664. Wilhelm und Else Heraeus-Seminar on Prebiotic Molecules in Space and Origins of Life on Earth

19 Mar 2018, 14:00 → 23 Mar 2018, 13:00 UTC

Physikzentrum Bad Honnef

How life originates is one of the outstanding questions of humankind. Different scientific communities, from astrophysicists to planetary scientists, from geochemists to biophysicists, all share the common aim of understanding how life on Earth originated and if life exists elsewhere in the Universe. Despite these common goals, it has been difficult to join forces and focus on the ‘big picture’, as different background and terminology often hinder fruitful interdisciplinary collaborations.  In this conference, we plan to bring together astrochemists working on the production of prebiotic molecules in space and their delivery to planet-forming regions; Solar System scientists working on the chemical composition of the most pristine material such as comets and primitive meteorites; the exoplanet community, in particular those working on exoplanet atmospheres; geochemists working on the primitive Earth and its conditions to host life; and biophysicists working on the very first steps that assembled pre-biotic molecules into the macromolecules used by terrestrial life.  We believe that fostering communication and interaction among the various groups is a pre-requisite to succeed in our quest on the origins of life.

In the past years there has been tremendous progress in astrochemistry, with the advent of the Atacama Large Millimeter and sub-millimeter Array (ALMA), the NOrthern Extended Millimeter Array (NOEMA), as well as on experimental and theoretical work. For example, complex organic molecules (with ≥ 6 atoms) have been detected in pre-stellar cores, branched alkyl molecules have been found close to our Galactic center, the first P-bearing molecule has been discovered in star forming regions, and the importance of gas-phase chemistry in the production of complex molecules in cold environment established. Links have been found between the deuterium and ¹⁵N fraction in interstellar clouds, around young stellar systems and that measured in comets and meteorites in our Solar System. Organic molecules found in young stellar systems have abundances similar to those measured in comets, suggesting a common mechanism in their production across the Galaxy. Glycine, important precursors of pre-biotic molecules and P-bearing species have been detected in the comet visited by Rosetta. A large number of amino acids, nucleobases and fatty acids are contained in the most pristine family of meteortites, once again suggesting important connections with early phases during the process of star and planet formation. Tremendous progress has also been made in detecting atmospheric signatures of exoplanets through spectroscopic methods, which provide important constraints on the atmospheric physical structure and chemical composition. The higher sensitivity of the future-generation telescopes, such as the James Webb Space Telescope (JWST) and the European Extremely Large Telescope (E-ELT), will revolutionize the exoplanetary research and open up new quantitative studies on planetary habitability; theoreticians are getting ready for the challenge, by providing quantitative predictions for future high sensitivity observations.

In the fields of geochemistry and biophysics, discoveries in recent years include the combination of replication and accumulation to overcome Spiegelman's survival of the shortest RNA string, sequence selection by phase transitions with DNA using non-equilibrium driving, the usage of non-equilibrium to drive polymerization of long lengths, managing a Polymerase Chain Reaction (PCR) like reaction only with an RNA ribozyme, enhanced modes of polymerization and ligation to create cofactors and ligate RNA, establishing a chemical synthesis network towards pyrimidines and amino acids from simple components in impact craters and the usage of crystallization as a mode of early purification and chiral selection.

Monday, 19 March

14:30 → 18:30 The first steps toward chemical complexity: from prestellar cores to protoplanetary disks: The first steps toward chemical complexity: from pre-stellar cores to protoplanetary disks. I.

observations, theories and experiments will be presented in this session, with the aim of linking the various steps in the process of star and planet formation and unveil the chemical evolution

14:30 Chemical processes and evolution from clouds to disks

Speaker: Ewine van Dishoeck (Leiden Observatory / MPE)

Ewine_BadHonnef_2018.pdf

15:15 Molecular complexity in star forming regions

Speaker: Arnaud Belloche (Max-Planck-Institut für Radioastronomie)

Talks Heraeus_Talk_Belloche.pdf

15:45 Forming Complex Molecules in Early Stages of Star Formation

Until recently, it was thought that the production of larger interstellar molecules proceeds by definite chemistries depending upon the physical conditions of the source. For cold and pre-stellar cores at 10 K, it was thought that ion-molecule processes dominate the large molecule chemistry and lead to the production of very unsaturated carbon-chain type species. For hot cores, it was thought that the production of more saturated, large terrestrial-like “complex” organic species (COMs) observed in the gas occurs mainly by a radical-radical grain surface chemistry that begins during the warm-up stage from pre-stellar to hot core and transfers the reaction products into the gas via thermal desorption at later stages. But recent observations, experiments, and theory have shown that this picture is hopelessly simplistic. The detection of gaseous COMs in cold and pre-stellar cores at 10 K indicates a complex picture in which these molecules are formed either in the gas-phase mainly by neutral-neutral reactions including radiative association, or on and in ice mantles by a variety of surface processes, some quite unusual, and then undergo non-thermal desorption into the gas. The exotic processes can occur via non-thermal mechanisms or via three-body mechanisms in which a collision on the surface activates a molecule to react with another species. The formation of COMs in warming cores by surface radical-radical association reactions has come under some theoretical attack, which shows that surface reactions are more complex than thought, and that some surface association reactions don’t occur or occur very slowly. On the other hand, assumed reductions of barriers against diffusion for surface reactions have led to enhanced reaction rates for association reactions on surfaces. Moreover, new extensions of ion-molecule theory to higher temperatures have been reported, in which thermal or non-thermal desorption leads to gas-phase species, which can be precursors to new sets of reactions. Examples of precursor molecules are (1) methane, which can lead to a gaseous warm carbon-chain chemistry (WCCC), leading to the production of C7H among other unsaturated hydrocarbons, and (2) ammonia, which can enhance the synthetic capability of ion-molecule reactions by reacting with molecular ions to produce NH4+ and neutrals significantly larger than those produced by dissociative recombinations with electrons. This latter mechanism is based on the premise that large abundances of ammonia can be desorbed into the gas via accretion shocks during warm-up. Finally, a completely new theory of the formation of larger molecules by radiolysis of ice mantles of dust grains by cosmic rays suggests that COMs and other species can be formed in both cold and hot regions. The radiolysis theory is supported by laboratory experiments. In summary, the production and efficiency of complex molecules is currently recognized to be far more complex than considered five years ago, and more work is needed to determine which of the many processes considered are dominant, if any. At least, we know that liquids are not involved, or do we?

Speaker: Prof. Eric Herbst (University of Virginia)

herbst.bad.honnef.2018.v3.pdf

16:15 Coffee break and posters

17:00 THE CHEMICAL AND PHYSICAL STRUCTURE OF THE HOT MOLECULAR CORE G31.41+0.31

The high-mass star-forming core G31.41+0.31 is one of the most chemically rich hot molecular cores in the Galaxy. In particular, the first detection outside the Galactic Center of the simplest sugar-like species, glycolaldehyde, has been obtained towards G31, and heavy complex molecules such as methyl formate, ethanol or ethylene glycol have also been observed. The chemical complexity of this core has been studied in detail by our group thanks to observations with multiple telescopes (ALMA, NOEMA, SMA, IRAM 30m, and GBT). In addition, high-angular resolution ALMA observations have allowed us to study the physical structure (temperature and density profiles) and the properties of the rotation and infall of the core. Physical and kinematical properties have been derived from complex organic molecules, including prebiotic species, which have proved to be excellent tracers to study star formation. In this contribution, I will also introduce the unbiased spectral line survey GUAPOS, to be carried out with ALMA covering the full Band 3 at 3mm.

Speaker: Maite Beltran (INAF-Osservatorio Astrofisico di Arcetri)

Beltran-Heraeus18.pdf

17:15 Carbon-chain growth in the Solar-type protocluster OMC-2 FIR4

Cyanopolyynes are carbon chains delimited at their two extremities by an atom of hydrogen and a cyano group, hence they could be excellent reservoirs of carbon. The simplest member, HC3N, is ubiquitous in the galactic interstellar medium, and it is detected also in external galaxies. Because of their potential to form (macro-)molecules of biogenic importance, understanding the growth of cyanopolyynes in regions forming stars similar to our Sun (and what affects it) is particularly relevant for pre-biotic astrochemistry. In the framework of the IRAM/NOEMA Large Program SOLIS (Seeds Of Life In Space), we have mapped the two simplest cyanopolyynes, HC3N and HC5N, in the protocluster OMC-2 FIR4, which is one of the closest and best known representatives of the environment in which the Sun may have been born. We find a HC3N/HC5N abundance ratio across the source in the range 1-30. The ratios ≤10 can be reproduced by chemical models only if the cosmic-ray ionisation rate ζ is 4 × 10-14 s-1. This large ζ is comparable to that measured in FIR4 by previous works and was interpreted as due to a flux of energetic (≥10 MeV) particles from embedded sources. A temperature gradient across FIR4 could also explain the observed change in the HC3N/HC5N line ratio, but even in this case a high constant cosmic-ray ionisation rate (of the order of 10-14 s-1) is necessary to reproduce the observations. Therefore, we find that energetic particle irradiation promotes the production of carbon chains. As irradiation was also present during the early phases of our Solar System, such energetic processes could have also promoted the production of important carbon reservoirs in the Solar Nebula. Such reservoirs could then be delivered to the early Earth to foster pre-biotic chemistry evolution.

Speaker: Francesco Fontani (INAF-Arcetri)

Fontani_BadHonnef-2018.pdf

17:30 From One to Two Dimensional Interstellar Carbon: A Synthesis of Laboratory, Observations, and Theory

In the last 50 years of astrochemical research, the realm of one-dimensional carbon chemistry (i.e. carbon chain molecules) has been well explored. Life, however, relies on two and three-dimensional carbon - branches, rings, bridges, and so forth. Here, we present the first rotational detection of a six-membered ring molecule in the interstellar medium (ISM), benzonitrile (c-C$_6$H$_5$CN), using deep Green Bank Telescope observations of TMC-1 combined with high-precision laboratory spectroscopy. We then explore the formation chemistry of this two-dimensional carbon molecule using a combined laboratory, quantum chemical, and modeling approach. We demonstrate the synthesis of cyclic species (benzene [c-C$_6$H$_6$] and benzonitrile) from simple, acyclic precursors, providing definitive evidence for facile bottom-up generation of two-dimensional carbon chemistry in the ISM. The results show that benzonitrile can already be used as a reliable proxy for the presence of benzene in the ISM, and that there may exist a much larger array of 'hidden' aromatic species just beyond the current sensitivity of spectral surveys.

Speaker: Brett McGuire (National Radio Astronomy Observatory)

Tuesday, 20 March

09:00 → 13:00 The first steps toward chemical complexity: from prestellar cores to protoplanetary disks: The first steps toward chemical complexity: from pre-stellar cores to protoplanetary disks. II.

observations, theories and experiments will be presented in this session, with the aim of linking the various steps in the process of star and planet formation and unveil the chemical evolution

09:00 Gas phase chemistry and molecular complexity: how far do they go?

Speaker: Nadia Balucani (Università degli Studi di Perugia)

09:45 Chemical Complexity in Pre-stellar Cores

Pre-stellar cores represent the initial conditions of Solar-system formation. In the past, these gravitationally collapsing condensations were believed to present a simple chemistry characterised by severe freezing-out of carbon-bearing species in their densest and coldest, innermost regions. However, thanks to the advent of higher-sensitivity instrumentation, it has become clear that pre-stellar cores show a higher level of chemical complexity as revealed by the detection of a wide variety of complex organic molecules in these objects. In this talk, I will present our recent observational work on the distribution of complex organic molecules in pre-stellar cores, and I will put them in context with respect to new theories of complex organics formation under extreme cold conditions.

Speaker: Izaskun Jimenez-Serra (Queen Mary University of London)

ijimenez-Bonn18-uploaded.pdf

10:15 Formation of interstellar complex molecules on dust grains

Speaker: Francois Dulieu (University of Cergy Pontoise)

11:30 Protostellar shocks as factories of interstellar complex organic molecules

The role of the pre-solar chemistry in the present chemical composition of the Solar System bodies is far to be understood. The molecular complexity builds up at each step of the process leading to star formation, starting from simple molecules and ending up in interstellar Complex Organic Molecules (iCOMs). It is of paramount importance to image the spatial distribution of iCOMs in order to investigate their association with different ingredients of the Sun-like star formation recipe (warm envelopes and cavities opened from hot jets, accretion disks and shocks). Thanks to the combination of the high-sensitivities and high-angular resolutions provided by the advent of new telescopes such as ALMA and NOEMA, it is now possible to image in details the earliest stages of the Sun-like star formation, thus inspecting the inner (less than 20-50 au from the driving protostar) jet. At these spatial scales a proper study of jets has to take into account also the effects connected with the accreting disk. In other words, it is time to study the protostellar jet-disk system as a whole. Shocks are precious diagnostic tools, given they enrich the gas phase with the species deposited onto the dust mantles and/or locked in the refractory dust cores. Basically, we have to deal with two kind of shocks: (i) high-velocity shocks produced by protostellar jets, and (ii) slow accretion shocks located close to the centrifugal barrier of the accretion disks. Both shocks are factories of iCOMs, which can be then efficiently used to follow both the kinematics and the chemistry of the inner protostellar systems. With this in mind, we will discuss recent results obtained in the framework of different large programs at mm and sub-mm wavelengths, such as SOLIS.

Speaker: Claudio Codella

codella_bonn18.pdf

11:45 Chemical modelling of formamide and methyl isocyanate in star-forming regions

Abstract

Comets are thought to contain relatively pristine material from the origin of the solar system, having condensed directly out of the pre-solar nebula (e.g., Mumma & Charnley 2011). It is postulated that comets may have even delivered some of the water and organic matter found on the Earth via impacts (e.g., Hartogh et al. 2011). Over 22 molecules have been identified in comets via radio observations (Crovisier et al. 2004), including organic species such as formamide (NH$_2$CHO, Biver et al. 2014). Formamide and methyl isocyanate are particularly interesting for their potential role in prebiotic chemistry (Saladino et al. 2012).
Formamide has been detected in a large variety of star-forming environments, as well as in Solar System comets, thus supporting the hypothesis that molecules with a strong prebiotic potential could have been delivered to Earth by comets after being synthesized in prestellar environments (e.g. Caselli & Ceccarelli, 2013).
Recently, methyl isocyanate (CH$_3$NCO) has been tentatively detected by the Rosetta spacecraftʼs Philae lander in the comet 67P/Churyumov–Gerasimenko (Goesmann et al. 2015). Methyl isocyanate has been detected for the first time recently towards SgrB2(N) (Halfen et al. 2015) and most recently towards Orion KL (Cernicharo et al. 2015). Finally, using all the available ALMA data, CH$_3$NCO has been detected for the first time towards a low-mass proto-star, IRAS16293$-$2422 (Martín-Doménech et al. 2017; Ligterink et al. 2017).

The chemistry of formamide and methyl isocyanate in the interstellar medium, and of its precursors, is highly uncertain. This chemistry has theoretically been explored only for massive hot cores at high temperatures (Garrod et al. 2013) but only a few modellings has been done for the chemistry of these molecules under the physical conditions found in pre-stellar cores or low-mass proto-stars. There is increased evidence that chemical processes unaccounted for in past theoretical modelling (e.g. UV photo-desorption, cosmic-ray-induced diffusion, and/or chemical reactive desorption) are required to explain the formation, and detection, of complex organics in those regions.

In this talk, I will present a detailed modelling of the chemistry of formamide and methyl isocyanate in star-forming regions such as pre-stellar cores (L1544) and hot corinos (IRAS16293$-$2422). This chemical modelling aims at fully characterising the main formation/destruction routes of these two species, establishing their expected abundances, and compare them to available observations. This study identifies their precursors and other related species, providing good molecular targets to test our models against observations. We finally use the established chemical network to predict the emission of formamide around gravitationally unstable discs, based on Smoothed Particles Hydrodynamics (SPH) simulations.

Representative figure

Final abundances as a function of time for NH$_2$CHO and two parent species for the four environments. The time-scale for which we obtain the best agreement between the modelling and observations is shown in vertical grey-scale. Observational constraints are shown in horizontal coloured area or in dashed lines for upper limits. For each source, the observed abundances are taken from the literature. Top left: IRAS 16293$-$2422 B hot corino: NH$_2$ (Hily-Blant et al. 2010), H$_2$CO (Ceccarelli et al. 2000), and NH$_2$CHO (López-Sepulcre et al. 2015). Top right: IRAS 16293$-$2422 cold envelope: same references as for the hot corino. Bottom left: L1544 core centre: NH$_3$ (Crapsi et al. 2007), H$_2$CO (Bacmann et al. 2003), and NH$_2$CHO (Jiménez-Serra et al. 2016). Bottom right: L1544 methanol peak: NH$_3$ (Crapsi et al. 2007), H$_2$CO: assumed the same as that of the core centre; NH$_2$CHO (Jiménez-Serra et al. 2016).

Speaker: Dr David Quénard (QMUL)

dquenard_Bonn.pdf

12:00 Complex molecules in PDRs and protoplanetary disks

Complex molecules are commonly detected in high- and low-mass star
forming regions. In the past years, however, complex species have been
detected in unexpected environments like photo-dominated regions
(PDRs). The great sensitivity and resolution power of ALMA has also
allowed us to start detecting and resolving complex species in
protopanetary disks.

I will show recent observations of complex organics in the
prototypical PDR, the Horsehead nebula. We detect H$_2$CO, CH$_3$OH,
HCOOH, CH$_2$CO, CH$_3$CHO, CH$_3$CCH, CH$_3$CN and HC$_3$N. We have
mapped the emission of the COMs, and find that some of them present
enhanced abundances in the UV-exposed PDR compared to the UV-shielded
dense core. This shows the importance of the interplay between the
solid and gas phase chemistry in the formation of (complex) organic
species, and confirm that ice photo-processing is an efficient
mechanism to release frozen species into the gas phase.

I will also show recent observations of complex organic molecules in
protoplanetary disks. We have detected CH$_3$CN and HC$_3$N in several
disks, and find consistent relative abundances between our disk
sample, protostellar envelopes and comets. I will also present new
spatially resolved ALMA observations of H$_2$CO, a key intermediate in
the formation of more complex species in ices. Contrary to CH$_3$OH,
H$_2$CO is readily observable in disks and could thus be used to trace
the cold organic reservoir in disks.

Speaker: viviana guzman (Joint ALMA Observatory)

12:15 The warm molecular region below the UV-shielded layer in disk atmospheres

The harsh radiation environment of disk surfaces is thought to be inhospitable to organic molecules. Indeed, the disk surface is sweltering atomic gas of several thousand Kelvin, well in excess of the dust temperature. However, as radiation is shielded by increasing column densities of dust the potential for molecules to form increases as both the photodissociation rates and temperatures decline. A critical transition occurs when the decreasing rate of molecular hydrogen destruction feeds back to the decrease in temperature and the increase in molecular line cooling. A molecular shielding layer forms that dramatically attenuates the stellar radiation. We will describe the observations that support this description of the hot molecular gas in the terrestrial-planet forming regions of disks and detail of the physical processes driving the heating. Below this hot molecular layer of species such as H$_2$, CO, H$_2$O, and OH, the organic molecules that would otherwise dissociate may form. Dust temperatures below the shielding layer are in a temperature regime that sensitvely determines the reaction rates for molecule formation. The dissipation of turbulent energy into heating the gas has the potential to dramatically increase the abundance of warm molecules in this layer. Indeed, measurements that constrain the abundance of warm prebiotic molecules may be diagnostic dynamical models of disk accretion and evolution.

Speaker: Mate Adamkovics (Clemson University)

Adamkovics.pdf

14:30 → 18:30 The Solar System: The Solar System. I.

14:30 Organics in meteorites: Interstellar, solar and/or parent body?

The most primitive meteorites, chondrites, preserve records of the prehistory and early history of our Solar System. The chondrites are composed of three basic components: chondrules and refractory inclusions set in a fine-grained matrix. Chondrules and refractory inclusions formed at high temperatures in the solar nebula. The fine-grained matrix also contains products of high temperature nebular processing, such as crystalline silicates. However, it also contains presolar circumstellar grains that formed around AGB stars and supernovae [1], as well as amorphous silicates that may include interstellar grains. The non-solar D/H of water accreted as ice by chondrites points to an interstellar contribution [2], and large D and 15N enrichments in chondritic organic material point to an interstellar or outer Solar System origin [3]. Overall, chondrites seem to have accreted ~5-10% of interstellar material in their matrices [4].

Thus, one might expect to be able to make a direct comparison between primitive meteorites and astronomical observations. However, chondrites also accreted short-lived radionuclides that internally heated their parent bodies, initially melting ices and promoting clay formation but, in many cases, temperatures subsequently became high enough to dehydrate them. This heating was necessary to lithify these cosmic sediments into ‘rocks’ that could be delivered to Earth. Unfortunately, it also has modified to varying degrees the organic material that they accreted.

The least heated chondrites contain several hundred ppm of complex suites of soluble organic compounds. The best studied of these include amino acids, amines, hydroxyl acids and carboxylic acids. These compounds exhibit almost complete structural diversity, pointing to abiotic synthesis. The dominance of alpha amino acids points to a Strecker-type synthesis involving HCN, NH3 and aldehydes/ketones. This synthesis seems to have occurred quite early as in the meteorites that experienced more extensive alteration of their silicates, amino acid abundances are much lower and carboxylic acids are much higher [5, 6], suggesting that there was progressive destruction of the amino acids. Interestingly, at the same time there appears to have been the development of up to 10-20% L enantiomer excesses in isovaline [6], one of the few more abundant amino acids that would not racemize in 4.5 billion years. Although H2, CO and CO2 would have been present in the nebula and in the meteorites, there is little evidence for the products of FTT synthesis.

The dominant organic material in chondrite matrices (up to 3-4 wt.%) is a macromolecular organic material (IOM) [3]. In bulk, its composition is similar to comet Halley CHON material and the refractory organic material in comet 67P dust [7]. It is composed of small, highly substituted aromatic moieties that are cross-linked by short, highly branched aliphatic chains and O functionality. At present, there is no consensus on how IOM formed.

It is interesting to speculate why, if many of the building block were present, life did not arise in meteorites. It may have been simply that there was insufficient time. Also, if, as some have suggested, meteorites/comets provided the prebiotic building blocks for life on Earth, it could only have been in objects that were mm-m-sized or less than a few hundred microns across. Otherwise, atmospheric entry and impact vaporization would have destroyed them. Given the low abundances of soluble organics, only if IOM was broken down by weathering on the early Earth could meteorites/comets have been potent sources of O-,N-bearing prebiotic molecules.

References:

[1] Nittler L.R. and Ciesla F. (2016) Ann. Rev. Astron. & Astrophys., 54, 53-93.

[2] Cleeves L.I. et al. (2014) Science, 345, 1590-1593.

[3] Alexander C.M.O’D. et al. (2017) Chemie der Erde - Geochem., 77, 227-256.

[4] Alexander C.M.O’D. et al. (2017) Meteorit. & Planet. Sci., 52, 1797-1821.

[5] Martins Z. et al. (2007) Meteorit. & Planet. Sci, 42, 2125-2136.

[6] Glavin D.P. et al. (2011) Meteorit. & Planet. Sci, 45, 1948-1972.

[7] Fray N. et al. (2016) Nature, 538, 72-74.

Speaker: Conel Alexander

Alexander.Bonn.2018.pdf

15:15 Prebiotic molecules in the Solar System, scenarios for the origin of life and implications for the emergence of life

Speaker: Dr Frances Westall (CNRS-CBM)

15:45 Formation of ices in the protosolar nebula and implications for the composition of outer planets

Speaker: Olivier Mousis (Aix-Marseille Université)

17:00 Interstellar ices as a source of complex organic molecules of interplanetary solar system objects

Complex organic molecules are detected in gas and solid phases of astrophysical objects. The origin of these molecules is still debated, but a large part is supposed to form at the surface of astrophysical icy grains. These icy grains that can be observed in dense molecular clouds are processed under high energetic processes (VUV photons, ions, electrons) during the star formation. Processing provides the activation of molecules initially present in these ices allowing the development of an important chemical reactivity. In some environments such as the solar nebula, these grains can be warmed releasing in the gas phase a large part of complex organic molecules initially formed at the surface or in the bulk of ice grains. The non-volatile molecules remain on the grains leading to the formation of refractory organic residues. A part of the processed grains can then accrete leading to the formation of interplanetary objects such as comets and asteroids. Therefore, some of the organic matter present in Solar System objects could originate from ices observed in the interstellar medium.
Based on laboratory experiments, we develop a strategy to investigate the potential correspondence between ices of astrophysical objects and organic molecules observed in the gas and refractory organic residues of these objects. We demonstrate the impact of the initial ice composition on the abundances of molecules observed in the gas phase as well as on the molecular composition of residues remaining after the desorption of the most volatile compounds. These information allow us to draw a first chemical link between ices observed in young stellar objects and the organic matter detected inside meteorites, daughters of interplanetary objects such as asteroids.
In addition, analyses of refractory organic residues show that prebiotic molecules such as amino acids, sugars, nucleobases and peptides are detected, which opens pathways to the development of a prebiotic chemistry on telluric planets from exogenous delivery of organic matter, depending on local environments of these planets.

References:

1. The gaseous phase as a probe of the astrophysical solid phase chemistry. N. Abou Mrad, F. Duvernay, R. Isnard, T. Chiavassa and G. Danger. The Astrophysical Journal, 2017, 846, 124
2. Photo and thermochemical evolution of astrophysical ice analogs as a source of soluble and insoluble organic materials in Solar System minor bodies. P. de Marcellus, A. Fresneau, R. Brunetto, G. Danger*, F. Duvernay, C. Meinert, U. J. Meierhenrich, F. Borondics, T. Chiavassa, L. Le Sergeant d’Hendecourt. Monthly Notices of the Royal Astronomical Society, 2017, 464, 114-120
3. Radical-induced chemistry from VUV photolysis of interstellar ice analogues containing formaldehyde. T. Butscher, F. Duvernay, G. Danger, T. Astronomy and Astrophysique, 2016, 593, A60.
4. Insight into the molecular composition of laboratory organic residues produced from interstellar/pre-cometary ice analogues using very high resolution mass spectrometry. G. Danger, A. Fresneau, N. Abou Mrad, P. de Marcellus, F.-R. Orthous-Daunay, F. Duvernay, V. Vuitton, L. Le Sergeant d’Hendecourt, R. Thissen, T. Chiavassa. Geochimica & Cosmochimica Acta, 2016, 189, 184-196.
5. Methanol ice VUV photo-processing: GC-MS analysis of volatile organic compounds. N. Abou Mrad, F. Duvernay, T. Chiavassa and G. Danger. Monthly Notices of the Royal Astronomical Society, 2016, 458, 1234-1241.
6. Characterization of interstellar/cometary organic residue analogs using very high resolution mass spectrometry, G. Danger, F-R. Orthous-Daunay, P. de Marcellus, P. Modica, V. Vuitton, F. Duvernay, L. Le Sergeant d’Hendecourt, R. Thissen, and T. Chiavassa, Geochimica & Cosmochimica Acta, 2013, 118, 184-201.

Acknowledgments

This work has been funded by the French national programs « Physique Chimie du Milieu Interstellaire » (P.C.M.I, Institut National des Sciences de l’Univers, Centre National de la Recherche Scientifique), the « Programme National de Planétologie » (P.N.P, INSU-CNRS), « Environnements Planetaires et Origines de la Vie » (E.P.O.V, CNRS), the CNES (Centre National d’Etudes Spatiales) from its exobiology program and a PhD grant from the Région Provence Alpes Côte d’Azur (PACA). This work was further supported by the ANR project RAHIIA_SSOM (Grant ANR-16-CE29-0015-01), the ANR project VAHIIA (Grant ANR-12-JS08-0001), the ANR project PeptiSystems (Grant ANR-14-CE33-0020-02) of the French Agence Nationale de la Recherche and finally the Fondation of Aix-Marseille University.

Speaker: Gregoire Danger (Aix-Marseille University)

20180312_WEHS_GDanger.pdf

17:15 Pre- and protostellar roots of cometary volatiles

Comet 67P/Churyumov–Gerasimenko has been studied with unique in situ measurements by various instruments aboard the Rosetta spacecraft. Data from ROSINA, COSAC, VIRTIS and MIRO have shown that the comet has a rich molecular inventory and that there is a complex relationship between production rates and correlations between various species. The currently available data on 67P/C-G is one of the best probes of the innate protosolar disk that evolved into our modern day Solar System. Similar chemical richness, including large complex organic species, extends beyond the Earth and our Solar System as attested by countless observations towards high- and some low-mass protostars. One of the best-studied low-mass systems is IRAS16293, which is thought to be analogous to the earlier phases of our Solar System. The region has been surveyed with the large unbiased Protostellar Interferometric Line Survey (PILS) with ALMA. This dataset has allowed this region to be studied within an unprecedentedly wide spectral range at high spectral and spatial resolutions; thereby, uncovering its full chemical inventory and the spatial distribution of the detected species. This ALMA data on IRAS16293 can be used to probe the extrasolar chemical content and the Rosetta measurements of 67P as a Solar System diagnostic. By deriving the relative ratios for simple species and complex organic molecules, direct comparisons can be drawn between the two to go after the origins of the chemical content of our Solar System. In this talk, results of such a comparative study will be presented, based on relative ratios of major and minor volatile species and the derivation of relative ratios within hierarchical families (e.g., formaldehyde, methanol and ethanol) to access the degree of relative complexity stemming from common parent species. These results give clues to the different radicals available in the ices for subsequent synthesis of larger molecules, shedding light on the dominant pathways to chemical complexity and the physical conditions that optimize such enrichment. The carried out comparative work between protostars and 67P gives hints on the uniqueness of the ingredients to life.

Speaker: Dr Maria Drozdovskaya (Center for Space and Habitability, Universität Bern)

20180320_EW-Heraeus-Seminar_Drozdovskaya.pdf

17:30 A reaction network for Chury’s chemistry

The landing of the ROSETTA module Philae in 2014 kicked up a lot of dust, figuratively as well as literally. The not-quite-as-planned landing displaced about 0.4 m³ of dust^[1], some of which ended up in the COSAC instrument^[2], where it warmed to around 20°C, releasing its volatiles. Although the COSAC instrument could never play out its full potential, it did acquire a few “sniff-mode” mass spectra of the gas in and around the lander. The mass spectrum acquired a few minutes after the first touchdown showed a large number of signals, which were attributed to 16 organic molecules, some of which had never before been detected on a comet^[2].

Due to the nature of the instrument, which was primarily a gas chromatograph, deconvolution of mass spectra containing multiple compounds is difficult, and will yield non-unique solutions. The COSAC interpretation of the results was disputed on the grounds that there are other possible solutions, which yield equal or better fits to the data^[3]. These suggestions however failed to address the problem of chemical cohesiveness, i.e. a mixture of compounds that makes sense from a chemical point of view.

Here, a chemical reaction network is proposed, that can explain why certain molecules were found on the comet, while others were not. Starting from the simple molecules water (H₂O), ammonia (NH₃), carbon monoxide (CO), and methane (CH₄), the presence of which on a comet is undisputed, a reaction network with just two basic types of reaction can explain the presence of all the molecules reported by COSAC, as well as a few molecules which were later detected by other instruments.

The reaction network is based on electron-induced chemistry, triggered by the interaction of molecules with secondary electrons. These low energy electrons typically have very large cross sections for the activation of molecules^[4], as well as being produced in vast numbers. These activated molecules or fragments can undergo subsequent chemical reactions, forming a wide variety of chemical products. These reactions can be studied in the lab, enabling the elucidation of specific reaction mechanisms, where up until recently the statistical recombination of radicals^[5] was the most often cited “mechanism” for the formation of organics in condensed phase.

References

[1] J.-P. Bibring et al. (2015) Science 349(6247):aac5116.

[2] F. Goesmann et al. (2015) Science 349(6247):aab0689.

[3] K. Altwegg et al. (2017) MNRAS 467(Suppl.2):S130-S141.

[4] E. Böhler et al. (2013) Chem. Soc. Rev. 42(24):9219-9231.

[5] C.J. Shen et al. (2004) Astron. Astrophys. 415(1):203–215.

Speaker: Jan Hendrik Bredehöft (Universität Bremen)

Wednesday, 21 March

09:00 → 13:00 The Solar System: The Solar System II.

09:00 Solar System formation and evolution: dynamical models and cosmochemical implications

Speaker: Alessandro Morbidelli (C.N.R.S.)

Hereus2018-morby-v2.pdf

09:45 Remote studies of organics in cometary comae

Speaker: Stefanie Milam (NASA/GSFC)

Milam_comets.pdf

10:15 Observations of Organic Chemistry on Titan

Speaker: Dr Steve Charnley (NASA)

11:30 Solid state chemistry driven by 1 keV electrons

Simple and complex species are expected to be formed in a variety of interstellar environments at the surface of ice grains by means of a combination of processes. Interstellar ice mantles are continuously exposed to energetic and non-energetic processing by photons, electrons, ions and atoms in different regions of the interstellar medium. Here I will focus on the chemical role of electrons on the surface ice chemistry in light of our latest laboratory results on the formation of molecules after exposure to 1 keV electron bombardment. We applied VUV, UV-vis and mid-IR absorption spectroscopy to study interstellar ices before and after irradiation. VUV and UV-vis spectra were obtained at the synchrotron facility ASTRID2 ISA, University of Aarhus, while mid-IR data was collected at the Molecular Astrophysics Lab at the Open University. Experimental results will help understanding the molecular complexity induced by the interaction of electrons and ices and will support past (e.g., Hubble Space Telescope) and future (JUICE - JUpiter ICy moons Explorer; http://sci.esa.int/juice/) astronomical missions.

Speaker: Sergio Ioppolo (Queen Mary University of London)

11:45 (Sub)millimeter Molecular Observations of Solar System Icy Worlds

The icy worlds in our Solar System (e.g. Europa, Enceladus, Ceres, Triton and Titan) possess surface organics, and possibly subsurface oceans, so are prime astrobiological targets in the search for Life. Space missions to these icy worlds have been the key to measuring their surface composition and assessing their subsurface composition through measurements of their outgassing plumes. However, the composition of the water ice and other organic and inorganic materials residing on the surfaces of these icy worlds, as well as their subsurface regions, including the putative internal oceans, can also be studied by Earth-based astronomical observations.

Among the many small icy solar-system bodies, recently water vapor from Ceres was detected by Herschel infrared space telescope and circumstantial evidence of the existence of water plumes from Europa via observations by Hubble space telescope was also reported. Ceres is the largest celestial body in Main Asteroid Belt and is also the sole dwarf planet in the inner solar system. Europa, on the other hand, is the 6th largest moon in the Solar System and the smallest Galilean moon of Jupiter. Data taken from Dawn spacecraft suggest that a subsurface layer of briny water ice, together with ammonia-rich clays, may exist on Ceres. Similar to another icy moon, Enceladus of Saturn, a global subsurface ocean was also inferred to exist below the ice crust of Europa from the diversity of surface geological features and the magnetic field measurements made by the Galileo spacecraft. We have hence observed with the 15-m James Clerk Maxwell Telescope (JCMT) and Atacama Large Millimeter/submillimeter Array (ALMA) to look for molecular emission in both Ceres’ and Europa’s exospheres. We will present preliminary results from our observations and discuss their astrobiological implications.

Speaker: Yo-Ling Chuang (National Taiwan Normal University)

12:00 Phosphorus: the missing prebiotic element… found in star-forming regions and comets

Phosphorus (P) is a key chemical biogenic element for the development of life[1,2,3,4], because P-compounds are unique to form large biomolecules such as deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), phospholipids (the structural components of all cellular membranes) and the adenosine triphosphate (ATP) molecule, from which all forms of life assume energy. Despite the critical biological importance of P, it is in remarkably short supply on Earth, which suggests a space origin of P. However, unlike other biogenic elements (C, N, O, S), P is barely detected in the interstellar medium (ISM), and thus our knowledge about P-chemistry is still poor. Our group started several projects to detect simple P-bearing molecules in space. Two complementary targets are being explored: i) parental star-forming cores, whose chemical composition could be inherited; ii) Solar System bodies, whose impact during the heavy bombardment may provide prebiotic molecules to the early Earth. In this talk, I will present the most recent results about the
study of P-bearing molecules (PO and PN) in star-forming regions[5,6] and the comet 67P/Churyumov-Gerasimenko[7]. Our analysis has allowed us to understand much better the origin of P in the ISM, and to draw a consistent thread between the chemical content of P in a primordial star-forming nebula and Solar System pristine material. These discoveries have strong implications on the highly debated predominant role of PO-based molecules (e.g., phosphates) [8,9] or PN-derivatives[10] in the supply of prebiotic species on our early Earth and consequently on the origin of life.

(References in the attached document)

Speaker: Víctor M. Rivilla (Osservatorio Astrofisico di Arcetri, OAA-INAF)

rivilla-Bad-Honeff-3.pdf

14:30 → 16:00 Exoplanets adn habitability: Exoplanets and habitability

14:30 Chemical Characterization of Extrasolar Planets

Speaker: Nikku Madhusudhan (University of Cambridge)

15:15 Dynamic and kinetic processes shaping exoplanet atmosphere chemistry

Speaker: Christiane Helling (University of St Andrews)

15:45 The chemical composition of protoplanets in a fragmenting disc

Speaker: John Ilee (Institute of Astronomy, Cambridge)

17:00 → 18:00 Poster Session

17:00 Electron-induced formation of formamide and isocyanic acid in condensed mixtures of carbon monoxide and ammonia

Formamide has been detected in many stellar and interstellar objects like the comet C/1995 O1 (Hale-Bopp),¹ in the solid phase of dust grains around the young stellar object W33A² and in the interstellar medium in general³. Formamide is proposed to be a key-molecule in the abiotic formation of important biomolecules⁴ and may be brought to planet Earth by the impact of dust particles or comets. However, there is still a debate on the formation mechanism of formamide. Observations with radio telescopes revealed that formamide and isocyanic acid have similar isotopic ratios⁵ and that their amounts correlate quiet well over a wide range of abundances⁶ suggesting that both species are chemically related to each other.
This contribution reports the electron-induced formation of formamide⁷ and isocyanic acid in condensed mixtures of CO and NH₃. The results can help to unravel the reaction mechanism leading to their formation in space since high-energy radiation of all kinds produce copious numbers of low-energy secondary electrons when interacting with condensed matter.⁸ The secondary electrons can trigger the formation of reactive species like radicals and ions by neutral dissociation (ND), dissociative electron attachment (DEA) or electron impact ionization (EI) which subsequently can react with adjacent molecules to form more complex molecules.⁸ To provide evidence for the formation of formamide and isocyanic acid upon electron exposure, we prepared multilayer films containing equal amounts of CO and NH₃ on a tantalum (Ta) substrate at cryogenic temperatures of ~30 K under UHV conditions and subsequently irradiate these films with low-energy electrons (E₀<20 eV). Formamide and isocyanic acid were identified from characteristic mass-over-charge ratios using post-irradiation thermal desorption spectrometry (TDS). Product yields of isocyanic acid and formamide show the same dependence on incident electron-energy and the amount of isocyanic acid correlates linear to the amount of formamide suggesting a common intermediate in the formation process. For the formation of formamide we recently proposed two reaction mechanisms.⁷ At energies above the ionization threshold, we proposed a mechanism triggered by EI whereas at energies below the ionization threshold we proposed a mechanism triggered by DEA.⁷ However, our current models for the formation of formamide initiated by EI or DEA do not provide a straightforward explanation for the formation of isocyanic acid. Our hypothesis is that ND to NH₃ produces a copious number of free hydrogen radicals which may react with an intermediate of the formamide production. This side reaction is favoured by the production of molecular nitrogen and may thus be very efficient. Future investigations may aim to determine ND cross sections for NH₃ which could help to verify the proposed mechanism.

References

(1) Bockelée-Morvan, D.; Lis, D.D.; Wink, J.E.; Despois,D.; Crovisier,J.; Bachiller, R. New molecules found in comet C/1995 O1 (Hale-Bopp). Investigating the link between cometary and interstellar material. Astron. Astrophys. 2000, 353 (3), 1101–1114.
(2) Schutte, W.A.; Boogert, A.C.A.; Tielens, A.G.G.M.; Whittet, D.C.B.P.; Gerakines, A.; Chiar, J.E.; Ehrenfreund, P.; Greenberg, J.M.; van Dishoeck, E.F.; de Graauw, Th. Weak ice absorption features at 7.24 and 7.41 μm in the spectrum of the obscured young stellar object W 33A. Astron. Astrophys. 1999, 343, 966–976.
(3) Solomon, P.M. Interstellar Molecules. Phys. Today 1973, 26, 32–40.
(4) Saladino, R.; Crestini, C.; Pino, S.; Costanzo, G.; Di Mauro, E. Formamide and the origin of life. Phys. Life Rev. 2012, 9 (1), 84–104.
(5) Coutens, A.; Jørgensen, J.K.; van der Wiel, M.H.D.; Müller, H.S.P.; Lykke, J.M.; Bjerkeli, P.; Bourke, T.L.; Calcutt, H.; Drozdovskaya, M.N.; Favre, C.; Fayolle, E.C.; Garrod, R.T.; Jacobsen, S.K.; Ligterink, N.F.W.; Öberg, K.I.; Persson, M.V.; van Dishoeck, E.F.; Wampfler, S.F. The ALMA-PILS survey: First detections of deuterated formamide and deuterated isocyanic acid in the interstellar medium. A&A 2016, 590, L6.
(6) López-Sepulcre, A.; Jaber, A.A.; Mendoza, E.; Lefloch, B.; Ceccarelli, C.; Vastel, C.; Bachiller, R.; Cernicharo, J.; Codella, C.; Kahane, C.; Kama, M.; Tafalla, M. Shedding light on the formation of the pre-biotic molecule formamide with ASAI. Mon. Not. R. Astron. Soc. 2015, 449 (3), 2438–2458.
(7) Bredehöft, J.H.; Böhler, E.; Schmidt, F.; Borrmann, T.; Swiderek, P. Electron-Induced Synthesis of Formamide in Condensed Mixtures of Carbon Monoxide and Ammonia. ACS Earth Space Chem. 2017, 1, 50–59.
(8) Arumainayagam, C.R.; Lee, H.; Nelson, R.B.; Haines, D.R. Low-energy electron-induced reactions in condensed matter. Surf. Sci. Rep. 2010, 65, 1–44.

Speaker: Fabian Schmidt (Universität Bremen)

17:15 Origins of Phosphorus Nitride in Star-forming Regions

Phosphorus is one of the crucial elements for life. It plays a central role in the structure of essential biotic molecules, such as nucleic acids (DNA and RNA), phospholipids (the skin of all cellular membranes) and the adenosine triphosphate (ATP), from which all forms of life assume energy (Pasek & Lauretta 2005).

Despite its importance, the chemistry of Phosphorus in the interstellar medium (ISM) is still poorly known.

The molecule of PN is one of the two P-bearing molecules detected in star-forming regions (PN & PO) (e.g. Turner & Bally 1987, Fontani et al. 2016, Rivilla et al. 2016), but it is still not clear under which conditions it is formed.
PN is a crucial species to understand the chemistry of interstellar P, because it has been proposed as precursor of other P-bearing species like PO, HNNP, HNPN, and HPNN (Rivilla et al. 2016, Bhasi et al. 2016). Moreover, PN-based derivatives have been proposed as very plausible prebiotic agents in the early Earth (Karki et al. 2017).

The few detections ($\sim$6) of PN reported in the literature before 2016 are associated with warm and turbulent sources, or even shocked material. However, Fontani et al. (2016) found some high-mass star-forming cores with PN(2-1) line widths smaller than 5 km/s. This indicates that PN can also arise from relatively quiescent and cold gas. This information challenges theoretical models that invoke either high desorption temperatures or grain sputtering from shocks to release phosphorus into the gas phase (Turner & Bally 1987, Charnley & Millar 1994).

In order to investigate the main chemical route that leads to the formation of PN and the main mechanism of desorption, we present multi-line observations of PN towards 9 massive dense cores in different evolutionary stages. We compared the results for the molecule of PN with other molecules, tracing different chemical and physical conditions: $\mathrm{SiO, SO, CH_{3}OH, N_{2}H^{+}}$.

The main result of our analysis is that in six out of nine sources the most important release mechanism of PN seems to be sputtering of dust grains in shocked regions, in good agreement with recent results in Galactic Center clouds (Rivilla et al. 2018). In fact, in these six sources the line profiles of PN are very well correlated with those of the two shock tracers SiO and SO. Moreover, the abundances of PN and those of SiO and SO show a faint but not negligible positive trend.

Nevertheless, this can not be the only mechanism since the line profiles of the three remaining sources do not show high-velocity wings (associated with shocked material), but narrow line widths. This confirms the previous results of Fontani et al. (2016), and reinforces the conclusion that the origin of PN is not to be considered unique, since it could form in both shocked and quiescent gas.

Speaker: Chiara Mininni (Università degli Studi di Firenze)

PosterChiaraMininni.pdf

17:30 Formation of interstellar methanol ice prior to the heavy CO freeze-out stage

The formation of methanol (CH3OH) on icy grains in cold interstellar clouds is generally related to hydrogenation reactions during the catastrophic CO freeze–out stage. This explains why CO and CH3OH are mixed in interstellar ices. Yet there are reasons to believe that CH3OH can also form at an earlier period of interstellar ice evolution in CO–poor and H2O–rich ices. Here we present a systematic laboratory study to investigate whether CH3OH can be formed in a H2O–rich interstellar ice environment through the solid–state reaction of CH4 and OH, recently investigated theoretically (Lamberts et al. 2017). Using RAIRS and TPD as diagnostic tools, we show that CH3OH formation at 10–20 K can also take place through the sequential chain, CH4 + OH → CH3 + H2O and CH3 + OH → CH3OH. The CH3OH formation efficiency for both schemes is compared, and the astronomical relevance of the formation channel investigated here is discussed.

Speaker: Danna Qasim (Leiden Observatory)

17:45 ASTRONOMICAL TRIPLETS: ALMA OBSERVATIONS OF C2H4O2 ISOMERS IN SGR B2 (N)

The C$_2$H$_4$O$_2$ triplet found in the interstellar medium (ISM) consists of
glycolaldehyde (CH$_2$OHCHO), acetic acid (CH$_3$COOH) and methyl formate
(HCOOCH$_3$ ). The forming mechanisms of their HCO-bearing components involve
both gas-phase and grain-surface processes whose relative roles are
fundamental questions in the fields of astrochemistry and astrobiology. Here, we
confirmed the detections of each species of C$_2$H$_4$O$_2$ toward Sgr B2(N) with the
more sensitive and larger bandwidth from ALMA Band 3 observations (A.
Belloche, 2012), providing us more transitions and more accurate continuum
subtraction. Based on these results, we derived the column density and imaged
the spatial distributions of the C$_2$H$_4$O$_2$ species. We reported the first high spatial
resolution submillimeter maps of CH$_2$OHCHO, CH$_3$COOH, and HCOOCH$_3$. The
difference in the morphology of the three isomers indicates that the acetic acid
might have a different formation mechanism from the others.

Speaker: Ci Xue

CiXue-poster.pdf

17:45 Chemical differentiation in the inner envelope of a young high-mass protostar

The origin of the highest mass stars is still an enigma in modern astrophysics. Only massive clumps, at the onset of star formation, can reveal the initial conditions and shed light on the necessary physical processes leading to their formation. High angular resolution observations with ALMA of the immediate vicinity of a young high-mass protostar reveals chemical signatures for shocks associated with the mass accretion process. These shocks have high CH3OH abundance, and are rich in complex organic molecules. This suggests a different chemical composition for the immediate vicinity of a high-mass protostar compared to the low-mass hot-corino type objects. I will discuss the chemical differentiation of our targeted high-mass protostar and put our results in context with the typical molecular composition observed towards high-mass hot-cores, and low-mass hot-corino type sources.

Speaker: Timea Csengeri

17:45 Chemical reactions in interstellar ices deposited on grains

In our laboratory we are currently bringing a new UHV setup to production. We will present this setup which enables us to reach conditions similar to those present in dense molecular clouds (T = 10 K, ρN = 105 cm-3). In combination with our laser ablation setup, which we use to produce realistic carbonaecous and silicate dust analoga, we will use the UHV setup to study the chemical interactions and chemical evolution of ices deposited on dusts, which resembles the icy grains in molecular clouds, under irradiation with Lyman α light. Furthermore, photostability mass spectrometical measurements of some species deposited on silicate dusts under irradiation with Lyman α light were studied, expanding the experiments in photodesorption to interactions with dusts. So far the chemistry of irradiated ices and photodesorption has only been studied on ideal substrates (McMurtry/Kaiser2010, Bertin/Linnartz2016, Kaiser/Mathies2010) but erosion of dusts under irradiation has been observed. Therefore we suppose that investigations of ices on dusts is crucial for understanding interstellar chemisty. In this poster we present our developed setup, quantum chemical results on ice/dust interactions and first experimental results.

Speaker: Mr Phillip Seeber (Max-Planck-Institut für Astronomie Heidelberg)

17:45 COMPLEX MOLECULE FORMATION IN TMC-1: A new approach using the physico-chemical ProDiMo code

The TMC-1 Molecular Cloud in Taurus has been used as astrochemical laboratory to test new approaches in computational chemistry to predict molecular abundances in interstellar space. TMC-1 has been observed to contain a large variety of complex molecules such as acids, alcohols and hydrocarbons. In the laboratory, the synthesis of such prebiotic molecules has been confirmed to occur when simple ices are exposed to ionising radiation such as UV, X-rays, electron or ion bombardment. In theoretical astrochemistry, it is understood that complex molecules preferentially form on dust grain surfaces, and for this work, we use the physico-chemical ProDiMo code with latest improvements in surface chemistry (see Thi, W.-F. et al. 2017, submitted) to study the formation of complex molecules in TMC-1. The model includes a sophisticated treatment H$_2$ and HD formation on cold and warm grain surfaces, as well as on hydrogenated PAHs. We discuss the influence of surface chemistry and H$_2$-formation on the resulting molecular concentrations as function of time and compare our results to other models available in the literature.

Speaker: Will Robson Monteiro Rocha (University of St. Andrews)

Poster_1_Will_Rocha.pdf

17:45 Experimental study of the chemical network of the hydrogenation of Methyl Isocyanide (CH$_3$NC) on interstellar dust grains

Methyl Isocyanide (CH$_3$NC) and Acetonitrile (CH$_3$CN) are two complex organic molecules (COMs) which are detected in the interstellar medium and in comets (Remijan et al.2005). They are nodes of the very entangled chemical network leading to the molecular complexity. We aim at exploring the solid-state chemistry which may lead to COMs.

We developed a new experimental set-up named VENUS, in which we can deposit different reactants together on the cold surface (10K-40K). CH$_3$NC/CH$_3$CN and H/D atoms were co-deposited at different temperatures in presence or absence of water. Thanks to Infrared spectroscopy and mass spectrometry, we detected products and remnants after completing the depositions.

We obtained the following observations and measurements :
i) Methyl Isocyanide reacts with H, but Acetonitrile is unreacted.
ii) The total reactivities are decreased with the increase of the surface temperature.
iii) Hydrogenations, isomerization, and fragmentations are competitive mechanisms.
iv) Isotopic effects are observed.
v) The presence of water enhances the hydrogenation.

We will present the experimental results and discuss the chemical network in details, unveiling the presence of activation barriers and (very likely) the role of the quantum tunneling in the formation of COMs on grains.

Reference

Remijan, A. J., Hollis, J. M., Lovas, F. J., Plusquellic, D. F., & Jewell, P. R. 2005. The Astrophysical Journal (632)

Speaker: Thanh Nguyen

17:45 Nitrogen fractionation in high-mass star forming cores across the Galaxy

There is a growing evidence that our Sun was born in a rich cluster that also contained massive stars (Adams, 2010; Taquet et al. 2016). Therefore, the study of the chemical content and chemical processes (such as fractionation) in high-mass star-forming regions is key to understand our chemical heritage. We are thus undertaking a huge observational effort to derive the $^{14}$N/$^{15}$N ratios in a large sample of massive star-forming cores, by means of different molecular tracers. In fact, molecules found in comets and other pristine Solar System bodies are enriched in $^{15}$N, because they show a lower $^{14}$N/$^{15}$N ratio with respect to the value representative of the Proto-Solar Nebula (PSN) (441$\pm$6, Marty et al. 2010), but the reasons of this enrichment cannot be explained by current chemical models. First of all, we have measured the $^{14}$N/$^{15}$N ratio in a sample of 27 high-mass star forming cores, from observations of HCN(1-0) and HNC(1-0) (Colzi et al. 2017), observed with the IRAM-30m Telescope. We have found values of the $^{14}$N/$^{15}$N ratio that are distributed remarkably well around that of the PSN value. Moreover, because these sources were divided into different evolutionary categories (high-mass starless cores, high-mass protostellar objects, and ultracompact H$_{II}$ regions), we have investigated the possible dependence of the isotopic ratio with evolution: we have found no statistically significant variations, suggesting that time does not seem to play a role in the fractionation of nitrogen. Therefore, the cause of $^{15}$N enrichment in pristine Solar System bodies is likely not due to the chemical evolution of the parent core. Afterwards, we have added to this initial sample 60 additional sources observed with the IRAM 30-m as well, for a total of 87 objects. We have computed the $^{14}$N/$^{15}$N ratios from the same molecules and we have found that these ratios are concentrated in the range $\sim$100 and $\sim$800 (Colzi et al., submitted to MNRAS). Thanks to the very large statistics and to the fact that these sources span a wide range of distances from the Galactic center, we have derived a new Galactocentric trend of $^{14}$N/$^{15}$N, for HNC and HCN. Moreover, we have estimated that the $^{14}$N/$^{15}$N ratio in the local interstellar medium is about 400, i.e. very close to the PSN value.

Speaker: Laura Colzi (University of Florence)

PosterLauraColzi-final.pdf

17:45 Studying the Photo-Stability of Amino Acids in Water Ice upon Vacuum UV Irradiation

The simplest amino acid, glycine, has recently been identified on the comet Churyumov–Gerasimenko (67P) [Altwegg et al., 2016]. Independent on how this and likely other amino acids have been formed - in-situ or inherited along the different chemical stages during comet formation in the Solar Nebula - the ice embedded amino acids have been exposed to radiation, including vacuum ultraviolet (VUV) radiation. We have systematically investigated in the laboratory the effect of VUV radiation (120-200 nm) [Ligterink et al. 2015] on glycine and phenylalanine at two low temperatures (10 & 100K) intimately mixed in water ice, as water is the most abundant ice in comets, on icy moons and interstellar dust grains. We present a new method to study the VUV photo-stability of amino acids in water ice and demonstrate the protective properties of water ice, as well as its effect on the photo-chemistry of amino acids [Bouwman 2009, et al. Kofman et al. in prep.]. The preliminary results indicate that water layers thicker than a few hundred nm are well capable of providing sufficient protection from VUV radiation to preserve amino acids, fully in line with the observations from the ROSETTA mission.

Speaker: Mr Vincent Kofman (Sackler Laboratory for Astrophysics, Leiden Observatory, Leiden University)

Heraeus_Poster_Kofman.pdf

17:45 The CORE Project: Chemical complexity of AFGL 2591

Hot cores are ideal laboratories for the formation of complex organic molecules. Here, we present a detailed observational and modeling study of the chemistry in the prototypical hot core region AFGL 2591. It evolves in unique conditions being isolated from other young OB stars with strong UV radiation. This region is part of the NOEMA (Northern Extended Millimeter Array) large program CORE targeting 20 of such regions. Observations were carried out with NOEMA from 217 GHz to 221 GHz and to include large-scale emission observations with the IRAM 30 m telescope were complemented.

Using the high spatial resolution (0.4", ~1300 AU at 3.3 kpc) we derived the physical structure (temperature and density) of the source using CH$_{3}$CN and H$_{2}$CO. About 30 molecules were identified and column densities were determined using the XCLASS software.

AFGL 2591 has a high molecular abundance (e.g. SO$_{2}$, HNCO, CH$_{3}$OH) and shows a rich diversity in complex molecules (C$_{2}$H$_{5}$CN, C$_{2}$H$_{3}$CN, CH$_{3}$OCHO, CH$_{3}$COCH$_{3}$, CH$_{3}$OCH$_{3}$). Some molecules show an asymmetric distribution around the protostar which indicates a complex structure on small scales due to disk accretion and the outflow.

As hot cores show a rich gas phase chemistry we want to further investigate the chemical abundance of AFGL 2591 with chemical models. For that we will use the derived temperature and density profile and the H$_{2}$ column density obtained from the 1.37 mm continuum emission. The aim is to understand the formation processes of the molecules and to determine the chemical age of the source.

Speaker: Caroline Gieser (MPIA)

Heraeus_Poster_Gieser.pdf

17:45 The effect of multi grain network in chemical composition in the ISM. A study of dense clouds using Nautilus multi grain code

Many chemical reactions occur at the surface of interstellar dust grains, producing a large diversity of molecules more or less complex. Most current astrochemical models include only a single size of grains (0.1 micron representing most of the mass of silicate grains) to study the formation and destruction of molecules on the dust surface. We have studied the effect of considering a distribution of grain sizes on the chemical evolution of various complex molecules in cold clouds in the ISM.
We used two different types of grain size distributions, MRN and WD. Each grain has its own grain number density which comes from either MRN or WD distribution. Other important parameters such as grain surface temperature or cosmic ray induced desorption also vary with grain sizes. We present abundance of various molecules including some complex molecules in gas phase and also on the surface of dust grains at different time interval during the simulation. We also compare our results with observed abundances in TMC-1 and L134N. We show how a multi grain model can be a better tool in explaining the observed abundances in these cold dense clouds.

Speaker: wasim iqbal (Postdoctoral Researcher)

Wasim_iqbal_poster.pdf

17:45 The efficiency of driving chemical reactions by a physical non-equilibrium is kinetically controlled

An out-of-equilibrium physical environment can drive chemical reactions into thermodynamically unfavorable regimes. Under prebiotic conditions such a coupling between physical and chemical non-equilibria may have enabled the spontaneous emergence of primitive evolutionary processes. Here, we study the coupling efficiency within a theoretical model that is inspired by recent laboratory experiments, but focuses on generic effects arising whenever reactant and product molecules have different transport coefficients in a flow-through system. In our model, the physical non-equilibrium is represented by a drift–diffusion process, which is a valid coarse-grained description for the interplay between thermophoresis and convection, as well as for many other molecular transport processes. As a simple chemical reaction, we consider a reversible dimerization process, which is coupled to the transport process by different drift velocities for monomers and dimers. Within this minimal model, the coupling efficiency between the non-equilibrium transport process and the chemical reaction can be analyzed in all parameter regimes. The analysis shows that the efficiency depends strongly on the Damköhler number, a parameter that measures the relative timescales associated with the transport and reaction kinetics. Our model and results will be useful for a better understanding of the conditions for which non-equilibrium environments can provide a significant driving force for chemical reactions in a prebiotic setting.

Speaker: Mr Tobias Goeppel (Physics of Complex Biosystems, Physics Department, Technical University of Munich)

17:45 THE ROLE OF EXTERNAL UV IRRADIATION FOR THE SURVIVAL OF ASTROPHYSICAL ICES IN ELIAS 29

Protostellar envelopes are usually approximated as spherical dense and cold regions around early-type stars during the initial phases of star formation. Such regions can harbour volatile and non-volatile astrophysical ices with desorption temperatures between 20 – 150 K. However, little is known about the role of external irradiation for the survival of ices in protostellar envelopes. In this work, we examine the effects of external irradiation on Elias 29, a Class I protostar, which is surrounded by several Young Stellar Objects as well as by two early B-type stars with luminosities around 1000 – 5000 L$_{\odot}$. We have used the Monte Carlo radiative transfer code RADMC-3D to find the dust temperature and UV mean intensity as it penetrates in Elias 29, leading to photodissociation and ice photodesorption. We calculate the half-life time of prebiotic molecules such as C$_2$H$_4$O$_2$ isomers (methyl formate and acetic acid) and CH$_3$OH embedded in a H$_2$O-ice matrix to understand the chemical complexity in this object. As a result, the external irradiation in Elias 29 is estimated to be $\sim$44$\chi_{ISRF}$, which drives two main effects at envelope: (i) change the snowline of volatile species (O$_2$, N$_2$, CH$_4$ and CO) to a toroidal-shaped form, and (ii) create an shielded region where complex molecules would survive longer lifetimes to be assimilated by the protoplanetary disk.

Speaker: Will Robson Monteiro Rocha (University of St. Andrews)

Poster_2_Will_Rocha.pdf

17:45 Two Complex Organic Molecules

Many interstellar molecules are known to have essential functions in terrestrial biochemistry. Observations of prebiotically important COMs thus enable us to better understand the origin of primitive organic materials found in our Solar System. Glycine and pyrimidine, the simplest amino acid and the building blocks of nucleic acid, respectively, were both detected in meteorites and comets. Although the formation of prebiotic molecules in extraterrestrial environments and their contribution to prebiotic chemistry remains unsettled, the connection between interstellar organic chemistry, meteoritic pyrimidines and amino acids, and the emergence of life on the early Earth would be strengthened with the discovery of interstellar glycine and pyrimidine. We will present our recent ALMA results on these two molecules.

Speaker: Yi-Jehng Kuan (National Taiwan Normal University)

Thursday, 22 March

09:00 → 13:00 Primitive Earth and conditions to host life

09:00 Influence of mineralogy on the preservation of biosignatures under simulated planetary conditions

Speaker: Zita Martins

09:45 Organic chemistry in the atmosphere of the early earth

Speaker: Nathalie Carrasco (University of Versailles Saint-Quentin)

Heraus_Seminar_BadHonnef-Carrasco-2018.pdf

10:15 From Astrochemistry to Astrobiology: the role of extraterrestrial ices in the build-up of a prebiotic chemistry on telluric planets.

Extraterrestrial ices are observed in many astrophysical environments linked to the formation of stars and planetary systems but also disks and various debris such as comets and asteroids. The chemical evolution of these ices following photo- and thermo-chemistry is routinely simulated in the laboratory. These simulations always end with the building up and recovery at room temperature, of organic residues. These residues, soluble in water, show the presence of many “molecular bricks of life” such as amino acids, nucleobases and sugars, including ribose, a key constituent of RNA. The similarities of these residues with organic materials in meteorites suggest a possible astrophysical scenario for the origin of organics in their parent bodies. Furthermore, the delivery of these organics onto the primitive Earth, or other telluric planets, may be important, if not essential, for the start-up, in some specific environment, of a prebiotic chemistry that may be considered as a far equilibrium evolving chemical system that may be simulated in the laboratory.

Speaker: Louis Le Sergant d hendecourt (CNRS)

11:30 Thermal gradients – a natural choice to support the origins of life

Life is a non-equilibrium system, which is nowadays maintained by a highly developed energy conversion machinery. Four billion years ago, other non-equilibrium mechanisms were needed to kick-start living processes. We propose ubiquitous heat fluxes as suitable driving force: Thermal gradients across water filled pores lead to a concurrent fluid convection and directed movement of dissolved charged molecules along the temperature difference. Combined, both effects accumulate the dissolved biomolecules in a length dependent manner. Oligonucleotides are pushed into a hydrogel phase, depending on their sequence and chirality: A mixture of strands with different sequence demixes into sequence-pure and homochiral hydrogels upon thermal accumulation, possibly selecting for interacting strands during the origin of life. The thermal non-equilibrium also creates and maintains a pH gradient over two units by the selective accumulation of charged buffer molecules, which shifts the local equilibrium in pH. In this system, early compartments of life may have cycled between different external pH conditions, implementing an important boundary condition for a primordial metabolism.

Speaker: Christof Mast (LMU Munich)

11:45 Fluid inclusions in Archaean rocks as window to the early evolution of organic molecules on Earth

One of the most fundamental questions for humanity is how life emerge on Earth and in this context how were the first prebiotic organic compounds formed and distributed. Therefore it is necessary to find and investigate environmental archives that retained information from the early Earth.
The analysis of fluid iclusions (FIs) is a widely used geochemical tool to determine thermobaric and chemical evolution of geologic systems. Most naturally grown crystals contain inclusions of other minerals, melts, fluids and gases, which were originally present at the mineral surfaces during crystal growth and then included. FIs are important archives and their investigation allows drawing conclusions on their original fluid composition. Several generations can be present and it is crucial to differentiate between primary FIs formed during mineral growth and secondary and pseudo-secondary FIs formed during later geological processes. These mineralogical aspects are essential when attributing ages to the rocks hosting FIs.
FIs also represent archives for organic matter e.g. in the form of hydrocarbons and biomarkers from which their biological origin can be inferred. The analysis of oil and natural gas in FIs has become an important tool in petroleum exploration to investigate porosity evolution, thermal history, source regimes and migration pathways alongside formation mechanisms, product types and quality.
Gas-liquid inclusions can be found in all types of rock. Aside from stable inorganic gases like N2, Ar, CO2, O2). FIs often contain methane and its homologues. A few concepts of the abiotic origin of CH4 and longer-chained hydrocarbons also exist and will be outlined. Sherwood Lollar studied the isotopic signatures of C1-C4 hydrocarbons in field samples pointing to CH4 as a precursor to forming longer-chained hydrocarbons.
Next to the classification of hydrocarbon formation into bacteriogenesis and thermogenesis further abiotic CH4 production pathways have to be considered (see Fig.1). The abiotic field can be subdivided in the more enriched 13C- and 2H values from high temperature volcanic-hydrothermal systems and serpentinised ultramafic rocks and the more depleted 13C- and 2H-values from crystalline igneous rocks and present day serpentinisation seeps.

Fig.1: δ13C and δ2H isotopic composition of biotically formed CH4 in subsoil petroleum systems (red: thermogenic; green: biogenic) and of abiotically formed CH4 (black-rimmed: abiotic) (Schreiber et al.).

Thermogenic processes also produce a variety of volatile organohalogens (VOX), mostly chlorinated and fluorinated alkanes, alkenes and alkynes, but also cyclic and aromatic halogenated compounds. Halogenated methanes are the prevailing molecules emitted by volcanoes. The studies of Harnisch and Eisenhauer as well as Harnisch et al. are ground-breaking in VOX analysis from FIs of rocks and minerals. They demonstrated that CF4 and SF6 are commonly present in natural fluorites and granites. Additionally, they detected CF2Cl2 and CFCl3 from a number of natural samples and CF3Cl, CHF3 and NF3 from one fluorite sample. A multitude of organohalogens have additionally been detected by Mulder at al. in FIs from rocks and minerals after grinding.

References

U. Schreiber, C. Mayer, O.J. Schmitz, P. Rosendahl, A. Bronja, M. Greule, F. Keppler, I. Mulder, T. Sattler, H.F. Schöler: Organic compounds in fluid inclusions of Archean quartz –
Analogues of prebiotic chemistry on early Earth. PLoS ONE (2017) 12(6) e0177570

I. Mulder, S.G. Huber, T. Krause, C. Zetzsch, K. Kotte, S. Dultz, H.F. Schöler: A new purge and trap headspace technique to analyze low volatile compoundsfrom fluid inclusions of rocks aand minerals
Chemical Geology (2013) 358:148–155

Speaker: Heinfried Schöler (Institute of.Earth Science, University of Heidelberg)

Heraeus_Talk_Schoeler.pdf

12:00 A Search for Phosphorus-bearing molecules in Solar-type Star Forming Regions

Despite a rather low elemental abundance of $\sim 3\times 10^{-7}$ (Asplund et al. 2009), Phosphorus is one of the main biogenic elements, present in all life forms on Earth. As such, phosphorus-bearing compounds, in particular their P--O bonds, play a key role in many biochemical and metabolic processes in living systems. However, Phosphorus chemistry in the interstellar medium has received relatively little attention until now and remains poorly known.

We present here the results of a systematic search for P-bearing molecules in solar-type star forming regions, in the course of the Large Program "Astrochemical Surveys At IRAM" (ASAI; Lefloch et al. 2018) with the IRAM 30m telescope. The sample comprised 10 objects illustrative of the different chemical stages of evolution of a sun-like protostar, from the early prestellar to the late protostellar (Class I) phase, and two protostellar shock regions.

Transitions of the simple PN and PO molecules were detected towards a subsample of protostars and a protostellar shock region. Physical conditions and molecular abundances were obtained for both species. We will discuss the results of our study, in particular the shock region, which was subsequently observed at high-angular resolution (2'') with the NOEMA interferometer. Our results imply a strong P depletion ($\approx 100$) in the quiescent cloud gas.
A simple modelling using the UCL_CHEM code coupled with a parametric C-shock model has allowed us to bring constraints on phosphorus chemistry and shows the important role played by atomic N in the formation and destruction routes of PO and PN.

Speaker: Bertrand Lefloch (CNRS/IPAG)

lefloch_codella_bonn18.pdf

14:30 → 18:30 The assembly of prebiotic molecules

14:30 Prebiotic Chemistry: Synthesis and Selection

Speaker: Matthew Powner (UCL)

15:15 Prebiotic origin of nucleosides in a formamide context

Speaker: Lorenzo Botta

15:45 Exploring the emergence of complexity with microfluidic droplets

The question of how life could have arisen from non-living molecular systems is not only fundamentally and philosophically interesting, but it requires us to closely examine the common features of life as we know it, and to imagine the possibilities for life as we do not know it. While much progress has been made elucidating possible chemical systems as candidates for early pre-biological reactions, little is known about the true catalytic and informational capabilities of small, prebiotically relevant molecules in compartmentalized, micron-scale systems. We address this by using droplet microfluidics to generate encapsulated molecular systems as protocell analogues. We use automated tools to generate, manipulate and analyze these systems in real time, enriching dynamic populations for rare entities and selecting entities of interest for reproduction, recombination and chemical analysis. Using these techniques, we aim to select compartmentalized systems that will provide insight on the origin of complexity from simple biochemical constituents.

Speaker: Dr Rebecca Turk-MacLeod (University of Glasgow)

17:00 The ethanol tree: possible gas-phase formation routes of glycolaldehyde, acetic acid and formic acid in ISM

The question of the formation of Complex Organic Molecules (COMs) in ISM is a main issue in the field of prebiotic chemistry. More particularly, glycolaldehyde is an important species in this context, especially because it is the simplest sugar-related compound. Indeed, it is thought to be able to be converted into short dipeptides[1] or amino acids[2] and to ease the formation of more complex sugars.[3]

Moreover, its key roles in ISM appear to be also remarkable since it has been detected in Sgr B2,[4] in high- and low- mass star forming regions[5] and more recently in shocked regions.[6]

In this contribution it is demonstrated, using a computational strategy integrating state-of-the-art electronic structure calculations and kinetic calculations, that the reaction between two widely diffuse species, that are hydroxyethyl radicals and atomic oxygen, can easily account for the formation of, not only glycolaldehyde, but also acetic and formic acids, species that can also be of interest in both prebiotic chemistry and interstellar medium.

[1] Pizzarello, S., Weber, A. L., 2004 Science 303: 1151

[2] Weber, A. L., Pizzarello, S. 2006 Proceedings of the National Academy of Sciences of the USA 103: 12713–12717

[3] Cantillo, D., Ávalos, M., Babiano, R., Cintas, P., Jiménez, J. L., Palacios, J. C. 2012 Chem. Eur. J. 18: 8795–8799.

[4] Hollis, J. M., Lovas, F. J., Jewell, P. R. 2000, ApJ, 540, L107

[5] Beltran, M. T., Codella, C., Viti, S., Neri, R., & Cesaroni, R. 2009, ApJ, 690, L93

[6] Lefloch B., Ceccarelli C., Codella C. et al. 2017, MNRAS, 469, L73

Speaker: Fanny Vazart (Scuola Normale Superiore di Pisa)

17:15 Recent Advances in Our Understanding of the Prebiotic Molecular Complexity in Astronomical Environments.

Over the past several years, observations of a variety of astronomical environments has led to the detection and characterization of new molecular species as well as to a better understanding of the physical and chemical conditions of these regions. Molecular material is now found in a host of Galactic and extragalactic environments and has been used as tracers of a variety of conditions including but certainly not limited to, PDRs, XDRs, shocks, diffuse gas, dense gas, HMCs and UC HII regions. In the era of large single dish telescopes and broadband interferometric arrays, we are truly getting a chemical picture of the universe. This presentation will look at the recent advances our team has made in the detection of new astronomical molecules especially at centimeter wavelengths and how these new detections are driving better and more complex theories of large molecule formation in astronomical environments.

Speaker: Anthony Remijan (NRAO)

Remijan_Prebiotic_HeraeusSeminar_BadHonnef_2018.pptx

Friday, 23 March

09:00 → 13:00 Steps toward evolution

09:00 RNA-catalyzed RNA replication

Speaker: Phil Holliger (MRC-LMB)

09:45 Transport reaction cycles as a prebiotic driving force

Speaker: Ulrich Gerland (Technical University of Munich)

10:15 Prebiotic and Synthetic RNA worlds

Speaker: Hannes Mutschler (MPI of Biochemistry)

11:30 From quantum computational physics to the origins of life

Computational approaches are nowadays a full, self-standing branch of chemistry, both for their quantum-based (“ab initio”) accuracy, and for its multiscale extent. In prebiotic chemistry, however, due to the instrinsic complexity of the chemical problems, ab initio atomistic simulations have so far had a limited impact, with the exception of a few relevant studies. Surprisingly, even the celebrated Miller experiments, which historically reported on the spontaneous formation of amino-acids from a mixture of simple molecules reacting under an electric discharge, have never been studied at the quantum atomistic level.
Here we set the general problem of chemical networks within new topology-based concepts, using search algorithms and social network data analysis. This allows a very efficient definition of reaction coordinates even in the complex chemical environments which are typical of likely prebiotic scenarii. We thus report on the first ab initio computer simulations, based on quantum physics and a fully atomistic approach, of Miller-like experiments in the condensed phase. Our study [1] shows that glycine spontaneously form from mixtures of simple molecules once an elec-tric field is switched on. We identify formic acid and formamide [2] as key intermediate products of the early steps of the Miller reactions, and the crucible of formation of complex biological molecules, as confirmed by our recent experimental and theoretical study on high-energy chemistry of formamide [3]. From a broader chemical perspective, we show that formamide plays the role of hub of a complex reaction network in both the gas and the condensed phase [4]. We are now going on a larger scale, studying the atomistic mechanisms of RNA nucleotides synthesis in fully realistic prebiotic solution environments [5], as well as, in a collaboration with NASA, the reaction networks of relevant amino-acids in meteoritic parent bodies, with the aim of addressing the origin of chirality [6]. All these results pave the way to novel computational approaches in the research of the chemical origins of life.

References:
[1] Saitta AM and Saija F (2014) Proceedings of the National Academy of Sciences USA 111:13768-13773.
[2] Saitta AM, Saija F, Pietrucci F, and Guyot F (2015) Proceedings of the National Academy of Sciences USA 112, E343-E343.
[3] Ferus M et al. (2017) Proceedings of the National Academy of Sciences USA, 114:4306-4311.
[4] Pietrucci F and Saitta AM (2015) Proceedings of the National Academy of Sciences USA 112, 15030-15035.
[5] Perez-Villa A et al. (2018) submitted.
[6] Pietrucci F et al. (2018) submitted.

Speaker: A. Marco Saitta (Université Pierre et Marie Curie - Sorbonne)

Marco_SAITTA BadHonnef_2018_short.pdf

11:45 Pyrite surface pre-treatment drives amino-acids molecular interaction process

Understanding the interaction between biomolecules, such as amino-acids, peptides or proteins, and surfaces is of importance in the fields of surface chemistry, catalysis and prebiotic chemistry. It has been found that a number of amino-acids self-organize to form well-ordered two-dimensional structures at metal surfaces (1). On the other hand, it is important to explore the role-play by different mineral surfaces related to prebiotic chemistry processes such as molecular adsorption and geochemistry. Minerals can be very promising surfaces for studying biomolecule-surface processes; among such minerals is pyrite. Pyrite (FeS2) is one of the most important and abundant sulfide minerals on earth. Additionally, due to its catalytic activity, pyrite surface plays an important role in heterogeneous catalysis. Furthermore, the study of pyrite’s physical properties and reactivity is also crucial to the ‘‘iron–sulfur world’’ (2). Wächtershäuser proposed that the first reactions that led to the formation of amino-acids did not occur in a bulk solution in the oceans (prebiotic soup theory) but on the surface of minerals (such as pyrite). In fact, minerals may adsorb and concentrate these biomolecules and catalyze reactions. Mineral surfaces could potentially have allowed for almost any type of general catalysis, with low specificity and efficiency.
Therefore, we focused our study on investigating by the use of complementary and powerful surface science techniques the possible role played by mineral surface reactivity. Furthermore, to obtain understanding on molecule/surface system, which includes information about the interaction and self-assembled processes of amino-acids on surfaces and the chemical state of the adsorbates depending on different experimental conditions like molecular coverage, environmental conditions (3-5). These studies are based on an innovative approach; molecule-surface systems under vacuum conditions. We report the results of a spectroscopic study, specifically X-ray photoemission spectroscopy (XPS) data, obtained for amino-acids adsorption on a natural pyrite surface and discuss spectroscopic evidence of different molecular adsorption mechanisms on the surface of pyrite constrained by pre-treatment conditions. This strategy is designed to be able to evaluate how diverse environments favor or inhibit molecular adsorption, and the crucial role play by pyrite surface chemically driving amino-acids interaction on the surface. The interaction of some functional groups may drive molecular interaction with the iron and sulfur chemical groups from pyrite surface. Successful adsorption of different amino-acids on a pyrite surface confirms the high reactivity of this surface, which could operate as a batch-reactor for prebiotic molecules. These studies could therefore shed light into prebiotic chemistry reactions.

Figure 1: XPS Spectroscopy evidence of pretreatment pyrite surface processes drives amino acid molecular adsorption.
References
(1) E. Mateo-Marti, C. Rogero, C. Gonzalez, J. Sobrado, P. De Andrés Rodriguez and J.A. Martín-Gago, Langmuir 26 (2010) 4113.
(2) G. Wächtershäuser, Chemistry&Biodiversity, 4, (2007) 584.
(3) M. Sanchez-Arenillas and E. Mateo-Marti, Chemical Physics 458 (2015) 92.
(4) M. Sánchez-Arenillas, E. Mateo-Martí, Phys.Chem.Chem.Phys, 18 (2016) 27219-27225.
(5) M. Sánchez-Arenillas, S. Galvez-Martinez, E. Mateo-Martí, Appl. Surf. Sci., 414 (2017) 303-312.

Speaker: Eva Mateo-Marti (Centro de Astrobiologia (INTA-CSIC))

12:00 Towards a microfluidic reactor for autonomous, microfluidic synthesis of RNA

One major unresolved question in the origin of life is the autonomous synthesis of nucleotides. Recent chemical advances have thrown light upon potential synthetic pathways for the production of nucleotides in the laboratory, starting from simple precursors [1]. However, so far the original experiments were performed in bulk chemistry, and the synthetic steps successively one by one, independently of each other. Therefore, the geological plausibility of such a scenario remains unexplored.
We will present advances in our study of the synthesis of activated nucleotides under emulated conditions of laminar, microfluidic flow in rocks pores, driving all the reactions under one single system sequentially and uninterruptedly. We have developed 3D-printed microfluidic devices to run the RNA synthesis autonomously and to recreate a scenario analogous to what could be found in porous volcanic rocks under evaporation settings. The flow is presently driven by peristaltic pumps, but our ongoing work aims to test the limits at which the reactions can be driven spontaneously by gravity or evaporation. We use finite-element modelling to design and test our microfluidic systems. Our methodology enables us to embed rock powders into the microfluidic systems, further increasing the geological plausibility of our tested scenarios and opening the door to studies of any other scenarios for the emergence of life.

[1] Powner, M. W., Gerland, B., & Sutherland, J. D. (2009). Synthesis of activated pyrimidine ribonucleotides in prebiotically plausible conditions. Nature, 459(7244), 239.

Speaker: Victor Sojo (LMU (Ludwig-Maximilian University of Munich))