Mars Global Surveyor's Mars Orbiter Camera (MOC) Wide-Angle Images (1999-2006): 2. Data Investigation Into North Polar Hood Formation, Broad Brightness Changes in Acidalia, and Seasonal Frost in Hellas

Mars Orbiter Camera Wide Angle images were taken from late 1999 through most of 2006, in both red and blue, providing nearly daily, nearly global coverage of Mars for approximately four Mars Years. Significant work has been published from those data, but there did not exist in a public archive a uniform, full time series of the processed data for easier analysis. The companion work to this (Robbins, 2023a, https://doi. org/10.1029/2022EA002673) presents that processing and quality control of the data, producing the full time series in both colors, in equirectangular and polar stereographic projections, in mosaics that have been binned into four different time intervals (daily, Delta L-s = 2 degrees, 5 degrees, and 10 degrees [approximate to 4 through 19 days]) and as approximately true-color composites. The multidimensional data set can be mined for surface and atmospheric variations on Mars. To demonstrate agreement with past work, several well-known trends are demonstrated in a review-style narrative format in Supporting Information S1, including changes after a global dust storm, seasonal frost variations at the poles, and surface variations. The data are analyzed further in the main text to demonstrate new qualitative and quantitative analyses of atmospheric and surface features: the North Polar Hood can form earlier than previously demonstrated, Acidalia has significant seasonal brightness variations that can be quantified, and the seasonal frost deposition and sublimation of Hellas can be quantified and shown to vary from year-to-year. These different investigations represent a small slice of what can be done now that these data are made available and easily accessible. Plain Language Summary The first modern craft to orbit Mars was NASA's Mars Global Surveyor, which had the Mars Orbiter Camera. A wide-angle component of that camera took daily global red- and blue-color images during the camera's lifetime, from 1999 through 2006. That data set has been reprocessed with more attention to data quality control, mosaicked, and grouped into several different time intervals for different types of scientific investigations, and an approximate true-color set of mosaics was also created. Those recently released mosaics reveal a dynamic world of huge cloud systems, changing surface patterns, seasonal changes in frost and ice cover, and vast polar cloud systems as each hemisphere slips into winter. To validate this new work, the reprocessed images are investigated and shown to reveal numerous broad types of surface and atmospheric changes that have been previously demonstrated by other researchers. To show new science that can be done with this work, the data were also examined to study how polar clouds merge together during winter, how the brightness of some features changes seasonally, and how frost builds and declines in a vast crater in winter.