Before dawn on the dustiest regions of Mars, surfaces measured at or below ∼148 K are common. Thermodynamics principles indicate that these terrains must be associated with the presence of CO2 frost, yet visible wavelength imagery does not display any ice signature. We interpret this systematic absence as an indication of CO2 crystal growth within the surficial regolith, not on top of it, forming hard‐to‐distinguish intimate mixtures of frost and dust, that is, dirty frost. This particular ice/regolith relationship unique to the low thermal inertia regions is enabled by the large difference in size between individual dust grains and the peak thermal emission wavelength of any material nearing 148 K (1–2 μm vs. 18 μm), allowing radiative loss (and therefore ice formation) to occur deep within the pores of the ground, below several layers of grains. After sunrise, sublimation‐driven winds promoted by direct insolation and conduction create an upward drag within the surficial regolith that can be comparable in strength to gravity and friction forces combined. This drag displaces individual grains, possibly preventing their agglomeration, induration, and compaction, and can potentially initiate or sustain downslope mass movement, such as slope streaks. If confirmed, this hypothesis introduces a new form of CO2‐driven geomorphological activity occurring near the equator on Mars and explains how large units of mobile dust are currently maintained at the surface in an otherwise soil‐encrusting world. Plain Language Summary Surface CO2 ice forms at all latitudes on Mars with a strong seasonal control. In this study, we show that diurnal CO2 ice is not observed in visible wavelength imagery in dusty terrains, where diurnal frost preferentially forms. We interpret this situation as the indication of the presence of hard‐to‐distinguish dirty frost, where ice crystals grow within the surficial regolith, not on top of it, resulting in apparent soil‐like dark ice. At sunrise, sublimation‐driven winds within the regolith are occasionally strong enough to displace individual dust grains, initiating and sustaining dust avalanches on steep slopes, forming ground features known as slope streaks. This model suggests that the CO2 frost cycle is an active geomorphological agent at all latitudes and not just at high or polar latitudes, and possibly a key factor maintaining mobile dust reservoirs at the surface. Key Points Near dawn, diurnal frost is not apparent on cold, dusty, low thermal inertia terrains These observations are consistent with a model of dirty diurnal CO2 frost, fluffing up the surface layer when it sublimes This mechanism could trigger dynamic phenomena on the Martian surface and lead to the formation of slope streaks