This is interesting because there is already some thinking that we may have contaminated Mars with the Viking probes from the 70s:
Do other star systems need protection from Earth life?
"The technology needed to send a robotic probe to another solar system is far in the future at best. But one scientist says it's not too soon to start thinking about how to avoid contaminating extrasolar planets with hitchhiking microbes from Earth. Even today's fastest spacecraft would take tens of thousands of years to reach the Sun's nearest neighbours, Proxima and Alpha Centauri, which lie just over 4 light years away and may host an Earth-like planet. But some proposed technologies – such as nuclear propulsion, solar sails, and antimatter drives – could theoretically get a spacecraft to other solar systems in a human lifetime."