Throughout the present paper, [L.sub.s] refers to the areocentric
longitude of the Sun measured from Mars; values of [L.sub.s] = 0[degrees], 90[degrees], 180[degrees], and 270 [degrees] refer to the beginning of spring, summer, fall, and winter in the northern hemisphere; all values of the areocentric
longitude in this paper are taken from the Astronomical Almanac for the years 2008, 2010-2015.
Fournier in the form of a spiral diagram in polar projection in Jarry-Deslonges' Observations des Surfaces Planetaires, or with a standard cartesian graphic: The angular planetocentric cap radius R, expressed in degrees of latitude is plotted on the ordinate, and the corresponding areocentric
longitude Ls is plotted on the abscissa.
longitude of the Sun from Mars is designated as [L.sub.s] and it determines the seasons on that planet; essentially, the beginning of the northern spring, summer, fall and winter are at [L.sub.s] = 0[degrees], 90[degrees], 180[degrees] and 270[degrees]).
The planet came to opposition on 2010 Jan 29 at high north declination, minimal disk diameter (14 arcsec) and areocentric
longitude (Ls) 44[degrees].
Throughout this report the areocentric
longitude ([L.sub.s]) is used to report the seasonal date.
Date limits of May 8-August 4 yield areocentric
longitudes (Ls) 186-240[degrees].