In August 2012, the Curiosity rover landed on Mars and began, well, roving around.

This car-sized robot carried a full suite of scientific instruments that could extend, poke,

and examine a variety of properties of the

Martian soil and atmosphere. One of those instruments was called the tunable laser spectrometer,

which was designed to precisely measure levels of oxygen, carbon dioxide, methane, and other

gases in the air of Mars.

And when it came to methane, the Curiosity rover found nothing.

Or at least nothing below its detection threshold of around five parts per billion,

meaning that if there was methane, there had to be less than that. But essentially,

it meant no methane, because last time I checked, five parts per billion is not a lot. And if that

were the end of the story, this would be the shortest episode of Ask a Spaceman I've ever made.

Closing credits, see you next time, the usual. But it's not. We haven't even done the

Patreon ad yet. It's not the end of the story because in late 2013 and early 2014,

Curiosity reported a spike in the levels of methane. And not just a little bit, but up to a

factor of 10. All of a sudden, there was 10

times more methane around the rover than there was before. And that's still not exactly a lot

of methane, but it is weird. And what's doubly weird is that after a few months, the spike

went away. The methane levels dropped back down below the

detection limits. And then a few months later, it spiked back up again. And then again and

again, in total curiosity measured seven methane spikes over the course of a few years.

And what's weirder, those spikes also seem to correspond with the course of a few years. And what's weirder, those spikes also seem to correspond

with the onset of the Martian summer. So now we have a mystery on our hands. We're getting

...