A lot of scientists and engineers who study Mars worry about planetary protection, the concern that biospheres on other worlds might be contaminated by microbes from Earth. It’s a bit like Star Trek’s prime directive, and NASA and other space agencies take pains to clean their robotic spacecraft of Earth-based life before launching them to other planets.

The discovery of periodic, briny water on the surface of Mars earlier this year reignited concerns about planetary protection, including whether the Curiosity rover was free enough of Earth-based microbes to investigate these features, known as recurring slope lineae (RSL). The problem becomes even worse when humans are thrown into the mix.

Therefore, some in the scientific community believe astronauts should remain off Mars until rovers and other probes have thoroughly studied the question of life on Mars. After the confirmation of present-day water on Mars, for example, The Planetary Society’s Emily Lakdawalla, wrote, “If we keep our filthy meatbag bodies in space and tele-operate sterile robots on the surface, we'll avoid irreversible contamination of Mars—and obfuscation of the answer to the question of whether we're alone in the solar system—for a little while longer. Maybe just long enough for robots to taste Martian water or discover Martian life.”

What, then, does this mean for SpaceX and its ambitions to send humans to Mars in the coming decades? According to the company’s founder, Elon Musk, not much. During the American Geophysical Union’s annual meeting in San Francisco this week, Musk was the featured guest at the Presidential Forum. While he mostly addressed climate issues, he was asked during the Q&A about the potential of humans to contaminate Mars.

Musk was unperturbed in his response. No, he said, it doesn’t really seem like there’s life on Mars. Certainly he would take steps to not extinguish any life that probes might find. “But I think the reality is that there isn't any life on the surface of Mars,” he said. “There may be microbial life deep underground where it's shielded from radiation and the cold. That's a possibility, but in that case, anything we do on the surface is not going to have a big impact on the subterranean life.”

Musk is not alone in these beliefs. Critics of overprotective planetary protection policies say they have inhibited the search for life on other worlds since the Viking landers on Mars. Those spacecraft were heated to 125 degrees Celsius for 30 hours before their launch to reduce bacterial spores, and there are even more stringent requirements for landers with the express purpose of searching for life.

These critics say no spacecraft can be absolutely sterilized, and therefore scientists can't have 100 percent confidence that no Earth-based contaminants have crossed space to Mars or any other world. Scientists also believe it very likely that meteorites originating from Earth have already transported bacteria to Mars, and if life exists, or ever has on Mars, vice versa.

Planetary protection protocols are maintained by the international Committee on Space Research. But as a private company, SpaceX is not bound by these protocols, and that’s especially so if it intends to go to Mars largely using private funds. For Musk, clearly, the priority is not protecting whatever extent life may exist on Mars. His goal is to provide humanity with a back-up plan in case something goes very, very wrong on Earth. “If we're a single planet species, there will eventually be some extinction event,” he said this week.

While SpaceX has yet to publicly disclose its plans for Mars, there is much discussion in online communities about significant announcements coming soon after the company returns its mainstay Falcon 9 rocket to flight later this month. Perhaps SpaceX will reveal more details about its ideas for a very big rocket, such as the BFR. You’ll have to work out that acronym for yourself.