The search for life on Mars may be hindered by the drive to prevent microbes from Earth from reaching the Red Planet.
Alberto Fairen of Cornell University and Dirk Schulze-Makuch from Washington State University, a pair of astrobiologists, wrote a commentary June 27 in the journal Nature Geoscience on the subject. In the piece, they argue that the sterilization requirements currently in place for Mars probes adds unnecessary costs and preparation time to missions, hindering the search for life there.
"'[P]lanetary protection requirements impose heavy financial burdens on Mars missions, partially explaining why no robots have searched for life on the Red Planet's surface since NASA's twin Viking landers ceased operations three decades ago," the researchers wrote.
Schulze-Makuch and Fairen argue in their article that life from Earth likely contaminated Mars long ago, brought there by meteor strikes in the distant past.
Although all NASA craft go through a sterilization procedure that removes most of the bacteria from probes, the procedure is not perfect. The Mars rover Curiosity, for instance, could only be cleaned to a point where 300,000 or fewer bacterial spores were still present on surfaces which could contaminate the alien landscape.
All of this sterilization - which is especially intense for spacecraft looking for life - can significantly raise the cost of a space mission. The Viking landers in the 1970's, for example, cost one billion dollars. Ten percent of that was spent sterilizing the twin craft, which included baking the landers at 233 degrees Fahrenheit for 30 hours.
Schulze and Fairen believe that these costly sterilization procedures, run by NASA's Office of Planetary Protection, should be waived for orbiters and most landers and rovers that head to the Red Planet. Mars probes looking for signs of life, however, should still be sterilized in order to not distort the readings, according to the scientists. With tight budgets, NASA could use the money currently allocated to sterilization procedures to finance more missions, the authors argue.
"If Earth microorganisms can thrive on Mars, they almost certainly already do; and if they cannot, the transfer of Earth life to Mars should be of no concern, as it would simply not survive," Schulze and Fairen wrote.
Mars and the Earth have exchanged materials through asteroid strikes for billions of years, more than other bodies in the solar system. The researchers did not discuss how sterilization procedures could affect missions to other worlds.