V5579 Sgr was a fast nova discovered in 2008 April 18.784 UT. We present the optical spectroscopic observations of the nova observed from the Castanet Tolosan, SMARTS and CTIO observatories spanning over 2008 April 23 to 2015 May 11. The spectra are dominated by hydrogen Balmer, Fe II and O I lines with P-Cygni profiles in the early phase, typical of an Fe II class nova. The spectra show He I and He II lines along with forbidden lines from N, Ar, S, and O in the nebular phase. The nova showed a pronounced dust formation episode that began about 20 days after the outburst. The dust temperature and mass were estimated using the WISE data from spectral energy distribution (SED) fits. The PAH-like features are also seen in the nova ejecta in the mid-IR Gemini spectra taken 522 d after the discovery. Analysis of the light curve indicates values of t2 and t3 about 9 and 13 days, respectively, placing the nova in the category of fast nova. The best fit cloudy model of the early decline phase JHK spectra obtained on 2008 May 3 and the nebular optical spectrum obtained on 2011 June 2 shows a hot white dwarf source with T-BB similar to 2.6 x 10(5) K having a luminosity of 9.8 x 10(36) ergs s(-1). Our abundance analysis shows that the ejecta is significantly enhanced relative to solar, O/H = 32.2, C/H = 15.5 and N/H = 40.0 in the early decline phase and O/H = 5.8, He/H = 1.5 and N/H = 22.0 in the nebular phase.

As comets journey into the inner solar system, they deliver particulates and volatile gases into their comae that reveal the most primitive materials in the solar system. Cometary dust particles provide crucial information for assessing the physicochemical conditions in the outer disk from which they formed. Compared to the volatiles and soluble organics, the refractory dust particles are more robust and may be traceable to other small bodies. Using data from the Spitzer Heritage Archive, we present thermal dust models of 57 observations of 33 comets observed spectroscopically with the NASA Spitzer Space Telescope. This comet spectral survey offers the opportunity to study comets with data from the same instrument, reduced by the same methods, and fitted by the same thermal model using the same optical constants. The submicron dust tends to be dominated by amorphous carbon, and the submicron silicate mass tends to be dominated by amorphous silicate materials. We discuss the implications of these findings as they relate to Mg-rich crystalline silicates, which are high-temperature condensates, as well as to potential ion irradiation of amorphous Mg:Fe silicates prior to their incorporation into comets. These results impact our understanding of the protoplanetary disk conditions of planetesimal formation. Lastly, we cannot definitively conclude that a distinct difference exists in the dust composition between the Oort cloud and Jupiter-family comet dynamical population as a whole.

The presence and distribution of preserved organic matter on the surface of Mars can provide key information about the Martian carbon cycle and the potential of the planet to host life throughout its history. Several types of organic molecules have been previously detected in Martian meteorites 1 and at Gale crater, Mars 2 – 4 . Evaluating the diversity and detectability of organic matter elsewhere on Mars is important for understanding the extent and diversity of Martian surface processes and the potential availability of carbon sources 1 , 5 , 6 . Here we report the detection of Raman and fluorescence spectra consistent with several species of aromatic organic molecules in the Máaz and Séítah formations within the Crater Floor sequences of Jezero crater, Mars. We report specific fluorescence-mineral associations consistent with many classes of organic molecules occurring in different spatial patterns within these compositionally distinct formations, potentially indicating different fates of carbon across environments. Our findings suggest there may be a diversity of aromatic molecules prevalent on the Martian surface, and these materials persist despite exposure to surface conditions. These potential organic molecules are largely found within minerals linked to aqueous processes, indicating that these processes may have had a key role in organic synthesis, transport or preservation.

Perseverance's Mastcam-Z instrument provides high-resolution stereo and multispectral images with a unique combination of spatial resolution, spatial coverage, and wavelength coverage along the rover's traverse in Jezero crater, Mars. Images reveal rocks consistent with an igneous (including volcanic and/or volcaniclastic) and/or impactite origin and limited aqueous alteration, including polygonally fractured rocks with weathered coatings; massive boulder-forming bedrock consisting of mafic silicates, ferric oxides, and/or iron-bearing alteration minerals; and coarsely layered outcrops dominated by olivine. Pyroxene dominates the iron-bearing mineralogy in the finegrained regolith, while olivine dominates the coarse-grained regolith. Solar and atmospheric imaging observations show significant intra- and intersol variations in dust optical depth and water ice clouds, as well as unique examples of boundary layer vortex action from both natural (dust devil) and Ingenuity helicopter-induced dust lifting. High-resolution stereo imaging also provides geologic context for rover operations, other instrument observations, and sample selection, characterization, and confirmation.

Comet C/2013 US 10 (Catalina) was a dynamically new Oort cloud comet whose apparition presented a favorable geometry for observations near close-Earth approach (≃0.93 au) at heliocentric distances ≲2 au when insolation and sublimation of volatiles drive maximum activity. Here we present mid-infrared 6.0 ≲ λ ( μ m) ≲ 40 spectrophotometric observations at two temporal epochs from NASA’s Stratospheric Observatory for Infrared Astronomy and the NASA Infrared Telescope Facility that yield an inventory of the refractory materials and their physical characteristics through thermal modeling analysis. The grain composition is dominated by dark dust grains (modeled as amorphous carbon) with a silicate-to-carbon ratio ≲0.9, little crystalline stoichiometry (no distinct 11.2 μ m feature attributed to Mg-rich crystalline olivine), and the submicron grain-size distribution peaking at ≃0.6 μ m. The 10 μ m silicate feature was weak, ≈12.8% ± 0.1% above the local continuum, and the bolometric grain albedo was low (≲14%). Comet C/2013 US 10 (Catalina) is a carbon-rich object. This material, which is well represented by the optical constants of amorphous carbon, is similar to the material that darkens and reddens the surface of comet 67P/Churyumov–Gerasimenko. We argue this material is endemic to the nuclei of comets, synthesizing results from the study of Stardust samples, interplanetary dust particle investigations, and micrometeoritic analyses. The atomic carbon-to-silicate ratio of comet C/2013 US 10 (Catalina) and other comets joins a growing body of evidence suggesting the existence of a C/Si gradient in the primitive solar system, providing new insight into planetesimal formation and the distribution of isotopic and compositional gradients extant today.

Introduction: Comet nuclei likely incorporated and preserved both processed nebular matter as well as material inherited from the interstellar medium (ISM). Thermal modeling and analyses of our IR spectral observations of five comets reveal cometary dust carbon-to-silicon (C/Si) atomic ratios much higher than carbonaceous chondrites [1], furthering the suggestion that our outer protoplanetary disk, the realm where comets formed, was rich in carbon [2]. Rocky bodies within the inner solar system are known to be generally depleted in carbon, which is the “carbon deficit” problem [3], whereas cometary C/Si atomic ratios are nearest to C/Si atomic ratios derived for the ISM and for our Sun (Fig. 1). This contrast indicates the materials present in the outer disk efficiently sequestered carbon from the abundant carbon reservoir inherited from the ISM. A gap in our disk, possibly attributed to Jupiter’s formation, may have inhibited transport of carbon from the outer to inner disk and sculpted compositions of minor bodies [4]. Cometary particles have diverse compositions and are porous aggregates. Measurements of cometary particles reveal a range of disk conditions contributed to the formation of different comets. Comet 26P/GriggSkjellerup’s IDPs have “ultra-primitive” materials with high concentrations of isotopically-presolar materials, whereas Stardust samples of comet 81P/Wild 2 include Type II micro chondrules like ‘Iris’ that formed ~2 Myr [5] after the earliest condensed materials such as CAIs (calcium aluminum inclusions). Rosetta’s COSIMA measurements and its COSISCOPE images of comet 67P/Churyumov-Gerasimenko (67P/C-G) particles demonstrate its particles contain 50% by weight IOMlike carbonaceous matter [6] and definitively the particles are hierarchical aggregates. MIDAS’ AFM revealed that some particles are highly porous [7] whereas the majority of particles have moderate porosities [8]. Rosetta’s VIRTIS-H spectra of the dark surface of comet 67P/C-G reveal spectral features of carbonaceous matter including aliphatic carbon, and ammonium salts [9,10], and relevant laboratory experiments considered Fe-sulfides [11] or carbon black as darkening agents [12]. These findings motivate our work to compute the IR optical properties of porous aggegates with high relative abundances of highly absorbing carbonaceous matter. Amorphous carbon is the only form of carbon common between Stardust samples, anhydrous IDPs, and Bells, Murchison, Orgueil and Tagish Lake [13]. A dark carbonaceous material is well-represented by the optical properties of amorphous carbon [1]. High atomic C/Si ratios for growing numbers of comets: Comet 67P/Churymov-Gerasimenko (67P/CG) and four other comets that we have observed and modeled [1], including the dynamically new comet C/ Figure 1. Atomic carbon-to-silicon ratios (C/Si) for various small bodies relevant to comets, obtained from our analyses of comets (red) and sources in the literature [1]. C/Si values are represented by black dots for chondrites (enstatite, ordinary, carbonaceous), Sun-grazing comets and comet 1P/Halley [3], green squares for chondritic porous (CP) interplanetary dust particles, purple squares for anhydrous IDPs, the brown-half moon for Rosetta COSIMA values of 67P/ C-G, the blue star for Ultra-Carbonaceous Antarctic Mircometeorites (UCAMMs). The interstellar medium atomic C/Si limit is depicted by the brown triangle, while the solar abundance values is given in the blue bowtie. Values for comets observed with SOFIA (+FORCAST) are indicated with the filled red circles and also including two other comets observed from ground-based facilities and analyzed with the same dust thermal model approach. The SOFIA observations of four comets reveals a subset of the comet population has cometary dust atomic ratios of C/Si much higher than carbonaceous chondrites suggesting that a significant carbon-rich reservoir existed in the regimes of comet formation in the outer protoplanetary disk. Comet C/1995 (O1) (Hale-Bopp) has C/Si nearer to CI. (Reproduced with permission from [1, fig. 7]. Copyright AAS). EH H LL L CV CO CM CI

In its 16 years of scientific measurements, the Spitzer Space Telescope performed a number of ground breaking and key infrared measurements of Solar System objects near and far. Targets ranged from the smallest planetesimals to the giant planets, and have helped us reform our understanding of these objects while also laying the groundwork for future infrared space-based observations like those to be undertaken by the James Webb Space Telescope in the 2020s. In this first Paper, we describe how the Spitzer Space Telescope advanced our knowledge of Solar System formation and evolution via observations of small outer Solar System planetesimals, i.e., Comets, Centaurs, and Kuiper Belt Objects (KBOs). Relics from the early formation era of our Solar System, these objects hold important information about the processes that created them. The key Spitzer observations can be grouped into 3 broad classes: characterization of new Solar System objects (comets D/ISON 2012 S1, C/2016 R2, 1I/`Oumuamua); large population surveys of known object sizes (comets, Centaurs, and KBOs); and compositional studies via spectral measurements of body surfaces and emitted materials (comets, Centaurs, and KBOs).

In its 16 years of scientific measurements, the Spitzer Space Telescope performed ground-breaking and key infrared measurements of Solar System objects near and far. Targets ranged from the smallest planetesimals to the giant planets; Spitzer helped us to reshape our understanding of these objects while also laying the groundwork for future infrared space-based observations like those to be undertaken by the James Webb Space Telescope in the 2020s. In this Review Article, we describe how Spitzer advanced our knowledge of Solar System formation and evolution through observations of small outer Solar System planetesimals-that is, comets, centaurs and Kuiper belt objects (KBOs). Relics from the early formation era of our Solar System, these objects hold important information about the processes that created them.We group Spitzer's key contributions into three broad classes: characterization of new Solar System objects (comets D/ISON 2012 S1, C/2016 R2 and 1I/'Oumuamua); large population surveys of known objects (comets, centaurs and KBOs); and compositional studies through spectral measurements of body surfaces and emitted materials. In the Spitzer Space Telescope's 16 years of operation, it observed many Solar System objects and environments. In this first Review Article of a pair, Spitzer's insights into comets, centaurs and Kuiper belt objects-all remnants of the Solar System's formation-are summarized.

The Mars Science Laboratory Curiosity rover conducted a reconnaissance traverse across the Pahrump Hills outcrop within Gale crater from Sols 780–797. During the traverse, the Mars Descent Imager (MARDI) acquired a continuous imaging record of primary and secondary sedimentary features throughout the outcrop. The characteristics of the features (laminae, resistant features, fractures, gray clasts) and their spatial distribution provide insight into the processes that contributed to the formation of Pahrump Hills. Thin, regular laminae (mm-scale) are ubiquitous in the bedrock, implying that depositional processes at that scale did not change appreciably during deposition of the mudstone succession at Pahrump Hills. Higher bedrock slopes correlate with undulatory bedrock surfaces, bedrock with elevated Mg contents, and fractures exhibiting wide, raised edges. These collective features are consistent with increased erosional resistance caused by greater quantities of erosionally-resistant, Mg-bearing cement within the bedrock permitted by coarser grain sizes. Resistant features exhibit a range of morphologies, elevated Mg contents, and do not deflect laminae within the bedrock. Their characteristics implicate the involvement of Mg-enriched fluids in a late diagenetic overprint affecting the bedrock. The variations of fracture fill and edge morphologies and chemistries further suggest repeated fracturing and fluid interaction events within the strata exposed at Pahrump Hills. Gray clasts strongly resemble fragments eroded from sandstone horizons interspersed throughout the Pahrump Hills outcrop.

Short-period comet 103P/Hartley 2 (103P) was the flyby target of the Deep Impact eXtended Investigation on 2010 November 4 UT. This comet has a small hyperactive nucleus, i.e., it has a high water production rate for its surface area. The underlying cause of the hyperactivity is unknown; the relative abundances of volatiles in the coma of 103P are not unusual. However, the dust properties of this comet have not been fully explored. We present four epochs of mid-infrared spectra and images of comet 103P observed from Gemini-South + T-ReCS on 2010 November 5, 7, 21 and December 13 UT, near and after the spacecraft encounter. Comet 103P exhibited a weak 10 mu m emission feature similar or equal to 1.14 +/- 0.01 above the underlying local 10 mu m continuum. Thermal dust grain modeling of the spectra shows the grain composition (mineralogy) was dominated by amorphous carbon and amorphous pyroxene with evidence for Mg-rich crystalline olivine. The grain size has a peak grain radius range of a(peak) similar to 0.5-0.9 mu m. On average, the crystalline silicate mass fraction is similar or equal to 0.24, fairly typical of other short-period comets. In contrast, the silicate-to-carbon ratio of similar or equal to 0.48-0.64 is lower compared to other short-period comets, which indicates that the flux measured in the 10 mu m region of 103P was dominated by amorphous carbon grains. We conclude that the hyperactivity in comet 103P is not revealing dust properties similar to the small grains seen with the Deep Impact experiment on comet 9P/Tempel 1 or from comet C/1995 O1 (Hale-Bopp).

Comet nuclei and D-type asteroids have several similarities at optical and near-IR wavelengths, including near-featureless red reflectance spectra, and low albedos. Mineral identifications based on these characteristics are fraught with degeneracies, although some general trends can be identified. In contrast, spectral emissivity features in the mid-infrared provide important compositional information that might not otherwise be achievable. Jovian Trojan D-type asteroids have emissivity features strikingly similar to comet comae, suggesting that they have the same compositions and that the surfaces of the Trojans are highly porous. However, a direct comparison between a comet and asteroid surface has not been possible due to the paucity of spectra of comet nuclei at mid-infrared wavelengths. We present 5-35 mu m thermal emission spectra of comets 10P/Tempel 2, and 49P/Arend-Rigaux observed with the Infrared Spectrograph on the Spitzer Space Telescope. Our analysis reveals no evidence for a coma or tail at the time of observation, suggesting the spectra are dominated by the comet nucleus. We fit each spectrum with the near-Earth asteroid thermal model (NEATM) and find sizes in agreement with previous values. However, the NEATM beaming parameters of the nuclei, 0.74-0.83, are systematically lower than the Jupiter-family comet population mean of 1.03 +/- 0.11, derived from 16- and 22-mu m photometry. We suggest this may be either an artifact of the spectral reduction, or the consequence of an emissivity low near 16 gm. When the spectra are normalized by the NEATM model, a weak 10-mu m silicate plateau is evident, with a shape similar to those seen in mid-infrared spectra of D-type asteroids. A silicate plateau is also evident in previously published Spitzer spectra of the nucleus of comet 9P/Tempel 1. We compare, in detail, these comet nucleus emission features to those seen in spectra of the Jovian Trojan D-types (624) Hektor, (911) Agamemnon, and (1172) Aneas, as well as those seen in the spectra of seven comet comae. The comet comae present silicate features with two distinct shapes, either trapezoidal, or more rounded, the latter apparently due to enhanced emission near 8 to 8.5 mu m. The surfaces of Tempel 2, Arend-Rigaux, and Hektor best agree with the comae that present trapezoidal features, furthering the hypothesis that the surfaces of these targets must have high porosities in order to exhibit a spectrum similar to a comet coma. An emissivity minimum at 15 mu m, present in the spectra of Tempel 2, Arend-Rigaux, Hektor, and Agamemnon, is also described, the origin of which remains unidentified. The compositional similarity between D-type asteroids and comets is discussed, and our data supports the hypothesis that they have similar origins in the early Solar System. (C) 2016 Elsevier Inc. All rights reserved.

We present mid-infrared spectra and images from the GEMINI-N (+Michelle) observations of fragments SW3-[B] and SW3-[C] of the ecliptic (Jupiter Family) comet 73P/Schwassmann-Wachmann 3 pre-perihelion. We observed fragment B soon after an outburst event (between 2006 April 16–26 UT) and detected crystalline silicates. The mineralogy of both fragments was dominated by amorphous carbon and amorphous pyroxene. The grain size distribution (assuming a Hanner modified power-law) for fragment SW3-[B] has a peak grain radius of μm, and for fragment SW3-[C], μm; both values are larger than the peak grain radius of the size distribution for the dust ejected from ecliptic comet 9P/Tempel 1 during the Deep Impact event ( μm). The silicate-to-carbon ratio and the silicate crystalline mass fraction for the submicron to micron-size portion of the grain size distribution on the nucleus of fragment SW3-[B] were and , respectively, while on the nucleus of fragment SW3-[C], they were and , respectively. The similarity in mineralogy and grain properties between the two fragments implies that 73P/Schwassmann-Wachmann 3 is homogeneous in composition. The slight differences in grain size distribution and silicate-to-carbon ratio between the two fragments likely arise because SW3-[B] was actively fragmenting throughout its passage, while the activity in SW3-[C] was primarily driven by jets. The lack of diverse mineralogy in the fragments SW3-[B] and SW3-[C] of 73P/Schwassmann-Wachmann 3 along with the relatively larger peak in the coma grain size distribution suggests the parent body of this comet may have formed in a region of the solar nebula with different environmental properties than the natal sites where comet C/1995 O1 (Hale-Bopp) and 9P/Tempel 1 nuclei aggregated.

Characterization of NEAs provides important inputs to models for atmospheric entry, risk assessment and mitigation. Diameter is a key parameter because diameter translates to kinetic energy in atmospheric entry. Diameters can be derived from the absolute magnitude, H(PA=0deg), and from thermal modeling of observed IR fluxes. For both methods, the albedo (pv) is important - high pv surfaces have cooler temperatures, larger diameters for a given Hmag, and shallower phase curves (larger slope parameter G). Thermal model parameters are coupled, however, so that a higher thermal inertia also results in a cooler surface temperature. Multiple parameters contribute to constraining the diameter. Observations made at multiple observing geometries can contribute to understanding the relationships between and potentially breaking some of the degeneracies between parameters. We present data and analyses on NEA 3691 Bede with the aim of best constraining the diameter and pv from a combination of thermal modeling and light curve analyses. We employ our UKIRT+Michelle mid-IR photometric observations of 3691 Bede's thermal emission at 2 phase angles (27&43 deg 2015-03-19 & 04-13), in addition to WISE data (33deg 2010-05-27, Mainzer+2011). Observing geometries differ by solar phase angles and by moderate changes in heliocentric distance (e.g., further distances produce somewhat cooler surface temperatures). With the NEATM model and for a constant IR beaming parameter (eta=constant), there is a family of solutions for (diameter, pv, G, eta) where G is the slope parameter from the H-G Relation. NEATM models employing Pravec+2012's choice of G=0.43, produce D=1.8 km and pv≈0.4, given that G=0.43 is assumed from studies of main belt asteroids (Warner+2009). We present an analysis of the light curve of 3691 Bede to constrain G from observations. We also investigate fitting thermophysical models (TPM, Rozitis+11) to constrain the coupled parameters of thermal inertia (Gamma) and surface roughness, which in turn affect diameter and pv. Surface composition can be related to pv. This study focuses on understanding and characterizing the dependency of parameters with the aim of constraining diameter, pv and thermal inertia for 3691 Bede.

The James Webb Space Telescope (JWST), as the largest space-based astronomical observatory with near-and mid-infrared instrumentation, will elucidate many mysterious aspects of comets. We summarize four cometary science themes especially suited for this telescope and its instrumentation: the drivers of cometary activity, comet nucleus heterogeneity, water ice in comae and on surfaces, and activity in faint comets and main belt asteroids. With JWST, we can expect the most distant detections of gas, especially CO2, in what we now consider to be only moderately bright comets. For nearby comets, coma dust properties can be simultaneously studied with their driving gases, measured simultaneously with the same instrument or contemporaneously with another. Studies of water ice and gas in the distant Solar System will help us test our understanding of cometary interiors, and coma evolution. The question of cometary activity in main belt comets will be further explored with the possibility of a direct detection of coma gas. We explore the technical approaches to these science cases and provide simple tools for estimating comet dust and gas brightness. Finally, we consider the effects of the observatory's non-sidereal tracking limits and provide a list of potential comet targets during the first five years of the mission.

Porous aggregate grains are commonly found in cometary dust samples and are needed to model cometary IR spectral energy distributions (SEDs). Models for thermal emissions from comets require two forms of silicates: amorphous and crystalline. The dominant crystal resonances observed in comet SEDs are from Forsterite (Mg2SiO4). The mass fractions that are crystalline span a large range from 0.0 25 AU at 1E6 yr) by inner disk materials (crystals) are challenged to yield the highend-range of cometary crystal mass fractions. However, in current thermal models, Forsterite crystals are not incorporated into larger aggregate grains but instead only are considered as discrete crystals. A complicating factor is that Forsterite crystals with rectangular shapes better fit the observed spectral resonances in wavelength (11.0-11.15 microns, 16, 19, 23.5, 27, and 33 microns), feature asymmetry and relative height (Lindley et al. 2013) than spherically or elliptically shaped crystals. We present DDA-DDSCAT computations of IR absorptivities (Qabs) of 3 micron-radii porous aggregates with 0.13 < or = fcrystal < or = 0.35 and with polyhedral-shaped Forsterite crystals. We can produce crystal resonances with similar appearance to the observed resonances of comet Hale- Bopp. Also, a lower mass fraction of crystals in aggregates can produce the same spectral contrast as a higher mass fraction of discrete crystals; the 11micron and 23 micron crystalline resonances appear amplified when crystals are incorporated into aggregates composed otherwise of spherically shaped amorphous Fe-Mg olivines and pyroxenes. We show that the optical properties of a porous aggregate is not linear combination of its monomers, so aggregates need to be computed. We discuss the consequence of lowering comet crystal mass fractions by modeling IR SEDs with aggregates with crystals, and the implications for radial transport models of our protoplanetary disk.