ALBERT

Description: We present the first comprehensive set of lunar exospheric line width and line width derived effective temperatures as a function of lunar phase (66 waxing phase to 79 waning phase). Data were collected between November 2013 and May 2014 during six observing runs at the National Solar Observatory McMath-Pierce Solar Telescope by applying high-resolution Fabry-Perot spectroscopy (R ~ 180,000) to observe emission from exospheric sodium (5,889.9509 , D2 line). The 3-arc min field of view of the instrument, corresponding to ~336 km at the mean lunar distance (384,400 km), was positioned at several locations off the lunar limb; only equatorial observations taken out to 950 km are presented here. We find the sodium effective temperature distribution to be approximately a symmetric function of lunar phase with respect to full Moon. Within magnetotail passage we find temperatures in the range of 2500-9000 K. For phase angles greater than 40deg we find that temperatures flatten out to ~1700 K.

Description: The presence of allophane and other nanophase materials on Mars indicates a time when water was intermittent and short lived. These materials likely represent partially altered or leached basaltic ash and therefore, could represent a geologic marker for where water was present on the Martian surface. Further, they may indicate regions of climate change, where surface water was not present long enough to form clays. Characterization of these materials is important for increasing spectral recognition capacities of our current Martian science array. Ongoing work suggests that variability in the Al:Si ratio of allophane can dictate the amount of both structural and adsorbed water in the crystalline structure.

Description: Lunar impact melt deposits have unique physical properties. They have among the highest observed radar returns at S-Band (12.6 cm wavelength), implying that they are rough at the decimeter scale. However, they are also observed in high-resolution optical imagery to be quite smooth at the meter scale. These characteristics distinguish them from well-studied terrestrial analogues, such as Hawaiian pahoehoe and a a lava flows. The morphology of impact melt deposits can be related to their emplacement conditions, so understanding the origin of these unique surface properties will help to inform us as to the circumstances under which they were formed. In this work, we seek to find a terrestrial analogue for well-preserved lunar impact melt flows by examining fresh lava flows on Earth. We compare the radar return and high-resolution topographic variations of impact melt flows to terrestrial lava flows with a range of surface textures. The lava flows examined in this work range from smooth Hawaiian pahoehoe to transitional basaltic flows at Craters of the Moon (COTM) National Monument and Preserve in Idaho to rubbly and spiny pahoehoe-like flows at the recent eruption at Holuhraun in Iceland. The physical properties of lunar impact melt flows appear to differ from those of all the terrestrial lava flows studied in this work. This may be due to (a) differences in post-emplacement modification processes or (b) fundamental differences in the surface texture of the melt flows due to the melts' unique emplacement and/or cooling environment. Information about the surface properties of lunar impact melt deposits will be critical for future landed missions that wish to sample these materials.

Description: In its 12th year of exploration and 1600 sols since arrival at the rim of the 22 km-diameter Noachian Endeavour impact crater, Mars Exploration Rover Opportunity traversed from the summit of the western rim segment "Cape Tribulation" to "Marathon Valley", a shallow trough dissecting the rim and the site of strong orbital detection of smectites. In situ analysis of the exposures within Marathon Valley is establishing some of the geologic and geochemical controls on the aqueous alteration responsible for smectite detection known to occur in crater rims throughout Noachian terrains of Mars.

Description: Asteroid threat assessment requires the quantification of both the impact likelihood and resulting consequence across the range of possible events. This paper presents a probabilistic asteroid impact risk (PAIR) assessment model developed for this purpose. The model incorporates published impact frequency rates with state-of-the-art consequence assessment tools, applied within a Monte Carlo framework that generates sets of impact scenarios from uncertain parameter distributions. Explicit treatment of atmospheric entry is included to produce energy deposition rates that account for the effects of thermal ablation and object fragmentation. These energy deposition rates are used to model the resulting ground damage, and affected populations are computed for the sampled impact locations. The results for each scenario are aggregated into a distribution of potential outcomes that reflect the range of uncertain impact parameters, population densities, and strike probabilities. As an illustration of the utility of the PAIR model, the results are used to address the question of what minimum size asteroid constitutes a threat to the population. To answer this question, complete distributions of results are combined with a hypothetical risk tolerance posture to provide the minimum size, given sets of initial assumptions. Model outputs demonstrate how such questions can be answered and provide a means for interpreting the effect that input assumptions and uncertainty can have on final risk-based decisions. Model results can be used to prioritize investments to gain knowledge in critical areas or, conversely, to identify areas where additional data has little effect on the metrics of interest.

Description: For the first time in human history, we will soon be able to apply to the scientific method to the question "Are We Alone?" The rapid advance of exoplanet discovery, planetary systems science, and telescope technology will soon allow scientists to search for life beyond our Solar System through direct observation of extrasolar planets. This endeavor will occur alongside searches for habitable environments and signs of life within our Solar System. While these searches are thematically related and will inform each other, they will require separate observational techniques. The search for life on exoplanets holds potential through the great diversity of worlds to be explored beyond our Solar System. However, there are also unique challenges related to the relatively limited data this search will obtain on any individual world.

Description: The Moon's South Pole-Aitken basin (SPA) is a high priority target for Solar System exploration, and sample return from SPA is a specific objective in NASA's New Frontiers program. Samples returned from SPA will improve our understanding of early lunar and Solar System events, mainly by placing firm timing constraints on SPA formation and the post-SPA late-heavy bombardment (LHB). Lunar Reconnaissance Orbiter Camera (LROC) images and topographic data, especially Narrow Angle Camera (NAC) scale (1-3 mpp) morphology and digital terrain model (DTM) data are critical for selecting landing sites and assessing landing hazards. Rock components in regolith at a given landing site should include (1) original SPA impact-melt rocks and breccia (to determine the age of the impact event and what materials were incorporated into the melt); (2) impact-melt rocks and breccia from large craters and basins (other than SPA) that represent the post-SPA LHB interval; (3) volcanic basalts derived from the sub-SPA mantle; and (4) older, "cryptomare" (ancient buried volcanics excavated by impact craters, to determine the volcanic history of SPA basin). All of these rock types are sought for sample return. The ancient SPA-derived impact-melt rocks and later-formed melt rocks are needed to determine chronology, and thus address questions of early Solar System dynamics, lunar history, and effects of giant impacts. Surface compositions from remote sensing are consistent with mixtures of SPA impactite and volcanic materials, and near infrared spectral data distinguish areas with variable volcanic contents vs. excavated SPA substrate. Estimating proportions of these rock types in the regolith requires knowledge of the surface deposits, evaluated via morphology, slopes, and terrain ruggedness. These data allow determination of mare-cryptomare-nonmare deposit interfaces in combination with compositional and mineralogical remote sensing to establish the types and relative proportions of materials expected at a given site. Remote sensing compositions, e.g., FeO, also constrain the relative abundances of components. Landing-site assessments use crater and boulder distributions, and slope and terrain rugge

Description: Carbon dioxide is an essential atmospheric component in martian climate models that attempt to reconcile a faint young sun with widespread evidence of liquid water at the planet's surface in the Noachian and Early Hesperian. Current estimates of ancient martian CO levels, derived from global inventories of carbon, and orbital detections of Noachian and Early Hesperian clay mineralbearing terrains indicate CO levels that are unable to support warm and wet conditions. These estimates are subject to various sources of uncertainty however. Mineral and contextual sedimentary environmental data collected by the Mars Science Laboratory rover Curiosity in Gale Crater provide a more direct means of estimating the atmospheric partial pressure of CO (P ) coinciding with a long-lived lake system in Gale crater at approximately 3.5 Ga. Results from a reaction transport model, which simulates mineralogy observed within the Sheepbed member at Yellowknife Bay by coupling mineral equilibria with carbonate precipitation kinetics and rates of sedimentation, indicate atmospheric levels in the 10's mbar range. At such low P levels, climate models are unable to warm Hesperian Mars anywhere near the freezing point of water and other gases are required to raise atmospheric pressure to prevent lakes from boiling away. Thus, lacustrine features of Gale formed in a cold environment by a mechanism yet to be determined, or the climate models lack an essential component that would serve to elevate surface temperatures, at least temporally and/or locally, on Hesperian Mars. Our results also impose restrictions on the potential role of atmospheric CO in inferred warmer conditions of the Noachian.

Description: A mission to land in the giant South Pole-Aitken (SPA) Basin on the Moon's southern farside and return a sample to Earth for analysis is a high priority for Solar System Science. Such a sample would be used to determine the age of the SPA impact; the chronology of the basin, including the ages of basins and large impacts within SPA, with implications for early Solar System dynamics and the magmatic history of the Moon; the age and composition of volcanic rocks within SPA; the origin of the thorium signature of SPA with implications for the origin of exposed materials and thermal evolution of the Moon; and possibly the magnetization that forms a strong anomaly especially evident in the northern parts of the SPA basin. It is well known from studies of the Apollo regolith that rock fragments found in the regolith form a representative collection of many different rock types delivered to the site by the impact process (Fig. 1). Such samples are well documented to contain a broad suite of materials that reflect both the local major rock formations, as well as some exotic materials from far distant sources. Within the SPA basin, modeling of the impact ejection process indicates that regolith would be dominated by SPA substrate, formed at the time of the SPA basin-forming impact and for the most part moved around by subsequent impacts. Consistent with GRAIL data, the SPA impact likely formed a vast melt body tens of km thick that took perhaps several million years to cool, but that nonetheless represents barely an instant in geologic time that should be readily apparent through integrated geochronologic studies involving multiple chronometers. It is anticipated that a statistically significant number of age determinations would yield not only the age of SPA but also the age of several prominent nearby basins and large craters within SPA. This chronology would provide a contrast to the Imbrium-dominated chronology of the nearside Apollo samples and an independent test of the timing of the lunar cataclysm.

Description: The Kepler spacecraft's imaging photometer monitored the Pluto system from October-December 2015 during Campaign 7 of the K2 extended mission. Kepler obtained an unprecedented and fortuitous nearly continuous 12-Pluto day lightcurve from measurements acquired every 30 min using long cadence sampling. This 3-month-long baseline anchors the Pluto+Charon lightcurve near the time of the New Horizons July 2015 encounter, observing at solar phase angles between 1.16 and 1.74. Long-term modeling of Pluto's lightcurve will ultimately reveal its long-term seasonal variation. K2's combined Pluto+Charon lightcurves measured at this epoch have an average total amplitude of 0.120+/- 0.006, 0.07 magnitudes smaller than the amplitude predicted by a static frost model (Buie and Tholen, 1989) projected from Hubble Space Telescope surface maps (Buie et al., 1992). Subtracting a static Charon lightcurve from the Pluto+Charon K2 lightcurve produces the same results. Likewise, we subtract each rotation model from the model for the first full rotation and find that the average difference of all variations is 0.017 +/- 0.008 magnitudes. Moreover, the difference between the first and last K2 rotation is 0.005 magnitudes, implying that there are no significant changes in the lightcurve during the 3 months of K2 observations. These results are consistent with seasonal transport on Pluto's surface and the predictions of Buratti et al. (2015a). However, a detailed understanding of the surface-atmosphere interactions associated with these phenomena requires decades of monitoring.