Thomas B. Mccord

Bear Fight Institute

Ceres, a nearly 1000-km diameter body located in the Solar System’s main asteroid belt, has been classified under many categories: planet, comet, asteroid, minor planet and, presently, dwarf planet. No matter what the designation, Ceres has experienced major planetary processes. Its evolution has been controlled by water, making it a most unusual,...

H2O-rich materials are locally exposed at the surface of Ceres as discovered from infrared reflectance spectra of the Visible and InfraRed mapping spectrometer (VIR) of the Dawn mission. Nine locations on Ceres exhibit diagnostic absorption bands of the H2O molecule at 2.00, 1.65 and 1.28 µm. The detections are all consistent with H2O ice mixed wit...

Knowledge of surface temperature and its variations as function of illumination conditions is key for understanding the thermodynamical properties, the chemical properties and the physical structure of the regolith (porosity, roughness) of planets and small bodies in the solar system. The surface temperature can be retrieved from near-infrared spec...

We present the first map of CO2 at the surface of Enceladus using data obtained by the Cassini Visible-Infrared Mapping Spectrometer (VIMS). In order to measure the weak and narrow CO2 absorption band depths around 4.26 µm, we improved: (1) the calibration of VIMS spectra; (2) the calculation of geographic coordinates; and (3) the projection techni...

This article presents the spectral parameter maps used in this Surface Composition of Ceres Special Issue. The definition and use of spectral parameters has always played a fundamental role in understanding the properties and composition of a planetary surface. Mapping proper spectral parameters, shows the global mineralogical diversity across Cere...

Ceres’ surface composition is of special interest because it is a window into the interior state and the past evolution of this dwarf planet. Disk-integrated telescopic spectral observations indicated that Ceres’ surface is hydroxylated, similar to but not exactly the same as some of the carbonaceous chondrite classes of meteorites. Furthermore, Ce...

We studied the surface composition of Ceres within the limits of the Ezinu quadrangle in the ranges 180 – 270°E and 21 – 66°N by analyzing data from Dawn's visible and near-infrared data from the Visible and InfraRed mapping spectrometer and from multispectral images from the Framing Camera. Our analysis includes the distribution of hydroxylated mi...

Neukum Crater, located at about 28°E/45°S at Noachis Terra on Mars, contains various geomorphological features that indicate a diverse geological history forming the crater during the past up to 4 Ga years. Most prominent features of this 102 km-crater are the large dark dune field and the two pits on its floor. The basaltic composition of the dune...

H2O-rich materials are locally exposed at the surface of Ceres as discovered from infrared reflectance spectra of the Visible and InfraRed mapping spectrometer (VIR) of the Dawn mission. Nine locations on Ceres exhibit diagnostic absorption bands of the H2O molecule at 2.00, 1.65 and 1.28 μm. The detections are all consistent with H2O ice mixed wit...

Solid CO2 surface deposits were reported in Enceladus’ South Polar Region by Brown et al. (2006). They noted that such volatile deposits are temporary and posited ongoing replenishment. We present a model for this replenishment by expanding on the Matson et al. (2012) model of subsurface heat and chemical transport in Enceladus. Our model explains...

So far, only two ice species have been identified by Rosetta/VIRTIS-M [1] on the surface of 67P/Churyumov-Gerasimenko during the pre-perihelion time: crystalline water and carbon dioxide ice. Water ice has been spectroscopically identified in three distinct modalities: 1) On the active areas of Hapi region where water ice changes its abundance with...

Rosetta observes sublimating surface ices Comets are “dirty snowballs” made of ice and dust, but they are dark because the ice sublimates away, leaving some of the dust behind on the surface. The Rosetta spacecraft has provided a close-up view of the comet 67P/Churyumov-Gerasimenko as it passes through its closest point to the Sun (see the Perspect...

On 6 March 2015, Dawn arrived at Ceres to find a dark, desiccated surface punctuated by small, bright areas. Parts of Ceres' surface are heavily cratered, but the largest expected craters are absent. Ceres appears gravitationally relaxed at only the longest wavelengths, implying a mechanically strong lithosphere with a weaker deep interior. Ceres'...

The spectral position of the 3.6 micron continuum peak measured on Cassini-VIMS I/F spectra is used as a marker to infer the temperature of the regolith particles covering the surfaces of Saturn's icy satellites. This feature is characterizing the crystalline water ice spectrum which is the dominant compositional endmember of the satellites' surfac...

Although water vapour is the main species observed in the coma of comet 67P/Churyumov-Gerasimenko and water is the major constituent of cometary nuclei, limited evidence for exposed water-ice regions on the surface of the nucleus has been found so far. The absence of large regions of exposed water ice seems a common finding on the surfaces of many...

We present the first global mapping and analysis of CO2 on the surface of Enceladus, and we report the largest concentrations of free CO2 on the southern polar region using the Visual and Infrared Mapping Spectrometer (VIMS) on Cassini. Free CO2 ice and complexed CO2 were already reported near the South Pole (Brown et al., Science, 2006; Hansen, LP...

Ice has been observed on other cometary surfaces as patches of pure ice mixed with the non-ice component of the surface. In case of comet 9P/Tempel 1, these ice patches were not directly linked with the comet gas activity and the main sources of gases were indicated in the comet interior. On comet 67P, VIRTIS observes surface ice mixed with a non-i...

Comet 67P/Churyumov-Gerasimenko undergoes periherm transit at 1.2 AU in August 2015. During this passage the illumination conditions above the south hemisphere of the nucleus rapidly improve becoming optimal for the retrieval of the surface properties by VIRTIS-M onboard Rosetta. A similar mapping of the surface at about 12.5 m/pixel and at solar p...

Abstract Here we present the spectral parameter maps used in this Surface Composition of Vesta Special Issue. The use of spectral parameters have been important since the first ground-based observations of Vesta as they can describe single mineralogic aspects as abundances or change in surface composition. Mapping these parameters over the surface...

Vesta's surface albedo variations and hydrated material content share similar spatial distribution. This observation is consistent with carbonaceous chondrite meteorites as a likely source material for dark surface units observed by the Dawn spacecraft, as presented by numerous publications. While these deposits have been studied extensively by ana...

The surface composition of the northern regions of Vesta, observed by the Dawn spacecraft, offers the possibility to test several hypotheses related to impact-related processes. We used mostly imaging spectrometry in the visible and near infrared to assess the distribution of mafic lithologies, hydrated components and albedo properties, and use the...

This paper will describe the major results obtained so far during the prelanding and initial escort phases (July 2014–February 2015) by the VIRTIS (Visible, Infrared and Thermal Imaging Spectrometer) dual channel spectrometer onboard Rosetta. The scientific goals of the VIRTIS instrument are related to the study of the nucleus surface composition a...

On comet 67P, VIRTIS observes surface water ice mixed with a non-ice organic rich refractory component, in a region were the localized water activity occurs. Moreover, the ice signature is variable with time and illumination conditions suggesting a cyclic process of sublimation-condensation of water ice on the comet surface. The cyclic replenishmen...

The Visible InfraRed Thermal Imaging Spectrometer, VIRTIS onboard ESA’s Rosetta mission has completed two extensive mapping campaigns of the 67P/Churyumov-Gerasimenko comet nucleus in August-September 2014. After calibration and geometrical projection on nucleus shape model, VIRTIS data were processed to retrieve the distribution of several spectra...

Vesta’s surface composition has been of special interest since early, disk-integrated telescopic spectral observations indicated that it is basaltic, differentiated and similar to the HED (howardite-eucrite-diogenite) class of meteorites. The Dawn mission, orbiting Vesta, provided a large and varied set of unique observations on the detailed minera...

The VIRTIS (Visible, Infrared and Thermal Imaging Spectrometer) instrument on board the Rosetta spacecraft has provided evidence of carbon-bearing compounds on the nucleus of the comet 67P/Churyumov-Gerasimenko. The very low reflectance of the nucleus (normal albedo of 0.060 ± 0.003 at 0.55 micrometers), the spectral slopes in visible and infrared...

In August 2014 ESA’s Rosetta mission has started the exploration of 67P/Churyumov-Gerasimenko comet nucleus. VIRTIS-M, the Visible InfraRed Thermal Imaging Spectrometer, onboard the orbiter (Coradini et al., 2007) has acquired the entire nucleus’ illuminated hemisphere in the 0.25-5.1 µm spectral range from a heliocentric distance of 3.2 AU. These...

We used Dawn spacecraft data to identify and delineate geological units and landforms in the Marcia quadrangle of Vesta as a means to assess the role of the large, relatively young impact craters Marcia (~63. km diam.) and Calpurnia (~53. km diam.) and their surrounding ejecta field on the local geology. We also investigated a local topographic hig...

Deposits of dark material appear on Vesta’s surface as features of relatively low-albedo in the visible wavelength range of Dawn’s camera and spectrometer. Mixed with the regolith and partially excavated by younger impacts, the material is exposed as individual layered outcrops in crater walls or ejecta patches, having been uncovered and broken up...

Water-ice-poor, 5-$\mu$m-bright material on Saturn's moon Titan has previously been geomorphologically identified as evaporitic. Here we present a global distribution of the occurrences of the 5-$\mu$m-bright spectral unit, identified with Cassini's Visual Infrared Mapping Spectrometer (VIMS) and examined with RADAR when possible. We explore the po...

Cassini/VIMS high-phase specular observations of Titan’s north pole during the T85 flyby show evidence for isolated patches of rough liquid surface within the boundaries of the sea Punga Mare. The roughness shows typical slopes of 6°±1°. These rough areas could be either wet mudflats or a wavy sea. Because of their large areal extent, patchy geogra...

Due to the strong evidence for aqueous processes at or near the surface, Mars is the most Earth-like body in the Solar System. After 10 years of ESA’s Mars Express orbiting the planet its High Resolution Stereo Camera (HRSC) covered about 90 % of the surface in stereo and color with resolutions up to 10 m/pixel [1]. Digital elevation models of up t...

We present global lithological maps of the Vestan surface based on Dawn mission's Visible InfraRed (VIR) Spectrometer acquisitions with a spatial sampling of 200 m. The maps confirm the results obtained with the data set acquired by VIR with a spatial sampling of 700 m, that the reflectance spectra of Vesta's surface are dominated by pyroxene absor...

The Dawn mission has provided new evidence strengthening the identification of asteroid Vesta as the parent body of the howardite, eucrite, and diogenite (HED) meteorites. The evidence includes Vesta's petrologic complexity, detailed spectroscopic characteristics, unique space weathering, diagnostic geochemical abundances and neutron absorption cha...

Titan's surface is obscured by a thick absorbing and scattering atmosphere, allowing direct observation of the surface within only a few spectral win-dows in the near-infrared, complicating efforts to identify and map geologi-cally important materials using remote sensing IR spectroscopy. We there-fore investigate the atmosphere's infrared transmis...

Observations from Cassini VIMS and ISS show localized but extensive surface brightenings in the wake of the 2010 September cloudburst. Four separate areas, all at similar latitude, show similar changes: Yalaing Terra, Hetpet Regio, Concordia Regio, and Adiri. Our analysis shows a general pattern to the time-sequence of surface changes: after the cl...

The surface of the asteroid Vesta has prominent near-infrared absorption bands characteristic of a range of pyroxenes, confirming a direct link to the basaltic howardite-eucrite-diogenite class of meteorites. Processes active in the space environment produce 'space weathering' products that substantially weaken or mask such diagnostic absorption on...

Localized dark and bright materials, often with extremely different albedos, were recently found on Vesta's surface. The range of albedos is among the largest observed on Solar System rocky bodies. These dark materials, often associated with craters, appear in ejecta and crater walls, and their pyroxene absorption strengths are correlated with mate...

Water plays a key role in the evolution of the terrestrial planets, and notably the occurrence of Earth’s oceans. However, the mechanism by which water has been incorporated into these bodies -including the Earth- is still extensively debated. Here we report the detection of widespread 2.8-µm OH absorption bands on the surface of asteroid Vesta by...

Dawn slipped into Vesta orbit on July 16, 2011, and began its orbital mapping of this most ancient intact body in the solar system. The geochemistry of the HED meteorites had predicted much about Vesta based on the similarity of its reflectance spectrum to that of the meteorites. The predictions were correct. Vesta is differentiated, and it has a b...

Vesta’s surface is characterized by abundant impact craters, some with preserved ejecta blankets, large troughs extending around the equatorial region, enigmatic dark material, and widespread mass wasting, but as yet an absence of volcanic features. Abundant steep slopes indicate that impact-generated surface regolith is underlain by bedrock. Dawn...

A New Dawn Since 17 July 2011, NASA's spacecraft Dawn has been orbiting the asteroid Vesta—the second most massive and the third largest asteroid in the solar system (see the cover). Russell et al. (p. 684 ) use Dawn's observations to confirm that Vesta is a small differentiated planetary body with an inner core, and represents a surviving proto-pl...

A New Dawn Since 17 July 2011, NASA's spacecraft Dawn has been orbiting the asteroid Vesta—the second most massive and the third largest asteroid in the solar system (see the cover). Russell et al. (p. 684 ) use Dawn's observations to confirm that Vesta is a small differentiated planetary body with an inner core, and represents a surviving proto-pl...

Data from the Dawn VIR (Visible InfraRed mapping Spectrometer) characterize and map the mineral distribution on Vesta, strengthen the Vesta - howardite, eucrite diogenite (HED) meteorite linkage and provide new insights into Vesta's formation and evolution.VIR data acquired during Approach, Survey and High Altitude Mapping (HAMO) orbits have provid...

Asteroid 4 Vesta is currently under investigation by NASA's Dawn orbiter. The Dawn Science Team is conducting mineralogical mapping of Vesta's surface in the form of 15 quadrangle maps, and here we report results from the mapping of Floronia quadrangle Av-5. The maps are based on the data acquired by the Visible and Infrared Mapping Spectrometer (V...

Asteroid 4 Vesta is currently observed by NASA's Dawn orbiter. The Dawn Team is conducting mineralogical mapping of the surface in the form of 15 quadrangle maps, and here we report results from the mapping of the two adjacent quadrangles Marcia (Av-8) and Numisia (Av-9). The mapping is based on a Framing Camera (FC) color band ratio and Visible an...

The occurrence of olivines on Vesta were first postulated from traditional petrogenetic models which suggest the formation of olivine as lower crustal cumulates. An indirect confirmation is given by their presence as a minor component in some samples of diogenite meteorites, the harzburgitic diogenites and the dunitic diogenites, and as olivine min...

Cassini ISS saw large-scale surface darkenings in the wake of a tropical cloudburst event in 2010 September. In concert with the abstract by Turtle et al., in this presentation we show that weeks to months after darkening the surfaces did not revert to their pre-cloudburst brightness, but rather became brighter. VIMS observations of four distinct a...

In the last few years Cassini-VIMS, the Visible and Infared Mapping Spectrometer, returned to us a comprehensive view of the Saturn's icy satellites and rings. After having analyzed the satellites' spectral properties (Filacchione et al. (2007a)) and their distribution across the satellites' hemispheres (Filacchione et al. (2010)), we proceed in th...

Before Dawn arrived at 4 Vesta only very low spatial resolution (~50 km) albedo and color maps were available from HST data. Also ground-based color and spectroscopic data were utilized as a first attempt to map Vesta’s mineralogical diversity [1-4]. The VIR spectrometer [5] onboard Dawn has ac-quired hyperspectral data while the FC camera [6] ob-t...

Vestarsquos spectrum has strong absorption centered near 0.9 and 1.9 $mu$m, indicative of Fe-bearing pyroxenes. Data from the Dawn VIR characterize and map the mineral distribution on Vesta, providing new insights into Vestarsquos formation and evolution.

Micoud crater shows important phyllosilicate detections. Our objective is to identify several types of phyllosilicates and other hydrated minerals in order to test the hypothesis of impact-induced hydrothermalism versus excavation models.

Vesta has been hammered by large impacts, including two large (400-500 km) basins at the South Pole, the largest basins in proportion to target radius so far seen in the solar system. Here we examine the global effects of impacts at planetary scales.

One of the great revelations of the Space Age is the role of impacts in reshaping planetary surfaces, especially large impact events of the type that may have formed the Moon or broken the asteroids. The giant Rheasilvia impact basin on Vesta [1] is the largest impact feature with respect to planetary size that has been observed to date. Here we re...

Differences in spectral albedo of the asteroid 4 Vesta were already observed by the Hubble multispectral images [1,2,3]. However, unusual regions of very low albedo on Vesta’s surface were first discovered by the Dawn Mission [4]. These “Dark Material Deposits” (DMD) are non-randomly distributed onto the surface and often are associated with geolog...

Deposits of dark material appear on Vesta’s surface as lower-albedo features in the visible wavelength framing camera (FC) images returned by the Dawn spacecraft [1,2]. Dark materials (DM) were found in the first images obtained during the mission's rotational characterization (RC) phase at distances of 5200 km (resolution 490 m/px). DM are often a...

NASA’s Dawn spacecraft entered orbit of the inner main belt asteroid 4 Vesta on July 15, 2011, and is spending one year in orbit to characterize the geology, chemical and mineralogical composition, topography, shape, and internal structure of Vesta before departing to asteroid 1 Ceres in late 2012. As part of the Dawn data analysis the Science Team...

The instruments on the Dawn spacecraft are exceptionally well suited to characterize and map the surface composition of Vesta in an integrated manner. These include a framing camera with multispectral capabilities, a high spectral resolution near-infrared imaging spectrometer, and a gamma-ray and neutron spectrometer. Three examples of issues addre...

The Dawn Mission is a revolutionary concept in planetary exploration. Within the cost cap of a low-cost Discovery mission, a spacecraft has been flown to the main asteroid belt and been put into orbit around its second most massive body, 4 Vesta. Vesta was clearly beginning its march to planet-hood when its accretion stopped, most probably by the f...

Approach imaging of Vesta by the Dawn spacecraft (Russell et al., 2007) show that the south polar topographic anomaly first observed by HST (Thomas et al., 1997), is a complex and unique geologic structure. A dense set of concentric arcuate, cuspate, and spiral inward-facing scarps and ridges form a coherent ~460-525 km wide annular feature. This r...

NASA's Dawn spacecraft arrived at the asteroid 4Vesta on July 15, 2011, and is now collecting imaging, spectroscopic, elemental abundance and radio science data during its one-year orbital mission. As part of the geological analysis of the surface, a series of 15 quadrangle maps are being produced based on multispectral Framing Camera images (FC: s...

NASA's Dawn spacecraft arrived at the asteroid 4Vesta on July 15, 2011, and is now collecting imaging, spectroscopic, and elemental abundance data during its one-year orbital mission. As part of the geological analysis of the surface, a series of 15 quadrangle maps are being produced based on Framing Camera images (FC: spatial resolution: ~65 m/pix...

NASA's Dawn spacecraft arrived at the asteroid 4Vesta on July 15, 2011, and is now collecting imaging, spectroscopic, and elemental abundance data during its one-year orbital mission. As part of the geological analysis of the surface, a series of 15 quadrangle maps are being produced based on Framing Camera images (FC: spatial resolution: ~65 m/pix...