Ben Teolis

• PhD
• Researcher at Southwest Research Institute

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...

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...

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...

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...

Extraterrestrial Atmosphere The detection of oxygen in the atmospheres of Jupiter's icy moons, Europa and Ganymede, and the presence of this gas as the main constituent of the atmosphere that surrounds Saturn's rings, has suggested the possibility of oxygen atmospheres around the icy moons that orbit inside Saturn's magnetosphere. Using the Ion Neu...

Jupiter’s icy moon, Europa, harbors a subsurface liquid water ocean; the prospect of this ocean being habitable motivates further exploration of the moon with the upcoming NASA Europa Clipper mission. Key among the mission goals is a comprehensive assessment of the moon’s composition, which is essential for assessing Europa’s habitability. Through...

Juno flew over the northern mid‐latitudes of Ganymede during orbit 34 of the Juno mission, reaching an altitude of 1,053 km (16:56:07.972 UTC) at a sub spacecraft latitude/longitude of 33.66N, 57.5W degrees on 7 June 2021. Between 16:43 and 17:02 UT, Juno pierced Ganymede's magnetosphere at a velocity relative to Ganymede of 18.57 km s⁻¹. Juno's in...

The MAss Spectrometer for Planetary EXploration (MASPEX) is a high-mass-resolution, high-sensitivity, multi-bounce time-of-flight mass spectrometer (MBTOF) capable of measuring minor species with abundances of sub-parts-per-million in Europa’s sputter-produced and radiolytically modified exosphere and in its oceanic plumes. The goal of the MASPEX-E...

Surface-bounded exospheres result from complex interactions between the planetary environment and the rocky body’s surface. Different drivers including photons, ion, electrons, and the meteoroid populations impacting the surfaces of different bodies must be considered when investigating the generation of such an exosphere. Exospheric observations o...

Gas-surface interactions at the Moon, Mercury and other massive planetary bodies constitute, alongside production and escape, an essential element of the physics of their gravitationally bound exospheres. From condensation and accumulation of exospheric species onto the surface in response to diurnal and seasonal changes of surface temperature, to...

We combine novel laboratory experiments and exospheric modeling to reveal that “dynamic” Ly-α photolysis of Plutonian methane generates a photolytic refractory distribution on Charon that increases with latitude, consistent with poleward darkening observed in the New Horizons images. The flux ratio of the condensing methane to the interplanetary me...

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...

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...

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...

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...

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...

During Cassini's final, spectacular months, in situ instruments made the first direct measurements of nanoparticles, finding an exceptionally large flow from the rings into Saturn's atmosphere. Cassini's Ion and Neutral Mass Spectrometer measured material in three altitude bands and found a global‐integrated flux of 2–20 × 10 ⁴ kg/s that is dominat...

Cassini's final phase of exploration The Cassini spacecraft spent 13 years orbiting Saturn; as it ran low on fuel, the trajectory was changed to sample regions it had not yet visited. A series of orbits close to the rings was followed by a Grand Finale orbit, which took the spacecraft through the gap between Saturn and its rings before the spacecra...

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...

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...

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...

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 CO$_2^+$ during both the R1 and R1.5 encounters. Ac...

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...

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...

Hydrothermal processes on Enceladus Saturn's moon Enceladus has a subsurface ocean covered by a layer of ice. Some liquid escapes into space through cracks in the ice, which is the source of one of Saturn's rings. In October 2015, the Cassini spacecraft flew directly through the plume of escaping material and sampled its chemical composition. Waite...

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...

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...

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...

We use Cassini INMS and UVIS Enceladus plume data to constrain the plume source properties and extrapolate the plume’s 3D structure and variability.

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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.

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,...

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...

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...

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...

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...

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....

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...

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...

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...

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...

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...

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.

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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....

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...

The condensed O2 found on Ganymede and Europa, and its relationship to tenuous O2 atmospheres have long been a puzzle considering the instability of solid oxygen at the relative high temperatures of the satellites. We report on the discovery that ion irradiation of microporous water ice exposed to gaseous oxygen enhances adsorption and retention of...

Thesis (Ph. D.)--University of Virginia, 2007. Includes bibliographical references.

The irradiation of the surface of icy satellites and ring particles by magnetospheric ions, energetic particles and electrons leads to the ejection by sputtering, of neutral species into the atmospheres of these bodies. Secondary ions are also emitted, and they can be picked-up by the local magnetic field and, eventually, form part of the magnetosp...

Condensed O-2 and ozone on the surfaces of some icy satellites are thought to originate from the radiolytic decomposition of surface water ice by the impact of energetic magnetospheric ions, but decades of laboratory studies have produced no evidence for ozone from the radiolysis of pure water ice. Here we report for the first time the production o...

We present results of the growth of thin films of crystalline H2O2 and H2O2*2H2O (dihydrate) in ultrahigh vacuum by distilling an aqueous solution of hydrogen peroxide. We traced the process using infrared reflectance spectroscopy, mass loss on a quartz crystal microbalance, and in a few cases ultraviolet-visible reflectance. We find that the diffe...

We present laboratory studies of the radiolysis of pure (97%) solid H2O2 films by 50 keV H+ at 17 K. Using UV-visible and infrared reflectance spectroscopies, a quartz-crystal microbalance, and a mass spectrometer, we measured the absolute concentrations of the H2O, O2, H2O2, and O3 products as a function of irradiation fluence. Ozone was identifie...

We address the question of the evolution of ices that have been exposed to radiation from stellar sources and cosmic rays. We studied in the laboratory the thermal evolution of a model ice sample: a mixture of water, hydrogen peroxide, dioxygen, and ozone produced by irradiating solid H2O2 with 50 keV H+ at 17 K. The changes in composition and rele...

We will discuss multiple experiments in our laboratory in the last year in relation to the properties of Enceladus, many with application to other icy regoliths. 1) dependence of sublimation on the aggregation state. 2) adsorption, trapping and desorption of atmospheric gases which have been treated independently, but should be considered as a com...

We have conducted experiments on the sputtering of water ice by 100 keV Ar+ between 20 and 150 K. Our findings indicate that the temperature dependence of the total sputtering yield is heavily influenced by the thermal and irradiation history of the ice, showing a complex dependence on irradiation fluence that is correlated to the ejection of O-2 m...

Plasma measurements were performed by the CAssini Plasma Spectrometer (CAPS) in the vicinity of Saturn's rings during orbit insertion on July 1, 2004. An analysis of the data has revealed the presence of an ionosphere above the A and B rings with O2+ and O+ as major ions, suggesting the existence of an atmosphere made up of molecular oxygen (Young...

We have studied the effects of ion irradiation on the porosity of amorphous ice using infrared and ultraviolet-visible (uv-vis)spectroscopy. Our findings indicate that ion irradiation induces compaction in porous ice. The density of the ice films rises asymptotically to a saturation value with increasing ion fluence. Irradiation also decreases the...

We measured the total sputtering yield of amorphous water ice for 100 keV H(+) as a function of the projectile incidence angle, and the angular distribution of the ejected H(2)O and O(2) molecules, using a quartz-crystal microbalance and mass spectrometry, respectively, at temperatures of 20 K and 100 K. The total sputtering yield follows a cos(-f)...

We have investigated the synthesis of carbon dioxide in amorphous carbon grains coated with amorphous water ice ( 0.1 microns thick) as a result of irradiation with 100 keV protons at 16 K and 120 K. The quantitative studies report a saturation column density of CO2 of the order of 3 - 9 x 1014 molecules/cm2, with more CO2 produced at lower tempera...

We are interested in the question of how oxygen exospheres are produced around icy objects in the outer solar system. To characterize the production, trapping and escape of O2 caused by magnetospheric particle bombardment of icy surfaces, we irradiated water ice films with 100 keV ions and studied the O2 emission at different temperatures and radia...

We have measured the sputtering of specific species during ion irradiation of water ice, labradorite, albite, anorthoclase, and olivine targets, to understand the importance of sputtering in the generation of atmospheres around icy satellites of the outer solar system by magnetospheric ions, and around the Moon and Mercury by the Solar wind. We use...

We will report recent measurements on the growth of ice from the vapor phase and ion irradiation, where we determined the density (porosity) of ice and its dependence of growth condition (direction of incident water flux, substrate temperature, annealing temperature, ion irradiation), and the emission of oxygen during ion irradiation. We will discu...

Airless bodies in space are subject to irradiation with energetic atomic particles, which generate atmospheres by sputtering and alter the surface composition. Astronomical observations with telescopes and space probes continuously provide new data that require new laboratory experiments for their interpretation. Many of these experiments also serv...

To understand chemical effects caused by ion beams in solids we study the simplest case, the formation of ozone in solid oxygen. We irradiate thin O2 films with 100 keV protons and study the fluence dependence of the sputtering of solid O2 with a microbalance and a mass spectrometer. The formation of ozone in the film after irradiation is identifie...