Current robotic missions to Mars that have not been appropriately cleaned and sterilized must steer clear of designated Special Regions to avoid introducing Earth-borne biological and organic contaminants. However, some experts claim that this strategy is hindering the discovery of martian life forms and ask if planetary protection policies governing Mars explorations should be relaxed in advance of human missions.
(The image above from NASA's Mars Reconnaissance Orbiter shows Malea Planum, a polar region in the Southern hemisphere of Mars, directly south of Hellas Basin, which contains the lowest point of elevation on the planet. The jagged saw-tooth dichotomy, over a grainy texture, seen in this close-up image. The region contains ancient volcanoes of a certain type, referred to as "paterae." Patera is the Latin word for a shallow drinking bowl, and was first applied to volcanic-looking features, with scalloped-edged calderas.)
In Searching for Life on Mars Before It Is Too Late, Alberto G. Fairén and coauthors from Centro de Astrobiologia, Cornell University, Technical University Berlin, the SETI Institute, and McGill University contend that the coexisting approaches of protecting Special Regions--which they suggest may be the most likely sites for finding martian life--and plans for human missions to Mars (that will spread terrestrial contaminants and make it more difficult to identify the biological components comprising martian microorganisms) are incompatible.
The authors propose a more thorough biological exploration of Mars over the next 10-20 years that would include access to the Special Regions with spacecraft that may be less clean than current requirements would allow.
Decades of robotic exploration have confirmed that in the distant past, Mars was warmer and wetter and its surface was habitable. However, none of the spacecraft missions to Mars have included among their scientific objectives the exploration of Special Regions, those places on the planet that could be inhabited by extant martian life or where terrestrial microorganisms might replicate.
A major reason for this is because of Planetary Protection constraints, which are implemented to protect Mars from terrestrial biological contamination. At the same time, plans are being drafted to send humans to Mars during the 2030 decade, both from international space agencies and the private sector.
These two parallel strategies for the exploration of Mars (i.e., delaying any efforts for the biological reconnaissance of Mars during the next two or three decades and then directly sending human missions to the planet) demand reconsideration because once an astronaut sets foot on Mars, Planetary Protection policies as we conceive them today will no longer be valid as human arrival will inevitably increase the introduction of terrestrial and organic contaminants and that could jeopardize the identification of indigenous Mars life.
In this study, the authors advocate for reassessment over the relationships between robotic searches, paying increased attention to proactive astrobiological investigation and sampling of areas more likely to host indigenous life, and fundamentally doing this in advance of manned missions.
It could be argued that a future proper life detection mission would not necessarily face problems in the exploration of Special Regions because it would have already set cleanliness standards that exceed the level of today's requirements. However, that would be wishful thinking. The reality is that the restrictions go to the extreme such that if the current NASA's Curiosity or the upcoming NASA's Mars2020 and ESA's ExoMars rovers came close to a Special Region, they would not be allowed to use their considerable (costly and difficult-to-put-there) instrumentation to sample and analyze for potential biosignatures because they are not cleaned to appropriate levels.
The best example of this is Curiosity, which was recently forbidden to attempt to sample and analyze readily accessible recurring slope lineae (RSLs, narrow streaks formed on the surface arguably as a result of contemporary water activity, where the instruments onboard would have been able at least to test whether they contained briny liquid water; as a result, we will have to put together another multibillion dollar mission (with a 40% chance of landing successfully, see the latest Schiaparelli attempt) to essentially do what Curiosity could do presently in Gale Crater (above).
NASA's Mars2020, which will introduce a drill to collect core samples of rocks and soils to search for signs of past microbial life (NASA Mars2020 mission overview), has likewise been directly required to avoid landing in Special Regions because it also will not be cleaned to appropriate levels.
The case of ExoMars is particularly dramatic as the first priority of the rover is to search for signs of past and present life on Mars (ESA's Scientific objectives of the ExoMars Rover, 2016); however, it has been explicitly banned to go to Special Regions because it will not comply with the minimum cleanliness requirements. As a consequence, the billion-dollar life-seeking mission ExoMars will be allowed to search for life everywhere on Mars, except in the very places where we suspect that life may exist. This incongruous situation has been stagnant for a long time and has delayed, sine die, a real quest for life on Mars.
The Daily Galaxy via Liebert Publishing
Image credits: NASA/JPL