Search Publications
Heavy Positive Ion Groups in Titan's Ionosphere from Cassini Plasma Spectrometer IBS Observations
Coates, Andrew J.; Lavvas, Panayotis; Waite, J. Hunter +4 more
Titan's ionosphere contains a plethora of hydrocarbons and nitrile cations and anions as measured by the Ion Neutral Mass Spectrometer and Cassini Plasma Spectrometer (CAPS) on board the Cassini spacecraft. Data from the CAPS Ion Beam Spectrometer (IBS) sensor have been examined for five close encounters of Titan during 2009. The high relative vel…
Volatile Composition and Outgassing in C/2018 Y1 (Iwamoto): Extending Limits for High-resolution Infrared Cometary Spectroscopy between 2.8 and 5.0 µm
Vervack, Ronald J., Jr.; Kawakita, Hideyo; DiSanti, Michael A. +7 more
We used the powerful high spectral resolution cross-dispersed facility spectrograph, iSHELL, at the NASA Infrared Telescope Facility (IRTF) to observe C/2018 Y1 (Iwamoto), a long-period comet from the Oort cloud. We report production rates for water and eight other parent molecules (native ices), C2H6, CO, CH4, H
Midsummer Atmospheric Changes in Saturn's Northern Hemisphere from the Hubble OPAL Program
Wong, Michael H.; Hueso, Ricardo; Sánchez-Lavega, Agustín +1 more
Using the Hubble Space Telescope, Saturn was observed in 2018, 2019, and 2020, just after the northern hemisphere summer solstice. Analysis of multispectral imaging data reveals three years of cloud changes associated with a 70° N storm that began in 2018. Additionally, there is an increase in equatorial brightness and perhaps haze optical depth a…
Constraining the Positive Ion Composition in Saturn's Lower Ionosphere with the Effective Recombination Coefficient
Vigren, Erik; Wahlund, Jan-Erik; Dreyer, Joshua +4 more
The present study combines Radio and Plasma Wave Science/Langmuir Probe and Ion and Neutral Mass Spectrometer data from Cassini's last four orbits into Saturn's lower ionosphere to constrain the effective recombination coefficient α300 from measured number densities and electron temperatures at a reference electron temperature of 300 K.…
A Case for a Small to Negligible Influence of Dust Charging on the Ionization Balance in the Coma of Comet 67P
Rubin, M.; Vigren, E.; Eriksson, A. I. +3 more
A recent work aided by Rosetta in situ measurements set constraints on the dust-to-gas mass emission ratio and the size distribution of dust escaping the nucleus of comet 67P/Churyumov-Gerasimenko near perihelion. Here we use this information along with other observables/parameters as input into an analytical model aimed at estimating the number d…
The Mars Orbiter for Resources, Ices, and Environments (MORIE) Science Goals and Instrument Trades in Radar, Imaging, and Spectroscopy
Murchie, Scott L.; Ehlmann, Bethany L.; Calvin, Wendy M. +9 more
The Mars Orbiter for Resources, Ices, and Environments (MORIE) was selected as one of NASA's 2019 Planetary Mission Concept Studies. The mission builds upon recent discoveries and current knowledge gaps linked to two primary scientific questions: (1) when did elements of the cryosphere form and how are ice deposits linked to current, recent, and a…
Variable X-Ray Emission of Comet 46P/Wirtanen
Bodewits, Dennis; Christian, Damian J.; Koutroumpa, Dimitra +3 more
In this paper, we present an analysis of X-ray and optical/ultraviolet (UV) data from the favorable (Δ ~ 0.077 au) 2018 apparition of comet 46P/Wirtanen. The comet was observed during three different epochs (before, during, and after perihelion) over a 1.5 month period using the X-Ray Telescope (XRT) and Ultraviolet and Optical Telescope (UVOT) in…
Exploring Ceres's Unusual Regolith Porosity and Its Implications for Volatile Retention
Heggy, Essam; Palmer, Elizabeth M.; Letertre, Thibaut +1 more
Asteroid Ceres, the only dwarf planet located in the inner solar system, shows unique surface mineralogy and geomorphology as observed by the Dawn mission. Of particular interest is understanding the role that upper regolith porosity plays in retaining volatiles and shaping Ceres' surface. Unfortunately, Ceres' near-surface porosity remains largel…
No Evidence for Time Variation in Saturn's Internal Magnetic Field
Cao, Hao; Bloxham, Jeremy; Moore, Kimberly M. +2 more
The time variation of a planetary magnetic field can reveal important aspects of a planet's interior structure. Searching for time variation in planetary magnetic fields other than Earth has proved challenging owing to the small number of spacecraft missions flown to date, but such a detection may be possible given a sufficiently long baseline for…
The Dark Side of Pluto
White, Oliver L.; Bertrand, Tanguy; McKinnon, William B. +10 more
During its departure from Pluto, New Horizons used its LORRI camera to image a portion of Pluto's southern hemisphere that was in a decades-long seasonal winter darkness, but still very faintly illuminated by sunlight reflected by Charon. Recovery of this faint signal was technically challenging. The bright ring of sunlight forward-scattered by ha…