If we find microbes on Mars, it will be difficult to exclude the possibility that we have accidentally brought them there from Earth.
Beagle 2 shows the fine line between success and failure in Mars exploration. There's a lot we can learn from it going forward.
Funding has been agreed for ESA's ExoMars rover, giving new hope that Europe could find life on Mars.
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.
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.