On Earth, atmospheric methane is a prominent sign of life. On Mars, the story is more complicated. Trace detections of methane, alongside glimpses of larger spikes, have fueled debates about biological and nonbiological sources of the gas. Now, NASA scientists have announced a new twist in the tale: Methane regularly rises to a peak in late northern summer in a seasonal pattern. The swings are larger than can be explained by the planet9s seasonal freeze-thaw cycles. The wiggles are a mystery within a larger mystery: claims of methane spikes an order of magnitude or two higher than the background. Some scientists say meteor showers could be responsible, by depositing carbonaceous material in the atmosphere that reacts to form methane. A close encounter on 24 January with debris from a comet could provide a chance to test the hypothesis.

中文翻译：

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火星甲烷随季节上升和下降

在地球上，大气中的甲烷是生命的显着标志。在火星上，故事要复杂得多。甲烷的微量检测，以及较大峰值的一瞥，引发了关于气体的生物和非生物来源的争论。现在，美国宇航局的科学家们宣布了这个故事的新转折：甲烷在北夏末以季节性模式定期上升到峰值。这种波动比行星的季节性冻融循环所能解释的要大。摆动是一个更大的谜团中的一个谜团：甲烷峰值比背景高一两个数量级。一些科学家表示，流星雨可能是造成这种现象的原因，因为它会在大气中沉积含碳物质，然后反应形成甲烷。1 月 24 日与彗星碎片的近距离接触可能会提供检验这一假设的机会。