The thermal desorption characteristics of 16 astrophysically relevant species from laboratory analogues of the icy mantles on interstellar dust grains have been surveyed in an extensive set of preliminary temperature programmed desorption experiments. The species can be separated into three categories based on behaviour. Water-like species have a single relevant desorption coincident with water. CO-like species show the volcano desorption and co-desorption of trapped molecules, monolayer desorption from the surface of water ice, and multilayer desorption if initially present in sufficient abundance in an outer layer separated from the water ice. Intermediate species show the two desorptions of trapped molecules, and may show a small monolayer desorption for molecules small enough to have a limited ability to diffuse through the structure of porous amorphous water ice. Methods by which the results obtained under laboratory conditions can be adapted for astrophysical situations are discussed.

/pdf/a-laboratory-survey-of-the-thermal-desorption-of-dojmdqhpqm.pdf

A laboratory survey of the thermal desorption of astrophysically relevant molecules

Stable, hydrogen-burning, M dwarf stars make up about 75% of all stars in the Galaxy. They are extremely long-lived, and because they are much smaller in mass than the Sun (between 0.5 and 0.08 MSun), their temperature and stellar luminosity are low and peaked in the red. We have re-examined what is known at present about the potential for a terrestrial planet forming within, or migrating into, the classic liquid–surface–water habitable zone close to an M dwarf star. Observations of protoplanetary disks suggest that planet-building materials are common around M dwarfs, but N-body simulations differ in their estimations of the likelihood of potentially habitable, wet planets that reside within their habitable zones, which are only about one-fifth to 1/50th of the width of that for a G star. Particularly in light of the claimed detection of the planets with masses as small as 5.5 and 7.5 MEarth orbiting M stars, there seems no reason to exclude the possibility of terrestrial planets. Tidally locked synchron...

/pdf/a-reappraisal-of-the-habitability-of-planets-around-m-dwarf-r8v4nl8nr0.pdf

A reappraisal of the habitability of planets around M dwarf stars.

Many organic compounds or their precursors found in meteorites originated in the interstellar or circumstellar medium and were later incorporated into planetesimals during the formation of the solar system There they either survived intact or underwent further processing to synthesize secondary products on the meteorite parent body The most distinct feature of CI and CM carbonaceous chondrites, two types of stony meteorites, is their high carbon content (up to 3% of weight), either in the form of carbonates or of organic compounds The bulk of the organic carbon consists of an insoluble macromolecular material with a complex structure Also present is a soluble organic fraction, which has been analyzed by several separation and analytical procedures Low detection limits can be achieved by derivatization of the organic molecules with reagents that allow for analysis by gas chromatography/mass spectroscopy and high performance liquid chromatography The CM meteorite Murchison has been found to contain more than 70 extraterrestrial amino acids and several other classes of compounds including carboxylic acids, hydroxy carboxylic acids, sulphonic and phosphonic acids, aliphatic, aromatic and polar hydrocarbons, fullerenes, heterocycles as well as carbonyl compounds, alcohols, amines and amides The organic matter was found to be enriched in deuterium, and distinct organic compounds show isotopic enrichments of carbon and nitrogen relative to terrestrial matter

Extraterrestrial Organic Compounds in Meteorites

Aims. We study the chemical origin of a set of complex organic molecules thought to be produced by grain surface chemistry in high mass young stellar objects (YSOs). Methods. A partial submillimeter line-survey was performed toward 7 high-mass YSOs aimed at detecting H 2 CO, CH 3 OH, CH 2 CO, CH 3 CHO, C 2 H 5 OH, HCOOH, HNCO and NH 2 CHO. In addition, lines of CH 3 CN. C 2 H 5 CN, CH 3 CCH, HCOOCH 3 , and CH 3 OCH 5 were observed. Rotation temperatures and beam-averaged column densities are determined. To correct for beam dilution and determine abundances for hot gas, the radius and H 2 column densities of gas at temperatures >100 K are computed using 850 μm dust continuum data and source luminosity. Results. Based on their rotation diagrams, molecules can be classified as either cold ( 100 K). This implies that complex organics are present in at least two distinct regions. Furthermore, the abundances of the hot oxygen-bearing species are correlated, as are those of HNCO and NH 2 CHO. This is suggestive of chemical relationships within, but not between, those two groups of molecules. Conclusions. The most likely explanation for the observed correlations of the various hot molecules is that they are "first generation" species that originate from solid-state chemistry. This includes H 2 CO, CH 3 OH, C 2 H 5 OH, HCOOCH 3 , CH 5 OCH 5 , HNCO, NH 2 CHO, and possibly CH 3 CN, and C 2 H 5 CN. The correlations between sources implies very similar conditions during their formation or very similar doses of energetic processing. Cold species such as CH 2 CO, CH 3 CHO, and HCOOH, some of which are seen as ices along the same lines of sight, are probably formed in the solid state as well, but appear to be destroyed at higher temperatures. A low level of non-thermal desorption by cosmic rays can explain their low rotation temperatures and relatively low abundances in the gas phase compared to the solid state. The CH 3 CCH abundances can be fully explained by low temperature gas phase chemistry. No cold N-containing molecules are found.

/pdf/testing-grain-surface-chemistry-in-massive-hot-core-regions-4znaiictu6.pdf

Testing grain-surface chemistry in massive hot-core regions

Surface Processes on Interstellar Amorphous Solid Water: Adsorption, Diffusion, Tunneling Reactions, and Nuclear-Spin Conversion

This technical note describes a novel solar simulation experiment designed to mimic the solar radiation experienced by the Organism/Organics Exposure to Orbital Stresses (O/OREOS) nanosatellite in low-Earth orbit. Thin films of organic compounds within hermetically sealed sample cells (identical to the films and cells of the spaceflight mission) were exposed to simulated AM0 solar radiation in the laboratory for a total of 6 months, and monitored for spectral changes at two-week intervals. The laboratory experiment accurately simulated ultraviolet and visible solar irradiance to within 2% from 200‐1000 nm and the Ly! (121.6 nm) emission line radiation to within 8%. Design and calibration parameters for the experiment are discussed in detail for this ground-based laboratory irradiation experiment, which was built as a complement to, and as scientific validation of, the O/OREOS SEVO experiment in space.

http://iopscience.iop.org/article/10.1088/0067-0049/210/2/15/pdf

Sevo on the ground: design of a laboratory solar simulation in support of the o/oreos mission

Laboratory IR spectra of 4-azachrysene in solid H2O

Infrared observations, combined with realistic laboratory simulations, have revolutionized our understanding of interstellar ice and dust, the building blocks of comets Ices in molecular clouds are dominated by the very simple molecules H2O, CH3OH, NH3, CO, CO2, and probably H2CO and H2 More complex species including nitriles, ketones, and esters are also present, but at lower concentrations The evidence for these, as well as the abundant, carbon-rich, interstellar, polycyclic aromatic hydrocarbons (PAHs) is reviewed Other possible contributors to the interstellar/pre-cometary ice composition include accretion of gas-phase molecules and in situ photochemical processing By virtue of their low abundance, accretion of simple gas-phase species is shown to be the least important of the processes considered in determining ice composition On the other hand, photochemical processing does play an important role in driving dust evolution and the composition of minor species Ultraviolet photolysis of realistic laboratory analogs readily 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 amides, ketones, and polyoxymethylenes (POMs) Inclusion of PAHs in the ices produces many species similar to those found in meteorites including aromatic alcohols, quinones and ethers Photon assisted PAH-ice deuterium exchange also occurs All of these species are readily formed and are therefore likely cometary constituents

/pdf/evolution-of-interstellar-ices-3i6fiez4jv.pdf

Evolution of interstellar ices.

https://digitalcommons.unl.edu/cgi/viewcontent.cgi?article=1083&context=nasapub

The coupling of a reflectron time-of-flight mass spectrometer with a cosmic simulation chamber: A powerful new tool for laboratory astrophysics

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Sevo on the ground: design of a laboratory solar simulation in support of the o/oreos mission

Laboratory IR spectra of 4-azachrysene in solid H2O

Evolution of interstellar ices.

The coupling of a reflectron time-of-flight mass spectrometer with a cosmic simulation chamber: A powerful new tool for laboratory astrophysics