The Prime Meridian of Mars and the Longitudes of the Viking Landers

Science  23 Sep 1977:
Vol. 197, Issue 4310, pp. 1277
DOI: 10.1126/science.897666


A new planetwide control net of Mars has been computed by a single large-block analytical triangulation derived from 17,224 measurements of 3,037 control points on 928 Mariner 9 pictures. The computation incorporated the new Viking determined direction of the spin axis and rotation rate of Mars. The angle V, measured from the vernal equinox to the prime meridian (areocentric right ascension) of Mars, was determined to be V = 148.368° + 350.891986°(JD - 2433282.5), where JD refers to the Julian date. The prime meridian of Mars passes through the center of the small crater Airy-O. The longitudes of the Viking landers are λ1= 47.82°±0.10° and λ2 = 225.590°±0.10°.