Curiosity’ Mars rover, which is currently rocking a site called the Gale Impact Crater on Mars, last week measured a stunning methane reading. Compared to the usual background concentration of less than 1 ppb (one in a billion), the amount of methane in the air jumps to 21 ppb, and satellites operating in Mars orbit can also detect abnormal methane readings in the Gale impact crater, so it can be ruled out as an instrument failure. To further confirm, scientists will take further careful sampling in the coming days to make sure the readings are correct. This isn’t the first time Curiosity has measured high methane readings on Mars, and in 2013, the year after landing, it had a 7 ppb peak and sparked scientists’ interest in the amount of methane on the planet’s surface. Curiosity then was able to measure methane density in the environment with high accuracy over a long period of time by improving measurement methods, and also found that density changes with the seasons. However, there has not been another peak in six years until this ultra-high reading earlier, three times the previous peak. Since methane is broken down at the slowest of a hundred years after exposure to sunlight on the surface of Mars, it can be confirmed that the measured methane will not remain in the Martian atmosphere, but will have a supplementary source. The most immediate explanation is that there are ancient methane reservoirs under the formation, allowing methane gas to seep out in small quantities for hundreds of millions of years, but scientists have not ruled out the possibility that they come from biological sources, converted by biological action. Both possibilities are of great importance to science — the discovery of Martian life would naturally provide easy-to-access fuel for the first humans, even if it is only a natural methane reservoir. But the next probe, Mars 2020, doesn’t have a dedicated methane analysis device, so for now, scientists have only a lot of guesswork, and there’s no reliable evidence of where the burst of methane came from. Perhaps the future will have to have a special task, in order to get the answer!