Nature has reached the point where they’re worrying about how clean we can keep our ships and rovers, so they don’t track our chemicals all over the Red Planet’s pristine mud:
In 2011, for example, researchers who analysed images from NASA’s Mars Reconnaissance Orbiter (MRO) spacecraft observed dark streaks a few metres wide that appeared and lengthened at the warmest time of the year, then faded in cooler seasons, reappearing in subsequent years. “This behaviour is easy to understand if these are seeps of water,” says planetary scientist Alfred McEwen of the University of Arizona in Tucson, who led that study. “Water will darken most soils.”
McEwen and his colleagues have now found the reappearing streaks near the equator, including in the gargantuan Valles Marineris canyon that lies just south of it. The MRO has turned up 12 new sites — each of which has hundreds or thousands of streaks — within 25 degrees of the equator.
Yet the possibility of running water could put the sites off-limits for future spacecraft unless they are carefully sterilized. The international guidelines of the Committee on Space Research (COSPAR) of the Paris-based International Council for Science say that sites that may host life, called ‘special regions’, should only be visited by probes that have been thoroughly treated to prevent microbes from hitching a ride from Earth. “You wouldn’t want to send a dirty spacecraft to these places because you’d have the potential to not discover what you’re looking for, but what you took with you,” says John Rummel, chair of COSPAR’s panel on planetary protection.
Spacecraft or their components that come into contact with special regions have to be sterilized meticulously with heat, hydrogen peroxide vapour or ionizing radiation to kill off as much Earth life as possible, rather than simply swabbed with alcohol. This raises the price of a mission, which could effectively end an intended visit to one of these areas, says McEwen. Indeed, heating the two Viking spacecraft in the 1970s is estimated to have represented 10% of the mission’s cost.