Back in June, NASA revealed two mind-blowing facts: that there is organic matter on Mars, and that levels of methane in the planet’s atmosphere ebb and flow over time. It’s pretty exciting news that shook our understanding of astrobiology. And while this isn’t necessarily proof that aliens are out there, much of our terrestrial methane was produced by living things. And as any child can tell you, if you smelled it, someone must have dealt it.

The recent methane findings “confront us with robust data that demand interpretation,” a team of international scientists wrote in a study published last week in Astrobiology. The study authors have done just that — they sorted out what measurements, experiments, and missions NASA and other space organizations should prioritize as they seek more evidence that Mars does (or did) support life.

In short, the scientists want to study Mars’ geological activity. They want to understand the relationship between these newly discovered organic compounds and the fluctuating methane in the atmosphere. Their goal is to find traces of other molecules and gases that might make it possible for some primitive, microscopic life forms to survive beneath the planet’s surface. Here’s what exactly they’re looking for.

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