Imagine sending paleontologists to the Olduvai Gorge to find evidence of hominin habitation, but to avoid at all costs venturing too close to any area that looks most promising for fossils.
This is roughly analogous to how NASA is approaching its recently announced confirmation of features on the Red Planet, likely evidence of flowing water. Called recurring slope lineae (RSL), these tracks created by water are reason for great excitement, especially because they are just the kind of formations that may be conducive to Martian biology.
Because one RSL is in range of the Curiosity rover, currently sniffing around Gale Crater, what should be a rare chance to follow up the discovery from orbit with in situ data instead creates a dilemma. NASA’s Office of Planetary Protection has advised the rover might contaminate the possibly moist soil with surviving Earth life that may have hitched a ride on it, and its Planetary Science Division is pondering whether it should allow Curiosity to live up to its name and take a detour to directly examine the intriguing hotspot—or at least zap it with its laser from a safe distance.
The biennial International Council for Science's Committee on Space Research (COSPAR) Planetary Protection Policy report recently updated its protocols about avoiding contamination on Mars by humans and their machines. (The U.S. is also a signatory to the Outer Space Treaty of 1967 that forbids contamination of “the moon and celestial bodies.”) The report classifies areas on Mars as “Special Regions” defined by their life-friendly conditions. (There are also “Uncertain Regions” that may later be found to hold some potential for breeding Earth critters.) These are bio-hotspots where water (liquid or ice), volcanism, caves, geothermal activity or methane concentrations are evident—in other words, every promising location where scientists might concentrate their searches for life.
Major discoveries such as evidence of flowing water have whet the public’s imagination. Shying away from bio-hotspots, along with not equipping probes to directly look for life surely dampens this enthusiasm. It could also dilute the political will to continue funding the multibillion-dollar assault on our ruddy neighbor into the next decade with a fleet of orbiters and rovers that will probably continue to report back “exciting” revelations of ancient floods, probable liquid water and the potential for life that always seems to be in locations we avoid on the Red Planet.
Although well intentioned, cordoning off life-friendly regions is too restrictive, given the probably unachievable standard of exploring for Martian biology only when researchers are assured no Earthly contamination would be introduced. (There is also concern with Martian biology contaminating Earth after two-way missions.) To rest easy, should we just forget direct investigation and limit ourselves to geologically interesting areas like those Curiosity and upcoming surface spacecraft are slated to visit? If we are really serious about planetary purity, we should only use telescopes. (Even orbiters may eventually crash and release surviving spores they might carry.) Such a purist approach would be absurd and unscientific. But what about our current legal and self-imposed restrictions? Are they also too limiting, and at odds with NASA’s long-term goals of sample-return and eventual human visitation?
Sad to say, it is a reasonable argument that unsterilized Curiosity should not directly investigate the nearby RSL without an assurance that it would not spread potential contamination beyond the site. (Although the rover is not equipped to directly search for life, it could add supporting evidence for the findings from orbit.)
Given the Red Planet’s potential for extant life—and the impossibility of guaranteeing sterility—the report recommends that we tread lightly in our search. Yet, some researchers think the whole idea of planetary protection is a waste of money and time, given the transfer of material that has occurred between the planets over the millennia and the almost negligible likelihood that any surviving Earth microbes could expand and multiply over large areas in Mars’s harsh environment.
Getting our equipment as clean as possible rather than designating areas on Mars off-limits seems like a more realizable way to keep any Earthly invaders from tangling with Martian beasties. But our current obsession with sterility makes the perfect the enemy of the good. Thanks to possible panspermia, we may never be certain any biology discovered on the Red Planet is native Martian life, unless it is something totally alien to our own DNA-based biology. And even if we don’t find home-grown Martians, but rather life that could be Mars-evolved microbes or fossils traceable to Earth, transplanted millions of years ago, this would be an extremely important discovery, too.
Rather than quarantine biologically interesting areas, space agencies should prep and equip future probes so we don’t have to continue skirting hotspots. Besides Scout landers and flyers, sample-return and deep drilling, NASA has proposed the Astrobiology Field Laboratory, which would be the first probe since Viking to directly look for life and possibly refire public enthusiasm. It would seem to make scientific sense to dispatch this and other life-searching rovers to accessible bio-hotspots after investing in and developing high-sterilization methods and other cleaning techniques to minimize false positives. It also is a good way to curtail contamination by sending easier-to-sterilize robotic life-searching rovers, landers and sample-return spacecraft before we plant germ-covered boots on our neighbor.
Relying on such measures doesn’t mean we have to stop regulating Mars exploration by region, however. The COSPAR guidelines are not inflexible, rather they are set to evolve with our increasing data about conditions on Mars and growing knowledge about the limits of survival for Earth microbes. Some Special Regions could remain off-limits, to be pristine forever. Others could sequentially be opened as we improve sterilization methodology and equipment. Of course, this may be more easily said than done, because we still have to learn how conducive Mars’s environment would be to transferring biological material between explored and protected regions.
The current restrictions serve us now but may inhibit future scientific inquiry and exploration. Opening Mars to more thorough robotic investigation should be done in an orderly way, and with the caveat that perfectly controlled laboratory conditions are not possible. Of course, it would be great to robotically find life before we face a new dilemma when the biggest contaminants of all—astronauts—press their boot prints into the possibly vital Martian soil.