Once people get there, Mars will be contaminated with Earth life.
NASA/Pat Rawlings, SAIC
NASA's InSight Mars lander touches down Nov. 26, part of a careful robotic approach to exploring the red planet. But human exploration of Mars will inevitably introduce Earth life. Are you OK with that?
Mars seen by Viking.
NASA / USGS
If we find microbes on Mars, it will be difficult to exclude the possibility that we have accidentally brought them there from Earth.
Images of the lost Beagle 2.
Beagle 2 shows the fine line between success and failure in Mars exploration. There's a lot we can learn from it going forward.
Mars seen by the Viking oriter.
Funding has been agreed for ESA's ExoMars rover, giving new hope that Europe could find life on Mars.
Artist’s impression of Schiaparelli landing.
ESA's second mission to Mars has become prey to the curse of the Red Planet – although the orbiter is heading for success, the Schiaparelli lander seems to have disappeared.
Schiaparelli separating from Trace Gas Orbiter.
If we do find life on Mars, it will be difficult to prove that we didn't bring it there from Earth. An insider talks us through what's at stake.