“Given this surprising result, we’ve reorganized the weekend to run a follow-up experiment,” Ashwin R. Vasavada, the project scientist for the mission, wrote to the science team in an email that was obtained by The Times.

The mission’s controllers on Earth sent new instructions to the rover on Friday to follow up on the readings, bumping previously planned science work. The results of these observations are expected back on the ground on Monday...

On Earth, microbes known as methanogens thrive in places lacking oxygen, such as rocks deep underground and the digestive tracts of animals, and they release methane as a waste product. However, geothermal reactions devoid of biology can also generate methane.