Search Publications
Negative ion chemistry in Titan's upper atmosphere
Lewis, G. R.; Coates, A. J.; Wahlund, J. -E. +5 more
The Electron Spectrometer (ELS), one of the sensors making up the Cassini Plasma Spectrometer (CAPS) revealed the existence of numerous negative ions in Titan's upper atmosphere. The observations at closest approach (∼1000 km) show evidence for negatively charged ions up to ∼10,000 amu/q, as well as two distinct peaks at 22±4 and 44±8 amu/q, and m…
An improvement to the volcano-scan algorithm for atmospheric correction of CRISM and OMEGA spectral data
Seelos, Frank P.; Murchie, Scott L.; Mustard, John F. +12 more
The observations of Mars by the CRISM and OMEGA hyperspectral imaging spectrometers require correction for photometric, atmospheric and thermal effects prior to the interpretation of possible mineralogical features in the spectra. Here, we report on a simple, yet non-trivial, adaptation to the commonly-used volcano-scan correction technique for at…
INMS-derived composition of Titan's upper atmosphere: Analysis methods and model comparison
Mandt, Kathleen E.; Waite, J. Hunter; Magee, Brian A. +3 more
The Cassini Ion and Neutral Mass Spectrometer (INMS) has recorded full altitude profile data from 20 low-altitude Titan encounters during the nominal mission (July 2004-2008). These encounters were TA, T5, T16, T18, T19, T21, T23, T25, T26, T28, T29, T30, T32, T36, T37, T39, T40, T41, T42, and T43. In this work we present an analysis of the data o…
The Circum-Hellas Volcanic Province, Mars: Overview
McCord, Thomas B.; HRSC Co-Investigator Team; Xiao, Long +13 more
Building on previous studies of volcanoes around the Hellas basin with new studies of imaging (High-Resolution Stereo Camera (HRSC), Thermal Emission Imaging System (THEMIS), Mars Orbiter Camera (MOC), High-Resolution Imaging Science Experiment (HiRISE), Context Imager (CTX)), multispectral (HRSC, Observatoire pour la Minéralogie, l'Eau, les Glace…
Recurrent energization of plasma in the midnight-to-dawn quadrant of Saturn's magnetosphere, and its relationship to auroral UV and radio emissions
Gurnett, D. A.; Dougherty, M. K.; Krimigis, S. M. +11 more
We demonstrate that under some magnetospheric conditions protons and oxygen ions are accelerated once per Saturn magnetosphere rotation, at a preferred local time between midnight and dawn. Although enhancements in energetic neutral atom (ENA) emission may in general occur at any local time and at any time in a Saturn rotation, those enhancements …
Extremely high reflection of solar wind protons as neutral hydrogen atoms from regolith in space
Barabash, Stas; Holmström, Mats; Futaana, Yoshifumi +7 more
We report on measurements of extremely high reflection rates of solar wind particles from regolith-covered lunar surfaces. Measurements by the Sub-keV Atom Reflecting Analyzer (SARA) instrument on the Indian Chandrayaan-1 spacecraft in orbit around the Moon show that up to 20% of the impinging solar wind protons are reflected from the lunar surfac…
The Mars express MARSIS sounder instrument
Gurnett, D.; Orosei, R.; Picardi, G. +16 more
The Mars advanced radar for subsurface and ionospheric sounding (MARSIS) on Mars Express is the first high-frequency sounding radar operating from orbital altitudes since the Apollo 17 Lunar Sounder flown in 1972. The radar operates from a highly elliptical orbit but acquires data only from altitudes lower than 1200 km. The periapsis altitude is 2…
Detection of dusty plasma near the E-ring of Saturn
Gurnett, D. A.; Hospodarsky, G. B.; Kurth, W. S. +12 more
We present several independent in-situ measurements, which provide evidence that charged dust in the E-ring interacts collectively with the dense surrounding plasma disk of Saturn, i.e., form a system of dust-plasma interaction. The results are based on data sampled by the Radio and Plasma Wave Science (RPWS) investigation onboard Cassini, which a…
Heavy ions, temperatures and winds in Titan's ionosphere: Combined Cassini CAPS and INMS observations
Young, D. T.; Waite, J. H.; Magee, B. A. +3 more
Multiple Titan encounters by the Cassini spacecraft have shown that ion chemistry in Titan's upper atmosphere is much more complex than previously thought. As well as showing a great variety of species present below 100 amu, they also include the detection of negative ions and of large abundances of ions above 100 amu. Here, we use data from two C…
On the ionospheric structure of Titan
Garnier, P.; Wahlund, J. -E.; Ågren, K. +4 more
In this study we present data from 17 Titan flybys showing that solar photons are the main ionisation source of Titan's dayside atmosphere. This is the first comprehensive study of Solar Zenith Angle (SZA) dependence of the electron number density and electron temperature at the ionospheric peak. The results show on average four times more plasma …