Gerhard Kminek

Detecting Pyrolysis Products from Bacteria on Mars

A pyrolysis/sublimation technique was developed to isolate volatile amine compounds from a Mars soil analogue inoculated with ∼10 billion Escherichia coli cells. In this technique, the inoculated soil is heated to 500°C for several seconds at Martian ambient pressure and the sublimate, collected by a cold finger, then analyzed using high performance liquid chromatography. Methylamine and ethylamine, produced from glycine and alanine decarboxylation, were the most abundant amine compounds detected after pyrolysis of the cells. A heating cycle similar to that utilized in our experiment was also used to release organic compounds from the Martian soil in the 1976 Viking gas chromatography/mass spectrometry (GC/MS) pyrolysis experiment. The Viking GC/MS did not detect any organic compounds of Martian origin above a level of a few parts per billion in the Martian surface soil. Although the Viking GC/MS instruments were not specifically designed to search for the presence of living cells on Mars, our experimental results indicate that at the part per billion level, the degradation products generated from several million bacterial cells per gram of Martian soil would not have been detected.

Relative Amino Acid Concentrations as a Signature for Parent Body Processes of Carbonaceous Chondrites

Most meteorites are thought to have originated from objects in the asteroid belt. Carbonaceous chondrites, which contain significant amounts of organic carbon including complex organiccompounds, have also been suggested to be derived from comets. The current model for the synthesis of organic compounds found in carbonaceous chondrites includes the survival of interstellarorganic compounds and the processing of some of these compounds on the meteoritic parent body. The amino acid composition of fiveCM carbonaceous chondrites, two CIs, one CR, and one CV3 havebeen measured using hot water extraction-vapor hydrolysis,OPA/NAC derivatization and high-performance liquid chromatography(HPLC). Total amino acid abundances in the bulk meteorites as well as the amino acid concentrations relative to glycine = 1.0for β-alanine, α-aminoisobutyric acid and D-alaninewere determined. Additional data for three Antarctic CM meteorites were obtained from the literature. All CM meteoritesanalyzed in this study show a complex distribution of amino acidsand a high variability in total concentration ranging from ∼15 300 to ∼5800 parts per billion (ppb), while the CIs show a total amino acid abundance of ∼4300 ppb. The relatively(compared to glycine) high AIB content found in all the CMs is astrong indicator that Strecker-cyanohydrin synthesis is thedominant pathway for the formation of amino acids found inthese meteorites. The data from the Antarctic CM carbonaceous chondrites are inconsistent with the results from the other CMs,perhaps due to influences from the Antarctic ice that were effective during their residence time. In contrast to CMs, the data from the CI carbonaceous chondrites indicate that the Strecker synthesis was not active on their parent bodies.

Radiation-Dependent Limit for the Viability of Bacterial Spores in Halite Fluid Inclusions and on Mars

Abstract Kminek, G., Bada, J. L., Pogliano, K. and Ward, J. F. Radiation-Dependent Limit for the Viability of Bacterial Spores in Halite Fluid Inclusions and on Mars. Radiat. Res. 159, 722–729 (2003). When claims for the long-term survival of viable organisms are made, either within terrestrial minerals or on Mars, considerations should be made of the limitations imposed by the naturally occurring radiation dose to which they have been exposed. We investigated the effect of ionizing radiation on different bacterial spores by measuring the inactivation constants for B. subtilis and S. marismortui spores in solution as well as for dry spores of B. subtilis and B. thuringiensis. S. marismortui is a halophilic spore that is genetically similar to the recently discovered 2-9-3 bacterium from a halite fluid inclusion, claimed to be 250 million years old (Vreeland et al., Nature 407, 897–900, 2000). B. thuringiensis is a soil bacterium that is genetically similar to the human pathogens B. anthracis and B. cereus (Helgason et al., Appl. Environ. Microbiol. 66, 2627–2630, 2000). To relate the inactivation constant to some realistic environments, we calculated the radiation regimen in a halite fluid inclusion and in the Martian subsurface over time. Our conclusion is that the ionizing dose of radiation in those environments limits the survival of viable bacterial spores over long periods. In the absence of an active repair mechanism in the dormant state, the long-term survival of spores is limited to less than 109 million years in halite fluid inclusions, to 100 to 160 million years in the Martian subsurface below 3 m, and to less than 600,000 years in the uppermost meter of Mars.

Searching for Traces of Life With the ExoMars Rover

Abstract The second ExoMars mission will be launched in 2020 to target an ancient landing site interpreted to possess a strong potential for preserving the physical and chemical biosignatures of fossil martian microorganisms, if they existed there. The mission will deliver a lander with instruments designed for atmospheric and geophysical investigations and a rover tasked with searching for signs of extinct life. The ExoMars rover will be equipped with a drill to collect material from outcrops and at depth (between 0 and 2xa0m). This subsurface sampling capability, coupled with novel analytic instruments, will provide the best chance yet to gain access to and characterize molecular biomarkers. Starting with a brief discussion of the ExoMars program, this chapter concentrates on the ExoMars rover. We describe its scientific underpinnings, the rover configuration, its Pasteur payload, its drill, and its sample processing systems and present the reference surface mission. We conclude by addressing desirable scientific attributes of the landing-site region. Large sections of this chapter were published previously in the work by Vago et al. (2017) .