Environmental regulations on Mars may be doing more harm than good. That's the conclusion of two scientists, astronomer Alberto G. Fairen of Cornell University and Dirke Schulze-Makuch of Washington State University, whose research was published in the journal Nature Geoscience in 2013. Their work promises to open an important debate about whether the scientific and ecological benefits of strong interplanetary environmental regulations outweigh their costs in terms of higher spacecraft construction and preparation budgets.
Planetary protection is carefully regulated by national and international law. Under the Outer Space Treaty of 1967, governments with active space programs committed to study other planets and moons in such a way "so as to avoid their harmful contamination," as well as preventing "adverse changes" here on Earth. To that end, spacefaring nations have established regulatory agencies, like NASA's Office of Planetary Protection in the United States. That office states that its primary mission "is to support the scientific study of chemical evolution and the origins of life in the solar system." As a secondary objective, the office also draws up rules to prevent a probe returning from another planet carrying suspected extraterrestrial microbes from spreading those microbes into Earth's environment.
Precautions currently taken for trips to Mars rate in the middle of a five-category plan established by the international Committee on Space Research, which include missions to bodies with absolutely no likelihood of life (like Mercury or the Moon), to planets or moons with at least some theoretical possibility of harbouring life (like Mars), to sample return missions which travel to such planets and then bring potential microbiotic life back to Earth, either intentionally or unintentionally. Under these regulations, Martian probes must undergo special and extensive preparation prior to launch. NASA, for instance, assembles such spacecraft in special clean rooms and then subjects them to extensive heating to kill any microbial life which made its way into the clean rooms.
It's these extensive precautions which Fairen and Schulze-Makuch think might be unnecessary. In theory, the precautions serve at least two purposes: They prevent contamination of alien environments with Earth life forms, and they reduce the possibility that a search for extraterrestrial life will inadvertently return a false positive result because it has detected bacteria that actually travelled with the spacecraft from Earth.
The problem is, say these authors, if interplanetary contamination was going to occur, it probably has already, despite our best efforts. Some bacteria might have made the journey on American space probes, which have been sent to Mars since the Viking probes first landed in the 1970s. Even if American protective measures succeeded completely, moreover, it's unlikely that the Soviet space program took similarly rigid precautions in launching its space probes. Finally, even if they did, small amounts of rock have been exchanged between Mars and Earth in the form of meteorites over the past several billion years, and bacteria could have made the trip that way, too.
What that means is that, one way or another, current planetary protection regulations probably don't help much when it comes to Mars. "If Earth microorganisms can thrive on Mars, they almost certainly already do," explain Fairen and Schulze-Makuch. On the other hand, "if they cannot, the transfer of Earth life to Mars should be of no concern, as it would simply not survive."
If planetary protection were a quick and simple checklist prior to launch, there would be no harm in continuing it anyway. However, interplanetary probes aren't cheap - NASA's latest Mars probe, Curiosity, has an estimated final price tag of about $2.5 billion - and the tedious process of clean room assembly followed by antimicrobial heating does add to the final cost. A simplified planetary protection policy could shave time off of spaceship construction, as well as money off of the probe's budget, both of which would free up people and resources for additional space projects.
Thus far, space probes have not been able to find any life on Mars, be it Earth-origin microbes or true extraterrestrial life. However, the new research is an important reminder that it might be possible to be too cautious when it comes to drawing up environmental regulations on Mars.
The original article, called "The Overprotection of Mars," was published by Nature Geoscience on June 27, 2013. A summary of the article, written for non-experts, is also available from Popular Science.