Panspermia--true or false?
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Environmental Microbiology↗
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A hitch-hiker's guide to Titan.
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Extraterrestrial Environment↗
Implementing planetary protection requirements for sample return missions.
NASA is committed to exploring space while avoiding the biological contamination of other solar system bodies and protecting the Earth against potential harm from materials returned from space. NASA's planetary protection program evaluates missions (with external advice from the US National Research Council and others) and imposes particular constraints on individual missions to achieve these objectives. In 1997 the National Research Council's Space Studies Board published the report, Mars Sample Return: Issues and Recommendations, which reported advice to NASA on Mars sample return missions, complementing their 1992 report, The Biological Contamination of Mars Issues and Recommendations. Meanwhile, NASA has requested a new Space Studies Board study to address sample returns from bodies other than Mars. This study recognizes the variety of worlds that have been opened up to NASA and its partners by small, relatively inexpensive, missions of the Discovery class, as well as the reshaping of our ideas about life in the solar system that have been occasioned by the Galileo spacecraft's discovery that an ocean under the ice on Jupiter's moon Europa might, indeed, exist. This paper will report on NASA's planned implementation of planetary protection provisions based on these recent National Research Council recommendations, and will suggest measures for incorporation in the planetary protection policy of COSPAR.
Containment of Biohazards↗
Planetary protection issues for Mars sample acquisition flight projects.
The planned NASA sample acquisition flight missions to Mars pose several interesting planetary protection issues. In addition to the usual forward contamination procedures for the adequate protection of Mars for the sake of future missions, there are reasons to ensure that the sample is not contaminated by terrestrial microbes from the acquisition mission. Recent recommendations by the Space Studies Board (SSB) of the National Research Council (United States), would indicate that the scientific integrity of the sample is a planetary protection concern (SSB, 1997). Also, as a practical matter, a contaminated sample would interfere with the process for its release from quarantine after return for distribution to the interested scientists. These matters are discussed in terms of the first planned acquisition mission.
Containment of Biohazards↗
Integrating public perspectives in sample return planning.
Planning for extraterrestrial sample returns--whether from Mars or other solar system bodies--must be done in a way that integrates planetary protection concerns with the usual mission technical and scientific considerations. Understanding and addressing legitimate societal concerns about the possible risks of sample return will be a critical part of the public decision making process ahead. This paper presents the results of two studies, one with lay audiences, the other with expert microbiologists designed to gather information on attitudes and concerns about sample return risks and planetary protection. Focus group interviews with lay subjects, using generic information about Mars sample return and a preliminary environmental impact assessment, were designed to obtain an indication of how the factual content is perceived and understood by the public. A research survey of microbiologists gathered information on experts' views and attitudes about sample return, risk management approaches and space exploration risks. These findings, combined with earlier research results on risk perception, will be useful in identifying levels of concern and potential conflicts in understanding between experts and the public about sample return risks. The information will be helpful in guiding development of the environmental impact statement and also has applicability to proposals for sample return from other solar system bodies where scientific uncertainty about extraterrestrial life may persist at the time of mission planning.
Containment of Biohazards↗
EXOCAM: Mars in a box to simulate soil-atmosphere interactions.
We present the principle of the EXOCAM chamber, devoted to the study of physical-chemical interactions between the atmosphere and the surface and subsurface in Mars conditions. The purpose of this experiment is to reach a better knowledge of the physical and chemical processes that altered the atmosphere-soil coupled system. We describe the scientific goals of EXOCAM, the multiple fields that will benefit from this experiment and the instrumentation that is devoted to the analysis of the results. We also give a description of the chamber and its main devices.
Astronomy↗
Detection of martian amino acids by chemical derivatization coupled to gas chromatography: in situ and laboratory analysis.
If there is, or ever was, life in our solar system beyond the Earth, Mars is the most likely place to search for. Future space missions will have then to take into account the detection of prebiotic molecules or molecules of biological significance such as amino acids. Techniques of analysis used for returned samples have to be very sensitive and avoid any chemical or biological contamination whereas in situ techniques have to be automated, fast and low energy consuming. Several possible methods could be used for in situ amino acid analyses on Mars, but gas chromatography would likely be the most suitable. Returned samples could be analyzed by any method in routine laboratory use such as gas chromatography, already successfully performed for analyses of organic matter including amino acids from martian meteorites. The derivatization step, which volatilizes amino acids to perform both in situ and laboratory analysis by gas chromatography, is discussed here.
Amino Acids↗
Experimental simulation of early Martian volcanic lightning.
A mixture of possible Martian volcanic gases were reproduced and irradiated by a high-energy infrared laser to reproduce the effects of lightning on the production of prebiotic molecules. The analysis of products were performed by a gas chromatograph interfaced in parallel with a FTIR-detector and a quadrupole mass spectrometer equipped with an electron impact and chemical ionization modes. The main products identified were hydrocarbons and an uncharacterized yellow film deposit. Preliminary results indicate the presence of hydrogen cyanide among the resultant compounds.
Evolution, Chemical↗
Formation of bioorganic compounds in simulated planetary atmospheres by high energy particles or photons.
Various types of organic compounds have been detected in Jupiter, Titan, and cometary coma. It is probable that organic compounds were formed in primitive Earth and Mars atmospheres. Cosmic rays and solar UV are believed to be two major energy sources for organic formation in space. We examined energetics of organic formation in simulated planetary atmospheres. Gas mixtures including a C-source (carbon monoxide or methane) and a N-source (nitrogen or ammonia) was irradiated with the followings: High energy protons or electrons from accelerators, gamma-rays from 60Co, UV light from a deuterium lamp, and soft X-rays or UV light from an electron synchrotron. Amino acids were detected in the products of particles, gamma-rays and soft X-rays irradiation from each gas mixture examined. UV light gave, however, no amino acid precursors in the gas mixture of carbon monoxide, nitrogen and nitrogen. It gave only a trace of them in the gas mixture of carbon monoxide, ammonia and water or that of methane, nitrogen and water. Yield of amino acid precursors by photons greatly depended on their wavelength. These results suggest that nitrogen-containing organic compounds like amino acid precursors were formed chiefly with high energy particles, not UV photons, in Titan or primitive Earth/Mars atmospheres where ammonia is not available as a predominant N-source.
Alanine↗
Survivability of biomolecules during extraterrestrial delivery: new results on pyrolysis of amino acids and poly-amino acids.
The hypothesis on exogenous origin of organic matter on the early Earth is strongly supported by the detection of a large variety of organic compounds (including amino acids and nucleobases) in carbonaceous chondrites. Whether such complex species can be successively delivered by other space bodies (comets, asteroids and interplanetary dust particles) is unclear and depends primarily on capability of the biomolecules to survive high temperatures during atmospheric deceleration and impacts to the terrestrial surface. Recent simulation experiments on amino acid and nucleic acid base pyrolysis under oxygen-free atmosphere demonstrated that simple representatives of these (considered thermally unstable) compounds can survive at 1-10% level a rapid heating at 500-600 degrees C. In the present work, we report on new data on the pyrolysis of amino acids and their homopolymers and discuss implications of their thermal behavior for extraterrestrial delivery.
Amino Acids↗
Partial pressures and nature of products. Application to the photolysis of PH3 and NH3 in the atmosphere of Jupiter and Saturn.
The photolysis of mixtures of gases containing NH3 or PH3 presents important differences mainly due to the strength of the X-H bond. On some examples, these differences are evidenced and the consequences for mixtures of gases containing these two compounds are shown: the photolysis of ammonia and ethylene mainly gives ethyl-, butyl- and hexylamine whereas the photolysis of phosphine and ethylene leads to ethyl- and vinylphosphine. When gaseous mixtures of NH3, PH3 and ethylene are photolyzed together, the presence of phosphine dramatically decreases the formation of nitrogen derivatives. The relevance of such lab studies to the atmospheres of Jupiter and Saturn is discussed.
Amines↗
Quantum chemical calculations of infrared spectra for the identification of unknown compounds by GC/FTIR/MS in exobiological simulation experiments.
Gas chromatography/Fourier transform IR spectroscopy/mass spectrometry (GC/FTIR/MS) is a powerful tool for the separation and unambiguous identification of complex mixtures of organic compounds, where the use of two kinds of spectra allows to significantly increase identification reliability. The simplest situation is when acquired spectra can be found in IR and MS databases, or appropriate standards are available; but this is not always the case. Some simulation experiments related to the origins of life and exobiology (e.g., simulation of amino acid pyrolysis during atmospheric entry of space bodies) can be a typical example when one encounters with numerous unknown compounds. To assist their identification by GC/FTIR/MS, recently we suggested quantum chemical calculations of infrared spectra in order to compare them to IR spectra acquired experimentally. The present work summarizes the results obtained by semi-empirical and ab initio methods, discusses their advantages and limitations, considering as test compounds some cyclic amides and amidines derived from amino acids, saturated and unsaturated nitriles (including those of interest for the Titan atmospheric chemistry), acetylenes and some other nitrogen compounds.
Amino Acids↗
Possible contribution of different energy sources to the production of organics in Titan's atmosphere.
A quantitative comparison of the products arising from the irradiation of a Titan's simulated atmosphere is presented. The energy sources used represent some of the main events that occur in the satellite's atmosphere. All of the compounds identified are classified in the hydrocarbon and nitrile chemical families. Almost all of the detected compounds in Titan's atmosphere are produced by one or more energy sources. The compounds with the highest energy yields include the C2 hydrocarbons, methanonitrile and ethanonitrile. The possibility of using some of the produced organics as tracer compounds during the Huygens descend to identify the leading energy form in the different atmospheric levels remains open.
Atmosphere↗
Chemical and optical behaviour of tholins, laboratory analogues of Titan aerosols.
Since 1997, after having identified for the first time C4N2 (the only molecule detected on Titan and undetected in the laboratory at this date) in a simulated atmosphere of Titan, our group intended to determine several properties (including optical behavior) of laboratory analogues of Titan's tholins. This article summarizes the results obtained in the frame of that program (observation by microscopy, solubility in hydrocarbons and nitriles, chemical composition, and optical behavior in the 200-900nm range), and finally investigates the following items: what are the key questions still remaining?; how to answer them?
Aerosols↗
Solid organic matter in the atmosphere and on the surface of outer Solar System bodies.
Many bodies in the outer Solar System display the presence of low albedo materials. These materials, evident on the surface of asteroids, comets, Kuiper Belt objects and their intermediate evolutionary step, Centaurs, are related to macromolecular carbon bearing materials such as polycyclic aromatic hydrocarbons and organic materials such as methanol and related light hydrocarbons, embedded in a dark, refractory, photoprocessed matrix. Many planetary rings and satellites around the outer gaseous planets display such component materials. One example, Saturn's largest satellite, Titan, whose atmosphere is comprised of around 90% molecular nitrogen N2 and less than 10% methane CH4, displays this kind of low reflectivity material in its atmospheric haze. These materials were first recorded during the Voyager 1 and 2 flybys of Titan and showed up as an optically thick pinkish orange haze layer. These materials are broadly classified into a chemical group whose laboratory analogs are termed "tholins", after the Greek word for "muddy". Their analogs are produced in the laboratory via the irradiation of gas mixtures and ice mixtures by radiation simulating Solar ultraviolet (UV) photons or keV charged particles simulating particles trapped in Saturn's magnetosphere. Fair analogs of Titan tholin are produced by bombarding a 9:1 mixture of N2:CH4 with charged particles and its match to observations of both the spectrum and scattering properties of the Titan haze is very good over a wide range of wavelengths. In this paper, we describe the historical background of laboratory research on this kind of organic matter and how our laboratory investigations of Titan tholin compare. We comment on the probable existence of polycyclic aromatic hydrocarbons in the Titan Haze and how biological and nonbiological racemic amino acids produced from the acid hydrolysis of Titan tholins make these complex organic compounds prime candidates in the evolution of terrestrial life and extraterrestrial life in our own Solar System and beyond. Finally, we also compare the spectrum and scattering properties of our resulting tholin mixtures with those observed on Centaur 5145 Pholus and the dark hemisphere of Saturn's satellite Iapetus in order to demonstrate the widespread distribution of similar organics throughout the Solar System.
Ammonia↗
Circular polarisation in star-forming regions: possible implications for homochirality.
Our discovery of high degrees of circular polarisation in some star-forming regions provides an attractive mechanism for the origin of homochirality. The largest degrees of circular polarisation, so far observed at near-infrared wavelengths, are thought to arise from the scattering of stellar radiation from aligned dust grains and are calculated to extend down to UV wavelengths. The extent of the region where circularly polarised light (CPL) of a single handedness originates is very large, and it is likely that the whole of a planetary system would see a single handedness of CPL also. We present the observational data, models of the scattering that leads to the production of CPL, and a model for the origin of homochirality. We also discuss briefly future laboratory and space-based experiments.
Astronomical Phenomena↗
Conception of the 'Chirality-Experiment' on ESA's mission ROSETTA to comet P46/Wirtanen.
In the last years extraterrestrial scenarios for the origin of homochirality in biological structures received considerable attention in the topical literature: Rubenstein and Bonner postulated a rapidly rotating neutron star emitting circularly polarised synchrotron radiation responsible for the first asymmetric synthesis; the group of Bailey published the observation of circular polarisation caused by Mie scattering from aligned dust grains in the Orion OMC-1 star-formation region that might provide an enantioselective effect on prochiral or racemic organic molecules. Rikken and Raupach observed a magnetochiral effect and considered extraterrestrial magnetic fields of sufficient strengths to introduce biomoleculars parity violation. With the aim to investigate these hypotheses among other theories describing the origin of biological asymmetry, our laboratory participates in the conception and development of ROSETTA's COSAC Experiment, that is designed to identify organic molecules in the cometary matter in situ. Within COSAC's 'Chirality Module' enantiomers will be separated gas chromatographically with the help of capillary columns coated with chirally active liquid films. This technique will allow the separation of specific chiral organic compounds out of the analysed cometary matter into their enantiomeric constituents. Both thermo conductivity and mass spectrometric detectors will be used to determine each enantiomer's amount and therefore the corresponding enantiomeric excesses. As a consequence of COSAC's 'Chirality-Experiment' far-reaching results are expected to investigate the various hypotheses about the first asymmetric synthesis.
Astronomy↗
Simulated cometary matter as a test for enantiomer separating chromatography for use on comet 46P/Wirtanen.
The Cometary Sampling and Composition Experiment on board of European Space Agency's cornerstone mission ROSETTA is designed to identify organic molecules in cometary matter in situ by a combined pyrolysis gas chromatographic and mass spectrometric technique. Its capillary columns coated with chiral stationary phases received considerable attention, because they are designed for separations of non-complex enantiomers to allow the determination of enantiomeric ratios of cometary chiral organic compounds and consequently to provide information about the origin of molecular parity violation in biomolecules. To get gas chromatographic access to organic compounds on the comet, where macromolecules and complex organic polymers of low volatility are expected to make up the main organic ingredients, the combination of two injection techniques will be applied. The pyrolysis technique performed by heating cometary samples stepwise to defined temperatures in specific ovens resulting in thermochemolysis reactions of polymers and a chemical derivatization technique, in which the reagent dimethylformamide dimethylacetal assists pyrolysis derivatization reactions in producing methyl esters of polar monomers. The combination of the reagent assisted pyrolysis gas chromatographic technique with enantiomer separating chromatography was tested with laboratory-produced simulated cometary matter.
Ammonia↗