We explore and evaluate various processes that could drive the variations in the volume mixing ratio (VMR) of atmospheric O₂ observed by the quadrupole mass spectrometer (QMS) of the Sample Analysis at Mars (SAM) instrument suite on the Mars Science Laboratory (MSL) Curiosity rover. First reported by Trainer et al. (), these ∼20% variations in the O₂ VMR on a seasonal timescale over Mars Years 31–34, in excess of circulation and transport effects driven by the seasonal condensation and sublimation of CO₂ at the poles, are significantly shorter than the modeled O₂ photochemical lifetime. While there remains significant uncertainty about the various processes we investigated (atmospheric photochemistry, surface oxychlorines and H₂O₂, dissolution from brines, and airborne dust), the most plausible driver is surface oxychlorines, exchanging O₂ with the atmosphere through decomposition by solar ultraviolet and regeneration via O₃. A decrease in O₃ from increased atmospheric H₂O would reduce the removal rate of O₂ from the atmosphere to form oxychlorines at the surface. This is consistent with the tentative observation that increases in O₂ are associated with increases in water vapor. A lack of correlation with the local surface geology along Curiosity’s traverse within Gale crater, the nonuniqueness of the relevant processes to Gale crater, and the short mixing timescales of the atmosphere all suggest that the O₂ variations are a regional, or even global, phenomenon. Nonetheless, further laboratory experiments and modeling are required to accurately scale the laboratory-measured rates to Martian conditions and to fully elucidate the driving mechanisms.

中文翻译：

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评估 MSL SAM 观测到的盖尔陨石坑氧气变化的大气和地表驱动因素

我们探索并评估了可能驱动火星科学实验室 (MSL) 火星样品分析 (SAM) 仪器套件的四极杆质谱仪 (QMS) 观测到的大气 O ₂体积混合比 (VMR) 变化的各种过程。）好奇号漫游车。由 Trainer 等人首先报道。 ()，在火星第 31-34 年的季节性时间尺度上，O ₂ VMR 的这些~20%的变化，超出了由两极CO ₂的季节性凝结和升华驱动的循环和运输效应，明显短于模拟O ₂光化学寿命。虽然我们研究的各种过程（大气光化学、表面氧氯和 H ₂ O ₂、盐水溶解和空气中的灰尘）仍然存在很大的不确定性，但最可能的驱动因素是表面氧氯，通过太阳能分解与大气交换O ₂紫外线和通过O ₃再生。由于增加的大气H _{2 O而导致的O 3}减少将降低O ₂从大气中在表面形成氧氯的去除速率。这与O ₂的增加与水蒸气的增加相关的初步观察是一致的。与好奇号在盖尔陨石坑内穿越的当地表面地质缺乏相关性、盖尔陨石坑相关过程的非唯一性以及大气的短混合时间尺度都表明O ₂变化是一种区域性甚至全球性现象。尽管如此，还需要进一步的实验室实验和建模，以准确地将实验室测量的速率调整到火星条件，并充分阐明驱动机制。