Recent evidence of exposed H₂O ice on Mars suggests that this ice was deposited as dusty (<∼1% dust) snow. This dusty snow is thought to have been deposited and subsequently buried over the last few million years. On Earth, freshly fallen snow metamorphoses with time into firn and, if deep enough, into glacier ice. While spectral measurements of martian ice have been made, no model of the spectral albedo of dusty martian firn or glacier ice exists at present. Accounting for dust and snow metamorphism is important because both factors reduce the albedo of snow and ice by large amounts. However, the dust content and physical properties of martian H₂O ice are poorly constrained. Here, we present a model of the spectral albedo of H₂O snow and ice on Mars, which is based on validated terrestrial models. We find that small amounts (<1%) of martian dust can lower the albedo of H₂O ice at visible wavelengths from ∼1.0 to ∼0.1. Additionally, our model indicates that dusty (>0.01% dust) firn and glacier ice have a lower albedo than pure dust, making them difficult to distinguish in visible or near-infrared images commonly used to detect H₂O ice on Mars. Observations of excess ice at the Phoenix landing site are matched by 350-μm snow grains with 0.015% dust, indicating that the snow has not yet metamorphosed into glacier ice. Our model results can be used to characterize orbital observations of martian H₂O ice and refine climate-model predictions of ice stability.

中文翻译：

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尘土飞扬的火星 H2O 雪和冰的光谱反照率

火星上暴露的 H ₂ O 冰的最新证据表明，这种冰以含尘（<~1% 的灰尘）雪的形式沉积。人们认为这些尘土飞扬的雪是在过去的几百万年中沉积并随后被掩埋的。在地球上，刚落下的雪会随着时间变质成冰，如果足够深，还会变成冰川冰。虽然已经对火星冰进行了光谱测量，但目前尚不存在尘土飞扬的火星冷杉或冰川冰的光谱反照率模型。考虑尘埃和雪的变质作用很重要，因为这两个因素都会大量减少雪和冰的反照率。然而，火星H ₂ O 冰的尘埃含量和物理性质受到的限制很差。在这里，我们提出了 H ₂的光谱反照率模型O 火星上的冰雪，它基于经过验证的陆地模型。我们发现少量 (<1%) 的火星尘埃可以将可见光波长下 H ₂ O 冰的反照率从 ~1.0 降低到 ~0.1。此外，我们的模型表明，尘土飞扬（>0.01% 尘土）和冰川冰的反照率低于纯尘土，这使得它们难以在通常用于检测火星上的H ₂ O 冰的可见光或近红外图像中区分。在凤凰城着陆点观测到的过量冰与 350 微米的雪粒相匹配，其中含有 0.015% 的灰尘，表明雪还没有变质成冰川冰。我们的模型结果可用于表征火星 H ₂ O 冰的轨道观测，并改进对冰稳定性的气候模型预测。