DPS 42nd Meeting Abs..

Session Number: 48Session Title: Laboratory ResearchSession Type: Poster48.01: Atomic Carbon Chemistry in Photolyzed Triton-like IcesAuthor Block: Paul Johnson 1 , R. Hodyss 1 , H. R. Howard 1 , J. D. Goguen 1 , I. Kanik 11 JPL.Presentaon Time: 10/4/2010 4:22 PM - 4:24 PMLocaon: Exhibit HallAbstract: We report photochemical studies of thin cryogenic ice films composed of N 2 , CH 4 and CO in raos similar to those on the surfaces of Neptune’slargest satellite, Triton, and on Pluto. Experiments were performed using a hydrogen discharge lamp, which provides an intense source of ultraviolet light in orderto elucidate the solar induced photochemistry of these icy bodies. Characterizaon via infrared spectroscopy showed that C 2 H 6 and C 2 H 2 , and HCO are formed bythe dissociaon of CH 4 into H and CH 3 and the subsequent reacon of these radicals within the ice. Other radical species, such as C 2 , C - 2 , CN, a nd CNN a re obs e rve d i nthe vi s i bl e a nd UV re gi ons of the s pe ctrum. The s e s pe ci e s i mpl y a ri ch che mi s try ba s e d on re a cons of a tomi c ca rbon wi th the N 2 ma tri x. We di s cus s the i mpl i ca ons of the forma on of the s era di ca l s for the che mi ca l e vol uon of Tri ton a nd Pl uto. Ul ma te l y, thi s work s ugge s ts tha t C - 2 , CN, HCO, and CNN may be found in significant quanes on the surfaces of Triton and Pluto and that new observaons of these objects in theappropriate wavelength regions are warranted.48.02: Radiaon Synthesis Of Carbon Dioxide From Ice-coated C-13 FoilAuthor Block: Ujjwal Raut 1 , D. Fulvio 1 , M. J. Loeffler 2 , R. A. Baragiola 11 University of Virginia, 2 NASA GSFC.Presentaon Time: 10/4/2010 4:24 PM - 4:26 PMLocaon: Exhibit HallAbstract: We have studied the synthesis of 13 CO 2 from 100 keV proton irradiaon of ~ 100 nm thick amorphous water ice film on top of an amorphous 13 C foil(95% isotopic purity, ~ 50 nm thick) at 20 and 120 K using infrared spectroscopy and microbalance techniques. In contrast to previous work, we use pure carboninstead of hydrogenated carbon grains (Mennella et.al., 2004). We also spuer clean the carbon surface using 100 keV Ar + to remove any atmosphericcontaminants prior to deposion of the water ice layer.At 20K, the producon of 13 CO 2 increases linearly with fluence and saturates at a column density of ~ 1 × 10 15 CO 2 cm -2 . At 120K, the CO 2 column densityincreases linearly with fluence at a rate ~ 43% higher than at 20 K. Further, the rate of CO 2 producon doubles following a fluence of 7 × 10 15 H + cm -2 . Thesaturaon column density at 120 K is ~ 2.7 × 10 15 CO 2 cm -2 , nearly three mes larger than at 20 K. The profile of the ν 3 absorpon feature due asymmetric stretchof the C-O bond indicates that the CO 2 produced from radiaon is dispersed in the water ice, as opposed to being in aggregates at both temperatures.We will discuss the radiaon-induced chemical processes near the water ice - carbon interface that are involved in the synthesis of carbon dioxide. In parcular,the formaon and trapping of O 2 from radiolysis of water ice at high temperatures (Teolis et.al. 2009) could play an important role in the enhancement of CO 2producon at 120K. The formaon of CO 2 via radiolysis of the water ice-carbon interface can contribute to the solid CO 2 observed on the interstellar grains andon the surfaces of the Jovian satellites such as Ganymede and Callisto.48.03: Thermal Conducvies of Two Basalc Achondrite MeteoritesAuthor Block: Guy Consolmagno 1 , C. P. Opeil 2 , D. T. Bri 31 Vacan Obs., Holy See (Vacan City State), 2 Boston College, 3 University of Central Florida.Presentaon Time: 10/4/2010 4:26 PM - 4:28 PMLocaon: Exhibit HallAbstract.Abstract: In our ongoing survey of the physical properes of meteorites, we have measured the thermal conducvity for the basalc achondritemeteorites Frankfort, a howardite likely to be typical of material on the surface of asteroid 4 Vesta, and Los Angeles, a shergote believed to have originated onMars, at temperatures ranging from 300K to 5K. From 300K to 100K, the conducvity of Frankfort decreases gradually from 1.6 to 1.2 W/mK; that of Los Angelesdrops from 0.9 to 0.5 W/mK. At lower temperatures the thermal conducvity of both meteorites connues to drop, but more rapidly, to values below 0.1 W/mK at10K. We find that for both meteorites the conducvity is significantly lower than would be expected from averaging the laboratory conducvies of theirconstuent minerals. These results are similar to results from measurements of ordinary chondrites (Opeil et al 2010, Icarus 208, 449). The monotonic decreaseof conducvity with temperature over this range is different from the expected conducvity of pure minerals, which tend to vary as 1/T. This indicates that, incommon with the ordinary chondrites, the conducvity we measure is controlled by the presence of shock-induced microcracks within the meteorites, whichprovide a barrier to the transmission of thermal energy via phonons. Thus these measurements may accurately describe the conducvity of material at thesurfaces of their parent bodies. However results from surface samples may significantly underesmate the actual conducvity of material deeper in the parentbodies, depending on how characterisc the shock history of these meteorites reflects material sll in place inside these bodies.48.04: Low-Energy Impacts onto Lunar RegolithAuthor Block: Laura M. Seward 1 , J. Colwell 1 , M. Mellon 21 University of Central Florida, 2 University of Colorado at Boulder.Presentaon Time: 10/4/2010 4:28 PM - 4:30 PMLocaon: Exhibit HallAbstract.Abstract: We are conducng a program of laboratory experiments to study low velocity impacts of 1 to 5 m/s into regolith. We use direct measurementof ejecta mass and high resoluon video tracking of ejecta parcle trajectories to derive ejecta mass velocity distribuons. We wish to characterize andunderstand the collision parameters that control the outcome of low velocity impacts into regolith, including impact velocity, impactor mass, target sizedistribuon, regolith depth, and target relave density, and to experimentally determine the funconal dependencies of the outcomes of low velocity collisions(ejecta mass and ejecta velocies) on the controlling parameters of the collision. Our goal is to understand the physics of ejecta producon and regolithcompacon in low energy impacts and experimentally validate predicve models for dust flow and deposion. We will present results from our ongoing studyshowing the posive correlaon between impact energy and ejecta mass. Our results show that the ejecta mass fracon decreases as a funcon of esmatedejecta mass velocity. We will also discuss the effect of pressure, target mass density, target mass type, impactor type, and how these factors may affect ourresults.48.05: Rate Constant Values for Some Hydrocarbon and Nitrogenous Species Reacons at Low Pressure and TemperatureAuthor Block: Gregory P. Smith 1