On Mars, there are aliens, and they came to the Earth. Paradoxically, this argument is designed to ease the process of sterilization, which must pass each spacecraft so as not to bring the Red Planet terrestrial microbes.
These limitations have made the search for life on Mars is costly and inefficient,
say Dirk Schulze-Makukh from the University of Washington and Alberto Fire at Cornell University (both - USA). Meanwhile, there is no perfect sterilization, and we are likely to have trace amounts of contaminating Mars terrestrial life forms.
And if sterilization is still useless, it should be sent to the Red Planet station and rovers that will dig deeper and a more complex experiments. Or, the money saved could be spent on creating a more diverse spacecraft.
A group retort sterilization in that it saves us from having to spend time and resources on false alarms, and the Martian ecosystem (if they exist) - from irretrievable change. One of the purposes of sterilization - protecting ourselves from the consequences of our own ignorance, emphasizes Catherine Conley of NASA.