Author
Carly Howett
Other affiliations: University of Oxford
Bio: Carly Howett is an academic researcher from Southwest Research Institute. The author has contributed to research in topics: Pluto & Enceladus. The author has an hindex of 34, co-authored 116 publications receiving 4028 citations. Previous affiliations of Carly Howett include University of Oxford.
Topics: Pluto, Enceladus, Saturn, Stratosphere, Titan (rocket family)
Papers published on a yearly basis
Papers
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TL;DR: In this article, a nonlinear optimal estimator for multivariatE spectral analySIS (NEMESIS) was developed to interpret observations of Saturn and Titan from the composite infrared spectrometer on board the NASA Cassini spacecraft.
Abstract: With the exception of in situ atmospheric probes, the most useful way to study the atmospheres of other planets is to observe their electromagnetic spectra through remote observations, either from ground-based telescopes or from spacecraft. Atmospheric properties most consistent with these observed spectra are then derived with retrieval models. All retrieval models attempt to extract the maximum amount of atmospheric information from finite sets of data, but while the problem to be solved is fundamentally the same for any planetary atmosphere, until now all such models have been assembled ad hoc to address data from individual missions.
In this paper, we describe a new general-purpose retrieval model, Non-linear Optimal Estimator for MultivariatE Spectral analySIS (NEMESIS), which was originally developed to interpret observations of Saturn and Titan from the composite infrared spectrometer on board the NASA Cassini spacecraft. NEMESIS has been constructed to be generally applicable to any planetary atmosphere and can be applied from the visible/near-infrared right out to microwave wavelengths, modelling both reflected sunlight and thermal emission in either scattering or non-scattering conditions. NEMESIS has now been successfully applied to the analysis of data from many planetary missions and also ground-based observations.
492 citations
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TL;DR: The New Horizons encounter revealed that Pluto displays a surprisingly wide variety of geological landforms, including those resulting from glaciological and surface-atmosphere interactions as well as impact, tectonic, possible cryovolcanic, and mass-wasting processes.
Abstract: The Pluto system was recently explored by NASA's New Horizons spacecraft, making closest approach on 14 July 2015. Pluto's surface displays diverse landforms, terrain ages, albedos, colors, and composition gradients. Evidence is found for a water-ice crust, geologically young surface units, surface ice convection, wind streaks, volatile transport, and glacial flow. Pluto's atmosphere is highly extended, with trace hydrocarbons, a global haze layer, and a surface pressure near 10 microbars. Pluto's diverse surface geology and long-term activity raise fundamental questions about how small planets remain active many billions of years after formation. Pluto's large moon Charon displays tectonics and evidence for a heterogeneous crustal composition; its north pole displays puzzling dark terrain. Small satellites Hydra and Nix have higher albedos than expected.
411 citations
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Lowell Observatory1, Massachusetts Institute of Technology2, Jet Propulsion Laboratory3, Southwest Research Institute4, Ames Research Center5, Search for extraterrestrial intelligence6, Goddard Space Flight Center7, University of Grenoble8, University of Maryland, College Park9, University of Virginia10, Johns Hopkins University Applied Physics Laboratory11, Stanford University12, Lunar and Planetary Institute13, Space Telescope Science Institute14, Planetary Science Institute15
TL;DR: The New Horizons team presents the complex surface features and geology of Pluto and its large moon Charon, including evidence of tectonics, glacial flow, and possible cryovolcanoes, as well as their analysis of the encounter data downloaded so far.
Abstract: The New Horizons spacecraft mapped colors and infrared spectra across the encounter hemispheres of Pluto and Charon. The volatile methane, carbon monoxide, and nitrogen ices that dominate Pluto's surface have complicated spatial distributions resulting from sublimation, condensation, and glacial flow acting over seasonal and geological time scales. Pluto's water ice "bedrock" was also mapped, with isolated outcrops occurring in a variety of settings. Pluto's surface exhibits complex regional color diversity associated with its distinct provinces. Charon's color pattern is simpler, dominated by neutral low latitudes and a reddish northern polar region. Charon's near-infrared spectra reveal highly localized areas with strong ammonia absorption tied to small craters with relatively fresh-appearing impact ejecta.
270 citations
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Ames Research Center1, Washington University in St. Louis2, Southwest Research Institute3, University of Virginia4, Lunar and Planetary Institute5, Search for extraterrestrial intelligence6, University of California, Santa Cruz7, Johns Hopkins University Applied Physics Laboratory8, Massachusetts Institute of Technology9, Jet Propulsion Laboratory10, Lowell Observatory11, Stanford University12, Goddard Space Flight Center13, University of Arizona14, Roane State Community College15, Planetary Science Institute16, United States Geological Survey17
TL;DR: Nasa’s New Horizons spacecraft has revealed a complex geology of Pluto and Charon, including evidence of tectonics, glacial flow, and possible cryovolcanoes, and these findings massively increase the understanding of the bodies in the outer solar system.
Abstract: NASA’s New Horizons spacecraft has revealed the complex geology of Pluto and Charon. Pluto’s encounter hemisphere shows ongoing surface geological activity centered on a vast basin containing a thick layer of volatile ices that appears to be involved in convection and advection, with a crater retention age no greater than ~10 million years. Surrounding terrains show active glacial flow, apparent transport and rotation of large buoyant water-ice crustal blocks, and pitting, the latter likely caused by sublimation erosion and/or collapse. More enigmatic features include tall mounds with central depressions that are conceivably cryovolcanic and ridges with complex bladed textures. Pluto also has ancient cratered terrains up to ~4 billion years old that are extensionally faulted and extensively mantled and perhaps eroded by glacial or other processes. Charon does not appear to be currently active, but experienced major extensional tectonism and resurfacing (probably cryovolcanic) nearly 4 billion years ago. Impact crater populations on Pluto and Charon are not consistent with the steepest impactor size-frequency distributions proposed for the Kuiper belt.
260 citations
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Planetary Science Institute1, Goddard Space Flight Center2, California Institute of Technology3, United States Geological Survey4, Scripps Institution of Oceanography5, Wheaton College (Massachusetts)6, Woods Hole Oceanographic Institution7, Cornell University8, Ames Research Center9, Southwest Research Institute10, University of Arizona11, University of Western Ontario12, Johns Hopkins University Applied Physics Laboratory13, Georgia Institute of Technology14, Massachusetts Institute of Technology15
TL;DR: To map out a coherent Ocean Worlds Program, significant input is required from studies here on Earth; rigorous Research and Analysis studies are called for to enable some future ocean worlds missions to be thoughtfully planned and undertaken.
Abstract: In this article, we summarize the work of the NASA Outer Planets Assessment Group (OPAG) Roadmaps to Ocean Worlds (ROW) group. The aim of this group is to assemble the scientific framework that will guide the exploration of ocean worlds, and to identify and prioritize science objectives for ocean worlds over the next several decades. The overarching goal of an Ocean Worlds exploration program as defined by ROW is to “identify ocean worlds, characterize their oceans, evaluate their habitability, search for life, and ultimately understand any life we find.” The ROW team supports the creation of an exploration program that studies the full spectrum of ocean worlds, that is, not just the exploration of known ocean worlds such as Europa but candidate ocean worlds such as Triton as well. The ROW team finds that the confirmed ocean worlds Enceladus, Titan, and Europa are the highest priority bodies to target in the near term to address ROW goals. Triton is the highest priority candidate ocean world to target in the near term. A major finding of this study is that, to map out a coherent Ocean Worlds Program, significant input is required from studies here on Earth; rigorous Research and Analysis studies are called for to enable some future ocean worlds missions to be thoughtfully planned and undertaken. A second finding is that progress needs to be made in the area of collaborations between Earth ocean scientists and extraterrestrial ocean scientists.
215 citations
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01 May 2011TL;DR: In this paper, the authors present an overview of the solar system and its evolution, including the formation and evolution of stars, asteroids, and free-floating planets, as well as their internal and external structures.
Abstract: 1. Introduction 2. Radial velocities 3. Astrometry 4. Timing 5. Microlensing 6. Transits 7. Imaging 8. Host stars 9. Brown dwarfs and free-floating planets 10. Formation and evolution 11. Interiors and atmospheres 12. The Solar System Appendixes References Index.
527 citations
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TL;DR: McKinnon et al. as mentioned in this paper reported that ammonia is present in the plume, along with various organic compounds, deuterium and, very probably, Ar-40, which provides strong evidence for the existence of at least some liquid water, given that temperatures in excess of 180 K have been measured near the fractures from which the jets emanate.
Abstract: Jets of water ice from surface fractures near the south pole of Saturn's icy moon Enceladus produce a plume of gas and particles. The source of the jets may be a liquid water region under the ice shell-as suggested most recently by the discovery of salts in E-ring particles derived from the plume-or warm ice that is heated, causing dissociation of clathrate hydrates. Here we report that ammonia is present in the plume, along with various organic compounds, deuterium and, very probably, Ar-40. The presence of ammonia provides strong evidence for the existence of at least some liquid water, given that temperatures in excess of 180 K have been measured near the fractures from which the jets emanate. We conclude, from the overall composition of the material, that the plume derives from both a liquid reservoir (or from ice that in recent geological time has been in contact with such a reservoir) as well as from degassing, volatile-charged ice. As part of a general comprehensive review of the midsize saturnian satellites at the conclusion of the prime Cassini mission, PI McKinnon and co-I Barr contributed to three review chapters.
495 citations
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University of Nantes1, Imperial College London2, Paris Diderot University3, University of Leicester4, European Space Research and Technology Centre5, University College London6, University of Oxford7, Max Planck Society8, Centre national de la recherche scientifique9, Spanish National Research Council10
TL;DR: The JUpiter ICy moons Explorer (JUICE) mission as mentioned in this paper was selected by ESA in May 2012 to perform detailed investigations of Jupiter and its system in all their interrelations and complexity with particular emphasis on Ganymede as a planetary body and potential habitat.
493 citations
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TL;DR: In this article, a nonlinear optimal estimator for multivariatE spectral analySIS (NEMESIS) was developed to interpret observations of Saturn and Titan from the composite infrared spectrometer on board the NASA Cassini spacecraft.
Abstract: With the exception of in situ atmospheric probes, the most useful way to study the atmospheres of other planets is to observe their electromagnetic spectra through remote observations, either from ground-based telescopes or from spacecraft. Atmospheric properties most consistent with these observed spectra are then derived with retrieval models. All retrieval models attempt to extract the maximum amount of atmospheric information from finite sets of data, but while the problem to be solved is fundamentally the same for any planetary atmosphere, until now all such models have been assembled ad hoc to address data from individual missions.
In this paper, we describe a new general-purpose retrieval model, Non-linear Optimal Estimator for MultivariatE Spectral analySIS (NEMESIS), which was originally developed to interpret observations of Saturn and Titan from the composite infrared spectrometer on board the NASA Cassini spacecraft. NEMESIS has been constructed to be generally applicable to any planetary atmosphere and can be applied from the visible/near-infrared right out to microwave wavelengths, modelling both reflected sunlight and thermal emission in either scattering or non-scattering conditions. NEMESIS has now been successfully applied to the analysis of data from many planetary missions and also ground-based observations.
492 citations