What causes the seasonal change in size of the Martian polar caps? During what season would the largest amount of dry ice be present at the polar cap?

Question

What causes the seasonal change in size of the Martian polar caps?  During what season would the largest amount of dry ice be present at the polar cap?

Ariana Acosta · Accepted Answer

#CO_2# from the Martian atmosphere condenses upon cooling, then evaporates upon warming. Thus the maximum amount of solid #CO_2# at either pole occurs during that hemisphere's winter.

Mars has a thin atmosphere, but the atmosphere it does have is mostly #CO_2# gas. On Earth this would remain gaseous year-round but Mars is cold enough to allow the #CO_2# to condense during winter, forming "dry ice". As we see on Earth, winter alternates between hemispheres, and for the same reason. Mars rotates around a tilted axis, which brings alternately more warmth from the Sun to the northern hemisphere and less to the southern hemisphere, then the reverse. The polar #CO_2# ice caps grow and shrink accordingly. Similar to Earth, we see condensation at the poles because they are typically colder than the area surrounding the Martian equator.

Lydia Allen · Answer

undefined The seasonal change in size of the Martian polar caps is primarily caused by the sublimation and deposition of carbon dioxide (CO2) ice, commonly known as dry ice. During Mars' winter, carbon dioxide freezes out of the atmosphere, forming a polar cap. In the spring and summer, sunlight causes the ice to sublimate directly into gas, reducing the size of the polar cap. The largest amount of dry ice would be present at the polar cap during Mars' winter season when the CO2 freezes out of the atmosphere.