Martian Seasons and Solar Longitude

Martian Solar Longitude Ls

The solar longitude Ls is the Mars-Sun angle, measured from the Northern Hemisphere spring equinox where Ls=0.
Ls=90 thus corresponds to northern summer solstice, just as Ls=180 marks the northern autumn equinox and Ls=270 the northern winter solstice.
Martian Solar longitude

Martian days (sols) and months

A martian year is 668.6 sols (martian solar days) long and a sol is 88775.245 seconds long.
Martian months are defined as spanning 30 degrees in solar longitude. Due to the eccentricity of Mars' orbit, martian months are thus from 46 to 67 sols long, as shown in the table below.

Month
number		 Ls range
(degrees)		 Sol range
 		 duration
(in sols)		 specificities
 
1 0 30 0.0 61.2 61.2 Northern Hemisphere Spring Equinox at Ls=0
2 30 60 61.2 126.6 65.4  
3 60 90 126.6 193.3 66.7 Aphelion (largest Sun-Mars distance) at Ls=71
4 90 120 193.3 257.8 64.5 Northern Hemisphere Summer Solstice at Ls=90
5 120 150 257.8 317.5 59.7  
6 150 180 317.5 371.9 54.4  
7 180 210 371.9 421.6 49.7 Northern Hemisphere Autumn Equinox at Ls=180
Dust Storm Season begins
8 210 240 421.6 468.5 46.9 Dust Storm Season
9 240 270 468.5 514.6 46.1 Perihelion (smallest sun-Mars distance) at Ls=251
Dust Storm Season
10 270 300 514.6 562.0 47.4 Northern hemisphere Winter Solstice at Ls=270
Dust Storm Season
11 300 330 562.0 612.9 50.9 Dust Storm Season
12 330 360 612.9 668.6 55.7 Dust Storm Season ends

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