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While there have been far fewer missions to the outer Solar System than to the inner Solar System, spacecraft destined for the giant planets have conducted a wide range of fundamental investigations, returning data that continues to reshape our understanding of these complex systems, sometimes decades after the data were acquired. These data are preserved and accessible from national and international planetary science archives. For all NASA planetary missions and instruments the data are available from the science discipline nodes of the NASA Planetary Data System (PDS). Looking ahead, the PDS will be the primary repository for giant planets data from several upcoming missions and derived datasets, as well as supporting research conducted to aid in the interpretation of the remotely sensed giant planets data already archived in the PDS.

A prototype rover carrying an astrobiology payload was developed and deployed at analog field sites to mature generalized system architectures capable of searching for biosignatures in extreme terrain across the Solar System. Specifically, the four-legged Limbed Excursion Mechanical Utility Robot (LEMUR) 3 climbing robot with microspine grippers carried three instruments: a micro-X-ray fluorescence instrument based on the Mars 2020 mission's Planetary Instrument for X-ray Lithochemistry provided elemental chemistry; a deep-ultraviolet fluorescence instrument based on Mars 2020's Scanning Habitable Environments with Raman and Luminescence for Organics and Chemicals mapped organics in bacterial communities on opaque substrates; and a near-infrared acousto-optic tunable filter-based point spectrometer identified minerals and organics in the 1.6-3.6 μm range. The rover also carried a light detection and ranging and a color camera for both science and navigation. Combined, this payload detects astrobiologically important classes of rock components (elements, minerals, and organics) in extreme terrain, which, as demonstrated in this work, can reveal a correlation between textural biosignatures and the organics or elements expected to preserve them in a habitable environment. Across10 field tests, milestones were achieved in instrument operations, autonomous mobility in extreme terrain, and system integration that can inform future planetary science mission architectures. Contributions include (1) system-level demonstration of mock missions to the vertical exposures of Mars lava tube caves and Mars canyon walls, (2) demonstration of multi-instrument integration into a confocal arrangement with surface scanning capabilities, and (3) demonstration of automated focus stacking algorithms for improved signal-to-noise ratios and reduced operation time.

Many tidally locked icy satellites in the outer Solar System show leading/trailing hemispherical asymmetries in the strength of near-infrared (NIR) H$_2$O ice absorption bands, in which the absorption bands are stronger on the leading hemisphere. This is often attributed to a combination of magnetospheric irradiation effects and impact gardening, which can modify grain size, expose fresh ice, and produce dark contaminating compounds that reduce the strength of absorption features. Previous research identified this leading/trailing asymmetry on the four largest classical Uranian satellites but did not find a clear leading/trailing asymmetry on Miranda, the smallest and innermost classical moon. We undertook an extensive observational campaign to investigate variations of the NIR spectral signature of H$_2$O ice with longitude on Miranda's northern hemisphere. We acquired 22 new spectra with the TripleSpec spectrograph on the ARC 3.5m telescope and 4 new spectra with GNIRS on Gemini North. Our analysis also includes 3 unpublished and 7 previously published spectra taken with SpeX on the 3m IRTF. We confirm that Miranda has no substantial leading/trailing hemispherical asymmetry in the strength of its H$_2$O ice absorption features. We additionally find evidence for an anti-Uranus/sub-Uranus asymmetry in the strength of the 1.5-$\mu$m H$_2$O ice band that is not seen on the other Uranian satellites, suggesting that additional endogenic or exogenic processes influence the longitudinal distribution of H$_2$O ice band strengths on Miranda., Comment: 40 pages, 19 figures. Accepted for publication in PSJ

The identity of the coloring agent(s) in Jupiter's atmosphere and the exact structure of Jupiter's uppermost cloud deck are yet to be conclusively understood. The Cr\`{e}me Br\^ul\'ee model of Jupiter's tropospheric clouds, originally proposed by Baines et al. (2014) and expanded upon by Sromovsky et al. (2017) and Baines et al. (2019), presumes that the chromophore measured by Carlson et al. (2016) is the singular coloring agent in Jupiter's troposphere. In this work, we test the validity of the Cr\`{e}me Br\^ul\'ee model of Jupiter's uppermost cloud deck using spectra measured during the Juno spacecraft's 5$^{\mathrm{th}}$ perijove pass in March 2017. These data were obtained as part of an international ground-based observing campaign in support of the Juno mission using the NMSU Acousto-optic Imaging Camera (NAIC) at the 3.5-m telescope at Apache Point Observatory in Sunspot, NM. We find that the Cr\`{e}me Br\^ul\'ee model cloud layering scheme can reproduce Jupiter's visible spectrum both with the Carlson et al. (2016) chromophore and with modifications to its imaginary index of refraction spectrum. While the Cr\`{e}me Br\^ul\'ee model provides reasonable results for regions of Jupiter's cloud bands such as the North Equatorial Belt and Equatorial Zone, we find that it is not a safe assumption for unique weather events, such as the 2016-2017 Southern Equatorial Belt outbreak that was captured by our measurements., Comment: 38 pages, 21 figures; Accepted for publication in AAS Planetary Science Journal

The proposed US Extremely Large Telescope (ELT) Program would secure national open access to at least 25% of the observing time on the Thirty Meter Telescope in the north and the Giant Magellan Telescope in the south. ELTs would advance solar system science via exceptional angular resolution, sensitivity, and advanced instrumentation. ELT contributions would include the study of interstellar objects, giant planet systems and ocean worlds, the formation of the solar system traced through small objects in the asteroid and Kuiper belts, and the active support of planetary missions. We recommend that (1) the US ELT Program be listed as critical infrastructure for solar system science, that (2) some support from NASA be provided to ensure mission support capabilities, and that (3) the US ELT Program expand solar-system community participation in development, planning, and operations.

There is an opportunity to advance solar system and extrasolar planetary studies that does not require new telescopes or new missions but better use and access to data sets. This approach leverages significant investment from space agencies in exploring the solar system and using those discoveries for the study of extrasolar planets.

Martian subsurface habitability and astrobiology can be evaluated via a lava tube cave, without drilling. MACIE addresses two key goals of the Decadal Survey (2013-2022) and three MEPAG goals. New advances in robotic architectures, autonomous navigation, target sample selection, and analysis will enable MACIE to explore the Martian subsurface., Comment: This paper was submitted to the Planetary and Astrobiology Decadal Survey in August 2020

Introduction. Pluto was first identified in 1930 and since that time has completed less than 40% of its orbit (248 Earth-years). Studies of Pluto's surface composition have been ongoing for only a small subset of this period, beginning with the first evidence for CH4 (methane) ice on the surface [1] only a few years before Pluto reached equinox in 1988 and perihelion in 1989. Therefore, the majority of spectroscopic studies have taken place during northern hemisphere spring, as Pluto recedes from the Sun. Since Pluto has a ~122° obliquity and an eccentric (e=0.25) orbit, these seasonal transitions ought to be extreme [2] and potentially observable over time. Simulations of Pluto's surface evolution suggest that the entire northern hemisphere, except for Sputnik Planitia, will be devoid of volatile ices (N2, CO, CH4) by 2030 [3]. Given that in 2015 New Horizons saw extensive deposits of volatile ices in the northern hemisphere [4,5] the removal process must occur relatively rapidly, if the models are correct. The duration of the New Horizons flyby was too brief to observe large-scale changes in surface composition or ice distribution. Observations. One method for evaluating changes on Pluto on timescales of a few years while accounting for rotational variability is to obtain spectra at the same sub-observer latitude and longitude roughly a year apart [6]. This cadence is made possible by the inclination of Earth's orbit with respect to the ecliptic, which presents a limited range of sub-observer latitudes on Pluto repeating ~14 months later. In order to quantify Pluto's short-term surface changes, while correcting for its rotational variability, we designed a spectroscopic observing program specifically to make use of these “matched pairs.” Pluto was observed on 13 nights between June 2014 and August 2017 using TripleSpec, a cross-dispersed spectrograph [7] at the Apache Point Observatory’s Astrophysical Research Consortium 3.5-meter telescope. These spectra were obtained at an average resolving power of ~3500 from 0.91 to 2.47 μm. Matched pairs typically corresponded to spectra obtained in June of one year and August of the next year, at roughly the same (±10°) sub-observer longitude, avoiding opposition where the viewing geometry at small phase angles affects band depth and width [8]. Pluto’s solar phase curve is also relatively flat between phase angles of 0.5-1.5° [9], the range over which the matched pair components were acquired. Therefore, any differences in viewing geometry do not significantly affect the spectra. Analysis and Results. To evaluate changes in surface composition over time, we computed integrated band areas for the 1.16, 1.19, 1.33, 1.66, and 1.72 μm CH4 absorption features in each of the corrected nightly spectra. We also calculated shifts in the band centers for the same features as a proxy for the amount of N2 in solution with CH4 [10]. The changes in CH4 band depth and band center position for each matched pair (later date minus newer date) are presented in Figures 1 and 2, respectively. Only those changes detected at ±5-σ for band depth and ±3-σ for band center shift were considered statistically significant. The only significant changes were detected between 2014-06-17 and 2015-08-19, centered on a sub-observer longitude of ~280°, which showed an increase in CH4 band areas as well as a blueshift in the band centers. No other matched pair showed a significant change over the corresponding time period. Discussion. Due to scheduling and weather, the majority of the matched pairs were obtained of the anti-Charon hemisphere, home to the bright, volatile-rich Sputnik Planitia. However, the only sub-observer hemisphere with a statistically significant band area increase included only a small portion of Sputnik but a large portion of the low-albedo, volatile-poor Cthulhu Macula [4,5]. The sub-observer hemisphere for the 2015-08-19/2014-06-17 matched pair was unique and contained the largest fraction of Cthulhu Macula. The increase in CH4 band areas and the blueshifting of the band centers in the spectra of one unique sub-observer hemisphere between June 2014 and August 2015, and the lack of strong evidence for any decrease in band areas on any sub-observer hemisphere, points to real short-term changes in Pluto's surface composition over this time frame. The lack of significant detections on other hemispheres centered on Sputnik does not necessarily indicate a lack of changes on those hemispheres. Sputnik is a large reservoir of volatile ices that models suggest undergoes little change over a Pluto orbit [3], so the spectra of these sub-observer hemispheres should be dominated by Sputnik’s contribution, drowning out smaller changes on other areas of the surface. Conversely, the 2015-08-19/2014-06-17 sub-observer hemisphere contains a large portion of the volatile-depleted Cthulhu Macula, which would amplify the same changes in surface composition in the spectra. On the sub-observer hemispheres not dominated by Sputnik, volatile N2 and CH4 ices are present primarily in the north polar region, with alternating latitudinal bands of CH4 diluted with N2 (55-90° N and 20-35° N) and N2 diluted with CH4 (35-55° N), as measured by New Horizons in 2015, about one month prior to the second half of the 2015-08-19/2014-06-17 matched pair [5]. The observed changes in the spectra of this sub-observer hemisphere indicate both an increase in CH4 concentration and an increase in N2 concentration in the north polar regions. While this sounds contradictory, it can be achieved by preferential sublimation of more-volatile N2 from latitudes northward of 55° as Pluto approaches northern hemisphere summer, resulting in an increase in CH4 concentration in those regions, combined with deposition of that N2 onto the latitudinal band from 35-55°. References. [1] Cruikshank, D.P., et al., 1976. Science 194, 835-837. [2] Binzel, R.P., et al., 2017. Icarus 287, 30-36. [3] Bertrand, T., Forget, F., 2016. Nature 540, 86-89. [4] Grundy, W.M., et al., 2016. Science 351, aad9189. [5] Protopapa, S., et al., 2017. Icarus 287, 218-228. [6] Grundy, W.M., et al., 2013. Icarus 223, 710-721. [7] Wilson, J.C., et al., 2004. SPIE 5492, 1295-1305. [8] Pitman, K., et al., 2017. P&SS 149, 23-31. [9] Verbiscer, A., et al., 2019. EPSC-DPS2019-1261. [10] Protopapa, S., et al., 2015. Icarus 253, 179-188.

The 2009 Lunar CRater Observation and Sensing Satellite (LCROSS) impact mission detected water ice absorption using spectroscopic observations of the impact-generated debris plume taken by the Shepherding Spacecraft, confirming an existing hypothesis regarding the existence of water ice in permanently shadowed regions within Cabeus crater. Ground-based observations in support of the mission were able to further constrain the mass of the debris plume and the concentration of the water ice ejected during the impact. In this work, we explore additional constraints on the initial conditions of the pre-impact lunar sediment required in order to produce a plume model that is consistent with the ground-based observations. We match the observed debris plume lightcurve using a layer of dirty ice with an ice concentration that increases with depth, a layer of pure regolith, and a layer of material at about 6 meters below the lunar surface that would otherwise have been visible in the plume but has a high enough tensile strength to resist excavation. Among a few possible materials, a mixture of regolith and ice with a sufficiently high ice concentration could plausibly produce such a behavior. The vertical albedo profiles used in the best fit model allows us to calculate a pre-impact mass of water ice within Cabeus crater of $5 \pm 3.0 \times 10^{11}$ kg and a mass concentration of water in the lunar sediment of $8.2 \pm 0.001$ %wt, assuming a water ice albedo of 0.8 and a lunar regolith density of 1.5 g cm$^{-3}$, or a mass concentration of water of $4.3 \pm 0.01$ %wt, assuming a lunar regolith density of 3.0. These models fit to ground-based observations result in derived masses of regolith and water ice within the debris plume that are consistent with \emph{in situ} measurements, with a model debris plume ice mass of 108 kg., 23 pages, 9 figures

We advocate for a mission concept study for a space telescope dedicated to solar system science in Earth orbit. Such a study was recommended by the Committee on Astrobiology and Planetary Science (CAPS) report "Getting Ready for the Next Planetary Science Decadal Survey." The Mid-Decadal Review also recommended NASA to assess the role and value of space telescopes for planetary science. The need for high-resolution, UV-Visible capabilities is especially acute for planetary science with the impending end of the Hubble Space Telescope (HST); however, NASA has not funded a planetary telescope concept study, and the need to assess its value remains. Here, we present potential design options that should be explored to inform the decadal survey., Whitepaper submitted to Planetary Science and Astrobiology Decadal Survey

Physical processing of Europan surface water ice by thermal relaxation, charged particle bombardment, and possible cryovolcanic activity can alter the percentage of the crystalline form of water ice compared to that of the amorphous form of water ice (the ''crystallinity'') on Europa's surface. The timescales over which amorphous water ice is thermally transformed to crystalline water ice at Europan surface temperatures suggests that the water ice there should be primarily in the crystalline form, however, surface bombardment by charged particles induced by Jupiter's magnetic field, and vapor deposition of water ice from Europan plumes, can produce amorphous water ice surface deposits on short timescales. The purpose of this investigation is to determine whether the Europan surface water ice crystallinity derived from ground-based spectroscopic measurements is in agreement with the crystallinity expected based on temperature and radiation modeling. Using a 1D thermophysical model of Europa's surface, we calculate a full-disk crystallinity of Europa's leading hemisphere by incorporating the thermal relaxation of amorphous to crystalline water ice and the degradation of crystalline to amorphous water ice by irradiation. Concurrently, we derive the full-disk crystallinity of Europa's leading hemisphere using a comparison of near-infrared ground-based spectral observations from Grundy et al. (1999), Busarev et al. (2018), and the Apache Point Observatory with laboratory spectra from Mastrapa et al. (2018) and the Ice Spectroscopy Lab at the Jet Propulsion Laboratory. We calculate a modeled crystallinity significantly higher than crystallinities derived from ground-based observations and laboratory spectra. This discrepancy may be a result of geophysical processes, such as by vapor-deposited plume material, or it may arise from assumptions and uncertainties in the crystallinity calculations., 27 pages, 6 figures, accepted for publication in Icarus

This white paper, written in support of NASA's 2023-2032 Planetary Decadal Survey, outlines 10 major questions that focus on the origin, evolution, and current processes that shape the atmospheres of Uranus and Neptune. Prioritizing these questions over the next decade will greatly improve our understanding of this unique class of planets, which have remained largely unexplored since the Voyager flybys. Studying the atmospheres of the Ice Giants will greatly inform our understanding of the origin and evolution of the solar system as a whole, in addition to the growing number of exoplanetary systems that contain Neptune-mass planets., Comment: 8 pages, 0 figures, White Paper submitted to the Astrobiology and Planetary Science Decadal Survey

The National Academy Committee on Astrobiology and Planetary Science (CAPS) made a recommendation to study a large/medium-class dedicated space telescope for planetary science, going beyond the Discovery-class dedicated planetary space telescope endorsed in Visions and Voyages. Such a telescope would observe targets across the entire solar system, engaging a broad spectrum of the science community. It would ensure that the high-resolution, high-sensitivity observations of the solar system in visible and UV wavelengths revolutionized by the Hubble Space Telescope (HST) could be extended. A dedicated telescope for solar system science would: (a) transform our understanding of time-dependent phenomena in our solar system that cannot be studied currently under programs to observe and visit new targets and (b) enable a comprehensive survey and spectral characterization of minor bodies across the solar system, which requires a large time allocation not supported by existing facilities. The time-domain phenomena to be explored are critically reliant on high spatial resolution UV-visible observations. This paper presents science themes and key questions that require a long-lasting space telescope dedicated to planetary science that can capture high-quality, consistent data at the required cadences that are free from effects of the terrestrial atmosphere and differences across observing facilities. Such a telescope would have excellent synergy with astrophysical facilities by placing planetary discoveries made by astrophysics assets in temporal context, as well as triggering detailed follow-up observations using larger telescopes. The telescope would support future missions to the Ice Giants, Ocean Worlds, and minor bodies across the solar system by placing the results of such targeted missions in the context of longer records of temporal activities and larger sample populations., Comment: A whitepaper submitted to the Planetary Science Decadal Survey

In this work we present the results of a spectral observing campaign of Pluto to search for temporal changes in surface composition on 1- to 3-year timescales. Near-infrared spectra of Pluto were obtained from June 2014 to August 2017 with the TripleSpec cross-dispersed spectrograph at the Apache Point Observatory's 3.5-meter Astrophysical Research Consortium (ARC) telescope. Observations were requested in order to obtain spectra of approximately the same sub-observer hemisphere $\sim$14 months apart, thus removing the effects of viewing geometry and rotation phase. Comparison of the CH$_4$ (methane) band areas and band center shifts between each component of these "matched pairs" revealed a surface in transition. Band areas for the 1.66 and 1.72 $\mu$m CH$_4$ absorption features exhibited a $>$5-$\sigma$ increase between 2014-06-17 and 2015-08-19, corresponding to a sub-observer hemisphere centered at $\sim$280$^{\circ}$E, with the latter date only 1 month after the New Horizons flyby of Pluto. The majority of matched pairs were obtained of the anti-Charon hemisphere, home to the bright, volatile-rich Sputnik Planitia, and did not present statistically significant changes in CH$_4$ band areas. CH$_4$ band center shifts, which provide information on the mixing state of CH$_4$ and N$_2$ in solid solution, were calculated between components of each matched pair, with no significant band shifts detected. The favored explanation for these combined results is the sublimation of more-volatile N$_2$ from the northern latitudes of Pluto in the lead-up to northern hemisphere summer solstice in 2029, leading to an increase in CH$_4$ concentration., Comment: 28 pages, 8 figures, 5 tables

The authors present an experimental demonstration of a fluidic-based plasmonic device for spectral analysis. The demonstrated device is based on the modification of surface plasmon resonance in periodically coupled metallic nanostructures using external refractive index perturbation for spectral analysis. The refractive index perturbation alters the resonance condition of the internal surface plasmon waves and introduces a spectral shift in the transmission band for spectral sampling. In this demonstration, precise control of the centre wavelength of the surface plasmon resonance was achieved by changing the local environment of the nanostructures via microfluidic channels. The fluidic-based approach has a great impact on existing resonance-based spectral analysis devices by offering an efficient way to acquire a very large number of spectral sampling.

The search for life and habitable environments on other Solar System bodies is a major motivator for planetary exploration. Due to the difficulty and significance of detecting extant or extinct extraterrestrial life in situ, several independent measurements from multiple instrument techniques will bolster the community's confidence in making any such claim. We demonstrate the detection of subsurface biosignatures using a suite of instrument techniques including IR reflectance spectroscopy, laser-induced breakdown spectroscopy, and scanning electron microscopy/energy dispersive X-ray spectroscopy. We focus our measurements on subterranean calcium carbonate field samples, whose biosignatures are analogous to those that might be expected on some high-interest astrobiology targets. In this work, we discuss the feasibility and advantages of using each of the aforementioned instrument techniques for the in situ search for biosignatures and present results on the autonomous characterization of biosignatures using multivariate statistical analysis techniques. Key Words: Biosignature suites-Caves-Mars-Life detection. Astrobiology 17, 1203-1218.

We discuss the development of a plasmonic spectrometer for in situ characterization of solar system surface and subsurface environments. The two goals of this effort are to (1) quantitatively demonstrate that a plasmonic spectrometer can be used to rapidly acquire high signal-to-noise spectra between 0.5–1.0 µm at a spectral resolution suitable for unambiguous detection of spectral slopes and features indicative of volatiles and characteristic surface mineralogies, and (2) demonstrate that this class of spectrometer can be used in conjunction with optical fibers to access subsurface materials and vertically map the geochemistry and mineralogy of subsurface layers, thereby demonstrating that a plasmonic spectrometer is feasible in a low-mass, low-power, compact configuration. Our prototype instrument, the Plasmonic Spectrometer for In situ CLassification Of Planetary Surfaces (PSICLOPS), consists of a broadband lamp/source, a fiber optic system to illuminate the sample surface and collect the reflected light, a mosaic filter element based on plasmon resonance, and a focal plane array detector. The critical filter element of the spectrometer is based on the internal plasmon resonance of metallic nanostructures. We developed a membrane-based plasmonic filter that can be directly implemented on an optical fiber. After developing a new fabrication process for nanostructures in thin Au membranes suspended in air, we found that we can control the central wavelength of the filter by changing the index of refraction of the surrounding medium. Therefore we explored several media (e.g. water, glycerol, and glucose) as a means of introducing a range of indices of refraction, and thus central wavelengths of the filter, using microfluidic channels. In addition to the development of the plasmon filter element, we constructed a testbed to explore the use of optical fibers for source illumination and signal transmission to the focal plane array. We discuss our preliminary design studies of the plasmonic nanostructure prototypes and their application to miniaturized instrumentation for in situ characterization of solar system surface and subsurface environments.

The New Mexico State University Acousto-optic Imaging Camera (NAIC) at the Apache Point Observatory 3.5-m telescope is collecting narrowband hyperspectral image cubes of Jupiter from 470–950 nm during the perijove passes of the Juno spacecraft. For operations prior to 2018, the focal plane used for NAIC was a 1024×1024 pixel2 backside illuminated, high quantum efficiency CCD. However, the narrowband images show evidence of “fringing”, due to “optical etaloning.” For much of our collected data, a flat-field correction successfully removes the fringing from the science images. However, for some absorption features, especially in Jupiter's prominent CH4 bands at ∼890 nm, differences in the illumination spectrum of the flat-field source and Jupiter leave residual fringing in the images. Observation of the fringe pattern in the flat-field images as a function of wavelength suggested we could assume a thickness function with a single layer involving a single reflective surface. The thickness of the sensor has a “dish-shaped” variation as a function of pixel position in addition to finely spaced surface polishing marks. Using a mathematical interference (fringe) model, we were able to solve for the 2-D physical thickness function of the CCD at each pixel by minimizing the mean square error between the fringe model and the pixel spectral data. Synthetic fringe frames were created using the 2-D thickness function and scaled with best-correction contrast values. The flat-field and Jupiter images were corrected separately for fringing with division by the synthetic fringe frames. Fringe-corrected Jupiter frames are divided by fringe-corrected flat field frames to yield the final Jupiter science images, which show little evidence of etaloning.

Here we present new ultraviolet–visible spectra of irradiated ammonium hydrosulfide (NH4SH), a reported jovian atmospheric cloud component, for a range of temperatures and radiation doses and make assignments to the spectral features. We show that the combination of radiolysis and thermal annealing of NH4SH causes the originally featureless ultraviolet–visible reflectance spectrum to evolve into one that absorbs in the ultraviolet–visible region. Furthermore, we find that our laboratory spectra resemble HST spectra below 500 nm, suggesting that the more stable reaction products of NH4SH radiolysis are likely an important component of the Great Red Spot.

Evidence of “fringing” due to optical etaloning was observed in narrowband hyperspectral image cubes of Jupiter collected prior to 2018 at the Apache Point Observatory 3.5-m telescope with the New Mexico State University Acousto-optic Imaging Camera. The etaloning resulted from the use of a back-illuminated, high quantum efficiency CCD. Otherwise successful flat-field correction was ineffective in removing fringes at some wavelengths associated with Jupiter’s absorption regions. We describe an etaloning correction method based on a mathematical interference model that assumes a single detection layer. A two-dimensional thickness function for the sensor layer was derived and found to have an overall “dish-shaped” variation along with some finely spaced surface polishing marks. Synthetic fringe frames corresponding to the flat-field and science images were created using the thickness function. Optimized contrast values were found for the synthetic frames and defringed images of Jupiter were generated by separately correcting flat-field and science images using the synthetic fringe frames before applying the final flat-field division. Quantitative analyses of defringed flat-field images showed fringe contrast reductions by factors of 2 to 8 on average and a disk-averaged spectrum of defringed Jupiter data compared favorably with an established spectrum. This defringing approach is applicable to other detectors that can be modeled with a single detection layer and where a sequence of spectral images with adequate wavelength resolution is available.

Submillimeter emission lines of carbon monoxide (CO) in Titan's atmosphere provide excellent probes of atmospheric temperature due to the molecule's long chemical lifetime and stable, well constrained volume mixing ratio. Here we present the analysis of 4 datasets obtained with the Atacama Large Millimeter/Submillimeter Array (ALMA) from 2012 to 2015 that contain strong CO rotational transitions. Utilizing ALMA's high spatial resolution in the 2012, 2014, and 2015 observations, we extract spectra from 3 separate regions on Titan's disk using datasets with beam sizes of ~0.3''. Temperature profiles retrieved by the NEMESIS radiative transfer code are compared to Cassini Composite Infrared Spectrometer (CIRS) and radio occultation science results from similar latitude regions. Small seasonal variations in atmospheric temperature are present from 2012 to 2015 in the stratosphere and mesosphere (~100-500 km) of spatially resolved regions. We measure the stratopause (320 km) to increase in temperature by 5 K in northern latitudes from 2012-2015, while temperatures rise throughout the stratosphere at lower latitudes. While retrieved temperature profiles cover a range of latitudes in these observations, deviations from CIRS nadir maps and radio occultation measurements convolved with the ALMA beam-footprint are not found to be statistically significant, and discrepancies are often found to be less than 5 K throughout the atmosphere. ALMA's excellent sensitivity in the lower stratosphere (60-300 km) provides a highly complementary dataset to contemporary CIRS and radio science observations. The demonstrated utility of CO emission lines in the submillimeter as a tracer of Titan's atmospheric temperature lays the groundwork for future studies of other molecular species, as temperature profiles are found to consistently vary with latitude in all three years by up to 15 K., Comment: 11 pages, 9 figures, 3 tables

Here we present our recent studies of proton-irradiated and unirradiated ammonium hydrosulfide, NH4SH, a compound predicted to be an important tropospheric cloud component of Jupiter and other giant planets. We irradiated both crystalline and amorphous NH4SH at 10-160 K and used IR spectroscopy to observe and identify reaction products in the ice, specifically NH3 and long-chained sulfur-containing ions. Crystalline NH4SH was amorphized during irradiation at all temperatures studied with the rate being the fastest at the lowest temperatures. Irradiation of amorphous NH4SH at approximately 10-75 K showed that 60-80% of the NH4 + remained when equilibrium was reached, and that NH4SH destruction rates were relatively constant within this temperature range. Irradiations at higher temperatures produced different dose dependence and were accompanied by pressure outbursts that, in some cases, fractured the ice. The thermal stability of irradiated NH4SH was found to be greater than that of unirradiated NH4SH, suggesting that an irradiated giant-planet cloud precipitate can exist at temperatures and altitudes not previously considered.

We present analysis of high spectral resolution NIR spectra of CO and H$_2$O in comet C/2009 P1 (Garradd) taken during its 2011-2012 apparition with the CSHELL instrument on NASA's Infrared Telescope Facility (IRTF). We also present analysis of observations of atomic oxygen in comet Garradd obtained with the ARCES echelle spectrometer mounted on the ARC 3.5-meter telescope at Apache Point Observatory and the Tull Coude spectrograph on the Harlan J. Smith 2.7-meter telescope at McDonald Observatory. The observations of atomic oxygen serve as a proxy for H$_2$O and CO$_2$. We confirm the high CO abundance in comet Garradd and the asymmetry in the CO/H$_2$O ratio with respect to perihelion reported by previous studies. From the oxygen observations, we infer that the CO$_2$/H$_2$O ratio decreased as the comet moved towards the Sun, which is expected based on current sublimation models. We also infer that the CO$_2$/H$_2$O ratio was higher pre-perihelion than post-perihelion. We observe evidence for the icy grain source of H$_2$O reported by several studies pre-perihelion, and argue that this source is significantly less abundant post-perihelion. Since H$_2$O, CO$_2$, and CO are the primary ices in comets, they drive the activity. We use our measurements of these important volatiles in an attempt to explain the evolution of Garradd's activity over the apparition., 35 pages, 10 figures, 9 tables, accepted for publication in Icarus

We describe the Sloan Digital Sky Survey IV (SDSS-IV), a project encompassing three major spectroscopic programs. The Apache Point Observatory Galactic Evolution Experiment 2 (APOGEE-2) is observing hundreds of thousands of Milky Way stars at high resolution and high signal-to-noise ratio in the near-infrared. The Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey is obtaining spatially-resolved spectroscopy for thousands of nearby galaxies (median redshift of z = 0.03). The extended Baryon Oscillation Spectroscopic Survey (eBOSS) is mapping the galaxy, quasar, and neutral gas distributions between redshifts z = 0.6 and 3.5 to constrain cosmology using baryon acoustic oscillations, redshift space distortions, and the shape of the power spectrum. Within eBOSS, we are conducting two major subprograms: the SPectroscopic IDentification of eROSITA Sources (SPIDERS), investigating X-ray AGN and galaxies in X-ray clusters, and the Time Domain Spectroscopic Survey (TDSS), obtaining spectra of variable sources. All programs use the 2.5-meter Sloan Foundation Telescope at Apache Point Observatory; observations there began in Summer 2014. APOGEE-2 also operates a second near-infrared spectrograph at the 2.5-meter du Pont Telescope at Las Campanas Observatory, with observations beginning in early 2017. Observations at both facilities are scheduled to continue through 2020. In keeping with previous SDSS policy, SDSS-IV provides regularly scheduled public data releases; the first one, Data Release 13, was made available in July 2016., Published in Astronomical Journal

We observed the Venusian 5577.3 A OI ( 1 S– 1 D) (oxygen green line) nightglow emission feature after solar flares, coronal mass ejections (CMEs), and solar wind streams from December 2010 to July 2012 using the high resolution Astrophysical Research Consortium Echelle Spectrograph on the Apache Point Observatory 3.5 m telescope. For the first time since 2004, we detected the green line. The emission is highly temporally variable, with the strongest emission detected being comparable to the previously known brightest detection, and to occur after each of the three types of solar events. We find the greatest emission occurs after CMEs and suggest that particle precipitation is the main contributor to green line emission.

We extracted physical atmospheric parameters from a 23 July 2008 single-chord stellar occultation of the star USNO-B1.0 0759-0739128 (I-band magnitude of 12.60) by Neptune using a light curve model fitting technique. We observed the occultation using the Agile CCD camera mounted on the Astrophysical Research Consortium 3.5 m telescope at Apache Point Observatory. We found isothermal temperatures of 116.5 ± 12.0 K and 154.0 ± 13.0 K for the immersion and emersion light curve profiles, respectively. We compare the stratospheric temperatures derived from the 2008 occultation to published temperatures of Neptune at similar atmospheric pressures derived from previous stellar occultations observed in the 1980s, and from long-term photometric measurements made routinely since the 1983–1990 occultation campaign. No obvious long-term temporal variation in stratospheric isothermal temperature is present. Fluctuations in the fitted isothermal temperature values, on the order of 20 K, is evident. We explore several hypotheses to explain the observed temperature variability of Neptune’s stratosphere, including seasonal variability, variations in the Lyman- α flux received at Neptune due to the 11-year solar cycle, diurnal variations, varying insolation due to heliocentric variability, IR and UV heating by hydrocarbons, aerosol precipitation, inertia-gravity wave dissipation, and effects due to atmospheric tidal perturbations by Triton. We investigate the effects of these mechanisms on the gradual temporal changes of Neptune’s stratospheric temperature and conclude that local variations in stratospheric temperature during each event, on the order of 20 K, are dominated by viscous dissipation of inertia-gravity waves.

We present analysis of high spectral resolution optical spectra of Comet 103P/Hartley taken during its Fall 2010 apparition. These spectra include transitions belonging to CN, C2, CH, NH2, and OI. We measure production rates and mixing ratios from these spectra. We find evidence for large changes in production rates (factors of a few) over the course of a nucleus rotation, in agreement with other measurements. We also measure variability with rotational phase in the CN/H2O and C2/CN ratios, which has not been previously reported for any comet. There may also be variability in the NH2/H2O ratio with rotational phase, but this trend is not as clear as for CN/H2O. We interpret the changing mixing ratios as due to H2O and C2 being released primarily from the icy grain halo, while the CN parent molecule comes directly from the nucleus. There is evidence that the CH/CN ratio is higher pre-perihelion than post-perihelion. We conclude that the observed CN and NH2 abundances are consistent with HCN and NH3 being the dominant parent molecules for these species. The C2 and CH abundances are higher than those of candidate parent molecules (C2H2 and CH4 respectively), so there must be another source for these molecules in 103P’s coma. Carbonaceous dust grains could serve as this source.

A superior mutual event of the Kuiper Belt binary system (79360) Sila-Nunam was observed over 15.47 h on UT 7/8 February 2013 by a coordinated effort at four different telescope facilities; it started approximately 1.5 h earlier than anticipated, the duration was approximately 9.5 h (about 10% longer than predicted), and was slightly less deep than predicted. It is the first full event observed for a comparably sized binary Kuiper Belt object. We provide predictions for future events refined by this and other partial mutual event observations obtained since the mutual event season began.

[1] The nature and mechanisms producing the chromophore agents that provide color to the upper clouds and hazes of the atmospheres of the giant planets are largely unknown. In recent times, the changes in red coloration that have occurred in large- and medium-scale Jovian anticyclones have been particularly interesting. In late June and early July 2008, a particularly color intense tropical red oval interacted with the Great Red Spot (GRS) leading to the destruction of the tropical red oval and cloud dispersion. We present a detailed study of the tropical vortices, usually white but sometimes red, and a characterization of their color spectral signatures and dynamics. From the spectral reflectivity in methane bands we study their vertical cloud structure compared to that of the GRS and BA. Using two spectral indices we found a near correlation between anticyclones cloud top altitudes and red color. We present detailed observations of the interaction of the red oval with the GRS and model simulations of the phenomena that allow us to constrain the relative vertical extent of the vortices. We conclude that the vertical cloud structure, vertical extent, and dynamics of Jovian anticyclones are not the causes of their coloration. We propose that the red chromophore forms when background material (a compound or particles) is entrained by the vortex, transforming into red once inside the vortex due to internal conditions, exposure to ultraviolet radiation, or to the mixing of two chemical compounds that react inside the vortex, confined by a potential vorticity ring barrier.

We present analysis of observations of the forbidden oxygen lines in Comet 103P/Hartley, the target of the Deep Impact Extended Investigation (DIXI), during its Fall 2010 apparition. We obtained the observations using the ARCES echelle spectrometer mounted on the Astrophysical Research Consortium (ARC) 3.5-m telescope at Apache Point Observatory. We detected the 5577, 6300, and 6364 A lines on all dates, and so were able to calculate the ratio of the 5577 A line intensity to the sum of the intensities of the 6300 A and 6364 A lines (the oxygen line ratio). A ratio of 0.05–0.1 would suggest that water is the dominant parent, while a higher ratio suggests that another volatile, such as CO2, is an important contributor to the O I population. We find a range of values for the oxygen line ratio varying from ∼0.05–0.13. This range includes values that are higher than those typically measured for comets observed at a similar heliocentric distance to 103P (∼1 AU). The higher measured ratio is likely a result of a higher intrinsic CO2 abundance in the material released from 103P than typical comets, as found by direct measurements of CO2 and H2O made by the DIXI spacecraft. The CO2/H2O ratio in 103P was also observed by the DIXI spacecraft to vary significantly with rotational phase of the nucleus, which explains the large range of oxygen line ratios observed. These observations of the forbidden oxygen lines in 103P, a comet for which a directly observed CO2/H2O ratio is available, suggest that high quality observations of the forbidden oxygen lines in comets can serve as a proxy for CO2/H2O ratio measurements.

The James Webb Space Telescope will enable a wealth of new scientific investigations in the near- and mid-infrared, with sensitivity and spatial/spectral resolution greatly surpassing its predecessors. In this paper, we focus upon Solar System science facilitated by JWST, discussing the most current information available concerning JWST instrument properties and observing techniques relevant to planetary science. We also present numerous example observing scenarios for a wide variety of Solar System targets to illustrate the potential of JWST science to the Solar System community. This paper updates and supersedes the Solar System white paper published by the JWST Project in 2010 (Lunine et al., 2010). It is based both on that paper and on a workshop held at the annual meeting of the Division for Planetary Sciences in Reno, NV in 2012., 52 pages (with figures), 32 figures; More information about JWST Solar System observations is available at http://www.stsci.edu/jwst/science/solar-system

This white paper examines the benefit of the upcoming James Webb Space Telescope (JWST) for studies of the Solar System's four giant planets: Jupiter, Saturn, Uranus, and Neptune. JWST's superior sensitivity, combined with high spatial and spectral resolution, will enable near- and mid-infrared imaging and spectroscopy of these objects with unprecedented quality. In this paper, we discuss some of the myriad scientific investigations possible with JWST regarding the giant planets. This discussion is preceded by the specifics of JWST instrumentation most relevant to giant-planet observations. We conclude with identification of desired pre-launch testing and operational aspects of JWST that would greatly benefit future studies of the giant planets.

著者人数: 87名, Accepted: 2011-02-08, 資料番号: SA1004099000

The oxygen green line is one of the most characteristic features in the terrestrial visible nightglow; it can be seen in the Venus nightglow, but with much greater intensity variation than in the terrestrial case. Here we synthesize our current understanding of the green line in the Venus nightglow and discuss what might be expected observationally in the rising phase of solar cycle 24.

The chromophores responsible for coloring the jovian atmosphere are embedded within Jupiter's vertical aerosol structure. Sunlight propagates through this vertical distribution of aerosol particles, whose colors are defined by omega-bar (sub 0)(lambda), and we remotely observe the culmination of the radiative transfer as I/F(lambda). In this study, we employed a radiative transfer code to retrieve omega-bar (sub 0)(lambda) for particles in Jupiter's tropospheric haze at seven wavelengths in the near-UV and visible regimes. The data consisted of images of the 2008 passage of Oval BA to the south of the Great Red Spot obtained by the Wide Field Planetary Camera 2 on-board the Hubble Space Telescope. We present derived particle colors for locations that were selected from 14 weather regions, which spanned a large range of observed colors. All omega-bar (sub 0)(lambda) curves were absorbing in the blue, and omega-bar (sub 0)(lambda) increased monotonically to approximately unity as wavelength increased. We found accurate fits to all omega-bar (sub 0)(lambda) curves using an empirically derived functional form: omega-bar (sub 0)(lambda) = 1 A exp(-B lambda). The best-fit parameters for the mean omega-bar (sub 0)(lambda) curve were A = 25.4 and B = 0.0149 for lambda in units of nm. We performed a principal component analysis (PCA) on our omega-bar (sub 0)(lambda) results and found that one or two independent chromophores were sufficient to produce the variations in omega-bar (sub 0)(lambda). A PCA of I/F(lambda) for the same jovian locations resulted in principal components (PCs) with roughly the same variances as the omega-bar (sub 0)(lambda) PCA, but they did not result in a one-to-one mapping of PC amplitudes between the omega-bar (sub 0)(lambda) PCA and I/F(lambda) PCA. We suggest that statistical analyses performed on I/ F(lambda) image cubes have limited applicability to the characterization of chromophores in the jovian atmosphere due to the sensitivity of 1/ F(lambda) to horizontal variations in the vertical aerosol distribution.

We observed Phoebe for 13 nights over a period of 55 days before, during, and after the 2005 Saturn opposition with the New Mexico State University (NMSU) 1-m telescope at Apache Point Observatory (APO) in Sunspot, NM and characterized the width and magnitude of Phoebe’s opposition surge in BVRI filters. Our observations cover a phase angle range of 4.87° to 0.0509°. We use a Hapke reflectance model incorporating shadow hiding and coherent backscatter to investigate the wavelength dependence of Phoebe’s opposition surge. We find a significant opposition surge magnitude of 55–58% between phase angles of 5° and 0°. We find the strongest opposition surge for phase angles less than 2° in the I-band. The coherent backscatter angular width is on the order of 0.50°. We find Phoebe’s albedo to be spectrally flat within our error limits, with a B-band albedo of 0.0855 ± 0.0031, a V-band albedo of 0.0856 ± 0.0023, an R-band albedo of 0.0843 ± 0.0020, and an I-band albedo of 0.0839 ± 0.0023. We compare Phoebe’s albedo, color, and opposition surge magnitudes and slopes with those of other outer solar system bodies and find similarities to Centaurs, Nereid, Puck, and Comets 19P/Borrelly, 9P/Tempel 1, and 81P/Wild 2. We find that this comparison supports the idea that Phoebe originated in the Kuiper Belt. We also discuss the caveats of using results from a Hapke reflectance model to derive specific surface particle properties.

We present a novel method of constructing streamlines to derive wind speeds within jovian vortices and demonstrate its application to Oval BA for 2001 pre-reddened Cassini flyby data, 2007 post-reddened New Horizons flyby data, and 1998 Galileo data of precursor Oval DE. Our method, while automated, attempts to combine the advantages of both automated and manual cloud tracking methods. The southern maximum wind speed of Oval BA does not show significant changes between these data sets to within our measurement uncertainty. The northern maximum dries appear to have increased in strength during this time interval, tvhich likely correlates with the oval's return to a symmetric shape. We demonstrate how the use of closed streamlines can provide measurements of vorticity averaged over the encircled area with no a priori assumptions concerning oval shape. We find increased averaged interior vorticity between pre- and post-reddened Oval BA, with the precursor Oval DE occupying a middle value of vorticity between these two.

We obtained near-infrared spectra of Uranus at NASA’s Infrared Telescope Facility during the planet’s September 2006 and September 2007 oppositions. Ratios between the spectra indicate that in 2006, Uranus’ methane windows appeared much brighter in the south than in the north, and that between 2006 and 2007 they grew dimmer in the south and brighter in the north; we interpret these variations to be primarily caused by changing brightness in Uranus’ upper cloud layer near 2 bars.