Mars Extant Life: What's Next? 2019 (LPI Contrib. No. 2108) 5007.pdf

VIKING LIFE DETECTION REVISITED: THE GOOD, THE BAD, AND THE UGLY. B. C. Clark1, 1Space Science Institute, 4750 Walnut St., Boulder, CO 80301, USA. [email protected]

Introduction: The Viking lander missions were Mantra of “If Life is anywhere, Life is everywhere” is the first and only attempts to robotically detect extant no longer accepted. Organics under pyrolysis can be life by in situ measurements on a planetary body. decomposed by soil oxidants. Only two ovens opera- Widely anticipated by scientists and the public, its re- tional in GCMS; 30 sec flash heating to 500 °C. sults were, in the end, disappointingly negative [1]. Project Constraints. The engineering P.M. could, What can be learned and applied to the future? [2]. and often did overrule the P.S. The Wolf-trap experi- The Good: The Viking Lander Biology Instrument ment was deleted, after huge VLBI cost overruns. (VLBI) squeezed 3 diverse and highly sensitive inves- The Ugly: Viking was an enormous engineering tigations inside an allocated volume of < 1 ft3. success, but in the minds of the public, a scientific fiz- Science. The VLBI experiments comprehensively zle. Expectations and hopes for detecting life were too searched for metabolic activities of heterotrophy, high, and too many scientists compounded disappoint- chemoautotrophy, and phototrophy. Samples were ment by proclaiming Mars yielded no significant sur- taken from the surface and under rocks. Incubation prises (except, “lots of rocks”). Results were the same conditions included dry, humid, and wet-gradient at both sites. Mars was becoming boring. modes. Experiments were conducted with and without Furthermore, many of the scientists had strongly es- added nutrients, up to “chicken soup”. Incubation and tablished reputations to defend. Humor was rare. For sterilization temperatures could be altered. GC col- most, this would be their one and only space mission. umns analyzed gases, and highly sensitive 14C monitors Unfortunately, two of the biologists who had initial- assayed for fixation and/or release of CO2/CO. (re- ly worked together on the experiment that gave partial view and critiques to be discussed.) positives reached extreme opposite conclusions: “Vi- The GCMS goal was analysis of composition of king detected life!”, vs “it not only didn’t detect life but soil organics down to ~ppb levels. It also provided Mars today is not a suitable abode”. Consequently, the semi-quantitative measurements of soil H2O. Detailed NASA Mars exploration program disappeared for the MS analysis of atmospheric composition and isotopes next 20 years. The flight-qualified 3rd lander never proved the SNC basaltic achondrites are meteorites flew, in spite of proposals for launches in 1979 and from Mars, preceding sample return by decades. Sans 1981, and in spite of POTUS having asked NASA how organics, the soil was found to be unexpectedly rich in soon another mission could be mounted. salts (S, Cl, Br) and an oxidant that decomposed with Post-Apollo, NASA officials were forbidden from humidification. Duricrusts enriched in MgSO4 were talking about or even simply studying human missions evidence of activity by liquid water. to the red planet. Mars was dead. Operations. The Project directed “casual dress” Today’s Reality: That Mars is a fascinating planet (no ties) and went “badgeless” (no Institutional ID’s). with a long, diverse history, much of which has in- Software updates were permitted during the Extended volved liquid H2O, is now widely recognized. Sample Mission (post ~90 days), simplifying Surface Ops. return for M2020 does not currently preserve cold The Bad: Engineering Constraints. Limited vol- temperatures needed for investigation of LR results. ume was available for science because the Saturn V Missions which emphasize more and more the im- had been de-scoped. Only up to 4 incubation chambers portance of “understanding” the complexities of small- were provided per investigation. At the time, VLBI er and smaller sedimentary settings (e.g., VRR) may was the most complex and expensive instrument ever intrigue scientists, but are less and less interesting to commissioned by NASA. the overall public, our most important stakeholders. Science. Small Team compared to today (50 for As Carl Sagan once told me, years after the Viking two landers vs 450 on MSL). Few early career scien- public disappointments, for future missions to Mars “it tists and no soil science experts. Testing of VLBI ex- still is all about Life.” Now is the time to reconsider periments emphasized non-Mars-like “Aiken soil.” the search for extant life and signs of its predecessors. Geochemistry of Mars was unknown (lunar basalt, “li- The search for biosignatures should continue, but in- monite”, high-silica analogs were all incorrect). Endo- vestigations for inducing emergence from dormancy lithic organisms could not be sampled. Viking-2 did and activation of metabolism should also be explored. not dig for ice. No exposures to H2 nutrient. A pub- References: [1] Klein, H.P. (1978), Icarus, 34, lished statement by Nobelist J. Lederberg prior to Vi- 666-674. [2] Clark, B.C. (2018), in Handbook of As- king pre-biased against life if organics not found. trobiology, V. M. Kolb, Ed., CRC Press, pp. 801-817.