bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photochemical Evolution of Interstellar/Precometary Organic Material
Authors: Allamandola Louis J. , Bernstein Max P. , Sandford Scott A. 
Published: July 2016

AbstractInfrared observations, combined with realistic laboratory simulations, have revolutionized our understanding of interstellar ice and dust, the building blocks of comets. Since comets are thought to be a major source of the volatiles on the primative earth, their organic inventory is of central importance to questions concerning the origin of life. Ices in molecular clouds contain the very simple molecules H2O, CH3OH, CO, CO2, CH4, H2, and probably some NH3and H2CO, as well as more complex species including nitriles, ketones, and esters. The evidence for these, as well as carbonrich materials such as polycyclic aromatic hydrocarbons (PAHs), microdiamonds, and amorphous carbon is briefly reviewed. This is followed by a detailed summary of interstellar/precometary ice photochemical evolution based on laboratory studies of realistic polar ice analogs. Ultraviolet photolysis of these ices produces H2, H2CO, CO2, CO, CH4, HCO, and the moderately complex organic molecules: CH3CH2OH (ethanol), HC(= O)NH2(formamide), CH3C(= O)NH2(acetamide), R-CN (nitriles), and hexamethylenetetramine (HMT, C6H12N4), as well as more complex species including polyoxymethylene and related species (POMs), amides, and ketones. The ready formation of these organic species from simple starting mixtures, the ice chemistry that ensues when these ices are mildly warmed, plus the observation that the more complex refractory photoproducts show lipid-like behavior and readily self organize into droplets upon exposure to liquid water suggest that comets may have played an important role in the origin of life.
Infrared Signatures of Prebiology - or Biology?
Authors: Wickramasinghe Nalin C. , Hoyle Fred , Al-Mufti Shirwan , Wallis Daryl H. 
Published: July 2016

AbstractData on infrared spectra of astronomical sources and on the unidentified infrared bands is reviewed and compared with a range of predictions from organic models of interstellar grains. The best fits to a wide range of data appear to require the widespread occurrence of functional groups distributed in exactly the proportions that characterise biosystems. The question of whether these agreements are consistent with extraterrestrial prebiology, or even cosmic biology is discussed.
Interaction of Energetic Particles with Extraterrestrial Ice
Authors: Pirronello Valerio 
Published: July 2016

AbstractThe interaction of energetic particles with ice mixtures can induce important chemical effects. Such interactions occur in several environments in space and may produce complex prebiotic molecules whose formation may help to shed some light on the fascinating problem of the origin of life in our Universe. Experimental work performed by several groups to simulate as closely as possible conditions and processes occurring in extraterrestrial scenarios is reported. Special attention is paid to applications of the results of laboratory investigations to interstellar and cometary environments.
Comets and Life on the Primitive Earth
Authors: Orò Juan , Cosmovici Cristiano B. 
Published: July 2016

AbstractComets may have contributed substantial amounts of water, volatiles and organic precursors such as HCN for the synthesis of biochemical compounds on the primitive Earth. This suggestion followed closely the prebiotic synthesis of adenine, purines and amino acids from HCN. Recent studies on the terrestrial heavy noble gases provide evidence that comets are the principal external source of Earth’s volatiles. During the encounter of comet Halley strong jets of CN, C2, C3and NH2were measured from Earth observatories, and by spacecraft mass spectrometry HCN, formaldehyde, adenine and many other organic compounds were detected, except amino acids. Obviously the latter require liquid water for their formation. Therefore upon capture of comets by the Earth, and melting of the frozen water, the synthesis of most biochemical compounds could take place readily. The detection of water, HCN and other organics of cometary origin after the impact of Comet SL-9 with Jupiter demonstrated the capability of survival of these molecules even after catastrophic events. Thus on the Earth HCN could be converted into purines, cyanacetylene, after hydration and condensation with urea, into pyrimidines, and formaldehyde into monosaccharides. In the presence of phosphates, which have been detected in cometary IDPs, nucleotides could also be synthesized. In conclusion, comets probably provided the necessary molecular precursors for the generation of life on the Earth.
Mars: was There an Ancient Eden?
Authors: Owen Tobias C. 
Published: July 2016

AbstractThe clear evidence of water erosion on the surface of Mars suggests an early climate much more clement than the present one. Using a model for the origin of inner planet atmospheres by icy planetesimal impact, it is possible to reconstruct the original volatile inventory on Mars, starting from the thin atmosphere we observe today. Evidence for cometary impact can be found in the present abundances and isotope ratios of gases in the atmosphere and in SNC meteorites. If we invoke impact erosion to account for the present excess of129Xe, we predict an early inventory equivalent to at least 7.5 bars of CO2. This reservoir of volatiles is adequate to produce a substantial greenhouse effect, provided there is some small addition of SO2(volcanoes) or reduced gases (cometary impact). Thus it seems likely that conditions on early Mars were suitable for the origin of life – biogenic elements and liquid water were present at favorable conditions of pressure and temperature. Whether life began on Mars remains an open question, receiving hints of a positive answer from recent work on one of the Martian meteorites. The implications for habitable zones around other stars include the need to have rocky planets with sufficient mass to preserve atmospheres in the face of intensive early bombardment.
Titan’s Atmosphere and Surface from Infrared Spectroscopy and Imagery
Authors: Coustenis Athena , Lellouch Emmanuel , Combes Michel , Wittemberg Renald , McKay Christopher P. , Maillard Jean-Pierre 
Published: July 2016

AbstractWe have performed observations of Titan in the near-infrared since 1991, using both spectroscopy and imagery. A higher geometric albedo is observed near the Greatest Eastern Elongation than near the Greatest Western Elongation or Conjunctions. The surface is within reach for telescopes at 1.075, 1.28, 1.6 and 2.0 micron, so we simulated Titan’s geometric albedo in order to derive the surface albedo at all longitudes. Titan’s leading hemisphere appears brighter than the trailing one by 20-25% at 1.08; 1.28 and 1.6 μm, and by 35% at 2.0 μm, with spectra compatible with H2O everywhere. We have then simulated the presence of a mountain on Titan covering 50% of the leading hemisphere disk, varying its height and introducing a higher surface albedo when required. We find that a relief can not reproduce the whole geometric albedo differences observed between the two hemispheres. Some other additional component bright at 1.0 and 2.0 μm must then be invoked. Candidates are tholins or CH4, which can exist on the top of a mountain if the temperature is lower than 90 K.
Missions to Mars: an Overview and a Perspective at the Turn of the Century
Authors: Marov Mikhail Ya. 
Published: July 2016

AbstractThe principal objectives of Mars exploration and their potential benefits involve many problems of scientific importance, technological developments and the general trend for future human settlements beyond the Earth. The comparative planetology approach emphasizes Mars and Venus as two extreme models of the climate evolution on the inner planets which are of great ecological importance. The climatic history of Mars is of particular interest because of the implications for life and global change on the Earth. The origin of life on the early Earth can also be related to the similar conditions on the two planets during the early phase of Solar system evolution. Mars has been central to the space programs of the former USSR and USA since the beginning of the space age, the most successful being the two Viking mission in 1976. These robotic missions, representing a period of baseline data collection, significantly expanded our knowledge but also gave rise to many new important questions. Dramatic shortfalls in the funding of space programs changed a short period of excitement culminating in the proclaimed human mission to Mars when the Cold War was over. A new strategy for planetary exploration (the «faster-cheaper-better» concept) tends to modify the former programs significantly. This new strategy at the turn of the century which, projected into the new millenium, strictly confines the targets in the Solar system and specifically Mars exploration. Nonetheless, it represents a challenge for the launch of capable small missions with significant scientific returns. Human flight and Mars settlement, while being considered as a milestone in the history of humankind and a multifaced endeavour, would require, however, a great investment of international resources.
Resolving the Continuum Emission from Disks around Ttauri Stars
Authors: Welch William Jack , Mundy Lee , Looney Leslie 
Published: July 2016

AbstractWe report recent observations at millimeter wavelengths in which we have been able to resolve the continuum emission from the proto-stars HLTau and L1551/LRS5. Baselines of over one kilometer have been recently added to the BIMA array, enabling angular resolutions of better than 0.5 arcsecond at 2.7 mm wavelength. Using this new resolution, we have been able to image the continuum from HLTau and L1551/IRS5, finding a disk of radius of the order of 100 AU for HLTau and a binary of about 45AU separation for L1551/IRS5.
Natural Masers and Lasers and Bioastronomy
Authors: Strelnitski Vladimir , Mazeh Tsevi 
Published: July 2016

AbstractWe discuss three possible applications of natural masers and lasers interesting to bioastronomy: 1) the study of protoplanetary circumstellar disks, 2) the study of extrasolar planets, 3) interstellar communications. Masers and lasers in hydrogen recombination lines are observed from the circumstellar disk of a massive star MWC349 A and serve as probes of the disk’s kinematics and structure. They give, in particular, some indications for avoidin the central (R≈ 40 AU) part of the disk, which may be caused by a forming planetary system. We demonstrate that masers (but not lasers) in molecular lines from the atmospheres of the recently discovered extrasolar planets on close orbits around their suns (51 Peg, τ Boo) can be detectable with theexisting ground-basedradioastronomical facilities. The importance of such a detection solicits a deeper analysis of general properties of the planetary masing and lasing and an analysis of the candidate lines to be searched. We argue against the use ofnaturallasers for SETI.
The Origin of Biological Information
Authors: Eigen Manfred 
Published: July 2016

What is the distinguishing feature of a living system that singularizes it from every non-living chemical ensemble, regardless of the extent of the complexity? The differentiable characteristic of the living system is information. Information assures the controlled reproduction of all the constituents, thereby ensuring the conservation of viability. Information – unlike energy – is not subject to a conservation law. Hence the fundamental question behind the origin of life is: How can information originate?Information theory, which was pioneered by Claude Shannon, cannot answer this question: this theory is most successful in dealing with problems of coding and transmission. In principle, the answer was formulated 130 years ago by Charles Darwin: The information that is unique for life evolves by virtue of natural selection. Today we can be more specific: natural selection is a non-equilibrium process. It is an inherent consequence of mutagenous self-replication at several levels of organization: for instance it is evident in molecules such as nucleic acids, in molecular complexes such as viruses and in autonomous formes of life such as micro- or higher organisms. New physical concepts have been introduced in order to deal quantitatively with the dynamics of the molecular generation of genetic information. They provide a physical foundation for Darwinian behaviour, yet they introduce major modifications in its interpretation. The lecture deals with these physical concepts, such as «sequence space», «quasi-species» and «hypercycles» and will scrutinize their adequacy for rationalizing experimental results obtained with molecular model systems and with viruses under natural conditions. Elucidating the principles of molecular self-organization has made possible to construct automated machines that make it possible for genetic information to evolve under controlled conditions in an abridged time scale.
Panspermina Revisited: Astrophysical and Biological Constraints
Authors: Wesson Paul S. , Secker Jeff , Lepock James R. 
Published: July 2016

AbstractWe have carried out a series of calculations involving bacteria and viruses embedded in dust grains that are ejected from our solar system by radiation pressure, and travel through space to other star systems. Under many conditions, this kind of panspermia is impractical, mainly because the ultraviolet radiation of the present Sun kills the micro-organisms. However, if the organisms are shielded by an absorbing material like carbon and if ejection takes place in the late-Sun (red giant) phase, there is a significant probability that these micro-organisms can reach another star system alive. In addition to panspermia with living micro-organisms, we note that it is possible to seed the Galaxy with dead ones, whose DNA fragments might provide the initial information necessary to start biological evolution in favorable environments.
Brain-Behavior Relations in Primates and Cetaceans: Implications for the Ubiquity of Factors Leading to the Evolution of Complex Intelligence
Authors: Marino Lori 
Published: July 2016

AbstractThis paper describes the results of a project aimed at addressing questions about the evolution of intelligence by utilizing comparisons of brain-behavior relations in cetaceans (dolphins and whales) and primates. Three specific questions were asked. First, have any cetaceans reached a hominid level of encephalization? Second, are cetacean-primate comparisons of brain organization useful for grappling with the differences that are bound to exist between any extraterrestrial organism and ourselves? Third, are there similarities in brain-behavior relations in cetaceans and primates that suggest behavioral evolution is shaped by general factors? Brain and body weights for cetacean and primate species were collected and compared with each other and with data on brain organization and social behavior. The results revealed that a hominid level of encephalization is not unique in mammalian history. Furthermore, cetacean-primate comparisons can be useful in understanding the different ways in which information processing systems can be organized. Finally, a comparison of the relation between encephalization and social group size in primates and cetaceans preliminarily suggests that similar mental capacities can be achieved through different independent evolutionary paths and that there may be factors common to behavioral evolution in all intelligent organisms.
Project Argus and the Challenge of Real-Time All-Sky Seti
Authors: Shuch H. Paul 
Published: July 2016

AbstractProject Argus, a global effort of the non-profit SETI League, Inc., seeks to achieve continuous microwave monitoring of all four pi steradians of space, in real time. This most ambitious SETI project ever undertaken without benefit of Government support will ultimately involve 5,000 small radiotelescopes worldwide, built, maintained and operated by private individuals (primarily radio amateurs and microwave experimenters), coordinated so as to miss no likely candidate signals, and providing independent verification of any interesting signals detected. Prototype stations went into operation in 1996; full sky coverage is planned for 2001. Sensitivity and range are assessed by comparison of current capabilities to those in place at the Ohio State Radio Observatory nineteen years ago, when the so-called «Wow!» signal was detected. The «Wow!» signal serves as a convenient benchmark, even though its exact nature remains unknown. Should a similar candidate signal appear during the fully deployed phase of Project Argus, it will not evade detection. Though utilizing just a small satellite TV dish as its antenna, each station achieves range and sensitivity on a par with the Ohio State Big Ear radio telescope, circa 1977. This paper explores the technological breakthroughs which have made this level of performance possible.
Upgrade of the Mini Spectrum Analyzer
Authors: Montebugnoli Stelio , Bortolotti Claudio , Buttaccio Salvo , Cattani Alessandro , Maccaferri Andrea , Maccaferri Giuseppe , Miani Cristiano , Orfei Alessandro , Roma Mauro , Tuccari Gino , D’Amico Nicola , Grueff Gavril 
Published: July 2016

AbstractThe upgrade of the mini spectrum analyzer, built at the Medicina radiotelescope station laboratories and devoted to the Jupiter-SL9 crash on July 94, is presented. The new version of the spectrometer allows precise spectroscopy measurements and it has just been used for the Hyakutake comet observations (May 96) with very promising results. The same system could be used in small SETI activities with a possible future involvement of the Medicina/Noto antennas in this program.
Seti Space Missions
Authors: Maccone Claudio 
Published: July 2016

AbstractSETI from space is currently envisaged in three ways: i) by large space antennas orbiting the Earth that could be used for both VLBI and SETI (VSOP and RadioAstron missions), ii) by a radiotelescope inside the Saha far side Moon crater and an Earth-link antenna on the Mare Smythii near side plain. Such SETIMOON mission would require no astronaut work since a Tether, deployed in Moon orbit until the two antennas landed softly, would also be the cable connecting them. Alternatively, a data relay satellite orbiting the Earth-Moon Lagrangian pointL2would avoid the Earthlink antenna, iii) by a large space antenna put at the foci of the Sun gravitational lens: 1) for electromagnetic waves, the minimal focal distance is 550 Astronomical Units (AU) or 14 times beyond Pluto. One could use the huge radio magnifications of sources aligned to the Sun and spacecraft; 2) for gravitational waves and neutrinos, the focus lies between 22.45 and 29.59 AU (Uranus and Neptune orbits), with a flight time of less than 30 years. Two new space missions, of SETI interest if ET’s use neutrinos for communications, are proposed.
A Search for Short-Term RV Variations in Early-Type Binaries
Authors: Lehmann H. , Scholz G. , Hildebrandt G. 
Published: July 2016

AbstractWe developed a procedure to disentangle the different radial velocity variations due to orbital motion, rotation, and pulsation based on an iterative mutual subtraction of orbital and short-term contributions. The method was successfully tested on a data set of over 2200 spectra of the eclipsing β Cep star EN Lac spanning a time interval of about 90 years. We further applied the procedure to early type binaries. For the A1 III star 21 Her we found short-term variations which indicate the presence of rotationally split nonradial pulsation (NRP) modes.
RR Lyrae Stars in the Globular NGC 3201: Light Curves, Reddening, and Distance
Authors: Layden Andrew 
Published: July 2016

RR Lyrae stars (RRL) are a favourite standard candle for globular clusters and other old stellar populations, yet recent absolute magnitude calibrations, MV(RR), span more than 0.2 mag. Precise distance estimates for nearby globular clusters will eventually be available through satellite-based trigonometric parallaxes (Layden, these proceedings), thus providing a resolution to this old problem.Here, we present a progress report on our high quality time-series photometry of RRL in the nearby globular cluster NGC 3201 - the first obtained for this cluster with a CCD. The resulting light curves provide accurate intensity-mean apparent magnitudes and reddening estimates, which will in turn be used to calibrate MV(RR) once a satellite-based parallax for NGC 3201 is available.
Using SX Phœnicis Variables in M55 and Theoretical Period-Luminosity (-Colour-Metallicity) Relations for Distance Determination
Authors: Petersen J.O. , Freyhammer L.M. 
Published: July 2016

AbstractTheoretical period-luminosity and period-luminosity-colour-metallicity relations are used to give distance estimates for the globular cluster M55 from detailed data for 24 SX Phœnicis variables published recently by Pych et al. (2001). With accurate determinations of effective temperatures for the SX Phe stars application of period-luminosity-colour-metallicity relations will lead to improved distances and more secure mode identifications.
Time Series CCD Photometry of the Globular Cluster M 53
Authors: Jeon Y.-B. , Kim S.-L. , Lee H. , Lee M.G. 
Published: July 2016

AbstractThrough time-series CCD photometry of the globular cluster M 53, we have discovered eight new SX Phoenicis type stars. All the new SX Phoenicis stars are located in the blue straggler star region in the color-magnitude diagram of M 53. In addition, we have obtained light curves for 45 known RR Lyrae stars.
SX Phe Variables in Globular Clusters
Authors: Rodríguez E. , López-González M.J. 
Published: July 2016

AbstractWe have compiled an extensive and up-dated list of SX Phe-type pulsators in globular clusters. In addition, SX Phe variables discovered in the Carina dwarf galaxy and other ones probably belonging to the Sagittarius dwarf galaxy are included. This catalogue is intended to be an up-dated list of all the SX Phe stars, in globular clusters and galaxies, known until now. The stars and their most significant parameters are listed together with references to studies of individual stars and notes for a number of variables. In addition, the references on the discovery for each variable and sources for photometry are also listed. Some relevant distributions are also analysed. The analysis of metal abundances and mean periods shows that both parameters are correlated in the sense that the periods of the variables are longer as the metallicity of the stellar system is higher.
Pulsating B-Type Stars in Young Open Clusters
Authors: Pigulski A. , Kopacki G. , Kołaczkowski Z. , Jerzykiewicz M. 
Published: July 2016

AbstractDuring the last several years about a dozen young northern clusters and associations have been observed in our program of searching for B-type variables. As far as B-type pulsators are concerned, we found that (i) young northern open clusters are a few times less abundant in β Cephei stars than the southern ones, (ii) all newly discovered SPB stars seem to be monoperiodic.
Astero-Oscillometry: Gauging Stars with Oscillations
Authors: Maintz M. , Rivinius Th. , Baade D. , Štefl S. 
Published: July 2016

AbstractAstero-oscillometry is presented as a new method for deriving stellar parameters on the basis of a physical modeling of line profile variability (lpv) caused by nonradial pulsation (nrp). First applications to rapidly rotating B-type stars show that the method is able to yield reasonable stellar parameters. The radii are systematically smaller compared to those derived by conventional methods. This could be attributed to possible effects of rapid rotation on stellar evolution. Since the method requires only one or a few pulsation modes to be excited, it is ideally suited to investigating early-type stars.