Mars has intrigued us humans down here on Earth for centuries, and the Red Planet isn't out of surprises.
While much of the public focus is on Mars' water supply—present and prehistoric—this latest mystery doesn't hinge on a liquid, but a gas. Specifically: methane.
Methane is common here on Earth. The gas is most commonly found emitting from the waste of humans and animals, absorbing heat that is becoming a growing concern for Earth's atmosphere.
But in the 16 years since it was discovered in Mars's atmosphere, the presence of methane—and its source—have remained a mystery.
In 2013, scientists at the European Space Agency and NASA both independently noted a marked rise in methane on the Red Planet. Because molecules in the gas quickly break down—usually in about 300 years—the continued presence of the gas points to a source that's still active.
Its presence points to two possibilities, both of which are intriguing.
One culprit could be a process called serpentinization, in which rock is changed through conditions requiring heat and water. If this is the case, the process could give scientists a lead on where to search for the presence of life.
Or they could have already found it.
The methane could be coming from methanogens, living organisms that thrive in low-oxygen areas.
Twitter users are just as curious as scientists.
But despite the immensity of the mystery, Earthlings still managed to make fart jokes.
Despite the crudeness, it's clear that there's still plenty to explore on and under the surface of Mars.