Space stinks, says Megan Garber at The Atlantic, though only an extremely thin slice of humanity will ever get to experience the sensation (at least for the time being). Astronauts returning to the space station's confines after a space walk have described the lingering aroma on their suits as everything from "hot metal" to "seared steak." Here, a guide to the phenomenon:

So what does space smell like?
"It is hard to describe," says astronaut Don Pettit, not as easy as "describing the palette sensations of some new food as 'tastes like chicken.'" His best effort: "A rather pleasant sweet metallic sensation." Another astronaut, Thomas Jones, describes it as a "distinct odor of ozone" that's also "sulfurous." Confusing matters, recent studies have shown that a giant dust cloud residing at the heart of our galaxy is made of ethyl formate, which gives raspberries their flavor and smells, some say, like rum. (Perhaps deep space smells "like a fruity summer cocktail," ventures Veronique Greenwood at Discover Magazine.)

What gives space its odor?
Most likely, a class of molecule called polycyclic aromatic hydrocarbons, says Greenwood. "These compounds form during combustion, which occurs during the death of stars." The molecules can be found all over Earth, too. There are even faint traces of the stuff, which is considered carcinogenic, in things like bacon and lunch meat.

Why does space's smell matter to researchers?
NASA researchers want to reproduce space's stench for training purposes, says The Atlantic's Garber. The idea is to help "acclimate astronauts to the odors of the extra-atmospheric event."

How will they do that?
They've hired scent chemist Steve Pearce to recreate the unique smell of the stars. In a previous project to try and mimic smell of the space station Mir, Pearce described the experience of "getting close" to the real thing: "Just imagine sweaty feet and stale body odor, mix that odor with nail polish remover and gasoline." Space, says Smithsonian Mag, "it's deep, dark, immense... and smelly."

Sources: The Atlantic, Discover Magazine, GizmodoSmithsonian Mag