How would humans decompose on Mars?

All this is why Connor and Passalacqua agree: A body on Mars, if left outside or even buried in the loose martian soil, would probably dry out and mummify.

The first few stages — algor mortis, livor mortis, and rigor mortis — would still take place, Connor says. But there might be almost no other overt signs of decomposition, she adds. Autolysis and putrefaction would continue until the body froze, with one significant caveat: Most of the bacteria in our body are aerobic, meaning they need oxygen to function. On Mars, only the anaerobic bacteria that don’t require oxygen could proliferate until freezing, which means putrefaction would be severely limited.

After freezing, the body would dry out as its moisture sublimated away, leaving a well-preserved, natural mummy behind, the likes of which might have made the ancient Egyptians jealous. “The desiccated tissues would likely be very stable for an indefinite period,” Connor says.

“If you think about those peat bog bodies from the Medieval period, I would assume it would be kind of like that,” Passalacqua says. Those bodies — also remarkably well preserved — are mummified in part because peat bogs are oxygen-poor environments, which again limit the body’s own breakdown and prevent most organisms from coming in and finishing the job.