Ben Teolis

Ben Teolis
Southwest Research Institute · Space Science and Engineering Division

PhD

About

106
Publications
11,046
Reads
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2,581
Citations
Additional affiliations
January 2007 - present
Southwest Research Institute
Position
  • Planetary Scientist
August 2000 - February 2007
University of Virginia
Position
  • Research Assistant

Publications

Publications (106)
Article
A Europa plume source, if present, may produce a global exosphere with complex spatial structure and temporal variability in its density and composition. To investigate this interaction we have integrated a water plume source containing multiple organic and nitrile species into a Europan Monte Carlo exosphere model, considering the effect of Europa...
Article
A Dione O2 and CO2 exosphere of similar composition and density to Rhea's is confirmed by Cassini spacecraft Ion Neutral Mass Spectrometer (INMS) flyby data. INMS results from three Dione and two Rhea flybys show exospheric spatial and temporal variability indicative of seasonal exospheres, modulated by winter polar gas adsorption and desorption at...
Article
Cassini Ion Neutral Mass Spectrometer (INMS) measurements from roughly a hundred Titan encounters over the Cassini mission yield neutral and ion densities systematically lower, by factors approximately 2 to 3, than estimates from several other spacecraft systems, including the Attitude and Articulation Control System, and Navigation system. In this...
Article
Sharp magnetic perturbations found by the Cassini spacecraft at the edge of the Rhea flux tube are consistent with field-aligned flux tube currents. The current system results from the difference of ion and electron gyroradii and the requirement to balance currents on the sharp Rhea surface. Differential-type hybrid codes that solve for ion velocit...
Article
Full-text available
The flyby measurements of the Cassini spacecraft at Saturn's moon Rhea reveal a tenuous oxygen (O(2))-carbon dioxide (CO(2)) atmosphere. The atmosphere appears to be sustained by chemical decomposition of the surface water ice under irradiation from Saturn's magnetospheric plasma. This in situ detection of an oxidizing atmosphere is consistent with...
Article
Full-text available
Plain Language Summary Charon's thin methane atmosphere undergoes “explosive” pulsations owing to the Pluto‐Charon's systems' near sideways tilt to the Sun, according to new computer simulations that we present here. Spring sunrise may drive polar methane frozen during the centuries long winter night back into Charon's atmosphere, causing the whole...
Article
Full-text available
Volatiles and refractories represent the two end-members in the volatility range of species in any surface-bounded exosphere. Volatiles include elements that do not interact strongly with the surface, such as neon (detected on the Moon) and helium (detected both on the Moon and at Mercury), but also argon, a noble gas (detected on the Moon) that su...
Preprint
Full-text available
The Cassini mission to the Saturn system discovered a plume of ice grains and water vapor erupting from cracks on the icy surface of the satellite Enceladus. This moon has a global ocean in contact with a rocky core beneath its icy exterior, making it a promising location to search for evidence of extraterrestrial life in the solar system. The prev...
Article
The Cassini mission to the Saturn system discovered a plume of ice grains and water vapor erupting from cracks on the icy surface of the satellite Enceladus. This moon has a global ocean in contact with a rocky core beneath its icy exterior, making it a promising location to search for evidence of extraterrestrial life in the solar system. The prev...
Article
Full-text available
We investigate a possible negative ion feature observed by the Cassini Plasma Spectrometer (CAPS) during a flyby of Saturn's moon Dione that occurred on 7 April 2010. By examining possible particle trajectories, we find that the observed particles are consistent with negative pickup ions originating near the moon's surface. We find that the mass of...
Article
The Pioneer and Voyager spacecraft made close-up measurements of Saturn’s ionosphere and upper atmosphere in the 1970s and 1980s that suggested a chemical interaction between the rings and atmosphere. Exploring this interaction provides information on ring composition and the influence on Saturn’s atmosphere from infalling material. The Cassini Ion...
Article
Full-text available
Radiolytic production has been proposed as a potential source for the molecular oxygen observed in comet 67P/Churyumov-Gerasimenko. Radiolysis can be exogenic or endogenic, the latter due to radionuclides present in the dust constitutive of the comet nucleus. We investigated the possibility of forming a significant amount of molecular oxygen throug...
Article
Full-text available
Saturn's largest icy moon, Rhea, hosts a tenuous surface-sputtered exosphere composed primarily of molecular oxygen and carbon dioxide. In this Letter, we examine Cassini Plasma Spectrometer velocity space distributions near Rhea and confirm that Cassini detected nongyrotropic fluxes of outflowing CO2+ during both the R1 and R1.5 encounters. Accoun...
Article
Full-text available
Despite the numerous modeling efforts of the past, our knowledge on the radiation-induced physical and chemical processes in Europa’s tenuous atmosphere and on the exchange of material between the moon’s surface and Jupiter’s magnetosphere remains limited. In lack of an adequate number of in situ observations, the existence of a wide variety of mod...
Article
During three low-altitude (99, 66, 66 km) flybys through the Enceladus' plume in 2011 and 2012, Cassini's ion neutral mass spectrometer (INMS) made its first high spatial resolution measurements of the plume's gas density and distribution, detecting in situ the individual gas jets within the broad plume. Since those flybys, more detailed Imaging Sc...
Article
O2, H2, and H2O2 radiolysis from water ice is pervasive on icy astrophysical bodies, but the lack of a self-consistent, quantitative model of the yields of these water products versus irradiation projectile species and energy has been an obstacle to estimating the radiolytic oxidant sources to the surfaces and exospheres of these objects. A major c...
Article
Saturn’s moon Enceladus has an ice-covered ocean; a plume of material erupts from cracks in the ice. The plume contains chemical signatures of water-rock interaction between the ocean and a rocky core. We used the Ion Neutral Mass Spectrometer onboard the Cassini spacecraft to detect molecular hydrogen in the plume. By using the instrument’s open-s...
Article
We have investigated the effects of porosity on the crystallization kinetics of amorphous solid water (ASW). Porosity in ASW films, condensed from the vapor phase at varying incidences at 10 K, was characterized using ultraviolet-visible interferometry and quartz crystal microgravimetry. The films were heated to crystallization temperatures between...
Conference Paper
The recent HST detection of possible cryovolcanic water vapor plumes at Europa, analogous to the plumes found by the Cassini spacecraft at Enceladus, constitutes a paradigm shift from a fully sputtered exosphere, to one potentially dominated, at least episodically, by a plume source. Europa’s higher gravity (contrary to Enceladus) is sufficient to...
Conference Paper
During four encounters between November 2009 and October 2015 (Table 1), the INMS operated in its Open Source Neutral Beam (OSNB) mode. Although 500 times less sensitive than the CSN mode, the OSNB mode has two advantages: 1) it can measure the velocities of the neutrals, and 2) it can measure reactive neutrals that might be affected by contact wit...
Conference Paper
We use Cassini INMS and UVIS Enceladus plume data to constrain the plume source properties and extrapolate the plume’s 3D structure and variability.
Article
During six encounters between 2008 and 2013, the Cassini Ion and Neutral Mass Spectrometer (INMS) made in situ measurements deep within the Enceladus plumes. Throughout each encounter, those measurements contained density variations that reflected the nature of the source, particularly of the high-velocity jets. Since the dominant constituent of th...
Article
We conducted a qualitative study to simulate the flux of volatile gases expected to occur at the lunar surface due to cometary impact or lunar outgassing events. A small sample cell containing 8.8 g of JSC-1A lunar soil simulant in a vacuum system with a base pressure of 1.5x10^-8 Torr was exposed to various gases using dynamic pressure dosing at r...
Conference Paper
We present results from our Europa global exospheric modeling, which includes both sputtering / radiolytic and potential plume sources, and a sophisticated treatment of the exosphere-surface interaction, i.e., surface adsorption, regolith diffusion, polar cold trapping, and re-sputtering of adsorbed materials. We consider the effect of Europa's gra...
Conference Paper
Cassini spacecraft magnetic field data at Saturn's moon Rhea reveal a field-aligned electric current system in the flux tube, which forms to satisfy the requirement to balance ion and electron currents on the moon's sharp surface. Unlike induction currents at bodies surrounded by significant atmospheres, Rhea's flux tube current system is not drive...
Conference Paper
During six encounters between 2008 and 2013, the Cassini Ion and Neutral Mass Spectrometer (INMS) made in situ measurements deep within the Enceladus plumes. Throughout each encounter, those measurements contained density variations that reflected the nature of the source, particularly of the high-velocity jets. Since the dominant constituent of th...
Article
The detection of Energetic Neutral Particles (ENP) above 10 eV can unequivocally relate a surface-bound exosphere to surface features and can monitor instantaneously the effect of plasma precipitation onto the surface. In the framework of a mission to Jupiter's moons, 2D imaging of plasma precipitation will provide important information on the plas...
Conference Paper
Cassini INMS has measured the composition of the plume of Enceladus on eight occasions with varying flyby geometries and speeds. It was observed that the early high velocity encounters indicated a significantly different measured composition than the later low velocity flybys. The higher velocity flybys contained a higher ratio of molecular hydroge...
Article
We present the first calculation of Europa's sputtering (ion erosion) rate as a function of position on Europa's surface. We find a global sputtering rate of 2×1027 H2O s-1, some of which leaves the surface in the form of O2 and H2. The calculated O2 production rate is 1×1026 O2 s-1, H2 production is twice that value. The total sputtering rate (inc...
Conference Paper
Recent Cassini Ion and Neutral Mass Spectrometer (INMS) observations of plumes and jets from Enceladus have an order-of-magnitude higher temporal and spatial resolution than earlier INMS measurements. These higher-resolution observations show areas of both high-velocity jets and lower-velocity diffuse plumes, similar to the results from the Cassini...
Conference Paper
We present far-ultraviolet (FUV) observations of Mimas and Tethys, which show evidence for likely seasonal variation in UV albedo across their surfaces. The ultraviolet is an important wavelength regime for studying the effects of photolytic and radiolytic processes, because primarily the uppermost layers of the regolith and grains are sensed in th...
Article
The magnetospheric plasma interaction with the large Galilean and Saturnian icy satellites involves a fascinating coupling of different physics: including (i) surface ion implantation, radiation chemical processing of the surface ice, and sputtering, (ii) formation, redistribution, escape, and surface recondensitation of sputtered exospheres of rad...
Conference Paper
Although designed for the higher densities in Titan's upper atmosphere, the Cassini Ion Neutral Mass Spectrometer (INMS) can observe the low-density particles in Saturn's inner magnetosphere (IM). Over the past five years, planning and implementing INMS observations of neutral molecules and water-group ions near the equatorial plane have steadily i...
Article
Full-text available
We have re-evaluated the Cassini Ion Neutral Mass Spectrometer (INMS) 12 C/ 13 C ratios in the upper atmosphere of Titan based on new calibration sensitivities and an improved model for the NH 3 background in the 13 CH 4 mass channel. The INMS measurements extrapolated to the surface give a 12 C/ 13 C in CH 4 of 88.5 ± 1.4. We compare the results t...
Article
We will present the recent finding of an O_2-CO_2 Dione exosphere by Cassini, and discuss modeling of the different north-south CO_2 density at Rhea, and the CO_2 abundance at Dione, indicating strongly seasonal CO_2 exospheres and polar frosts.
Article
We studied electrostatic charging of ice films induced by the impact of 1-200-keV Ar(+) ions and their subsequent discharging postirradiation. We derived the positive surface electrostatic potential from the kinetic energy of sputtered molecular ions and with a Kelvin probe. Measurements were performed as a function of film thickness, temperature,...
Article
Mimas and Tethys make a good comparative case for investigating weathering processes and effects. The Saturnian system is a complicated mix of neutrals, icy E-ring grains, moons, cold plasma and energetic particles. The interactions between these populations produce observable effects on the surfaces on the icy moons. The ultraviolet is a key place...
Article
The effect of magnetospheric plasma bombardment on the icy satellites is reviewed. Suggested effects range from the production and stripping of an atmosphere to modification of the chemistry and thermal properties of the surface. There has been speculation on the role of the incident plasma particles beginning with early ground based observation of...
Article
We present an improved model of the interaction between Enceladus' plume and Saturn's magnetospheric plasma using the hybrid simulation code A.I.K.E.F. (adaptive ion kinetic electron fluid). For the first time, we combine measurements from multiple instruments of Cassini: we use a Monte-Carlo model to describe the neutral density in the plume in ag...
Article
Measurements of Rhea's sputter-produced O2 and CO2 exosphere during the Cassini spacecraft's March 2, 2010 and January 11, 2011 low-altitude polar flybys have yielded a unique up close characterization of the exospheric physics. Data from the Ion Neutral Mass Spectrometer shows spatial and temporal variability consistent with a diurnal and seasonal...
Article
Full-text available
The Cassini E3, E5, and E7 encounters with Enceladus probed the south polar plumes, where the Ion and Neutral Mass Spectrometer (INMS) measured neutral H2O molecular densities up to ˜109 cm-3. We have constructed a physical model for the expected water density in the plumes, based on supersonic radial outflow from one or more of the surface vents....
Article
Full-text available
Apparent changes in the plume volatile composition measured by the Cassini Ion Neutral Mass Spectrometer as a function of the flyby speed have resulted in a more complete understanding of the plume's volatile and granular compounds. We present a baseline volatile makeup and suggest the existence of condensed high-molecular weight organic compounds...
Conference Paper
We present a re-analysis of the Cassini Ion Neutral Mass Spectrometer (INMS) isotope ratios based on updated sensitivity values [1] and apply a basic atmospheric model to compare the INMS measurements with the revised Huygens Gas Chromatograph Mass Spectrometer (GCMS) isotopic ratios for 14N/15N in N2 and 12C/13C in CH4 [2]. The revised ratios for...
Conference Paper
We present new measurements of Rhea's O2 - CO2 exosphere from Cassini's 11 January 2011 south polar flyby revealing time variability in the gas density and distribution at this Saturnian icy satellite (Figs. 1-2). The existence of an exosphere; first suggested by Cassini Plasma Spectrometer observations of outflowing pickup ions, was recently confi...
Article
Full-text available
The Cassini Ultraviolet Imaging Spectrograph (UVIS) observed an occultation of the Sun by the water vapor plume at the south polar region of Saturn's moon Enceladus. The Extreme Ultraviolet (EUV) spectrum is dominated by the spectral signature of H2O gas, with a nominal line-of-sight column density of 0.90 0.23 × 1016 cm-2 (upper limit of 1.0 × 101...
Article
We report experimental studies of 100 keV Ar + ion irradiation of ice leading to the formation of molecular oxygen and its trapping and ejection from the surface, at temperatures between 80 and 150 K. The use of a mass spectrometer and a quartz-crystal microbalance and sputter depth profiling at 20 K with low energy Ar ions allowed us to obtain a c...
Conference Paper
We will discuss the Cassini spacecraft's detection of an O2-CO2 exosphere at Saturn's icy satellite Rhea, including its origin, distribution, and Cassini's observations of pickup ions as evidence for ionization as a major exospheric loss mechanism.
Article
Cassini's encounters with Enceladus in 2008 and 2009, E3, E5 and E7, probed the south polar dust plume and produced exciting INMS measurements of the neutral H2O density. Of all these encounters, E7 had the closest approach to the Enceladus south pole, and it is the first time that INMS directly detected the jet features in the plume. We have const...
Article
In 2008, the Cassini ion neutral mass spectrometer (INMS) investigation made in situ measurements of neutral species near Saturn's equatorial plane within 0.5 Saturn radii (RS) of the orbit of Enceladus. After removing the large background and modeling to interpret instrumental effects, the data provide rough constraints on the neutral distribution...
Article
We report on the measurements of the Cassini Ion Neutral Mass Spectrometer (INMS) of the density and structure of Enceladus' south polar plume during the E3 and E5 flybys on 12 March and 9 October 2008. Using a Monte Carlo simulation, we analyze the dependence of the INMS gas inlet transmittance on spacecraft pointing and the effect on the measurem...
Article
Full-text available
1] In addition to being the major source of neutral gas and dust particles for the Saturnian E‐ring and, ultimately, heavy ions for the Saturnian inner magnetosphere, Enceladus exhibits geological activity that has made it an object of recent intensive study. The interest has significantly increased after Cassini flybys in 2005 provided a detailed...
Article
Full-text available
We present the discovery of a tenuous oxygen-carbon dioxide atmosphere at Saturn's icy moon Rhea by the Cassini Ion Neutral Mass Spectrometer (INMS). The atmosphere is generated mainly by the bombardment of Rhea's trailing hemisphere by Saturn's co-rotating heavy-ion plasma. This first of its kind in-situ detection of an oxidizing extraterrestrial...
Article
Full-text available
Jets of water ice from surface fractures near the south pole of Saturn's icy moon Enceladus produce a plume of gas and particles. The source of the jets may be a liquid water region under the ice shell - as suggested most recently by the discovery of salts in E-ring particles derived from the plume - or warm ice that is heated, causing dissociation...
Article
Full-text available
Jets of water ice from surface fractures near the south pole1 of Saturn's icy moon Enceladus produce a plume of gas and particles2, 3, 4, 5. The source of the jets may be a liquid water region under the ice shell—as suggested most recently by the discovery of salts in E-ring particles derived from the plume6—or warm ice that is heated, causing diss...
Article
We have found that irradiation with 50-150 keV protons enhances gas adsorption in nanoporous amorphous ice by creating high-energy binding sites. If irradiation is done in vacuum, the ice is compacted and does not adsorb significantly in subsequent exposure to gas. If irradiation occurs while the ice is exposed to an ambient O-2 pressure, adsorptio...
Article
We report experimental studies of 100 keV Ar(+) ion irradiation of ice leading to the formation of molecular oxygen and its trapping and ejection from the surface, at temperatures between 80 and 150 K. The use of a mass spectrometer and a quartz-crystal microbalance and sputter depth profiling at 20 K with low energy Ar ions allowed us to obtain a...
Article
Full-text available
Observations made with the Cassini Ion and Neutral Mass Spectrometer (INMS) during two close flybys of Enceladus on 12 March and 9 October 2008 reveal the presence of ammonia, complex organics such as benzene, and deuterium in the gas plume as well as the probable presence of radiogenic argon. The INMS data provide compelling evidence for the exist...
Article
In 2008 and 2009, the Cassini Ion Neutral Mass Spectrometer (INMS) investigation made in situ measurements of neutral species near the equatorial plane in a torus within 0.5 Saturn radii (Rs) of the orbit of Enceladus. The observations are made in the Closed Source Neutral (CSN) mode, which is the most sensitive mode for measuring neutrals. These o...
Article
The composition of the gas plume emanating from Enceladus' southern pole has been measured twice by the Cassini Ion Neutral Mass Spectrometer. The plume contains 90% water vapor, with small percentages (1 to 4%) of methane, carbon dioxide, and an unresolved contribution from both molecular nitrogen and carbon monoxide. Trace amounts of more complex...
Article
We have characterized the porosity of vapor-deposited amorphous solid water (ice) films deposited at 30-40 K using several complementary techniques such as quartz crystal microgravimetry, UV-visible interferometry, and infrared reflectance spectrometry in tandem with methane adsorption. The results, inferred from the gas adsorption isotherms, revea...
Article
Laboratory simulations of processes on astronomical surfaces that use infrared reflectance spectroscopy of thin films to analyze their composition and structure often ignore important optical interference effects which often lead to erroneous measurements of absorption band strengths and give an apparent dependence of this quantity on film thicknes...
Article
We report a very low density (similar to 0.5 g/cm(3)) structure of solid ozone. It is produced by irradiation of solid oxygen with 100 keV protons at 20 K followed by heating to sublime unconverted oxygen. Upon heating to 47 K the porous ozone compacts to a density of similar to 1.6 g/cm(3) and crystallizes. We use a detailed analysis of the main i...
Article
We have studied the compaction of vapor-deposited amorphous solid water by energetic ions at 40 K. The porosity was characterized by ultraviolet-visible spectroscopy, infrared spectroscopy, and methane adsorption/desorption. These three techniques provide different and complementary views of the structural changes in ice resulting from irradiation....
Article
Measurements of the sputtering yield of solid O-2 by 25-240-keV H+ show that it is double valued in its dependence on electronic stopping power. We propose that this is because the electronic sputtering yield is dominated by repulsion of ions in the ionization track of the projectile which, at low velocities, is augmented near the surface due to th...