Spectroscopy comets

For remote sensing, spectroscopy at THz frequencies holds the key to our ability to remotely sense enviromnents as diverse as primaeval galaxies, star and planet-fonuing molecular cloud cores, comets and planetary atmospheres. 

Throughout the book I have tried to constrain the wonders of imagination inspired by the subject by using simple calculations. Can all of the water on the Earth have been delivered by comets if so, how many comets How do I use molecular spectroscopy to work out what is happening in a giant molecular cloud Calculations form part of the big hard-sell for astrochemistry and they provide a powerful control against myth. I have aimed the book at second-year undergraduates who have had some exposure to quantum mechanics, kinetics, thermodynamics and mathematics but the book could easily be adapted as an introduction to all of these areas for a minor course in chemistry to stand alone. 

Kurt Varmuza was bom in 1942 in Vienna, Austria. He studied chemistry at the Vienna University of Technology, Austria, where he wrote his doctoral thesis on mass spectrometry and his habilitation, which was devoted to the field of chemometrics. His research activities include applications of chemometric methods for spectra-structure relationships in mass spectrometry and infrared spectroscopy, for structure-property relationships, and in computer chemistry, archaeometry (especially with the Tyrolean Iceman), chemical engineering, botany, and cosmo chemistry (mission to a comet). Since 1992, he has been working as a professor at the Vienna University of Technology, currently at the Institute of Chemical Engineering. 

Spectroscopy covers a very wide area which has been widened further since the mid-1960s by the development of lasers and such techniques as photoelectron spectroscopy and other closely related spectroscopies. The importance of spectroscopy in the physical and chemical processes going on in planets, stars, comets and the interstellar medium has continued to grow as a result of the use of satellites and the building of radiotelescopes for the microwave and millimetre wave regions. 

Carbonates are common in hydrous meteorites and hydrous IDPs, where they are believed to have formed by parent-body aqueous processing. Since simple models of cometary evolution involve no aqueous processing, carbonates were generally presumed not to occur in comets. However, carbonates have also been detected by infrared spectroscopy in the dust shell around evolved stars and in protostars, where liquid water is not expected (Ceccarelli et al. 2002 Kemper et al. 2002). Indeed, Toppani et al. (2005) have performed experiments that indicate that carbonates can be formed by non-equilibrium condensation in circumstellar environments where water is present as vapor, not as liquid. Detections of carbonates in other exosolar systems are reported by Ceccarelli et al. (2002) and Chiavassa et al. (2005). 

Both the analysis of Comet Wild 2 dust particles (Brownlee et al. 2006) and infrared spectroscopy of dust particles from comets Halley, Hale-Bopp, and Tempel 1 (Lisse et al. 2006) have shown that crystalline silicates are common constituents of comets. The presence of crystalline silicates in comets indicates that the crystallization of amorphous interstellar silicates occurred in the comet-forming region... 

The recent ai roach of large comets such as IP/Halley, C71996 B2 Hyakutake, and C/1995 Ol Hale-Bopp to the Earth provided a good opportunity to investigate the detailed composition of cometary ices by various methods such as mass spectrometry, infrared spectroscopy, and radio emission. The composition of interstellar ices is compared with that of the cometary ices in Table 9.3. It is striking that cometary and interstellar ices have quite comparable relative molecular abundances. 

Herzberg contributed to the field of atomic and molecular spectroscopy, where he and his colleagues determined the structures of a large number of diatomic and polyatomic molecules, the structures of free radicals, and the identification of certain molecules in planetary atmospheres, in comets, and in interstellar space. In 1971 he was awarded the Nobel Prize in chemistry for his contributions to the knowledge of electronic structure and geometry of molecules, particularly free radicals. ... 

Information on the chemical composition of active comets is available from two different "reservoirs , viz. solid debris and sublimated volatile species. The former is extracted by IR spectroscopy of the dust tail and dust trails in the comet s orbit, from collected IDPs, possibly a fraction of CI carbonaceous meteorites, and from meteor data. Information on species in the comet coma and plasma tail is obtained by UV-VIS-IR spectroscopy and radio astronomy. 

Comets EUV spectroscopy in-situ dust collection (see also IDPs) Cl chondritic meteorites Ar abundance, upper limits for He, Ne. Stem 1999a. Stardust mission Lodders and Osborne 1999 Ehrenfreund et al. 2001. 

Noble gases are intrinsically difficult to detect by spectroscopy. For example, solar photospheric spectra, which form the basis for solar abundance values of most elements, do not contain lines from noble gases (except for He, but this line cannot be used for abundance determinations). Yet, ultraviolet spectroscopy is the only or the major source of information on noble gas abundances in the atmospheres of Mercury and comets. In the Extreme Ultraviolet (EUV), photon energies exceed bond energies of molecules and the first ionization potential of all elements except F, He, and Ne, so that only these elements are visible in this part of the spectrum (Krasnopolsky et al. 1997). Other techniques can be used to determine the abundance of He where this element is a major constituent. Studies of solar oscillations (helioseismology) allow a precise determination of the He abundance in the solar interior, and the interferometer on the Galileo probe yielded a precise value for the refractive index and hence the He abundance in the upper atmosphere of Jupiter (see respective sections of this chapter). 

Krasnopolsky VA, Mumma MJ (2001) Spectroscopy of comet Hyakutake at 80-700 A First detection of solar wind charge-transfer emissions. Astrophys J 549 629-634 Krasnopolsky VA, Bowyer S, Chakrabarti S, Gladstone GR, McDonald JS (1994) First measurement of helium on Mars implications for the problem of radiogenic gases on the terrestrial planets, learns 109 337-351... 

Special kinds of telescopes allow astrochemists to perform spectroscopy on the light (or any type of electromagnetic radiation, not just visible light) coming from a star or other celestial body. Certain features of this radiation allow chemists to measure the quantities of different elements emd the surface temperatures of objects like stars and comets. 

Redmond MP, Comet SM, Woodall SD et al (2011) Probing the local coordination environment and nuclearity of uranyl(VI) complexes in non-aqueous media by emission spectroscopy. Dalton Trans 40 3914-3926... 

C. Arpigny, F. Dossin, J. Manfroid, P. Magain, A.C. Danks, D.L. Lambert, C. Sterken Spectroscopy, photometry and direct filter imagery of comet P/Halley. ESO Messenger 45, 10 (1986)... 

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