Holistic Mapping of the Present-day Martian Seasonal CO₂ Frost. I. Frost Detection within Global Visible, Thermal, and Spectral Data Sets

A dominant driver of Martian atmospheric, landscape, and landform activity is the annual cycle of CO 2 and water, seasonally moving between atmospheric gases and surface frost. Orbital data set-based maps of the distribution of seasonal frost provide a broad look at how these volatiles move through time and space, as documented in past analyses. These past works typically take the form of a global study using a single, coarse-resolution, global data set or a spatially targeted site study combining data from multiple instruments. However, there does not yet exist a global map incorporating data sets from both the kilometer-resolution maps of the contiguous seasonal cap with landform-scale (about 10 m to hundreds of meters) patches of frost. Therefore, we produce a comprehensive, global map of the seasonal distribution of CO 2 frost through a single Mars year, integrating the information contained in visible (HiRISE/Context Camera), thermal (Mars Climate Sounder/THEMIS), and spectral (CRISM) data sets so as to generate 2.4 billion frost probability estimates. Combining global instrument data across diverse spectral, spatial, and temporal regimes required the rigorous application of multiple data science methods and a multidisciplinary collaboration between data scientists and planetary scientists. We produce two papers: this first focuses on the analysis of the individual data sets, highlighting key data science techniques and metrics used to capture the underpinning physical science intuition within robust and efficient autonomous “frost detection” methods. We generate, for each data set, 36 frost probability maps showing the distribution of surface CO 2 frost through a Mars year, with a temporal resolution of 10° L s and a spatial resolution of 64 points-per-degree.