Permanently shadowed regions (PSRs) at the lunar poles may contain substantial water ice, but radar signatures at PSRs could indicate water ice or large block populations. Mini-RF radar and Lunar Reconnaissance Orbiter Camera Narrow Angle Camera (LROC NAC) products were used to assess block abundances where radar signatures indicated potential ice deposits. While the majority of PSRs in this study indicated large block populations and a low likelihood of water ice, one crater – Rozhdestvenskiy N – showed indirect indications of water ice in its interior.
Chloride deposits indicate regions where the last substantial liquid water existed on Mars. Major ion abundances and expected precipitation sequences of terrestrial chloride brines could provide context for assessing the provenance of martian chloride deposits. Chloride minerals are most readily distinguished in the far-infrared (45+ μm), where their fundamental absorption features are strongest. Multiple chloride compositions and textures were characterized in far-infrared emission for the first time. Systematic variations in the spectra were observed; these variations will allow chloride mineralogy to be determined and large variations in texture to be constrained.
In the present day, recurring slope lineae (RSL) may indicate water flow, but fresh water is not stable on Mars. However, dissolved chloride could allow liquid water to flow transiently. Using Thermal Emission Imaging System (THEMIS) data, I determined that RSL are most likely not fed by chloride-rich brines on Mars. Substantial amounts of salt would be consumed to produce a surface water flow; therefore, these features are therefore thought to instead be surface darkening due to capillary wicking.
The discovery of cryovolcanic features on Charon and the presence of ammonia hydrates on the surfaces of other medium-sized Kuiper Belt Objects suggests that cryovolcanism may be important to their evolution. A two-dimensional, center-point finite difference, thermal hydraulic model was developed to explore the behavior of cryovolcanic conduits on midsized KBOs. Conduits on a Charon-surrogate were shown to maintain flow through over 200 km of crust and mantle down to radii of R = 0.20 m. Radii higher than this became turbulent due to high viscous dissipation and low thermal conductivity. This model was adapted to explore the emplacement of Kubrik Mons. Steady state flow was achieved with a conduit of radius R = 0.02 m for a source chamber at 2.3 km depth. Effusion rates computed from this estimated a 122 - 163 Myr upper limit formation timescale.
I then investigate the transport of water in disks with different variable α profiles. While radial temperature profile sets the location of the water snowline (i.e., inside of which water is present as vapor; outside of which, as ice on solids), it is the rates of diffusion and drift of small icy solids and diffusion of vapor across the snow line that determine the radial water distribution. All of these processes are highly sensitive to local $\alpha$. I calculate the effect of radially varying α on water transport, by tracking the abundance of vapor in the inner disk, and fraction of ice in particles and larger asteroids beyond the snow line. I find one α profile attributable to winds and hydrodynamical instabilities, and motivated by meteoritic constraints, to show considerable agreement with inferred water contents observed in solar system asteroids.
Finally, I calculate the timing of gap formation due to the formation of a planet in disks around different stars. Here, I assume that pebble accretion is the dominant mechanism for planetary growth and that the core of the first protoplanet forms at the water snow line. I discuss the dependence of gap timing to various stellar and disk properties.
Many lunar impact melt rocks are complex mixtures of glassy and crystalline “melt” materials and inherited clasts of pre-impact minerals and rocks. If analyzed in bulk, these samples can yield complicated incremental release 40Ar/39Ar spectra, making it challenging to uniquely interpret impact ages. Here, I have used a combination of high-spatial resolution 40Ar/39Ar geochronology and thermal-kinetic modeling to gain new insights into the impact histories recorded by such lunar samples.
To compare my data to those of previous studies, I developed a software tool to account for differences in the decay, isotopic, and monitor age parameters used for different published 40Ar/39Ar datasets. Using an ultraviolet laser ablation microprobe (UVLAMP) system I selectively dated melt and clast components of impact melt rocks collected during the Apollo 16 and 17 missions. UVLAMP 40Ar/39Ar data for samples 77135, 60315, 61015, and 63355 show evidence of open-system behavior, and provide new insights into how to interpret some complexities of published incremental heating 40Ar/39Ar spectra. Samples 77115, 63525, 63549, and 65015 have relatively simple thermal histories, and UVLAMP 40Ar/39Ar data for the melt components of these rocks indicate the timing of impact events—spanning hundreds of millions of years—that influenced the Apollo 16 and 17 sites. My modeling and UVLAMP 40Ar/39Ar data for sample 73217 indicate that some impact melt rocks can quantitatively retain evidence for multiple melt-producing impact events, and imply that such polygenetic rocks should be regarded as high-value sampling opportunities during future exploration missions to cratered planetary surfaces. Collectively, my results complement previous incremental heating 40Ar/39Ar studies, and support interpretations that the Moon experienced a prolonged period of heavy bombardment early in its history.
Most asteroids originated in larger parent bodies that underwent accretion and heating during the first few million years of the solar system. We investigated the parent body of S-type asteroid 25143 Itokawa by developing a computational model which can approximate the thermal evolution of an early solar system body. We compared known constraints on Itokawa’s thermal history to simulations of its parent body and constrained its time of formation to between 1.6 and 2.5 million years after the beginning of the solar system, though certain details could allow for even earlier or later formation. These results stress the importance of precise data required of the material properties of asteroids and meteorites to place better constraints on the histories of their parent bodies. Additional mathematical and computational details are discussed, and the full code and data is made available online.
During the Dawn mission, bright spots were discovered on the surface of the dwarf planet Ceres, which were determined to be evaporite deposits of sodium carbonate, ammonium carbonate, and hydrohalite. These deposits are significant because they indicate the presence of subsurface water and potential geologic activity on Ceres. These evaporites form from the brine-water mixture in the deep Ceres reservoir, which likely possesses the conditions ideal for forming complex organics. Here, we report the results of a suite of laboratory techniques (CHN Elemental Analyzer, Secondary Ion Mass Spectrometry, Fourier-Transform Infrared Spectroscopy, Gas Chromatography, and Brunauer-Emmett-Teller Analysis) for quantifying the likelihood of primordial carbon survival and distribution in analog materials found on Ceres, particularly in salt evaporates. We are specifically looking at if the amino acid glycine can be preserved in sodium chloride crystals. Our results conclude that if the Ceres brine reservoir is saturated with organics, and with the lower limits that we have for our instrumentation thus far, these techniques should be more than sufficient to measure glycine content should we ever receive samples from Ceres.