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This work updates and expands on results of our long-term radar-driven observational campaign of main-belt asteroids (MBAs) focused on Bus–DeMeo Xc- and Xk-type objects (Tholen X and M class asteroids) using the Arecibo radar and NASA Infrared Telescope Facilities (Ockert-Bell, M.E., Clark, B.E., Shepard, M.K., Rivkin, A.S., Binzel, R.P., Thomas, C.A., DeMeo, F.E., Bus, S.J., Shah, S. [2008]. Icarus...
We have developed and optimized a seasonal, radiative–convective model of Saturn’s upper troposphere and stratosphere. It is used to investigate Saturn’s radiatively-forced thermal structure between 3 and 10 −6 bar, and is intended to be included in a Saturn global climate model (GCM), currently under development. The main elements of the radiative transfer model are detailed as well as the...
The extreme pressures reached during jetting, a process by which material is squirted out from the contact point of two colliding objects, causes melting and vaporization at low impact velocities. Jetting is a major source of melting in shocked porous material, a potential source of tektites, a possible origin of chondrules, and even a conceivable origin of the Moon. Here, in an attempt to quantify...
Synchrotron X-ray powder diffraction has been used to explore the water-rich (<50wt.% H 2 SO 4 ) region of the sulfuric acid and water binary phase diagram at temperatures between 80 and 285K. The phase relations that are determined demonstrate that, on laboratory timescales, sulfuric acid hydrates crystallize as mixtures of phases. Four forms of sulfuric acid hydrates were observed...
We analyze a sample of 139 near-Earth asteroids (NEAs), defined as those that reach perihelion distances q<1.3au, and that also fulfill the conditions of approaching or crossing Jupiter’s orbit (aphelion distances Q>4.8au), having Tisserand parameters 2<T<3 and orbital periods P<20yr. In order to compare the dynamics, we also analyze a sample of 42 Jupiter family comets (JFCs) in near-Earth...
We have calculated the coherence and detectable lifetimes of synthetic near-Earth object (NEO) families created by catastrophic disruption of a progenitor as it suffers a very close Earth approach. The closest or slowest approaches yield the most violent ‘s-class’ disruption events where the largest remaining fragment after disruption and reaccumulation retains less than 50% of the parent’s mass....
On November 4th, 2010, the Deep Impact eXtended Investigation (DIXI) successfully encountered comet 103P/Hartley 2, when it was at a heliocentric distance of 1.06AU. Spatially resolved near-IR spectra of comet Hartley 2 were acquired in the 1.05–4.83μm wavelength range using the HRI-IR spectrometer. We present spectral maps of the inner ∼10km of the coma collected 7min and 23min after closest approach...
We present results from a new grid-free 2D plasma simulation code applied to a small, unmagnetized body immersed in the streaming solar wind plasma. The body was purposely modeled as an irregular shape in order to examine photoemission and solar wind plasma flow in high detail on the dayside, nightside, terminator and surface-depressed ‘pocket’ regions. Our objective is to examine the overall morphology...
We analyzed the spatial and temporal characteristics of the surface temperature at the northern water ice annulus on Mars that is left behind the receding seasonal carbon dioxide cap in springtime. Using OMEGA hyperspectral images we show that water ice without carbon dioxide ice coverage lasts for 10–30days between 55° and 70°N. The longest water ice coverage without CO 2 ice is observed...
We present two numerical models designed to reproduce the temperatures of the illuminated Saturn rings as measured by the CASSINI-CIRS instrument. Our models are constrained by all available temperature measurements performed on the illuminated rings since SOI. Both models reproduce well the variations of temperature under any illumination and observation geometry. One model is derived from a purely...
The Mercury Atmospheric and Surface Composition Spectrometer on the MESSENGER spacecraft has observed calcium emission in Mercury’s exosphere on a near-daily basis since March 2011. During MESSENGER’s primary and first extended missions (March 2011 – March 2013) the dayside calcium exosphere was measured over eight Mercury years. We have simulated these data with a Monte Carlo model of exospheric...
Idealized Earth-like general circulation models (GCMs) have been extensively used to study superrotation on so-called “slowly rotating” bodies like Venus and Titan, however they tend to have difficulty producing superrotation if only the rotation rate is reduced to Titan- or Venus-like values. The Rossby number, R O =U/2ΩL, which characterizes the influence of rotation on the circulation,...
The atmosphere of Titan is mainly composed of N 2 and CH 4 which are the source of various C x H y N z photochemical volatiles products. Laboratory simulations of the Titan’s atmospheric reactivity were mainly interested in the study of the complex organic chemistry which leads to the formation of analogues of Titan’s aerosols, called tholins. These studies...
From Space Telescope Imaging Spectrograph (STIS) observations of Uranus in 2012, when good views of its north polar regions were available, we found that the methane volume mixing ratio declined from about 4% at low latitudes to about 2% at 60–80°N. This depletion in the north polar region of Uranus in 2012 is similar in magnitude and depth to that found in the south polar regions in 2002. This similarity...
The Texas Echelon cross Echelle Spectrograph (TEXES), mounted on NASA’s Infrared Telescope Facility (IRTF), was used to map mid-infrared ammonia absorption features on both Jupiter and Saturn in February 2013. Ammonia is the principle reservoir of nitrogen on the giant planets, and the ratio of isotopologues (15N/14N) can reveal insights into the molecular carrier (e.g., as N 2 or NH 3...
Titan has a significant atmosphere composed primarily of nitrogen and methane with a significant organic haze component. Its nitrogen-rich atmosphere, abundant organics, and liquid surface make this moon of interest as a prebiotic laboratory at the planetary scale and one of the best targets for studying prebiotic planetary organic chemistry. In our previous work, we have investigated the chemical...
Volatile abundances in Jupiter-family Comet 81P/Wild 2 were measured on four dates in February and March 2010 using high-dispersion (λΔλ∼2.5×10 4 ) infrared spectroscopy with NIRSPEC at the W.M. Keck Observatory. H 2 O was detected on all dates, including measurements on UT March 29 of lines from the ν 2 +ν 3 −ν 2 hot-band not previously targeted in comets....
The atmospheric electrical conductivity measured by the Permittivity, Wave and Altimetry (PWA) subsystem on board the Huygens probe, during the landing mission on Titan, has been modeled in the present work. Previous modeling studies showed a Galactic Cosmic Ray (GCR) peak of conductivity at a higher altitude and a quantitative overestimation in the altitude range 0–100km compared to that observed...
The flashes from meteoroid impacts on the Moon are useful in determining the flux of impactors with masses as low as a few tens of grams. A routine monitoring program at NASA’s Marshall Space Flight Center has recorded over 300 impacts since 2006. A selection of 126 flashes recorded during periods of photometric skies was analyzed, creating the largest and most homogeneous dataset of lunar impact...
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