# Does the background follow a seasonal cycle? · Mars methane puzzle > Three answers have been proposed. None is ahead on the evidence yet. Three are still possible. Source: https://mysteriesdept.com/mysteries/mars-methane/questions/QST0D7EXX785WEM/does-the-background-follow-a-seasonal-cycle Publisher: Mysteries Department Licence: CC BY 4.0 (credit Mysteries Department and link the page) Updated: 2026-10-26T11:58:00+00:00 --- **0** # Does the background follow a seasonal cycle? Asked 26 Oct 2026 by [**apollo** ](https://mysteriesdept.com/u/apollo)·Part of [Is there methane in the air at Gale crater?](https://mysteriesdept.com/mysteries/mars-methane/questions/QST0D7EXWQM6TWB/is-there-methane-in-the-air-at-gale-crater)·3 answers·0·0 following **Three answers, none ahead** None is ahead yet. See what would settle it. ## Where it stands Three answers have been proposed. None is ahead on the evidence yet. Three are still possible. ## Why it matters A repeatable seasonal cycle would point to a planetary process tied to temperature or pressure⁠[[1]](https://mysteriesdept.com/sources/SRC0D7EXME03TED/background-levels-of-methane-in-mars-atmosphere-show-strong); its absence would remove one of the patterns a source model must explain⁠[[2]](https://mysteriesdept.com/sources/SRC0D7EXNN22J9Y/statistical-analysis-of-curiosity-data-shows-no-evidence-for). ## Answers 3 [**Background methane varies seasonally from about 0.24 to 0.65 ppbv.** ](https://mysteriesdept.com/mysteries/mars-methane/answers/ANS0D7EY23G5D79/background-methane-varies-seasonally-from-about-0-24-to-0-65) Tested, but the results don't decide it Evidence: 1 for Disputed [**None of these.** ](https://mysteriesdept.com/mysteries/mars-methane/answers/ANS0D7EY32R7M67/none-of-these) Not tested enough to call either way Evidence: none yet Still possible [**The data do not show a seasonal cycle beyond what noise or stochastic variation produces.** ](https://mysteriesdept.com/mysteries/mars-methane/answers/ANS0D7EY2K40K95/the-data-do-not-show-a-seasonal-cycle-beyond-what-noise-or) Tested, but the results don't decide it Evidence: 1 for Disputed ## History 1. 2018[Webster et al. puts forward: background methane varies seasonally from about 0.24 to 0.65 ppbv.](https://mysteriesdept.com/sources/SRC0D7EXME03TED/background-levels-of-methane-in-mars-atmosphere-show-strong) 1. 2018[Webster et al.: a strong, repeatable seasonal variation over five years, larger than predicted from known processes.](https://mysteriesdept.com/sources/SRC0D7EXME03TED/background-levels-of-methane-in-mars-atmosphere-show-strong)For: Background methane varies seasonally from about 0.24 to 0.65 ppbv. 1. 2020[Gillen et al. puts forward: the data do not show a seasonal cycle beyond what noise or stochastic variation produces.](https://mysteriesdept.com/sources/SRC0D7EXNN22J9Y/statistical-analysis-of-curiosity-data-shows-no-evidence-for) 1. 2020[Gillen et al.: gaussian-process regression finds the 2018 data as a whole not consistent with seasonal variability.](https://mysteriesdept.com/sources/SRC0D7EXNN22J9Y/statistical-analysis-of-curiosity-data-shows-no-evidence-for)For: The data do not show a seasonal cycle beyond what noise or stochastic variation produces. 1. 26 Oct 2026Asked on this site ## Discussion 0 [Add to the discussion](https://mysteriesdept.com/signin?next=/mysteries/mars-methane/questions/QST0D7EXX785WEM/does-the-background-follow-a-seasonal-cycle%23discussion) Help with this question [ **Propose an answer** Something the evidence could support or rule out ] [ **Propose an answer** Something the evidence could support or rule out ](https://mysteriesdept.com/signin?next=/mysteries/mars-methane/questions/QST0D7EXX785WEM/does-the-background-follow-a-seasonal-cycle%23add-answer) [ **Add evidence** A result for or against an answer ] [ **Add evidence** A result for or against an answer ](https://mysteriesdept.com/signin?next=/mysteries/mars-methane/questions/QST0D7EXX785WEM/does-the-background-follow-a-seasonal-cycle%23add-evidence) [ **Ask a sub-question** A smaller question that would help settle this one ] [ **Ask a sub-question** A smaller question that would help settle this one ](https://mysteriesdept.com/signin?next=/mysteries/mars-methane/questions/QST0D7EXX785WEM/does-the-background-follow-a-seasonal-cycle%23add-question) [ **Add a source** A paper, archive record or image ] [ **Add a source** A paper, archive record or image ](https://mysteriesdept.com/signin?next=/mysteries/mars-methane/questions/QST0D7EXX785WEM/does-the-background-follow-a-seasonal-cycle%23add-source) Where it fits Mars methane puzzle [**Is there methane in the air at Gale crater?** ](https://mysteriesdept.com/mysteries/mars-methane/questions/QST0D7EXWQM6TWB/is-there-methane-in-the-air-at-gale-crater)Key question · 3 answers, inconclusive **Does the background follow a seasonal cycle?** You're here · 3 answers, inconclusive [If the rover is right, why does the orbiter see no methane?](https://mysteriesdept.com/mysteries/mars-methane/questions/QST0D7EXWZE752X/if-the-rover-is-right-why-does-the-orbiter-see-no-methane)Open · 2 answers, inconclusive [ Ask a question under this one ]