MRO-MCS observed cold spots during the Martian year 34 global dust storm

Abstract

The weather and climate on Mars depend heavily on the characteristics of dust, CO₂ ice, and water ice. These aerosols, suspended in the Martian atmosphere, play a critical role in determining the thermal equilibrium, wind circulation, momentum, and mass transfer. The ‘cold spots’ are those radiometrically cold areas where the temperature is less than the CO₂ frost point, and they have the maximum probability of CO₂ ice formation. The CO₂ frost point temperature around the northern autumn varies from ∼136–150 K at the surface, while it varies from 140 to 123 K at an altitude range of 5–30 km above the Martian surface. On Mars, global dust storms (GDS) drastically alter the microphysical characteristics of CO₂ ice aerosols, besides their geographical and vertical distributions. With the help of the Mars Climate Sounder (MCS) onboard NASA's Mars Reconnaissance Orbiter (MRO), an attempt is made to investigate the cold spot regions' vertical, temporal, and spatial variability during the Martian Year 34 GDS for the latitude range 60°-90°N. The GDS impacts solar insolation and modifies the circulation pattern, stimulating cold spot formation. Atmospheric cold spots (ACSs) are confined only to the northern polar region, while the surface cold spots (SCSs) are distributed across the planet. However, the majority of the SCSs are identified near the north polar region due to the northern winter. The GDS prevents the formation of ACSs at lower altitudes, prominently near the north pole (∼80°-87°N), while it encourages their formation at lower latitudes (∼65°-80°N) by shading the insolation. While there is no fluctuation in the total number of SCSs in the vicinity of the north pole, the spatial distribution of SCSs does fluctuate. The GDS impedes the formation of SCSs over the entire planet, especially near the south pole and tropical region. Both ACSs and SCSs start to surge in number after weakening of the GDS in latitude ranges 60°-90°N. These findings help advance the knowledge of CO₂ ice formation by offering new insights relating to the thermodynamical characteristics of the Martian climate system and their association with dust storms.