The stability of the residual carbon dioxide cap near the south pole of Mars is currently not well understood. The cap's survival depends on its radiation budget, controlled by the visible albedo and infrared emissivity. We investigated the role of CO₂ snowfall in altering the albedo and emissivity, leading to the observed asymmetry in the net CO₂ accumulation at the two poles. Uncontaminated snowfall increases albedo, and lowers emissivity, due to scattering by optically thick clouds and granular surface deposits. Data from the Mars Climate Sounder (MCS) show that fall and winter snowfall is correlated with higher springtime albedo at both poles. For the seasonal CO₂ deposits in each polar region >60° latitude, we find mean albedo values of 0.39 in the north and 0.51 in the south, and winter 32‐μm emissivity values of 0.84 in the north and 0.87 in the south. Using a radiative transfer model and the MCS data, we find that the north polar deposits have ∼10× higher dust content than those in the south, explaining the ∼31% lower albedo of the north seasonal cap during spring. Our model shows that greater amounts of snowfall can explain the ∼4% lower emissivity of the north polar seasonal cap. These findings demonstrate that winter snowfall and dust transport affect the composition of Mars' seasonal ice caps and polar energy balance. Snowfall and dust loading are therefore important in modeling the CO₂ cycle on Mars, as well as the planet's long‐term climate variations.

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降雪，发射率和火星季节性极帽反照率的不对称性：火星气候探测仪观测

目前尚不清楚火星南极附近的二氧化碳残留上限的稳定性。顶盖的寿命取决于其辐射预算，并受可见反照率和红外发射率的控制。我们调查了CO ₂降雪在改变反照率和发射率中的作用，导致在两个极点的净CO ₂积累中观察到不对称性。由于光学上厚厚的云层和颗粒状表面沉积物的散射，未受污染的降雪增加了反照率并降低了发射率。火星气候探测仪（MCS）的数据显示，秋季和冬季降雪与两极的春季反照率较高有关。对于季节性CO ₂在每个纬度大于60°的极区沉积，我们发现北部的平均反照率值为0.39，南部为0.51，冬季的32μm发射率值为北部为0.84，南部为0.87。利用辐射传输模型和MCS数据，我们发现北极沉积物的尘埃含量比南部沉积物高约10倍，这解释了春季春季北部季节性帽的反照率低约31％。我们的模型表明，更大的降雪量可以解释北极季节上限的发射率降低约4％。这些发现表明，冬季降雪和尘埃运输会影响火星季节性冰盖的组成和极地能量平衡。因此，降雪和粉尘负荷对模拟火星的CO ₂循环以及地球的长期气候变化非常重要。