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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2007.11.020 Byline: Eric E. Palmer, Robert H. Brown Keywords: Iapetus; Ices Abstract: Carbon dioxide has been detected associated with Iapetus' dark material by the Cassini spacecraft. This CO.sub.2 may be primordial and/or resulting from ongoing production by photolysis of water-ice in the presence of carbonaceous material [Allamandola, L.J., Sandford, S.A., Valero, G.J., 1988. Icarus 76, 225-252]. Although any primordial CO.sub.2 would likely be complexed with the dark material and thus stable against thermal transport to Iapetus' poles [Buratti, B.J., and 28 colleagues, 2005. Astrophys. J. 622, L149-L152], active production of CO.sub.2 would result in some fraction of the CO.sub.2 being mobile enough to allow the accumulation of CO.sub.2 at Iapetus' poles. We develop a computer model to simulate ballistic transport of CO.sub.2 ice on Iapetus, accounting for Iapetus' gravitational binding energy and polar cold traps. We find that the residence time of CO.sub.2 ice outside the polar regions is very short; a sheet of CO.sub.2 ice near the equator of Iapetus decreases in thickness at a rate of 50 mmayear.sup.-1. The sublimated CO.sub.2 will ballistically move around Iapetus until it reaches the polar cold traps where it can be sequestered for up to 15 years. If the total surface inventory of CO.sub.2 exceeds 3x10.sup.7 kg, the polar ice cap will be permanent. While CO.sub.2 is moving around the surface, a small percentage will eventually reach escape velocity and be lost from the system. As such, a seasonal polar cap is lost at rate of 12% every solar orbit as the CO.sub.2 moves between the two polar cold traps. Author Affiliation: Lunar and Planetary Laboratory, 1629 E. University Blvd., The University of Arizona, Tucson, AZ 85721-0092, USA Article History: Received 5 February 2007; Revised 9 November 2007

We present global-scale maps of Titan from the Visual and Infrared Mapping Spectrometer (VIMS) instrument on Cassini. We map at 64 near-infrared wavelengths simultaneously, covering the atmospheric windows at 0.94, 1.08, 1.28, 1.6, 2.0, 2.8, and 5 [micro]m with a typical resolution of 50 km/pixel or a typical total integration time of 1 s. Our maps have five to ten times the resolution of ground-based maps, better spectral resolution across most windows, coverage in multiple atmospheric windows, and represent the first spatially resolved maps of Titan at 5 [micro]m. The VIMS maps provide context and surface spectral information in support of other Cassini instruments. We note a strong latitudinal dependence in the spectral character of Titan's surface, and partition the surface into 9 spectral units that we describe in terms of spectral and spatial characteristics. Keywords: Titan

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.icarus.2006.02.006 Byline: Rachel M.E. Mastrapa (a), Robert H. Brown (b) Keywords: Ices; Infrared observations; Kuiper belt objects; Radiation chemistry; Spectroscopy Abstract: We have found that 0.8 MeV proton irradiation of crystalline H.sub.2O-ice results in temperature dependent amorphization. The H.sub.2O-ice's phase was determined using the near infrared spectrum from 1.0 [mu]m (10,000 cm.sup.-1) to 2.5 [mu]m (4000 cm.sup.-1). In crystalline H.sub.2O-ice, the 1.65-[mu]m (6061 cm.sup.-1) band is strong while it is nearly absent in the amorphous spectrum [Schmitt, B., Quirico, E., Trotta, F., Grundy, W.M., 1998. In: Schmitt, B., de Bergh, C., Festou, M. (Eds.), Solar System Ices. Kluwer Academic, Norwell, MA, 1998, pp. 199-240]. In this experiment, at low temperatures (9, 25, and 40 K), irradiation of crystalline H.sub.2O-ice produced the amorphous H.sub.2O-ice's spectrum. However, at 50 K, some crystalline absorptions persisted after irradiation and at 70 and 100 K the crystalline spectrum showed only slight changes after irradiation. Our results agree with previous H.sub.2O-ice irradiation studies examining the crystalline peaks near 44 and 62 [mu]m by Moore and Hudson [Moore, M.H., Hudson, R.L., 1992. Astrophys. J. 401, 353-360] and near 3.07 [mu]m by Strazzulla et al. [Strazzulla, G., Baratta, G.A., Leto, G., Foti, G., 1992. Europhys. Lett. 18, 517-522] and by Leto and Baratta [Leto, G., Baratta, G.A., 2003. Astron. Astrophys. 397, 7-13]. We present a method of measuring band areas to quantify the phase and radiation dose of icy Solar System surfaces. Author Affiliation: (a) Astrophysics Branch, NASA Ames Research Center, Mail Stop 245-6, Moffett Field, CA 94035-1000, USA (b) Department of Planetary Sciences, The University of Arizona, Tucson, AZ 85721, USA Article History: Received 6 December 2005; Revised 14 February 2006

We present the first spectrum through the L band of an irregular satellite from the outer Solar System. Spectra of Himalia (JVI) were obtained with the Visual and Infrared Mapping Spectrometer (VIMS) onboard the Cassini spacecraft. The Himalia spectrum is essentially featureless, showing a slight red slope and the suggestion of an absorption at 3[micro]m that might indicate the presence of water in some form. Better measurements of the spectrum of Himalia, particularly in the region of the apparent 3-[micro]m band, could help determine whether water is present, and if so, in what form. Keywords: Satellites of Jupiter; Infrared observations: Spectroscopy

A report of the detection of the C-H hydrocarbon band complex at 3.4/[micro]m in an asteroid spectrum, by D. P. Cruikshank and R. H. Brown (1987, Science 238, 183-184) is not confirmed by recent data of higher quality. Spectra of the same asteroid and six other low-albedo asteroids do not show this feature, which if present would indicate the presence of hydrocarbons and might link these asteroids with certain classes of carbonaceous meteorites. Key Words: asteroid composition; infrared observations; organic chemistry; spectroscopy; asteroid surfaces.

A near-infrared spectrum of Neptune's satellite Nereid was obtained at the Keck Observatory on 1997 May 1. The spectrum shows two absorptions near 1.54 and 2.03 [[micro]meter] and is well matched by a synthetic spectrum of an intimate mix of low-temperature, particulate water ice and dark, blue-colored material. Comparisons of Nereid's spectrum with those of other objects such as the Centaurs 1997 [CU.sub.26] and 5145 Pholus, and Neptune's largest regular satellite Proteus, admit the possibility that Nereid is a primordial satellite of Neptune (and perhaps its only remaining one) rather than a captured object, but more data are needed to rule out one scenario or the other. Key Words: Nereid; surface composition; surfaces, icy; spectroscopy.

An analysis of the absorption coefficients of solid nitrogen (N) shows that it's near-infrared spectrum is temperature dependent. The observed spectrum is in the region of fundamental vibrational transition and its first overtone. The temperature of nitrogen in Solar System objects can be calculated using the results obtained from groundbased spectroscopic measurements and spectrum analysis in the overtone region. The experiment is done in the temperature range of 35 to 60 K.

Spectroscopic observations of Pluto reveal that the nitrogen ice on Pluto has a temperature of 40 Kelvin. This is higher than the temperature of nitrogen on the satellite Triton. The study indicates that the nitrogen on the planet is concentrated at the polar caps of the planet and absent in the equatorial region.

Asteroid 16 Psyche is likely the metal-rich core of a larger differentiated parent body which suffered a catastrophic collision. During July 1994, Psyche presented a near-equatorial aspect and we repeatedly measured its visible (0.5-0.9 [micro]m) spectrum over its rotation to search for variations which might arise if large mafic silicate units remain on its surface. Within our measurement precision of 1%, we find no evidence for any significant variation in Psyche's visible reflectance spectrum. Comparisons with mixture models suggest that if any olivine is present, its large-scale distribution does not vary by more than 15% if it resides in a state physically separated from the metal phase. The upper limit for any olivine variation is 30% if it exists in an intimate mixture with metal.

We report the first detection and profile characterization of thermal emission from the surface of Venus at 0.85 and 0.90 [micro]m, observed in the first planetary spectrum acquired by the Visual-Infrared Mapping Spectrometer onboard the Cassini spacecraft en route to the Saturn system. The strength and shape of these two newly observed nightside emissions agree with theoretical predictions based on the strength of the strong emission observed at 1.01 [micro]m. These emissions, together with previously-reported surface emission features at 1.01, 1.10, and 1.18 [micro]m, potentially provide a new technique for remotely mapping the mineralogical composition of the venusian surface. [C] 2000 Academic Press Key Words: Venus; spectrophotometry; surfaces, Planets; Venus, surface; minerology.

Using the CoCo Cold Coronagraph at NASA's Infrared Telescope Facility on Manna Kea, we observed the uranian satellites Miranda, Puck, Portia, and Rosalind and the neptunian satellite Proteus in the near infrared (JHK) to determine the albedos of those faint satellites. In V-J, all of Puck, Portia, Rosalind, and Proteus are very blue, similar to the colors of many icy satellites and of water ice. The satellites we observed have a wide range of J-H colors, with Miranda being blue, Proteus being gray, and Puck, Portia, and Rosalind being red. For the satellites for which we could determine H-K (Miranda, Puck, and Proteus), the colors are gray to red. As a whole, spectrally, these five satellites lie between icy Solar System satellites (e.g., saturnian satellites or the major uranian satellites) and Kuiper belt objects. The redness of Proteus and Puck and perhaps other satellites suggests the presence of organic material, although the redness is also similar to that of C- and D-class asteroids and some outer jovian moons. In all cases, diagnostic spectral features could be masked by broadband photometry. [C] 2000 Academic Press Key Words: satellites of Uranus; satellites of Neptune; infrared observations; spectrophotometry; ices.

Abstract: We have found that 0.8 MeV proton irradiation of crystalline H2O–ice results in temperature dependent amorphization. The H2O–ice''s phase was determined using the near infrared spectrum from 1.0 μm (10,000 cm−1) to 2.5 μm (4000 cm−1). In crystalline H2O–ice, the 1.65-μm (6061 cm−1) band is strong while it is nearly absent in the amorphous spectrum [Schmitt, B., Quirico, E., Trotta, F., Grundy, W.M., 1998. In: Schmitt, B., de Bergh, C., Festou, M. (Eds.), Solar System Ices. Kluwer Academic, Norwell, MA, 1998, pp. 199–240]. In this experiment, at low temperatures (9, 25, and 40 K), irradiation of crystalline H2O–ice produced the amorphous H2O–ice''s spectrum. However, at 50 K, some crystalline absorptions persisted after irradiation and at 70 and 100 K the crystalline spectrum showed only slight changes after irradiation. Our results agree with previous H2O–ice irradiation studies examining the crystalline peaks near 44 and 62 μm by Moore and Hudson [Moore, M.H., Hudson, R.L., 1992. Astrophys. J. 401, 353–360] and near 3.07 μm by Strazzulla et al. [Strazzulla, G., Baratta, G.A., Leto, G., Foti, G., 1992. Europhys. Lett. 18, 517–522] and by Leto and Baratta [Leto, G., Baratta, G.A., 2003. Astron. Astrophys. 397, 7–13]. We present a method of measuring band areas to quantify the phase and radiation dose of icy Solar System surfaces. [Copyright &y& Elsevier]