Planet Four: CO2 jets formed by basal sublimation in Mars' southern polar regions

Dynamic processes of the Martian southern seasonal CO₂ ice caps have revealed phenomena unlike any detected previously on Earth. In the winter, CO₂ condenses to form a translucent slab of permeable ice. During late spring and summer, basal sublimation creates high-pressure gas below the slab and, breaking through weak spots in this ice, high-velocity CO₂ jets deposit unfamiliar dark spots and blotches on the Martian surface. Fans are spots with directed shape that have been influenced by local winds, while elliptic blotches are purely controlled by eruption physics. The number, time history, eccentricity, and area covered of the blotches all document factors essential to our understanding of the spring sublimation process and spring winds (indicating their absence), as well as our predictions to quantify the relationship between the timing of seasonal activity to global dust storms. We used data from the Planet Four catalog which involved an online citizen science project where volunteers mapped the shapes and sizes of the blotches visible in orbital images from Mars Reconnaissance Orbiter's (MRO) High Resolution Imaging Science Experiment (HiRISE) camera, taken in southern spring during Mars Years 29 and 30. Our findings evaluate the areas and eccentricities of the blotches at numerous locations monitored by HiRISE, presenting newborn discernments into the regional and temporal variability of the strength of CO₂ jets.