an extensivegeodetic control network of the planet Mars based onMariner 9 and earlier photographs.[2][3] The Mariner 9 Geodesy/Cartography Group proposed that the prime meridian of Mars be defined by the center of Airy-0, which was selected byHarold Masursky,Gerard de Vaucouleurs, and Merton Davies at a Group meeting on 14 August 1972.[4]
It was named in honor of the BritishAstronomer Royal SirGeorge Biddell Airy (1801–1892), who in 1850 built thetransit circle telescope atGreenwich. The location of that telescope was subsequently chosen to define the location of Earth's prime meridian.
The origin of the longitude system for Mars is now defined by assigning a longitude of 47.95137° west to the Viking 1 lander.... The longitude uncertainty within which landed resources can be determined by radiometric tracking is now ... significantly smaller than the uncertainty of determining the center of the ~500 m diameter Airy-0, the time has come to transition the orientation of the longitude system from being based on Airy-0 to the much smaller Viking 1 lander, for which there are extensive radiometric tracking data.
