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PubMed2002

Studying marine microorganisms from space.

Microorganisms are but a few micrometers in diameter and are not visible to the naked eye. Yet, the large numbers of microorganisms present in the oceans and the global impact of their activities make it possible to observe them from space. Here a few examples of how microorganisms can be studied from satellites are presented. The first case is the best known: the main pigment used in photosynthesis (chlorophyll a) can be determined from satellites. These kinds of studies have contributed a tremendous amount of understanding about the distribution and dynamics of primary production in the oceans. Two other examples will concern analysis of heterotrophic prokaryotic production and estimates of dimethyl sulfide (DMS) concentration and flux to the atmosphere. These three processes are of fundamental importance for the functioning of the biosphere. Marine microbes carry out about half of the total primary production in the planet. A substantial fraction of the respiration in the oceans is due to the activity of heterotrophic prokaryotes. Finally, the flux of DMS to the atmosphere is believed to constitute one of the mechanisms by which the biota can regulate climate. The global implications of microbial processes in the oceans can only be addressed with the help of satellites.

Chlorophyll↗
PubMed2005

Production of low molecular weight hydrocarbons by volcanic eruptions on early Mars.

Methane and other larger hydrocarbons have been proposed as possible greenhouse gases on early Mars. In this work we explore if volcanic processes may have been a source for such molecules based on theoretical and experimental considerations. Geologic evidence and numerical simulations indicate that explosive volcanism was widely distributed throughout Mars. Volcanic lightning is typically produced in such explosive volcanism. Therefore this geologic setting was studied to determine if lightning could be a source for hydrocarbons in volcanic plumes. Volcanic lightning was simulated by focusing a high-energy infrared laser beam inside of a Pyrex reactor that contained the proposed volcanic gas mixture composed of 64% CH(4), 24% H(2), 10% H(2)O and 2% N(2), according to an accretion model and the nitrogen content measured in Martian meteorites. The analysis of products was performed by gas chromatography coupled to infrared and mass spectroscopy. Eleven hydrocarbons were identified among the products, of which acetylene (C(2)H(2)) was the most abundant. A thermochemical model was used to determine which hydrocarbons could arise only from volcanic heat. In this case, acetylene and ethylene are formed at magmatic temperatures. Our results indicate that explosive volcanism may have injected into the atmosphere of early Mars approximately 6 x 10(12) g yr(-1) of acetylene, and approximately 2 x 10(12) g yr(-1) of 1,3-butadiyne, both produced by volcanic lightning, approximately 5 x 10(11) g yr(-1) of ethylene produced by volcanic heat, and 10(13) g yr(-1) of methane.

Evolution, Chemical↗
PubMed2006

Early inner solar system impactors: physical properties of comet nuclei and dust particles revisited.

During the epoch of early bombardment, terrestrial planets have been heavily impacted by cometary nuclei and cometary dust particles progressively injected in the interplanetary medium. Stardust and Deep Impact missions confirm that the nuclei are porous, loosely consolidated objects, with densities below 1,000 kg m(-3), and that they often release small fragments of ices and dust. Recent numerical simulations of the light scattering properties of cometary dust particles indicate that they are highly porous, most likely fractal, and rich in absorbing organics compounds (with a mixture ratio of e.g. 33 to 60% in mass for comet Hale-Bopp). Taking into account the fact that porous structures survive more easily than compact ones during atmospheric entry, such results reinforce the scenario of the early terrestrial planets enrichment--in organics needed for life to originate--by comets.

Cosmic Dust↗
PubMed2006

Astrobiology and biological chirality.

The emerging discipline of astrobiology could gain valuable support from research dealing with the problems of biological chirality. The most profitable fields of common interest are: (a) living organisms under extraterrestrial conditions, (b) extraterrestrial signatures of life and (c) origin(s) of biological chirality. These areas of complementary and overlapping fields are analysed on the basis of selected references.

Astronomy↗
PubMed2006

Galileo Avionica's technologies and instruments for planetary exploration.

Several missions for planetary exploration, including comets and asteroids, are ongoing or planned by the European Space Agencies: Rosetta, Venus Express, Bepi Colombo, Dawn, Aurora and all Mars Programme (in its past and next missions) are good examples. The satisfaction of the scientific request for the mentioned programmes calls for the development of new instruments and facilities devoted to investigate the body (planet, asteroid or comet) both remotely and by in situ measurements. The paper is an overview of some instruments for remote sensing and in situ planetary exploration already developed or under study by Galileo Avionica Space & Electro-Optics B.U. (in the following shortened as Galileo Avionica) for both the Italian Space Agency (ASI) and for the European Space Agency (ESA). Main technologies and specifications are outlined; for more detailed information please refer to Galileo Avionica's web-site at: http://www.galileoavionica.com .

Astronomy↗
PubMed2006

Characterizing extrasolar terrestrial planets with reflected, emitted and transmitted spectra.

NASA and ESA are planning missions to directly detect and characterize terrestrial planets outside our solar system (nominally NASA-Terrestrial Planet Finder and ESA-DARWIN missions). These missions will provide our first opportunity to spectroscopically study the global characteristics of those planets, and search for signs of habitability and life. We have used spatially and spectrally-resolved models to explore the observational sensitivity to changes in atmospheric and surface properties, and the detectability of surface biosignatures, in the globally averaged spectra and light-curves of the Earth. Atmospheric signatures of Earth-size exoplanets might be detected, in a near future, by stellar occultation as well. Detectability depends on planet's size, atmospheric composition, cloud cover and stellar type. According to our simulations, Earth's land vegetation signature (red-edge) is potentially visible in the disk-averaged spectra, even with cloud cover, and when the signal is averaged over the daily time scale. Marine vegetation is far more difficult to detect. We explored also the detectability of an exo-vegetation responsible for producing a signature that is red-shifted with respect to the Earth vegetation's one.

Astronomy↗
PubMed2006

Studies of biominerals relevant to the search for life on Mars.

The evidence of the water erosion on Mars is particularly interesting since present climatic conditions are such that liquid water cannot exist at the surface. But, if water was present on the planet in the past, there may have been life, too. Since the discovery of carbonates on Mars also may have very important implications on the possibility that life developed there, we are studying minerals that can have biotic or abiotic origin: calcite (CaCO(3)) and aragonite, a metastable state of calcite.We have analysed biomineral aragonite, in the form of recent sea shells, as well as crystals of mineral aragonite. Infrared spectroscopy in the 2-25 mum wavelength range reveals that, after thermal processing, the biotic samples have a different spectral behaviour from the abiotic ones. As a result, it is possible to distinguish abiotic mineral aragonite from aragonite of recent biological origin.Obviously, if life existed in the past on the Red Planet, we could expect to find "ancient" biotic carbonates, which should therefore be investigated, in order to search for a way of discriminating them from abiotic minerals. For this reason, at the beginning we have considered samples of crushed fossil shells of aragonite composition. Afterwards, in order to take into account that fossilization processes almost always produce a transformation of metastable form (aragonite) into more stable form (calcite), we also studied samples of mineral calcite and different types of fossils completely transformed into calcite. All these biotic fossil samples show the same spectral behaviour as the fresh biotic material after thermal annealing at 485 degrees C. Instead, the calcite behaves like abiotic aragonite.Furthermore, it is known that seashells and other biominerals are formed through an intimate association of inorganic materials with organic macromolecules. The macromolecules control the nucleation, structure, morphology, crystal orientation and spatial confinement of the inorganic phase: this differentiates biominerals from minerals. Analysing the aragonite or calcite fossils with a Scanning Electron Microscope, we found that the fossilization process did not modify the structure of the biominerals which maintain their microscopic characteristics. Looking at the morphology of fossil biominerals, it is evident that the crystals are arranged in complex architectures compared with the compact structure of the mineral crystals. In conclusion, the properties and structure of the biominerals are different from those of the minerals. The rapid increase of the crystalline structure developed under biotic conditions makes these minerals less resistant to thermal treatments, compared with samples of abiotic origin. This result holds both for recent shells as well as all fossil samples. The spectroscopic behaviour of all analysed calcium carbonates of biotic origin is different from that of the abiotic one. Therefore, the infrared spectroscopy is a valid technique to discern the origin of the samples and a powerful tool for analysing in-situ and "sample-return" Mars missions specimens. Also Optical and Scanning Electron Microscopy can be useful to support this type of studies.

Calcium Carbonate↗
PubMed2007

The role of supernova neutrinos on molecular homochirality.

Electroweak parity violating interaction between supernova (SN) neutrinos and electrons of a simple chiral molecule is studied related to the origin of molecular homochirality. Appearance of supernova remnants inside molecular clouds favours the interaction of SN-neutrinos with interstellar molecules, leading to a energetic difference between the two enantiomers of the order of 10(-5) eV. This energetic difference is closer to the thermic energy of the interstellar medium, so molecular homochirality could be enhanced in molecular clouds containing supernova remnants inside it due to neutrino interaction.

Elementary Particles↗
PubMed2004

Eight-dimensional methodology for innovative thinking about the case and ethics of the Mount Graham, Large Binocular Telescope project.

This paper introduces the Eight Dimensional Methodology for Innovative Thinking (the Eight Dimensional Methodology), for innovative problem solving, as a unified approach to case analysis that builds on comprehensive problem solving knowledge from industry, business, marketing, math, science, engineering, technology, arts, and daily life. It is designed to stimulate innovation by quickly generating unique "out of the box" unexpected and high quality solutions. It gives new insights and thinking strategies to solve everyday problems faced in the workplace, by helping decision makers to see otherwise obscure alternatives and solutions. Daniel Raviv, the engineer who developed the Eight Dimensional Methodology, and paper co-author, technology ethicist Rosalyn Berne, suggest that this tool can be especially useful in identifying solutions and alternatives for particular problems of engineering, and for the ethical challenges which arise with them. First, the Eight Dimensional Methodology helps to elucidate how what may appear to be a basic engineering problem also has ethical dimensions. In addition, it offers to the engineer a methodology for penetrating and seeing new dimensions of those problems. To demonstrate the effectiveness of the Eight Dimensional Methodology as an analytical tool for thinking about ethical challenges to engineering, the paper presents the case of the construction of the Large Binocular Telescope (LBT) on Mount Graham in Arizona. Analysis of the case offers to decision makers the use of the Eight Dimensional Methodology in considering alternative solutions for how they can proceed in their goals of exploring space. It then follows that same process through the second stage of exploring the ethics of each of those different solutions. The LBT project pools resources from an international partnership of universities and research institutes for the construction and maintenance of a highly sophisticated, powerful new telescope. It will soon mark the erection of the world's largest and most powerful optical telescope, designed to see fine detail otherwise visible only from space. It also represents a controversial engineering project that is being undertaken on land considered to be sacred by the local, native Apache people. As presented, the case features the University of Virginia, and its challenges in consideration of whether and how to join the LBT project consortium.

Arizona↗
PubMed1994

Gas chromatographic column for the storage of sample profiles.

The concept of a sample retention column that preserves the true time profile of an analyte of interest is studied. This storage system allows for the detection to be done at convenient times, as opposed to the nearly continuous monitoring that is required by other systems to preserve a sample time profile. The sample storage column is essentially a gas chromatography column, although its use is not the separation of sample components. The functions of the storage column are the selective isolation of the component of interest from the rest of the components present in the sample and the storage of this component as a function of time. Using octane as a test substance, the sample storage system was optimized with respect to such parameters as storage and readout temperature, flow rate through the storage column, column efficiency and storage time. A 3-h sample profile was collected and stored at 30 degrees C for 20 h. The profile was then retrieved, essentially intact, in 5 min at 130 degrees C.

Atmosphere↗
PubMed1986

A priori predictions of the rotational constants for protonated formaldehyde and protonated methanol.

Protonated formaldehyde and protonated methanol are candidate interstellar molecules and models for classes of protonated oxygen compounds. Ab initio molecular orbital theory has been used to compute rotational constants to guide spectroscopic searches both in the laboratory and in space. The ab initio results are empirically corrected to account for systematic deficiencies in the theory and zero-point vibrational effects; they are expected to be accurate to approximately +/-2%. For H2COH+ the resultant constants are (in GHz) A = 194.3, B = 34.28, and C = 29.14; for H3COH2+ A = 103.7, B = 21.18, and C = 20.30.

Astronomical Phenomena↗
PubMed1987

Deuterium hyperfine structure in interstellar C3HD.

The deuterium nuclear quadrupole hyperfine structure of the transition 1(10)-1(01) of the ring molecule cyclopropenylidene-d1 (C3HD) has been observed in emission from interstellar molecular clouds. The narrowest linewidths (approximately 7 kHz) so far observed are in the cloud L1498. The derived D coupling constants Xzz = 186.9(1.4) kHz, eta=0.063(18) agree well with correlations based on other molecules.

Astronomical Phenomena↗
PubMed1989

A priori predictions of the rotational constants for HC13N, HC15N, C5O.

Ab initio molecular orbital theory is used to estimate the rotational constant for several carbon-chain molecules that are candidates for discovery in interstellar space. These estimated rotational constants can be used in laboratory or astronomical searches for the molecules. The rotational constant for HC13N is estimated to be 0.1073 +/- 0.0002 GHz and its dipole moment 5.4 D. The rotational constant for HC15N is estimated to be 0.0724 GHz, with a somewhat larger uncertainty. The rotational constant of C5O is estimated to be 1.360 +/- 2% GHz and its dipole moment 4.4. D.

Carbon↗
PubMed1991

Ab initio study of C + H3+ reactions.

The reaction C + H3+ --> CH(+) + H2 is frequently used in models of dense interstellar cloud chemistry with the assumption that it is fast, i.e. there are no potential energy barriers inhibiting it. Ab initio molecular orbital study of the triplet CH3+ potential energy surface (triplet because the reactant carbon atom is a ground state triplet) supports this hypothesis. The reaction product is 3 pi CH+; the reaction is to exothermic even though the product is not in its electronic ground state. No path has been found on the potential energy surface for C + H3+ --> CH2(+) + H reaction.

Astronomical Phenomena↗
PubMed1992

Ab initio predictions on the rotational spectra of carbon-chain carbene molecules.

We predict rotational constants for the carbon-chain molecules H2C=(C=)nC, n=3-8, using ab initio computations, observed values for the earlier members in the series, H2CCC and H2CCCC with n=1 and 2, and empirical geometry corrections derived from comparison of computation and experiment on related molecules. H2CCC and H2CCCC have already been observed by radioastronomy; higher members in the series, because of their large dipole moments, which we have calculated, are candidates for astronomical searches. Our predictions can guide searches and assist in both astronomical and laboratory detection.

Astronomical Phenomena↗
PubMed1991

Correlated Si isotope anomalies and large 13C enrichments in a family of exotic SiC grains.

A suite of morphologically distinctive silicon carbide (SiC) grains from the Orgueil and Murchison carbonaceous chondrite meteorites contains Si and C of highly anomalous isotopic composition. All of the SiC grains in this suite are characterized by a distinctive platy morphology and roughly developed hexagonal crystal forms that allow them to be distinguished from other types of SiC found in the host meteorites. The delta 29Si and delta 30Si values of individual SiC crystals deviate from those of normal solar material by more than 100%, while the delta 13C values range from 150 to 5200%. Isotopically normal C and Si are not found in any of these SiC crystals. The SiC grains belonging to this morphological suite are isotopically distinct from fine-grained SiC aggregates and other morphological types of SiC in unequilibrated meteorites. The 29Si/28Si and 30Si/28Si ratios of these platy grains are well correlated and define a linear array that does not pass through the composition of normal, solar Si. This behavior contrasts sharply with the diverse and poorly correlated Si isotopic compositions shown by the total SiC population. We suggest that the distinctive morphological characteristics and comparatively simple Si isotope systematics identify the platy SiC crystals as a genetically related family, formed around a single, isotopically heterogeneous presolar star or an association of related stars. The enrichments in 13C and the Si isotope systematics of the platy SiC are broadly consistent with theoretical models of nucleosynthesis in low-mass, carbon stars on the asymptotic giant branch. The Si isotope array most plausibly reflects mixing between 28Si-rich material, inherited from a previous generation of stars, and material enriched in 29Si and 30Si, produced in intershell regions by neutron capture during He-burning. 13C is also produced in intershell regions by proton reactions on 12C seed nuclei and is carried with s-process nuclei to the stellar envelope by convection which penetrates down to the He shell. The absence of a correlation between the Si and C isotopic compositions of the SiC suggests either episodic condensation of SiC, extending over several thermal pulses, in the atmosphere of a single star, or derivation of the SiC from several stars characterized by different rates of 13C production. In the multiple star scenario, the linear correlation of the 29Si/28Si and 30Si/28Si ratios among the platy SiC indicates that these stars evolved from a common Si seed composition under similar conditions of neutron-capture nucleosynthesis. The 29Si/30Si ratio of the SiC, inferred by us to be produced by neutron capture in the stellar interior, is distinct from values calculated from models of nucleosynthesis in AGB stars.

Astronomical Phenomena↗
PubMed1990

Aliphatic hydrocarbons of the Murchison meteorite.

The indigenous organic compounds of carbonaceous chondrites have been difficult to characterize because of problems arising from terrestrial contamination. The fall of the Murchison meteorite (CM2) provided pristine samples which allowed the resolution of some prior ambiguities as, for example, in the case of the amino acids. However, the nature of the aliphatic hydrocarbons has remained unclear. Shortly after the Murchison fall, one laboratory found them to be mainly cycloalkanes; another found, in order of abundance, branched alkanes, olefins, and cycloalkanes; while a third reported predominantly n-alkanes followed by methyl alkanes and olefins. We have reinvestigated this question using benzene-methanol as the extraction solvent, silica-gel chromatography for fractionation of the extract, and GC-MS, and IR and NMR spectroscopic techniques for the analyses. When interior samples were obtained and the analyses carried out under conditions that minimized environmental contaminants, we have found the principal aliphatic components of the Murchison meteorite to be a structurally diverse suite of C15 to C30 branched alkyl-substituted mono-, di-, and tricyclic alkanes. Comparative analyses were carried out on the Murray (CM2), Allende (CV3), and New Concord (L6) chondrites that illustrate the nature of the contamination problem encountered with carbonaceous chondrites.

Alkanes↗