Showing papers by "Carly Howett published in 2018"
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Lowell Observatory1, Massachusetts Institute of Technology2, Southwest Research Institute3, Jet Propulsion Laboratory4, Johns Hopkins University Applied Physics Laboratory5, Ames Research Center6, Search for extraterrestrial intelligence7, Pierre-and-Marie-Curie University8, California Institute of Technology9, Goddard Space Flight Center10, Stanford University11, Washington University in St. Louis12, George Mason University13, University of California, Santa Cruz14
TL;DR: In this paper, the authors explore how a steady supply of atmospheric haze might affect three distinct provinces on Pluto, and they pose the question of why they each look so different from one another if the same haze material is settling out onto all of them.
62 citations
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Ames Research Center1, Search for extraterrestrial intelligence2, Southwest Research Institute3, Massachusetts Institute of Technology4, University of Tennessee5, Lowell Observatory6, Goddard Space Flight Center7, Centre national de la recherche scientifique8, Space Telescope Science Institute9, University of Virginia10, Johns Hopkins University Applied Physics Laboratory11
TL;DR: In this article, the authors performed a pixel-by-pixel analysis of Nix's disk-resolved spectra and found that the surface is consistent with a uniform crystalline H2O-ice fraction, and a ǫ∼ 50% variation in the normalized band area of the 2.21µm band with a minimum associated with the red blotch seen in color images.
60 citations
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01 Jan 2018
TL;DR: The visible and thermal observations of the surface expression of the plume fractures are reviewed and the current state of understanding of the processes that connect the surface to the underlying ocean is reviewed.
Abstract: Since the discovery of activity at the south pole of Enceladus, enormous progress has been made in interpreting the rich data from the multiple instruments on the Cassini spacecraft to understand what is happening below the visible surface. In this chapter, we review the visible and thermal observations of the surface expression of the plume fractures. We then review the current state of understanding of the processes that connect the surface to the underlying ocean, constrained by these observations and by the properties of the plume itself, which are described in more detail in the chapter in this volume by Goldstein et al. 2. SURFACE OBSERVATIONAL CONSTRAINTS
24 citations
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Massachusetts Institute of Technology1, Lowell Observatory2, Southwest Research Institute3, Ames Research Center4, Search for extraterrestrial intelligence5, University of Maryland, College Park6, Goddard Space Flight Center7, Lunar and Planetary Institute8, Centre national de la recherche scientifique9, Johns Hopkins University Applied Physics Laboratory10
TL;DR: The data returned from NASA's New Horizons spacecraft have given us an unprecedented, detailed look at the Pluto system as discussed by the authors, where the Ralph/MVIC (Multispectral Visible Imaging Camera) is composed of 7 independent CCD arrays on a single substrate.
23 citations
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Ames Research Center1, Washington University in St. Louis2, Southwest Research Institute3, Johns Hopkins University Applied Physics Laboratory4, Search for extraterrestrial intelligence5, Lowell Observatory6, Massachusetts Institute of Technology7, California Institute of Technology8, Lunar and Planetary Institute9, Planetary Science Institute10, University of Virginia11, University of Arizona12, University of Idaho13
21 citations
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TL;DR: The New Horizons encounter with the cold classical Kuiper Belt object (KBO) 2014 MU69 (informally named 'Ultima Thule', hereafter Ultima) on 1 January 2019 will be the first time a spacecraft has ever closely observed one of the free-orbiting small denizens of the kuiper belt as mentioned in this paper.
Abstract: The New Horizons encounter with the cold classical Kuiper Belt object (KBO) 2014 MU69 (informally named 'Ultima Thule,' hereafter Ultima) on 1 January 2019 will be the first time a spacecraft has ever closely observed one of the free-orbiting small denizens of the Kuiper Belt. Related to but not thought to have formed in the same region of the Solar System as the comets that been explored so far, it will also be the largest, most distant, and most primitive body yet visited by spacecraft. In this letter we begin with a brief overview of cold classical KBOs, of which Ultima is a prime example. We give a short preview of our encounter plans. We note what is currently known about Ultima from earth-based observations. We then review our expectations and capabilities to evaluate Ultima's composition, surface geology, structure, near space environment, small moons, rings, and the search for activity.
19 citations
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TL;DR: In this article, the authors summarize the unanswered questions for the main icy moons of Saturn, including Mimas, Enceladus, Tethys, Dione, Rhea, Hyperion, Iapetus, and Phoebe, for the disciplines of surface composition, geology, thermal properties, plume activity, interiors, and interactions between Saturn's magnetosphere and the moons.
7 citations
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4 citations
01 Oct 2018
TL;DR: These maps confirm the presence of the Pac-Man thermal anomaly and show that while Tethys' bolometric Bond albedo varies negligibly outside and inside the anomaly, the thermal inertia varies dramatically, which may provide evidence of regional variations in surface roughness effects.
Abstract: On 11th April 2015 Cassini's Composite Infrared Spectrometer (CIRS) made a series of observations of Tethys' daytime anti-Saturn hemisphere over a nine-hour time period. During this time the sub-spacecraft position was remarkably stable (0.3° S to 3.9° S; 153.2° W to 221.8° W), and so these observations provide unprecedented coverage of diurnal temperature variations on Tethys' anti-Saturn hemisphere. In 2012 a thermal anomaly was discovered at low latitudes on Tethys' leading hemisphere; it appears cooler during the day and warmer at night than its surroundings (Howett et al., 2012) and is spatially correlated with a decrease in the IR3/UV3 visible color ratio (Schenk et al., 2011). The cause of this anomaly is believed to be surface alteration by high-energy electrons, which preferentially bombard low-latitudes of Tethys' leading hemisphere (Schenk et al., 2011; Howett et al., 2012; Paranicas et al. 2014; Schaible et al., 2017). The thermal anomaly was quickly dubbed "Pac-Man" due to its resemblance to the 1980s video game icon. We use these daytime 2015 CIRS data, along with two sets of nighttime CIRS observations of Tethys (from 27 June 2007 and 17 August 2015) to make maps of bolometric Bond albedo and thermal inertia variations across the anti-Saturn hemisphere of Tethys (including the edge of its Pac-Man region). These maps confirm the presence of the Pac-Man thermal anomaly and show that while Tethys' bolometric Bond albedo varies negligibly outside and inside the anomaly (0.69±0.02 inside, compared to 0.71±0.04 outside) the thermal inertia varies dramatically (29±10 J m-2 K-1 s-1/2 inside, compared to 9±4 J m-2 K-1 s-1/2 outside). These thermal inertias are in keeping with previously published values: 25±3 J m-2 K-1 s-1/2 inside, and 5±1 J m-2 K-1 s-1/2 outside the anomaly (Howett et al., 2012). A detailed analysis shows that on smaller spatial-scales the bolometric Bond albedo does vary: increasing to a peak value at 180° W. For longitudes between ~100° W and ~160° W the thermal inertia increases from northern to southern latitudes, while the reverse is true for bolometric Bond albedo. The thermal inertia on Tethys generally increases towards the center of its leading hemisphere but also displays other notable small-scale variations. These thermal inertia and bolometric Bond albedo variations are perhaps due to differences in competing surface modification by E ring grains and high-energy electrons which both bombard Tethys' leading hemisphere (but in different ways). A comparison between the observed temperatures and our best thermal model fits shows notable discrepancies in the morning warming curve, which may provide evidence of regional variations in surface roughness effects, perhaps again due to variations in surface alteration mechanisms.