More seriously, they send only sterilized landers to Mars, to avoid killing all life there (if there is any), and to avoid the problem of finding in a few years

More seriously, they send only sterilized landers to Mars, to avoid killing all life there (if there is any), and to avoid the problem of finding in a few years the contamination we sended there. More info https://en.wikipedia.org/wiki/Planetary_protection https://en.wikipedia.org/wiki/Planetary_protection