We present 5-20 mu m Spitzer/IRS spectroscopy toward stars behind dark molecular clouds. We present preliminary results from the Serpens dark cloud to show the variation between environments within a cloud. We are surveying 3 clouds with varying levels of star formation activity. Serpens has the highest level of activity from our 3 clouds. We show that location as well extinction can cause variations in ice composition. We also find that some lines of sight contain organic molecules such as methane and methanol, and the first detection of acetylene ice in the interstellar medium. We believe the high extinction lines of sight have been enriched by star formation activity near those lines of sight.

We present new spectroscopic observations of the 3.4μm absorption feature in a Seyfert 2 galaxy and a ULIRG. A signature of C–H bonds in aliphatic hydrocarbons, the 3.4μm feature indicates the presence of organic material in Galactic and extragalactic dust. The feature in these galaxies closely resembles that seen in the Galactic diffuse ISM and in newly-formed dust in a protoplanetary nebula. This similarity implies a common composition for the hydrocarbon component of interstellar dust in a range of galaxy types, and one which is resistant to processing in the interstellar and/or circumnuclear medium.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The SETI Institute, the California Academy of Sciences, NASA Ames Research Center, and San Francisco State University have developed standards-based curriculum materials for a one-year high school integrated science course centered on the unifying theme of evolution. Scientists, teachers, curriculum writers, and media specialists are currently finalizing six modules that integrate astronomical, geological, and biological sciences as well as the history of science and technology. The sequence of lessons in each module is designed to promote students' understanding and skills as defined by the National Science Education Standards and Benchmarks for Science Literacy. The modules cover: Cosmic Evolution, Planetary Evolution, Origin of Life, Evolution of Life, Hominid Evolution, and the Evolution of Technology. The core lessons for all six modules are provided via CD-ROM, including instructional guidelines, science background information, and additional resources (print, audiovisual, software, WWW sites, and databases). These products will be published as a complete set for use as a yearlong science course and will also be available as individual modules for use in discipline-based courses. Evolutionary change is a powerful framework for studying our world and our place therein. It is a story of epic size, capable of inspiring awe and of expanding our sense of time and place. This story is the basis of Voyages Through Time.

Spectra of objects which lie along several lines of sight through the diffuse interstellar medium (ISM) all contain an absorption feature near 3.4 mu m (2950 cm(-1)) which has been attributed to saturated aliphatic hydrocarbons on interstellar grains. The similarity of the absorption bands near 3.4 mu m along different lines of sight reveals that the carrier of this band lies in the diffuse dust. A remarkable similarity between the spectrum of the diffuse dust and an organic extract from the Murchison meteorite suggests that some of the interstellar organic material may be preserved in primitive solar system bodies. The recent discovery of the 3.4 mu m absorption feature in other galaxies has led to comparisons between the extragalactic, galactic, and solar system organics. The comparisons show strong similarities in position peaks and profile structure between the three spectra. However, the absence, in our own galaxy, of the aliphatic hydrocarbon signature in the spectra of dense cloud objects is puzzling in the light of the widespread distribution of the aliphatic material throughout the diffuse medium and the short time scales thought to govern the transition of that material back into dense molecular clouds. The connection between the diffuse ISM dust and solar system objects is made more difficult to understand if the aliphatics are truly absent in the dense cloud phase where proto-solar nebulae must form. In an effort to further investigate the 3.4 mu m absorption feature in the diffuse ISM, comparisons of the diffuse medium dust to several materials which have been proposed as ''fits'' to the 3.4 mu m feature are presented. The optical depth/extinction tau/A(V) ratio for the 3.4 mu m (2950 cm(-1)) band is higher toward the galactic center than toward sources which sample the interstellar medium in the local neighborhood. A similar trend has been observed previously for silicates, indicating that the two materials may be simultaneously enhanced in the galactic center. Such a trend is consistent with the presence of grains composed of silicate cores and organic refractory mantles.

To better constrain and quantify the composition of material in the diffuse interstellar medium (ISM), absorption spectra between 3600 and 2700 cm-1 (2.8 and 3.7 microns) have been taken of objects which have widely varying amounts of visual extinction along different lines of sight. The spectra of these objects contain a broad feature centered at approximately 3300 cm-1 (approximately 3.0 microns), attributed to O-H stretching vibrations, and/or a feature near 2950 cm-1 (3.4 microns) attributed to C-H stretching vibrations. The lack of correlation between the strengths of these two bands indicates that they do not arise from the same molecular carrier. The features in the 3100-2700 cm-1 (3.2-3.7 microns) region fall into one of two classes. We attribute the first class of features to material in the diffuse ISM on the basis of the similarity between the band profiles along the very different lines of sight to Galactic center source IRS 7 and VI Cygni #12. Similar features are also reported for Galactic center source IRS 3, Ve 2-45, and AFGL 2179. Higher resolution spectra of the objects OH 01-477 and T629-5, which are known to be M stars, are dominated by a series of narrow bands in this region. These bands are largely due to OH in the stars' photospheres. While the spectra of OH 01-477 and T629-5 are likely to contain C-H absorption from diffuse ISM dust, the strength of the overlapping photospheric OH features presently prevents us from quantifying the depths of the interstellar C-H feature towards these objects. The interstellar feature for Galactic center source IRS 7 has subpeaks near 2955, 2925, and 2870 cm-1 (+/- 5 cm-1), which we attribute to C-H stretching vibrations in the -CH2- and -CH3 groups of aliphatic hydrocarbons. These band positions fall within 5 cm-1 of the values normal for saturated aliphatics. The absence of a distinct band near 2855 cm-1 suggests that the material contains small amounts of electronegative groups like -O-H or -C triple bond N. The relative strengths and profiles of the 2955 and 2925 cm-1 features towards five objects suggests an average diffuse ISM line-of-sight -CH2-/-CH3 ratio of about 2.5, indicating the presence of relatively complex organic materials. The strengths of the subpeaks at 2925 and 2955 cm-1, due to -CH2- and -CH3 groups, respectively, correlate with visual extinction, strongly suggesting that the C-H stretching band is a general feature of the material along different lines of sight in the diffuse ISM. We find average ratios of A nu/tau(2925 cm-1) = 240 +/- 40 and A nu/tau(2955 cm-1) = 310 +/- 90 for the objects we have observed. We deduce that 2.6%-35% of the cosmic carbon in the ISM is tied up in the carrier of this band with the most likely value falling near 10%. The interstellar C-H band is remarkably similar to the feature in lab residues produced by irradiating analogs of dense molecular cloud ices. This is consistent with a model in which the hydrocarbon component in the diffuse interstellar medium consists of complex hydrocarbons containing aliphatic side chains and bridges which are produced in dense molecular clouds and subsequently modified in the diffuse medium.