Planetary prowler – the NASA Mars 2020 rover – scouring the Red Planet to select samples for eventual return to Earth.
Credit: NASA/JPL


A battleground of debate is brewing regarding the search for life on Mars.

The crux of the discussion is whether or not planetary protection rules are stifling our exploratory space missions.

Special regions

Last month, in the August 11 issue of Science, staff writer Paul Voosen wrote about the fear of microbial taint that curbs Mars explorers.

NASA Mars Reconnaissance Orbiter’s HiRISE image of recurring slope lineae in Melas Chasma, Valles Marineris. Arrows point out tops and bottoms of a few lineae.
Credit: NASA/JPL-Caltech/University of Arizona

In summary, the Science story explains: “In the coming years, NASA’s Curiosity rover will pass rocks on Mars that, seen from orbit, seem to host mysteriously intermittent dark streaks – perhaps marking seasonal water seeps that could host martian life. But NASA’s planetary protection office, charged with keeping earthly microbes from colonizing other bodies, has said it may nix a visit. It fears that Curiosity could contaminate this so-called special region because the rover was not fully sterilized before launch.”

Primed for a shakeup

The Science article summary explains that “many planetary scientists, however, believe that now is the time to loosen restrictions on visiting these areas, before human exploration contaminates the planet. And, after years of stasis, the planetary protection office seems primed for a shakeup, thanks to an internal move and potential change in leadership, along with outside review of its policies by independent scientists.”

Mars expedition probes the promise that Mars was home address for past, and possibly life today.
Credit: NASA


Humans on Mars: trouble ahead

Kicking up Mars dust on the topic is a forum article that has just been published in the journal Astrobiology. Lead author is Alberto G. Fairén, a visiting scientist at Cornell University.

Co-authors of the article are Victor Parro of the Centro de Astrobiologı´a (CSIC-INTA), Madrid, Spain; Dirk Schulze-Makuch of the Center of Astronomy and Astrophysics, Technical University Berlin, Berlin, Germany; and Lyle Whyte of the Department of Natural Resource Sciences, McGill University, Que´bec, Canada.

Titled “Searching for Life on Mars Before It Is Too Late” makes the case that 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.”

Advocated in the article is need for a 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 crewed missions to Mars.

NASA’s Curiosity rover is now exploring Gale Crater/Mt. Sharp area since August 2012.
Credit: NASA/JPL-Caltech

Wanted: twofold change of strategy

The forum article adds that “if we, the Mars community, are truly committed to determine whether life ever existed or still exists on Mars, we propose here a twofold change of strategy.”

  • First – allow immediate access to the Special Regions for vehicles with the cleanliness level of Curiosity, Mars2020, or Europe’s ExoMars.
  • Second – existing laboratory robotic technology must be made flight ready in the search for biochemical evidence of life, and in particular, the development of robotic nucleic acid sequencing instrumentations for future in situ detection and/or sample return.

This forum article is sure to ripple through the astrobiology community, the Committee on Space Research (COSPAR) engaged in setting guidelines for planetary protection, as well as officials in planetary protection in the U.S. and in other countries.

To read this open access article in Astrobiology, Volume 17, Number 10, 2017, go to:

3 Responses to “Searching for Life on Mars…Before It Is Too Late!”

  • In my 1999 interview with the late microbiologist Carl Woese, who the discovered the third domain of life on Earth (the extremophiles), he said this about NASA’s MSR plans:

    “All they (Martian microbes) would have to do is perceive earth-life as a source of food and have the capacity to harvest it. If they had amino acids very similar to ours, and liked the same carbon compounds, that would be enough to make us attractive to them. Earth-life might in turn find the alien life a good food source, but that by no means implies they would wipe it out. Even if the NASA assumptions are reasonable, their argument does not rule out arguments based on different reasonable assumptions. When the entire biosphere hangs in the balance (at least multicellular life), it is adventuristic to the extreme to bring Martian life here. Sure, there is a chance it would do no harm; but that is not the point. Unless you can rule out the chance that it might do harm, you should not embark on such a course.”


    Barry E. DiGregorio – Director for the International Committee Against Mars Sample Return (ICAMSR)

  • Alfred McEwen says:

    We have been intensively monitoring the region around Curiosity rover (41 HiRISE images) and there is no clear indication of dark slope streaks with the temporal behavior interpreted as evidence for water elsewhere on Mars. For MSL, this is much ado about nothing. Even if all Planetary Protection restrictions were lifted, the Curiosity science team should not go out of their way to visit one of the slope streaks they can reach, unless there is sufficient interest in understanding dry mass wasting as the science objective. Or maybe they should go just to help alleviate unwarranted fears about martian microbes. If Mars microbes exist, they have been arriving at Earth for billions of years via meteorites, so the claim that “the entire biosphere hangs in the balance” is irrational.

  • Dr. McEwen,

    It appears that MSL may have already passed over a “Special Region” (moist soil) on SOL 532 demonstrating that NASA really does not know the full extent or where subsurface liquid water (special regions) might occur:

    From this NASA article “MRO Sees Ice on Mars Exposed by Meteor Impacts” we find:

    “The ice exposed by fresh impacts suggests that NASA’s Viking Lander 2, digging into mid-latitude Mars in 1976, might have struck ice if it had dug 10 centimeters (4 inches) deeper. The Viking 2 mission, which consisted of an orbiter and a lander, launched in September 1975 and became one of the first two space probes to land successfully on the Martian surface. The Viking 1 and 2 landers characterized the structure and composition of the atmosphere and surface. They also conducted on-the-spot biological tests for life on another planet.”

    Regarding the issue of extant microbes on Mars, no other life detection experiments have been sent to Mars since the Viking Landers in 1976. Yet two of the Viking Lander microbiologists on that mission have maintained that their results from Martian soil were consistent with extant microbial life. Here both Gilbert V. Levin and Patricia Ann Straat report:

    “While mentioning Viking as an example of the high cost of spacecraft sterilization, Voosen fails to mention that Viking’s Labeled Release life detection experiment (G.V. Levin and P.A. Straat, Astrobiology, 16 (10), 798-810, 2016) obtained strong evidence for extant life. These results have never been duplicated non-biologically. Nor does he mention that Levin and Straat have published (ibid) their conclusion that the LR detected life in the topsoil of Mars. Even with its high bar to acceptance of life on Mars, NASA concedes that the LR life detection results remain “ambiguous.” So, there is a chance that life exists on Mars. Even if small, this chance must be taken seriously, because of the huge adverse impact on terrestrial life and environment should that risk materialize and be pathogenic.”

    It would seem the burden of proof for extant microbes on Mars and any damage they could possibly cause to Earth’s biosphere now lay with NASA and other space faring nations planning to return Martian samples to Earth. This will be the new “biological battleground” within the planetary protection community. It will not only impact plans to return Martian samples to earth but also sending humans to Mars. We need a definitive answer to the Mars life issue without a threat to Earth’s biosphere before both of these missions can proceed.


    Barry E. DiGregorio

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