Planetary exploration in the time of astrobiology: Protecting against biological contamination

Rummel, John D.

doi:10.1073/pnas.061021398

Cited by 98 publications

(48 citation statements)

References 18 publications

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“…A specific and timely concern is the nature of analogs that are appropriate for forthcoming missions that will engage in biological studies of in situ and returned Martian samples. For example, it is conceivable that materials used in simulations of a sample return mission would, for the purpose of verifying the curation and dispersal procedures, be subject to the same planetary protection regulations as a real sample (Rummel 2001). As part of such a process, qualification samples with no detectable organic content would be needed.…”

Section: Resultsmentioning

confidence: 99%

Analysis and survival of amino acids in Martian regolith analogs

Garry

Kate

Martins

et al. 2006

Meteorit & Planetary Scien

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Abstract-We have investigated the native amino acid composition of two analogs of Martian soil, JSC Mars-1 and Salten Skov. A Mars simulation chamber has been built and used to expose samples of these analogs to temperature and lighting conditions similar to those found at low latitudes on the Martian surface. The effects of the simulated conditions have been examined using high-performance liquid chromatography (HPLC). Exposure to energetic ultraviolet (UV) light in vacuum appears to cause a modest increase in the concentration of certain amino acids within the materials, which is interpreted as resulting from the degradation of microorganisms. The influence of low temperatures shows that the accretion of condensed water on the soils leads to the destruction of amino acids, supporting the idea that reactive chemical processes involving H 2 O are at work within the Martian soil. We discuss the influence of UV radiation, low temperatures, and gaseous CO 2 on the intrinsic amino acid composition of Martian soil analogs and describe, with the help of a simple model, how these studies fit within the framework of life detection on Mars and the practical tasks of choosing and using Martian regolith analogs in planetary research.

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Section: Resultsmentioning

confidence: 99%

Analysis and survival of amino acids in Martian regolith analogs

Garry

Kate

Martins

et al. 2006

Meteorit & Planetary Scien

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“…The goal of planetary protection as stated in NASA policy is prevention of forward and backward contamination (42). This policy applies directly to the control of terrestrial organisms contaminating spacecraft intended to land, orbit, fly by, or be in the vicinity of extraterrestrial bodies.…”

Section: Discussionmentioning

confidence: 99%

“…This policy applies directly to the control of terrestrial organisms contaminating spacecraft intended to land, orbit, fly by, or be in the vicinity of extraterrestrial bodies. Viking mission landers were terminally heat sterilized to decrease the risk of forward contamination of Mars and to ensure that terrestrial microorganisms did not contaminate the life detection experiments (42). However, the cost of designing and assembling the Viking landers was increased dramatically due to this requirement.…”

Section: Discussionmentioning

confidence: 99%

Survival of Spacecraft-Associated Microorganisms under Simulated Martian UV Irradiation

Newcombe

Schuerger

Benardini

et al. 2005

Appl Environ Microbiol

128

103

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Spore-forming microbes recovered from spacecraft surfaces and assembly facilities were exposed to simulated Martian UV irradiation. The effects of UVA (315 to 400 nm), UVA؉B (280 to 400 nm), and the full UV spectrum (200 to 400 nm) on the survival of microorganisms were studied at UV intensities expected to strike the surfaces of Mars. Microbial species isolated from the surfaces of several spacecraft, including Mars Odyssey, X-2000 (avionics), and the International Space Station, and their assembly facilities were identified using 16S rRNA gene sequencing. Forty-three Bacillus spore lines were screened, and 19 isolates showed resistance to UVC irradiation (200 to 280 nm) after exposure to 1,000 J m ؊2 of UVC irradiation at 254 nm using a low-pressure mercury lamp. Spores of Bacillus species isolated from spacecraft-associated surfaces were more resistant than a standard dosimetric strain, Bacillus subtilis 168. In addition, the exposure time required for UVA؉B irradiation to reduce the viable spore numbers by 90% was 35-fold longer than the exposure time required for the full UV spectrum to do this, confirming that UVC is the primary biocidal bandwidth. Among the Bacillus species tested, spores of a Bacillus pumilus strain showed the greatest resistance to all three UV bandwidths, as well as the total spectrum. The resistance to simulated Mars UV irradiation was strain specific; B. pumilus SAFR-032 exhibited greater resistance than all other strains tested. The isolation of organisms like B. pumilus SAFR-032 and the greater survival of this organism (sixfold) than of the standard dosimetric strains should be considered when the sanitation capabilities of UV irradiation are determined.When vegetative cells of Bacillus species are confronted with low nutrient abundance, the bacteria can initiate the process of sporulation, in which the growing cells differentiate into dormant spores (48). Spores do not metabolize at a detectable level and are highly resistant to several perturbations, such as heat and exposure to UV and gamma radiation (33). Due to this intrinsic resistance spores are ubiquitous in the environment and have been found both above and below the surface of the Earth (33, 38).The resistance of spores has prompted agencies such as the National Aeronautics and Space Administration (NASA), the Department of Homeland Security, and others to study sporulating bacteria more closely (1,2,9,11,15,36,43,50). Recently, in several microbial diversity surveys performed over a period of 3 years, 125 aerobic microbial strains were isolated from spacecraft assembly facilities (20,24,25,52,53), and their phylogenetic affiliations were determined (23, 54). Eighty-five percent of these strains were identified as gram-positive bacteria. About 65% of the strains cultivated survived heat shock protocols used to isolate sporulating bacteria (2). Members of the genus Bacillus were the predominant microbes among the heat shock survivors (Ͼ91%). A total of 15 different Bacillus species were identified. Bacillus licheniformis ...

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“…Several investigations, both culture based and culture independent, have demonstrated that a variety of bacterial taxa are repeatedly isolated under clean room conditions (18,24,26; P. Vaishampayan, S. Osman, G. Andersen, and K. Venkateswaran, submitted for publication). However, despite a growing understanding of the diverse microbial populations present in SAC, predicting the true risk of any such microbes' compromising the findings of extraterrestrial life detection efforts remains a significant challenge (30). A better understanding of the distribution and frequency at which high-risk contaminant microbes are encountered on spacecraft surfaces would significantly aid in assessing the threat of forward contamination (33).…”

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confidence: 99%