A5078630469- Astro and Planetary Science
- Planetary Science and Exploration
- Atmospheric Ozone and Climate
- Ionosphere and magnetosphere dynamics
- Solar and Space Plasma Dynamics
- Isotope Analysis in Ecology
- Atmospheric and Environmental Gas Dynamics
- Atmospheric chemistry and aerosols
- Geology and Paleoclimatology Research
- Space Exploration and Technology
- Space Science and Extraterrestrial Life
- Methane Hydrates and Related Phenomena
- Stellar, planetary, and galactic studies
- Geomagnetism and Paleomagnetism Studies
- Astrophysics and Star Formation Studies
- Scientific Research and Discoveries
- Space exploration and regulation
- Spectroscopy and Laser Applications
- Spacecraft and Cryogenic Technologies
- History and Developments in Astronomy
- Geophysics and Gravity Measurements
- Gamma-ray bursts and supernovae
- Radioactive element chemistry and processing
- Molecular Spectroscopy and Structure
- Atmospheric aerosols and clouds
George Mason University
2011-2022
Southwest Research Institute
2016-2018
Goddard Space Flight Center
2018
University of Alaska Fairbanks
2016
United States Naval Research Laboratory
1990-2000
Hampton University
1997
Johns Hopkins University
1987-1997
University of Wuppertal
1997
United States Navy
1989
California Institute of Technology
1983-1985
New Horizons unveils the Pluto system In July 2015, spacecraft flew through at high speed, humanity's first close look this enigmatic on outskirts of our solar system. a series papers, team present their analysis encounter data downloaded so far: Moore et al. complex surface features and geology its large moon Charon, including evidence tectonics, glacial flow, possible cryovolcanoes. Grundy analyzed colors chemical compositions surfaces, with ices H 2 O, CH 4 , CO, N NH 3 reddish material...
The New Horizons mission has provided resolved measurements of Pluto's moons Styx, Nix, Kerberos, and Hydra. All four are small, with equivalent spherical diameters $\approx$40 km for Nix Hydra ~10 Styx Kerberos. They also highly elongated, maximum to minimum axis ratios $\approx$2. have high albedos ( $\approx$50-90 %) suggestive a water-ice surface composition. Crater densities on imply ages $\gtrsim$ 4 Ga. small rotate much faster than synchronous, rotational poles clustered nearly...
Polar mesospheric clouds (PMCs) have been measured in the infrared for first time by Halogen Occultation Experiment (HALOE). PMC extinctions retrieved from measurements at eight wavelengths show remarkable agreement with model spectra based on ice particle extinction. The spectrum of has a unique signature, and HALOE‐model thus provides physical confirmation that water is primary component PMCs. effective radii were estimated HALOE order fit extinctions.
A three‐dimensional, stationary, two‐fluid plasma model for electrons and one ion species was developed to understand the local interaction of Io's atmosphere with Io torus formation ionosphere. Our calculates, self‐consistently, density, velocity temperatures ions electrons, electric field a given neutral imposed conditions but assumes magnetic constant homogeneous Jovian field. With only photoionization in pure SO 2 it is impossible correctly measurements by Galileo spacecraft. collisional...
The Voyager 1 ultraviolet spectrometer (UVS) solar occultation and airglow data obtained during the Titan flyby are analyzed for composition thermal structure of upper atmosphere relative importance excitation processes. From optical depth profiles inferred by Smith et al. (1982, J. Geophys. Res. 87, 1351–1359) evening terminator, entrance occulatation, an asymptotic temperature T∞ = 175 K, a CH4 mixing ratio increasing from 0.06 ± 0.01 at 1000 km to 0.20 0.02 1400 derived. not sufficient...
A radiative-thermal conduction model for the vertical thermal structure of Io's atmosphere is developed with solar heating by SO2 absorption in UV and near-IR bands non-LTE cooling SO2v1 , v2, v3, vibrational rotational lines. The predicts existence a mesopause when surface pressure exceeds ∼10 nbar. radiative time constant establishing mesosphere/mesopause on Io only ∼20 min, whereas thermaspheric about 1 hr. These constants are significantly shorter than diurnal scale competitive dynamical...
Satellite observations by the Middle Atmosphere High Resolution Spectrograph Investigation (MAHRSI) have produced global measurements of hydroxyl (OH) in atmosphere. These reveal a sharp peak OH density near an altitude 65 to 70 km and are thus consistent with from Halogen Occultation Experiment (HALOE) on NASA Upper Research (UARS), which showed unexplained H 2 O layer at same level. Analysis stratopause (about 50 kilometers) coincident ozone Cryogenic Infrared Spectrometers Telescopes for...
A radiative–conductive model for the vertical thermal structure of Pluto's atmosphere is developed with a non-LTE treatment solar heating in CH43.3 μm and 2.3 bands, radiative exchange cooling CH47.6 band, LTE by CO rotational line emission. The includes effects opacity vibrational energy transfer CH4molecule. Partial thermalization absorbed radiation bands rapid from stretch modes to bending generates high altitude at sub-microbar pressures. Heating exceeds 3.3 approximately factor 6 occurs...
We present an updated model for the photochemistry of Io's atmosphere and ionosphere use this to investigate sensitivity chemical structure vertical transport rates. SO2is assumed be dominant atmospheric gas, with minor molecular sodium species such as Na2S or Na2O released by sputtering venting from surface. Photochemical products include SO, O2, S, O, Na, NaO, NaS, Na2. consider both "thick" "thin" SO2atmospheres that encompass range allowed recent HST millimeter-wave observations,...
Millimeter-wave observations of Io with the IRAM 30 m telescope have allowed detection two rotational lines SO at 219.949 and 138.178 GHz in Io's atmosphere. The can be fitted by assuming that gaseous is collocated SO2 on a restricted fraction surface. In this case, SO/SO2 mixing ratio 3%-10%, agreement predictions from one-dimensional photochemical models suggesting vertical eddy diffusion coefficient range 3 × 107 to 108 cm2 s-1. Alternatively, could constitute tenuous, global atmosphere...
A two‐dimensional chemical transport model has been used to examine the physical processes governing of high levels thermospheric nitric oxide (NO) downward into middle atmosphere. Three different facets this are studied. The first facet involves diffusion from thermosphere summertime mesopause region. second advection by mean meridional circulation in wintertime mesosphere and effects planetary wave mixing on latitudinal gradient NO. third is residual amount NO deposited springtime upper...
Ground‐based microwave spectroscopy measurements of mesospheric CO and H 2 O vertical mixing ratio profiles are used to infer rates in the upper mesosphere. The data consistently imply eddy diffusion coefficients 70‐ 85‐km region ≲(1–2) × 10 5 cm s −1 during spring through summer at mid‐latitudes. Although chemical acceleration transport is substantial for 3 below mesopause, divergences their associated fluxes modest, with most a factor effect on concentrations measured variability gravity...
From December 1986 until April 1987 ground‐based microwave observations of the diurnal variation mesospheric ozone were made over Bern, Switzerland. These data sufficient quality to define characteristic behavior mixing ratio during winter and equinoctial conditions. The observed peaks at ∼74 km, where its amplitude is about a factor 6. At 65 km 3, whereas 55 it only 1.4. One‐dimensional model calculations accurately reproduce relative equinox, suggesting that value photolysis rate...