During late 2013 and early 2014, the Northern Hemisphere of Mars faced Earth. This provided a prime opportunity for studying its North Polar Cap (NPC). The writer measured the cap size during the intervals 30° < Ls < 70° and 82° < Ls < 134°. (The areocentric longitude of the Sun from Mars is designated as Ls and it determines the seasons on that planet; essentially, the beginning of the northern spring, summer, fall and winter are at Ls = 0°, 90°, 180° and 270°). NPC latitude measurements were made with the software package WinJupos. The mean latitudes were measured for 23 four-degree intervals of Ls. Wilcoxon Signed Rank Tests at the 90% confidence level are consistent with there being no statistical difference between the NPC in 2000 and both 2013 and 2011-2012 for 30° < Ls < 70°. Based on this same test there is a statistical difference for the NPC in 2002 and 2009-2010 compared to 2000. Therefore, it is concluded that the NPC may show interannual differences. Essentially, the NPC stopped shrinking at Ls = 82°. Its mean latitude for 82° < Ls < 134° was 81.9° ± 0.3° which is equivalent to a mean radius of 480 ± 18 km. This is nearly the same value that was measured between 1905 and 1971.
Schmude, Richard W. Jr.
"The North Polar Cap of Mars,"
Georgia Journal of Science, Vol. 72, No. 2, Article 1.
Available at: https://digitalcommons.gaacademy.org/gjs/vol72/iss2/1