# P. Schenk's research while affiliated with Universities Space Research Association and other places

## Publications (612)

Article
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On 7 June 2021, Juno crossed the orbital path of Jupiter’s moon Ganymede, flying within 1,046 km of the surface. Juno’s low‐light‐sensitive Stellar Reference Unit (SRU) navigation camera captured an image of the satellite’s dark side in a region of Xibalba Sulcus illuminated solely by Jupiter‐shine. Collected at high incidence angle with 670–920 m/...
Article
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During the Juno Mission's encounter with Ganymede on 7 June 2021, the Juno camera (JunoCam) acquired four images of Ganymede in color. These images covered one‐sixth of Ganymede at scales from 840 m to ∼4 km/pixel. Most of this area was only previously imaged by Voyager 1 in 1979, at lower spatial resolution and poorer image quality. No changes wer...
Article
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Plain Language Summary It has become apparent over the last few years that small asteroids and comets are very underdense compared with the materials they are made of. This means that their total porosities are likely quite high, in excess of 70%, both as tiny voids within particles (so‐called microscopic porosity) and spaces between particles (mac...
Preprint
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The New Horizons spacecraft returned images and compositional data showing that terrains on Pluto span a variety of ages, ranging from relatively ancient, heavily cratered areas to very young surfaces with few-to-no impact craters. One of the regions with very few impact craters is dominated by enormous rises with hummocky flanks. Similar features...
Article
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NASA's New Horizons mission performed the first flyby of a small Kuiper Belt Object (KBO), (486958) Arrokoth on 1 January 2019. The fast flyby revealed a fascinating, flattened, contact binary replete with a variety of unexpected geologic terrains. However, the irregular shape and constraints imposed by the fast flyby makes it a challenge to unders...
Article
Full-text available
The New Horizons spacecraft returned images and compositional data showing that terrains on Pluto span a variety of ages, ranging from relatively ancient, heavily cratered areas to very young surfaces with few-to-no impact craters. One of the regions with very few impact craters is dominated by enormous rises with hummocky flanks. Similar features...
Article
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Dawn revealed that Ceres is a compelling target whose exploration pertains to many science themes. Ceres is a large ice- and organic-rich body, potentially representative of the population of objects that brought water and organics to the inner solar system, as well as a brine-rich body whose study can contribute to ocean world science. The Dawn ob...
Article
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We used New Horizons LORRI images to measure the optical-band (0.4 ≲ λ ≲ 0.9 μ m) sky brightness within a high-galactic-latitude field selected to have reduced diffuse scattered light from the Milky Way galaxy (DGL), as inferred from the IRIS all-sky 100 μ m map. We also selected the field to significantly reduce the scattered light from bright sta...
Article
The NASA Dawn mission revealed that the floor of Occator crater on the dwarf planet Ceres (in the main asteroid belt between Mars and Jupiter) is populated with small quasi-conical hills. Many of these features exhibit morphometric properties that are like those of ice-cored periglacial hills called pingos. Alternatively, some of these Cerean hills...
Preprint
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We used New Horizons LORRI images to measure the optical-band ($0.4\lesssim\lambda\lesssim0.9{\rm\mu m}$) sky brightness within a high galactic-latitude field selected to have reduced diffuse scattered light from the Milky Way galaxy (DGL), as inferred from the IRIS all-sky $100~\mu$m map. We also selected the field to significantly reduce the scat...
Article
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Outer solar system impact bombardment is largely unconstrained. Although recent data from the Jupiter, Saturn, and Pluto systems have produced new constraints, analysis is incomplete without inclusion of the Uranus system. We reanalyze Uranus system crater populations with recent improvements in processing of Voyager 2 imaging. No consensus in crat...
Article
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Rhea's exosphere is thought to originate from sources of carbon, water ice and other volatiles that arrived at Rhea by bombardment. Its seasonal variability is directly driven by polar surface temperatures allowing surface adsorption, and the persistence of source volatiles require that seasonal temperatures remain sufficiently cold to retain them....
Article
Delivery of significant volumes of howardite–eucrite–diogenite (HED) meteorites from Vesta to Earth is linked to the largest impact events on that protoplanet, especially the giant Rheasilvia basin. Dawn mapping of Rheasilvia reveals a well-preserved impact structure with extensive deformation patterns and moderate superposed cratering. Spiral and...
Preprint
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At least two active plumes were observed on Neptune's moon Triton during the Voyager 2 flyby in 1989. Models for Triton's plumes have previously been grouped into five hypotheses, two of which are primarily atmospheric phenomena and are generally considered unlikely, and three of which include eruptive processes and are plausible. These hypotheses...
Article
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The orientation and morphology of the bilobate, cold classical Kuiper belt object (486958) Arrokoth (formerly 2014 MU69) is consistent with a slow, tidal merger of a close binary. However, the discrepancy between Arrokoth's present‐day rotation (15.9 hr) and synchronous rotation for nominal cometary densities near ∼500 kg/m³ implies reduction (up t...
Article
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Sputnik Planitia on Pluto is a vast plain consisting of a nitrogen ice deposit filling a broad topographic depression, likely an impact basin. The basin displays a broad, raised rim and is surrounded by numerous extensional fault systems, each with characteristic orientations with respect to the basin center. The nitrogen ice exerts a large mechani...
Article
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Morphometric studies of impact craters on icy moons can be used to understand modification of crater topography. Several processes (e.g., viscous relaxation, ejecta deposition, repeated and overlapping impacts) act to shallow crater depth and relax the crater wall slope to similar or varying extents. Resolving these processes can help constrain the...
Article
At least two active plumes were observed on Neptune's moon Triton during the Voyager 2 flyby in 1989. Models for Triton's plumes have previously been grouped into five hypotheses, two of which are primarily atmospheric phenomena and are generally considered unlikely, and three of which include eruptive processes and are plausible. These hypotheses...
Preprint
Full-text available
Neptune's moon Triton shares many similarities with Pluto, including volatile cycles of N2, CH4 and CO, and represents a benchmark case for the study of surface-atmosphere interactions on volatile-rich KBOs. Within the context of New Horizons observations of Pluto as well as recent Earth-based observations of Triton, we adapt a Plutonian VTM to Tri...
Article
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The Neptune Odyssey mission concept is a Flagship-class orbiter and atmospheric probe to the Neptune-Triton system. This bold mission of exploration would orbit an ice-giant planet to study the planet, its rings, small satellites, space environment, and the planet-sized moon Triton. Triton is a captured dwarf planet from the Kuiper Belt, twin of Pl...
Article
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Neptune's moon Triton shares many similarities with Pluto, including volatile cycles of N2, CH4 and CO, and represents a benchmark case for the study of surface-atmosphere interactions on volatile-rich Kuiper Belt objects. The observations of Pluto by New Horizons acquired during the 2015 flyby and their analysis with volatile transport models (VTM...
Article
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The topography of Neptune’s large icy moon Triton could reveal important clues to its internal evolution, but has been difficult to determine. New global digital color maps for Triton have been produced as well as topographic data for <40% of the surface using stereogrammetry and photoclinometry. Triton is most likely a captured Kuiper Belt dwarf p...
Preprint
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One of the clearest but unresolved questions for Europa is the thickness of its icy shell. Europa's surface is resplendent with geological features that bear on this question, and ultimately on its interior, geological history, and astrobiological potential. We characterize the size and topographic expression of circular and subcircular features cr...
Article
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Triton is an important signpost in understanding the diverse populations of both ocean worlds and Kuiper Belt objects (KBOs). As a likely ocean world, it is unique by virtue of its kidnapped history from the Kuiper Belt: its large orbital inclination makes it the only ocean world thought to be primarily heated by obliquity tides. It is volatile-ric...
Article
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New Horizons images of the illuminated nonencounter hemisphere (far side) of Charon display geomorphic features that are consistent with features observed in the highest-resolution images of the encounter hemisphere. Scarps, ridges, craters, and one area of smooth plains are identified. These features support previous hypotheses of global expansion...
Article
We perform geomorphological analysis and modeling of the Lagrangian satellites of Dione and Tethys, based on images obtained by Cassini's Imaging Science Subsystem camera and a digital elevation model covering Helene's Saturn-facing and leading sides. Helene's cratered surface has been heavily modified by mass flows as indicated by pronounced crate...
Technical Report
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1MotivationInvestigation of Uranus or Neptune would advancefundamental understanding ofmany key issues in Solar System formation:1) how ice giantsformed and migrated through the Solar System;2) whatprocesses control the current conditions of this class of planet, its rings, satellites, and magnetospheres; 3) how the rings and satellites formed and...
Article
Both endogenic and exogenic formation mechanisms have been proposed for the equatorial ridge on Saturn's moon Iapetus. With photogeological mapping and crater statistics, we find that the morphology of the ridge is best explained by an exogenic origin, principally by the accretion onto the moon's surface of an orbiting ring of material.
Preprint
Chaos terrains are characterized by disruption of preexisting surfaces into irregularly arranged mountain blocks with a chaotic appearance. Several models for chaos formation have been proposed, but the formation and evolution of this enigmatic terrain type has not yet been fully constrained. We provide extensive mapping of the individual blocks th...
Article
One of the clearest but unresolved questions for Europa is the thickness of its icy shell. Europa's surface is resplendent with geological features that bear on this question, and ultimately on its interior, geological history, and astrobiological potential. We characterize the size and topographic expression of circular and subcircular features cr...
Article
Full-text available
Article
Io is a priority destination for solar system exploration. The scope and importance of science questions at Io necessitates a broad portfolio of research and analysis, telescopic observations, and planetary missions — including a dedicated New Frontiers class Io mission.
Article
Io is a priority destination for solar system exploration, as it is the best natural laboratory to study the intertwined processes of tidal heating, extreme volcanism, and atmosphere-magnetosphere interactions. Io exploration is relevant to understanding terrestrial worlds (including the early Earth), ocean worlds, and exoplanets across the cosmos.
Article
The radio thermal emission from Pluto was observed from the New Horizons spacecraft at a wavelength of 4.2 cm along two scans across the planetary disk shortly after closest approach to Pluto on 14 July 2015. The measurements were performed as part of the New Horizons Radio Science Experiment (REX) using the 2.1 m High Gain Antenna (HGA) and the sp...
Article
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Plain Language Summary Studying the topography of planetary bodies provides key insights into the geologic processes of their surfaces and interiors. In this work we develop a topography data set for Pluto and Charon by mapping variations in the height along the worlds’ edges in images from New Horizons. We analyze the data to determine roughness u...
Article
High-resolution mapping of Ceres, Vesta and the icy satellites of Saturn, Uranus and Pluto reveals a rich variety of well-preserved impact crater morphologies on these low gravity bodies. These objects provide a natural laboratory to study effects of composition on crater formation processes under similar surface gravity conditions (though mean imp...
Article
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We used existing data from the New Horizons Long-range Reconnaissance Imager (LORRI) to measure the optical-band (0.4 ≲ λ ≲ 0.9 μ m) sky brightness within seven high–Galactic latitude fields. The average raw level measured while New Horizons was 42–45 au from the Sun is 33.2 ± 0.5 nW m ⁻² sr ⁻¹ . This is ∼10× as dark as the darkest sky accessible t...
Article
Newly processed global imaging and topographic mapping of Uranus's five major satellites reveal differences and similarities to mid-sized satellites at Saturn and Pluto. Three modes of internal heat redistribution are recognized. The broad similarity of Miranda's three oval resurfacing zones to those mapped on Enceladus and (subtly) on Dione are li...
Preprint
We used existing data from the New Horizons LORRI camera to measure the optical-band ($0.4\lesssim\lambda\lesssim0.9{\rm\mu m}$) sky brightness within seven high galactic latitude fields. The average raw level measured while New Horizons was 42 to 45 AU from the Sun is $33.2\pm0.5{\rm ~nW ~m^{-2} ~sr^{-1}}.$ This is $\sim10\times$ darker than the d...
Article
Cassini mapping of Saturn’s mid‐sized icy moons of well‐preserved complex craters in the 45–95 km size range provides insight into cratering processes at lower surface gravity and on icy targets. These craters are characterized by steep rim scarps, rugged hummocky floor deposits of curvilinear ridges and scarps, and rugged conical central peaks. Po...
Article
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En echelon fissures 100–300 km long on Europa are found to be concentric and external to arcuate troughs previously attributed to true polar wander (TPW) of Europa's ice shell, strengthening the case for TPW. Fissures are composed of parallel faults distributed over 10‐to‐20‐km‐wide zones, with deformation focused in a main fissure 1–2 km wide and...
Article
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The intimate mixture of ice and silicate within the uppermost few kilometres of Ceres influences its geology and the evolution of its subsurface. Both ground ice and cryovolcanic processes have been hypothesized to form geologic terrains on Ceres, including within Occator crater, where they have been suggested to influence the post-impact surface e...
Preprint
Pluto's terrains display a diversity of crater retention ages ranging from areas with no identifiable craters to heavily cratered terrains. This variation in crater densities is consistent with geologic activity occurring throughout Pluto's history and also a variety of resurfacing styles, including both exogenic and endogenic processes. Using esti...
Article
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Before acquiring highest-resolution data of Ceres, questions remained about the emplacement mechanism and source of Occator crater’s bright faculae. Here we report that brine effusion emplaced the faculae in a brine-limited, impact-induced hydrothermal system. Impact-derived fracturing enabled brines to reach the surface. The central faculae, Cerea...
Article
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Hydrothermal processes in impact environments on water-rich bodies such as Mars and Earth are relevant to the origins of life. Dawn mapping of dwarf planet (1) Ceres has identified similar deposits within Occator crater. Here we show using Dawn high-resolution stereo imaging and topography that Ceres’ unique composition has resulted in widespread m...
Article
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Ceres, the only dwarf planet in the inner Solar System, appears to be a relict ocean world. Data collected by NASA’s Dawn spacecraft provided evidence that global aqueous alteration within Ceres resulted in a chemically evolved body that remains volatile-rich¹. Recent emplacement of bright deposits sourced from brines attests to Ceres being a persi...
Preprint
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Ice giants are the only unexplored class of planet in our Solar System. Much that we currently know about these systems challenges our understanding of how planets, rings, satellites, and magnetospheres form and evolve. We assert that an ice giant Flagship mission with an atmospheric probe should be a priority for the decade 2023-2032.
Article
Impact craters form as point-like explosions on solar system bodies, excavating a cavity within the surface. Most information about the impactor itself is lost, save its energy, such that the target itself controls much of the final crater size and shape given the energy input. For this reason, impact craters are a useful probe of surface differenc...
Article
The dominant topographic features on two-lobed Kuiper Belt object (486958) Arrokoth (provisionally designated 2014 MU69) are scattered, small, circular depressions or pits up to ~1.0 km across and curvilinear troughs observed near the terminator during the New Horizons encounter of 01 January 2019. With important exceptions, evidence for an endogen...
Article
Chaotic terrains are characterized by disruption of preexisting surfaces into irregularly arranged mountain blocks with a “chaotic” appearance. Several models for chaos formation have been proposed, but the formation and evolution of this enigmatic terrain type has not yet been fully constrained. We provide extensive mapping of the individual block...
Preprint
The Kuiper Belt is a distant region of the Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU69, a Cold Classical Kuiper Belt Object, a class of objects that have never been heated by the Sun and are therefore well preserved since their formation. Here we describe initial results from these encounter observa...
Article
The New Horizons spacecraft provided near-global observations of Pluto that far exceed the resolution of Earth-based datasets. However, most previous Pluto New Horizons analyses focused on the New Horizons encounter hemisphere (i.e., the anti-Charon hemisphere containing Sputnik Planitia). In this work, we summarize and interpret data on Pluto's “f...
Preprint
Full-text available
The Cold Classical Kuiper Belt, a class of small bodies in undisturbed orbits beyond Neptune, are primitive objects preserving information about Solar System formation. The New Horizons spacecraft flew past one of these objects, the 36 km long contact binary (486958) Arrokoth (2014 MU69), in January 2019. Images from the flyby show that Arrokoth ha...
Preprint
The outer Solar System object (486958) Arrokoth (provisional designation 2014 MU$_{69}$) has been largely undisturbed since its formation. We study its surface composition using data collected by the New Horizons spacecraft. Methanol ice is present along with organic material, which may have formed through radiation of simple molecules. Water ice w...
Article
Examining Arrokoth The New Horizons spacecraft flew past the Kuiper Belt object (486958) Arrokoth (also known as 2014 MU 69 ) in January 2019. Because of the great distance to the outer Solar System and limited bandwidth, it will take until late 2020 to downlink all the spacecraft's observations back to Earth. Three papers in this issue analyze rec...
Article
Full-text available
Examining Arrokoth The New Horizons spacecraft flew past the Kuiper Belt object (486958) Arrokoth (also known as 2014 MU 69 ) in January 2019. Because of the great distance to the outer Solar System and limited bandwidth, it will take until late 2020 to downlink all the spacecraft's observations back to Earth. Three papers in this issue analyze rec...
Preprint
The New Horizons spacecraft provided near global observations of Pluto that far exceed the resolution of Earth-based data sets. Most Pluto New Horizons analysis hitherto has focused on the encounter hemisphere of Pluto (i.e., the antiCharon hemisphere containing Sputnik Planitia). In this work, we summarize and interpret data on the far side (i.e.,...
Article
Full-text available
We present a comprehensive global catalog of the geomorphological features with clear or potential relevance to subsurface ice identified during the Dawn spacecraft’s primary and first extended missions at Ceres. We define eight broad feature classes and describe analyses supporting their genetic links to subsurface ice. These classes include: rela...
Article
We investigated five large landslides identified in the Serenity Chasma region of Charon. The identification of these landslides involved a search for these features in images taken by cameras onboard the New Horizons spacecraft. Various landslide properties were analyzed based on their morphologies using a digital terrain model of the region. We f...
Article
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Several ejecta deposits on Ceres display morphological characteristics not commonly associated with dry ballistic emplacement. We characterized 30 examples of fluidized appearing ejecta (FAE) on Ceres and identified two distinct morphological populations: cuspate/lobate FAE and channelized FAE. The cuspate/lobate FAE typically display one or more o...
Article
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We analyze landslides on Ceres using several quantitative approaches to constrain the composition and structure of the top few kilometers of Ceres' crust. We focus on a subset of archetypal landslides classified morphologically as thick, steep‐snouted “type 1” (T1) flows and thin spatulate “type 2” (T2) flows (Schmidt et al., 2017, https://doi.org/...
Article
The Kuiper Belt is a distant region of the outer Solar System. On 1 January 2019, the New Horizons spacecraft flew close to (486958) 2014 MU69, a cold classical Kuiper Belt object approximately 30 kilometers in diameter. Such objects have never been substantially heated by the Sun and are therefore well preserved since their formation. We describe...