NASA’s Curiosity mission first detected recurring seasonal methane variations in Mars’s atmosphere.
Curiosity’s Sample Analysis at Mars instrument detected a background level of methane and occasional short-lived spikes in Gale crater. Later observations showed a seasonal pattern, with methane generally increasing during the northern summer and decreasing during the colder season.
Methane is scientifically important because it can be produced by geological processes or by biological activity. Curiosity’s measurements do not establish that life exists on Mars. They show that methane is present and that its concentration changes in ways scientists are still working to explain.
The measurements also exposed an important complication: methane seen at Gale crater has not always matched measurements made from orbit. Possible explanations include local atmospheric behavior, instrument differences, or methane being destroyed or trapped near the surface. The result remains an active research topic.