Martian cold spot regions and associated properties during the 2018 global dust storm using MRO/MCS observations

Abstract

The weather and climate on Mars depend heavily on the characteristics of dusts and aerosols. Dust, CO2, ice, water ice, etc., suspended in the air, play a critical role in the thermal equilibrium, circulation, and transfer of momentum in Mars' atmosphere. Cold spot regions are those radiometrically cold areas where the temperature is less than the CO2 frost point temperature. These regions have the maximum probability of CO2 ice formation. On Mars, global dust storms (hereafter, GDS) drastically change the microphysical characteristics of CO2 ice aerosols, besides their geographical and vertical distributions. With the help of the Derived Data Record (DDR) version 5 obtained from the Mars Climate Sounder (MCS) instrument on board the NASA’s Mars Reconnaissance Orbiter (MRO) mission, an attempt is made to investigate the origin of cold spots, their spatial and temporal variation, etc. The work focuses on the cold spot regions' vertical, temporal, and spatial variation during the Martian Year 34 GDS. GDS affected the latitudinal variation of ice cap formation and solar insolation, which in turn impacted the cold spot formation. Cold spot regions were found only at the surface levels at the south pole. Most North Pole cold spots formed on the polar nights, and during the global dust storm season, the cold spot regions in the northern hemisphere started to develop outside the polar ring and at lower altitudes as well. Also, during dust storms, there is a high concentration of dust at higher altitudes, which provides a nucleation site for CO2 ice, leading to the formation of polar hood clouds.