Tracking the northern seasonal cap retreat of Mars using computer vision

• Published in: Icarus (New York, N.Y. 1962) Vol. 390; p. 115295
• Main Authors: Acharya, Pruthviraj J., Smith, Isaac B., Calvin, Wendy M.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 15-01-2023
• Subjects: Mars; North pole; Polar cap recession; Mars; Polar cap recession; North pole
• ISSN: 0019-1035; 1090-2643
• DOI: 10.1016/j.icarus.2022.115295

Using polar stereographic images from the Mars Color Imager (MARCI), we use Python to autonomously track the Northern Polar Seasonal Cap (NPSC) recession from Mars Years (MY) 29 to MY 35 between Ls = 10° and Ls = 70°. We outline the cap and find an ellipse of best fit. We then compare our results to previously published recession rates, that were manually tracked, and find them to be consistent. Our process benefits from being automated, which increases the speed of tracking and allows us to monitor the recession with higher Ls fidelity than past studies. We find that most MYs have a local minimum recession rate at Ls = ∼32° and a local maximum at Ls = ∼51°. We also find that MY 30 experiences a rapid latitude increasing event that involves ∼1° Ls of a rapid increase and ∼ 5° Ls of slower recession, which then increases above the interannual average rate. We interpret this to be the result of a major sublimation driven by off-polar winds. We also discover divergent effects in the recession and size of the NPSC following the MY 28 and MY 35 global dust storms. MY 29's cap is significantly smaller and retreats slower than the multi-year average, whereas MY 35's cap is slighter larger and retreats very close to the average. We hypothesize that the diverging behavior of the caps in post-storm years can be a result of the differences in the date of onset and the duration of the storms.
•Autonomously tracking the North Polar Seasonal Cap retreat for MY for MY 29 to MY 35 between Ls = 0° and Ls = 70°•Most MYs behaved very similarly to each other with similar recession rates•Seasonal and interannual behavior is identified, especially for the MY 28 and MY 34 global dust storms