Online Astronomy eText: The Planets / The Sky
The Seasons on Mars Link for sharing this page on Facebook
(more details to be added in next iteration of the page)
     (1) The seasons on Mars are similar to those on Earth but much colder because it is (on the average) nearly 50 million miles further from the Sun, and longer because its year is nearly twice as long as ours. Daytime temperatures in "temperate" zones are usually around 25 degrees below zero Fahrenheit, and nighttime temperatures nearly 100 degrees colder. During a summer heat wave temperatures in "tropical" regions might exceed 60 Fahrenheit degrees, but such "high" temperatures are unusual. Near the Poles, summer temperatures are far below zero Fahrenheit, and winter temperatures more than 200 degrees below zero, causing the primarily carbon dioxide atmosphere to freeze out as "dry ice".
     (2) Because of Mars' nearly 10% eccentricity and lack of oceans there is a noticeable difference between perihelion summer and aphelion summer, both in temperature and the number and intensity of dust storms. During aphelion summer, temperatures rarely rise above the freezing point of water, but at perihelion summer temperatures may be 30 degrees above freezing. The large temperature differences between the summer and winter hemispheres frequently cause dust devils and dust storms, but they are relatively rare near aphelion, and far more common near perihelion. Near perihelion summer dust storms occasionally cover 1/3 to 1/2 of the surface of the planet, and every few perihelion summers the entire planet may become engulfed in dust storms so dense that even the highest peaks are not visible from space.
     (3) Because of Mars' nearly 10% eccentricity its seasons have very unequal length. Even for the Earth, there is a difference of a few days in the lengths of the seasons; but on Mars the differences are measured in months, not days. With an orbital period of almost two years, the average length of a season is almost six months; but near perihelion, seasons may be a month or two shorter, and near aphelion a month or two longer than the average length. As a result, a Martian calendar would be far more unequally divided than ours. (There would also be a small difference in the way dates are calculated, in that Martian calendars would use Martian days (called "sols"), which are almost 40 minutes longer than the 24 hour long day used on Earth. This can cause problems for those tracking Martian spacecraft and landers, as they live in a permanent state of jet lag, starting each day's shift about 40 minutes later than the previous day.)