Two researchers have concluded that sterilizing spacecraft heading to Mars is largely a waste of money.
As far as Mars is concerned, say Fairén and Schulze-Makuch, such efforts are probably in vain since “Earth life has most likely already been transferred to Mars.” Meteorite impacts have had 3.8 billion years to spread Earth life forms to Mars. Several Earth spacecraft have visited Mars without undergoing the sterilization procedures now in place. If organisms transferred to Mars over the eons failed to survive, modern organisms would likely face the same fate. If they did survive, say Fairén and Schulze-Makuch, “it is too late to protect Mars from terrestrial life, and we can safely relax the planetary protection policies.”
They also note that NASA’s “Office of Planetary Protection is like an interplanetary Environmental Protection Agency” and that its “‘detailed and expensive’ efforts to keep Earth microorganisms off Mars are making missions to search for life on the red planet ‘unviable.’”