But, an almost complete kill of 99.9 percent is not a total kill. Out of the 40 million SAFR spores sent to space, 267 were able to reactivate upon their return, and while that’s not very much given the starting number, it’s what many of the remaining 267 had in common that has Smith confounded.

A large number of the surviving 267 spores showed evidence of a very common genetic change called a single nucleotide polymorphism, or a SNP (snip). A SNP is a kind of genetic do-si-do between base pairs when an A changes to a T and so on. It may not result in any change of gene expression, or it may serve to be a benefit, or even cause disease, they aren’t exactly sure. In 2008 a team out of JPL led by Kasthuri Venkateswaran went so far as to send samples of SAFR-032 to live outside of the International Space Station for 18 months. Unlike E-Mist, the ISS samples weren’t exposed at different intervals, and were run in unison with controlled simulations on the ground. Some of the ISS microbes were exposed to less sunlight, and they tended to survive in greater numbers.

But like Smith’s microbes, the samples that were subject to direct U.V. radiation were mostly killed. The few that managed to survive the vacuum of space for 18 months had undergone changes to the proteins associated with genetic expression. Their offspring also showed an even greater resistance to UV-C exposure, the most harmful category of U.V. radiation, than those in the control group on Earth. Nine years later, Venkat and the team are still trying to make sense of the data. “And what’s particularly interesting,” Smith says, “is that those that were alive from the ISS experiment also ended up showing a resistance to antibiotics.” The type of SNPs that changed the survivors from E-Mist were varied. Some experienced an A to a T swap, others a C to a T, and some of those were in cartridges that were exposed for different lengths of time to the sun. While both teams aren’t exactly sure what the genetic changes mean in either of the experiments, they suspect that they may be playing a role in their survival.

For planetary-protection purposes, resistant strains like SAFR-032 pose an interesting problem. Scientists are learning how to kill them, and direct sunlight seems to do the trick. But, on Mars in particular, there are dust storms that sweep up the fine rusty regolith, coating robotic rovers like powdered sugar on a pancake. Over time those layers build up, and while the gentle breeze that is sure to follow can clean the spacecraft, it’s not a guarantee that there won’t be a coating of dirt just thick enough to protect the bacteria from the Martian sunlight.

Inactive microorganisms like SAFR-032 have been found attached to dust as far back as 200 years ago. When Charles Darwin returned to England on the H.M.S Beagle he brought back with him a collection of dust that had settled on his ship while sailing off the coast of Africa. After looking through the microscope he made a note that there appeared to be dead microbes like fungus and bacteria mixed into the dust. Just 10 years ago scientists were able to experiment with some of those 200-year-old samples in a lab, and successfully brought them back to life. What Darwin thought were remains, was just an evolved temporary state of a very living thing.