Showing papers by "Brett W. Denevi published in 2018"

Calibration, Projection, and Final Image Products of MESSENGER’s Mercury Dual Imaging System

Abstract: We present an overview of the operations, calibration, geodetic control, photometric standardization, and processing of images from the Mercury Dual Imaging System (MDIS) acquired during the orbital phase of the MESSENGER spacecraft’s mission at Mercury (18 March 2011–30 April 2015). We also provide a summary of all of the MDIS products that are available in NASA’s Planetary Data System (PDS). Updates to the radiometric calibration included slight modification of the frame-transfer smear correction, updates to the flat fields of some wide-angle camera (WAC) filters, a new model for the temperature dependence of narrow-angle camera (NAC) and WAC sensitivity, and an empirical correction for temporal changes in WAC responsivity. Further, efforts to characterize scattered light in the WAC system are described, along with a mosaic-dependent correction for scattered light that was derived for two regional mosaics. Updates to the geometric calibration focused on the focal lengths and distortions of the NAC and all WAC filters, NAC–WAC alignment, and calibration of the MDIS pivot angle and base. Additionally, two control networks were derived so that the majority of MDIS images can be co-registered with sub-pixel accuracy; the larger of the two control networks was also used to create a global digital elevation model. Finally, we describe the image processing and photometric standardization parameters used in the creation of the MDIS advanced products in the PDS, which include seven large-scale mosaics, numerous targeted local mosaics, and a set of digital elevation models ranging in scale from local to global.

Global Distribution and Spectral Properties of Low‐Reflectance Material on Mercury

Abstract: MERCURY. Rachel L. Klima (Rachel.Klima@jhuapl.edu), David T. Blewett, Brett W. Denevi, Carolyn M. Ernst, Elizabeth A. Frank, James W. Head, III, Noam R. Izenberg, Scott L. Murchie, Larry R. Nittler, Patrick N. Peplowski, and Sean C. Solomon. Johns Hopkins University Applied Physics Laboratory, Laurel, MD 20723, USA; Carnegie Institution of Washington, Washington, DC 20015, USA; Brown University, Providence, RI 02912, USA; Lamont-Doherty Earth Observatory, Columbia University, Palisades, NY 10964, USA.

Curie: Constraining Solar System Bombardment Using In Situ Radiometric Dating

Abstract: The leading, but contentious, model for lunar impact history includes a pronounced increase in impact events at around 3.9 Ga. This late heavy bombardment would have scarred Mars and the terrestrial planets, influenced the course of biologic evolution on the early Earth, and rearranged the very architecture of our Solar System. But what if it's not true? In the last decade, new observations and sample analyses have reinterpreted basin ages and "pulled the pin" on the cataclysm - we may only have the age of one large basin (Imbrium). The Curie mission would constrain the onset of the cataclysm by determining the age of a major pre-Imbrium lunar basin (Nectaris or Crisium), characterize new lunar lithologies far from the Apollo and Luna landing sites, including the basalts in the basin-filling maria and olivine-rich lithologies in the basin margins, and provide a unique vantage point to assess volatiles in the lunar regolith from dawn to dusk.

Mercury's Global Evolution

Abstract: MESSENGER’s exploration of Mercury has revealed a rich and dynamic geological history and provided constraints on the processes that control the planet’s internal evolution. That history includes resurfacing by impacts and volcanism prior to the end of the late heavy bombardment and a subsequent rapid waning of effusive volcanism. MESSENGER also revealed a global distribution of thrust faults that collectively accommodated a decrease in Mercury’s radius far greater than thought before the mission. Measurements of elemental abundances on Mercury’s surface indicate the planet is strongly chemically reduced, helping to characterize the composition and manner of crystallization of the metallic core. The discovery of a northward offset of the weak, axially aligned internal magnetic field, and of crustal magnetization in the planet’s ancient crust, places new limits on the history of the core dynamo and the entire interior. Models of Mercury’s thermochemical evolution subject to these observational constraints ...

The Irregular Mare Patch Exploration Lander (IMPEL) SmallSat Mission Concept

Abstract: CONCEPT. D. S. Draper1, J. D. Stopar2, S. J. Lawrence1, B. Denevi3, K. John1, L. Graham1, J. Hamilton1, Z. Fletcher3, J. Gruener1, and S. Bertsch1, 1Astromaterials Research and Exploration Science Division, NASA Johnson Space Center, Houston TX 77058, david.draper@nasa.gov; 2Lunar and Planetary Institute, 3600 Bay Area Blvd., Houston TX 77058; 3Applied Physics Laboratory, The Johns Hopkins University, Laurel, Maryland 20723.

Examining the Distribution and Concentration of Carbon on Mercury

Abstract: Introduction: Distinctive low-reflectance material (LRM) was first observed on Mercury in Mariner 10 flyby images [1]. Visible to near-infrared reflectance spectra of LRM are flatter than the average reflectance spectrum of Mercury, which is strongly red sloped (increasing in reflectance with wavelength). From Mariner 10 and early MErcury, Surface, Space, ENvironment, GEochemistry, and Ranging (MESSENGER) flyby observations, it was suggested that a higher content of ilmenite, ulvöspinel, carbon, or iron metal could cause both the characteristic dark, flat spectrum of LRM and the globally low reflectance of Mercury [1,2]. Once MESSENGER entered orbit, low Fe and Ti abundances measured by the X-Ray and Gamma-Ray Spectrometers ruled out ilmenite and ulvöspinel as important surface constituents [3,4] and implied that LRM was darkened by a different phase, such as carbon or small amounts of microor nanophase iron or iron sulfide dispersed in a silicate matrix. Low-altitude thermal neutron measurements of three LRM-rich regions confirmed an enhancement of 1–3 wt% carbon over the global abundance, supporting the hypothesis that the darkening agent in LRM is carbon [5]. Here, using the final calibration of the Mercury Dual Imaging System (MDIS) 8-color global mosaic, we examine the distribution and spectral properties of LRM on a global scale, and extrapolate the results of Peplowski et al. [5] to place bounds on the carbon abundance of different LRM deposits across Mercury. Distribution of Low Reflectance Material: LRM is distributed across Mercury, typically having been excavated from depth by craters and basins. In contrast to the brighter high reflectance plains (HRP) and smooth plains deposits, which exhibit morphological evidence of volcanism [e.g., 6-8], LRM is not associated with flow features or other evidence of a volcanic origin. Older LRM boundaries are generally diffuse, and grade into low-reflectance blue plains (LBP). Because of the common lack of sharp geologic boundaries, LRM has been defined primarily based on albedo and spectral shape, isolated through principal components (PC) analyses of MDIS color images [9]. LRM is the darkest material on Mercury, with an albedo of 4–5% at 560 nm (compared to a global 560-nm albedo of ~6%), and it exhibits a spectral slope that is substantially less red than the rest of Mercury. The low iron content of Mercury’s surface results in a lack of the spectral absorption bands typically used to map mafic minerals on planets and asteroids. Thus, mathematical transformations such as PC analysis are required to map subtle spectral differences. For example, the second principal component (PC2), captures a combination of spectral slope and curvature, isolating LRM and hollows as one endmember, with red material and HRP as the other end member. LBP and intermediate plains (IP) are transitional from LRM to HRP [10]. In [5], concentrated LRM exposures were defined as regions with a photometrically corrected reflectance of <5% (at 560 nm wavelength) and a PC2 value of <0.023. This value corresponds with the lower ~25% of the range of PC2 values for the whole planet. The resulting LRM map, overlain on the global color mosaic, is shown in Fig. 1a. There are some regional concentrations where many moderate sized craters or several larger basins excavated LRM in close proximity to one another. LRM is most immediately recognizable visually when excavated by craters and deposited onto high-reflectance red plains (HRP, as in Caloris basin), due to the contrasting reflectance and spectral slopes of the different stratigraphic layers. However, it is also abundant throughout the oldest, rough terrains, where its boundaries are more difficult to delineate as they grade into LBP. In these older terrains LRM is still apparently associated with crater ejecta, but the high density of craters excavating LRM results in a patchy distribution of low-reflectance, low-PC2 material.