Amy Barr Mlinar

Amy Barr Mlinar
Planetary Science Institute

PhD

About

120
Publications
12,379
Reads
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1,909
Citations
Citations since 2016
30 Research Items
1022 Citations
2016201720182019202020212022050100150
2016201720182019202020212022050100150
2016201720182019202020212022050100150
2016201720182019202020212022050100150
Introduction
Amy Barr Mlinar currently works at Planetary Science Institute. Amy does research in Astrophysics, Geophysics and Fluid Dynamics.
Additional affiliations
April 2015 - present
Planetary Science Institute
Position
  • Senior Researcher
September 2011 - September 2014
Brown University
Position
  • Professor (Assistant)
August 2006 - August 2011
Southwest Research Institute
Position
  • Principal Investigator

Publications

Publications (120)
Article
Context. With seven planets, the TRAPPIST-1 system has among the largest number of exoplanets discovered in a single system so far. The system is of astrobiological interest, because three of its planets orbit in the habitable zone of the ultracool M dwarf. Aims. We aim to determine interior structures for each planet and estimate the temperatures...
Article
Full-text available
Satellite formation is a natural by-product of planet formation. With the discovery of nu- merous extrasolar planets, it is likely that moons of extrasolar planets (exomoons) will soon be discovered. Some of the most promising techniques can yield both the mass and radius of the moon. Here, I review recent ideas about the formation of moons in our...
Article
The formation of satellites is thought to be a natural by-product of planet formation in our Solar System, and thus, moons of extrasolar planets (exomoons) may be abundant in extrasolar planetary systems, as well. Exomoons have yet to be discovered. However, moons larger than 0.1 Earth masses can be detected and characterized using current transit...
Article
The Giant Impact is currently accepted as the leading theory for the formation of Earth's Moon. Successful scenarios for lunar origin should be able to explain the chemical composition of the Moon (volatile content and stable isotope ratios), the Moon's initial thermal state, and the system's bulk physical and dynamical properties. Hydrocode simula...
Preprint
The ultracool M-dwarf star TRAPPIST-1 is surrounded by seven planets configured in a resonant chain. Transit-timing variations have shown that the planets are caught in multiple three-body resonances and that their orbits are slightly eccentric, probably caused by resonant forcing. The current values of the eccentricities could be a remnant from th...
Article
The ultracool M-dwarf star TRAPPIST-1 is surrounded by seven planets configured in a resonant chain. Transit-timing variations have shown that the planets are caught in multiple three-body resonances and that their orbits are slightly eccentric, probably caused by resonant forcing. The current values of the eccentricities could be a remnant from th...
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
Full-text available
The TRAPPIST-1 planetary system consists of seven planets within 0.05 au of each other, five of which are in a multi-resonant chain. These resonances suggest the system formed via planet migration; subsequent tidal evolution has damped away most of the initial eccentricities. We used dynamical N-body simulations to estimate how long it takes for th...
Preprint
Full-text available
The TRAPPIST-1 planetary system consists of seven planets within 0.05 au of each other, five of which are in a multi-resonant chain. {These resonances suggest the system formed via planet migration; subsequent tidal evolution has damped away most of the initial eccentricities. We used dynamical N-body simulations to estimate how long it takes for t...
Article
Full-text available
The satellite of (225088) 2007 OR 10 was discovered on archival Hubble Space Telescope images and along with new observations with the WFC3 camera in late 2017 we have been able to determine the orbit. The orbit's notable eccentricity, e ≈ 0.3, may be a consequence of an intrinsically eccentric orbit and slow tidal evolution, but may also be caused...
Preprint
Full-text available
The satellite of (225088) 2007 OR10 was discovered on archival Hubble Space Telescope images and along with new observations with the WFC3 camera in late 2017 we have been able to determine the orbit. The orbit's notable eccentricity, e$\approx$0.3, may be a consequence of an intrinsically eccentric orbit and slow tidal evolution, but may also be c...
Article
The satellite of (225088) 2007 OR 10 was discovered on archival Hubble Space Telescope images and along with new observations with the WFC3 camera in late 2017 we have been able to determine the orbit. The orbit's notable eccentricity, e ≈ 0.3, may be a consequence of an intrinsically eccentric orbit and slow tidal evolution, but may also be caused...
Article
Full-text available
Context. New estimates of the masses and radii of the seven planets orbiting the ultracool M-dwarf TRAPPIST-1 star permit improved modelling of their compositions, heating by tidal dissipation, and removal of tidal heat by solid-state convection. Aims. Here we compute the heat flux due to insolation and tidal heating for the inner four planets. Met...
Preprint
Full-text available
Context. New estimates of the masses and radii of the seven planets orbiting the ultracool M-dwarf TRAPPIST-1 star permit improved modelling of their compositions, heating by tidal dissipation, and removal of tidal heat by solid-state convection. Aims. Here, we compute the heat flux due to insolation and tidal heating for the inner four planets. Me...
Preprint
Full-text available
Ammonia, if present in the ice shells of icy satellites, could lower the temperature for the onset of melting to 176 K and create a large temperature range where partial melt is thermally stable. The evolution of regions of ammonia-rich partial melt could strongly influence the geological and thermal evolution of icy bodies. For melt to be extracte...
Article
Full-text available
Ammonia, if present in the ice shells of icy satellites, could lower the temperature for the onset of melting to 176 K and create a large temperature range where partial melt is thermally stable. The evolution of regions of ammonia-rich partial melt could strongly influence the geological and thermal evolution of icy bodies. For melt to be extracte...
Conference Paper
Full-text available
The Toolbox for Research and Exploration (TREX) is a NASA SSERVI (Solar System Exploration Research Virtual Institute) node. TREX (trex.psi.edu) aims to decrease risk to future missions, specifically to the Moon, the Martian moons, and near- Earth asteroids, by improving mission success and assuring the safety of astronauts, their instruments and s...
Article
Fatigue can cause materials that undergo cyclic loading to experience brittle failure at much lower stresses than under monotonic loading. We propose that the lithospheres of icy satellites could become fatigued and thus weakened by cyclical tidal stresses. To test this hypothesis, we performed a series of laboratory experiments to measure the fati...
Preprint
Full-text available
Fatigue can cause materials that undergo cyclic loading to experience brittle failure at much lower stresses than under monotonic loading. We propose that the lithospheres of icy satellites could become fatigued and thus weakened by cyclical tidal stresses. To test this hypothesis, we performed a series of laboratory experiments to measure the fati...
Article
Icy satellites experience billions of cycles of tidal stress over their histories. Cyclic loading can increase microcrack density and reduce the brittle yield stress of materials in a process known as fa-tigue[1]. If fatigue occurs on icy satellites it could lower the brittle yield stress near the surface, possibly facilitating increased geologic a...
Conference Paper
"Ocean planets " are a class of H 2 O-rich exoplanets [1-7] roughly resembling larger versions of the satellites in our outer solar system [2-3, 8-9]. Geophysical processes operating on these cold, low density worlds may therefore be similar to processes operating on our solar system's icy moons. Explosive cryovolcanism has been observed on several...
Article
Studies of a large frost-filled basin on Pluto show that this feature altered the dwarf planet's spin axis, driving tectonic activity on its surface, and hint at the presence of a subsurface ocean. See Letters p.86, p.90, p.94 & p.97
Article
The New Horizons spacecraft has found evidence for geologic activity on the surface of Pluto, including extensional tectonic deformation of its water ice bedrock (see Moore et al., 2016, "The Geology of Pluto and Charon through the Eyes of New Horizons", Science 351, 1284-1293). One mechanism that could drive extensional tectonic activity is global...
Article
Kuiper Belt objects with absolute magnitude less than 3 (radius ~􏰀500 km), the dwarf planets, have a range of different ice/rock ratios, and are more rock-rich than their smaller counterparts. Many of these objects have moons, which suggests that collisions may have played a role in modifying their compositions. We show that the dwarf planets fall...
Conference Paper
Here, we simulate the thermal evolution of Pluto to understand its present day internal structure and tectonic environment. We find that the thermal conductivity and density of the silicate core strongly control Pluto’s thermal evolution. Changes in these parameters lead to two different thermal evolution pathways: 1) Pluto forms an ocean that surv...
Conference Paper
Full-text available
Based on the Europa Clipper mission concept, NASA's Europa Multiple Flyby Mis- sion, planned for launch in 2022, will perform more than 40 flybys of Europa with altitudes at closest ap- proach as low as 25 km. The instrument payload includes the Europa Imaging System (EIS), a camera suite designed to transform our understanding of Euro- pa through...
Article
A giant impact between an iron-enriched planetary embryo and the proto-Earth can create a moon with 30% terrestrial material by mass.
Article
Miranda, an icy moon of Uranus, is one of the most visually striking and enigmatic bodies in the solar system. Three polygonal-shaped regions of intense deformation, dubbed “coronae,” dominate the surface of Miranda. Here we use numerical methods to show that sluggish-lid convection in Miranda’s ice shell, powered by tidal heating, can simultaneous...
Article
Full-text available
Iapetus, the outermost regular satellite of Saturn, has a drastic albedo dichotomy and an equatorial circumferential ridge that reaches heights of 20 km and widths of 70 km. This moon is thought to have formed concurrently with Saturn, and so would have experienced an intense bombardment after its formation. The ridge, which has been inferred to be...
Article
Ridge-and-trough terrain is a common landform on outer Solar System icy satellites. Examples include Ganymede’s grooved terrain, Europa’s gray bands, Miranda’s coronae, and several terrains on Enceladus. The conditions associated with the formation of each of these terrains are similar: heat flows of order tens to a hundred milliwatts per meter squ...
Article
Saturn's moon Iapetus has an equatorial ridge system, which may be as high as 20 km, that may have formed by endogenic forces, such as tectonic and convective forces, or exogenic processes such as debris infall. We use high-resolution topographic data to conduct a topographic analysis of the ridge, which suggests a predominantly triangular morpholo...
Article
The driving force behind extensional ridge-and-trough terrains on many icy satellites may be solid-state convection in an ice shell with a weak upper surface.
Article
Using recent morphological investigations of Iapetus' ridge along with our cratering model, we constrain the outer system planetesimal disk mass.
Article
We simulate convection in Miranda’s ice shell to test the hypothesis that coronae formed by convection-driven resurfacing during an episode of tidal heating.
Article
Late accretion of a “veneer” of compositionally diverse planetesimals may introduce chemical heterogeneity in the mantles of the terrestrial planets. The size of the late veneer objects is an important control on the angular momenta, eccentricities, and inclinations of the terrestrial planets, but current estimates range from meter-scale bodies to...
Article
Vertical transport processes across ice shells are important for questions of habitability and planetary protection. We present an inventory of processes, their applications to icy worlds of interest, and disconnects in the vertical transport chain.
Article
Monte Carlo modeling indicates mercurian LRM variation does not require crustal heterogeneities and its distribution is indicative of primordial composition.
Article
The relatively young, bright grooved terrain covers over half of Ganymede’s sur- face is characterized by zones of intense local deformation [1]. Mechanisms proposed for the formation of grooved terrain include extensional faulting, cryovolcanism and convection-driven lithospheric spreading [2-4]. Lithospheric spreading has been suggested as a mech...
Data
This video is also available on YouTube -- https://www.youtube.com/watch?v=N4pYH4JFkxk
Article
Coauthors: R. T. Pappalardo (1), F. Bagenal (2), A. C. Barr (3), B. G. Bills (1), D. L. Blaney (1), D. D. Blankenship (4), W. Brinckerhoff (5), J. E. P. Connerney (5), K. Hand (1), T. Hoehler (6), W. Kurth (7), M. McGrath (8), M. Mellon (9), J. M. Moore (6), D. A. Senske (1), E. Shock (10), D. E. Smith (11), T. Gavin (1), G. Garner (1), T. Magner (...
Article
The Europa Science Definition Team reports on its study of three Europa mission concepts: a Europa orbiter, a Europa multiple-flyby mission, and a Europa lander.
Article
Electromagnetic (EM) investigation depths are larger on Venus than Earth due to the dearth of water in rocks, in spite of higher temperatures. Whistlers detected by Venus Express proved that lightning is present, so the Schumann resonances ∼10–40Hz may provide a global source of electromagnetic energy that penetrates ∼10–100km. Electrical conductiv...
Article
Assessment of Europa's habitability, as an overarching science goal, will progress via a comprehensive investigation of Europa's subsurface ocean, chemical composition, and internal dynamical processes. The National Research Council's Planetary Decadal Survey placed an extremely high priority on Europa science but noted that the budget profile for...
Article
We present a scenario for building the equatorial ridge and de-spinning Iapetus through an impact-generated disk and satellite. This impact puts debris into orbit, forming a ring inside the Roche limit and a satellite outside. This satellite rapidly pushes the ring material down to the surface of Iapetus, and then itself tidally evolves outward, th...
Article
Orbital radar sounding has been suggested as a means of determining the subsurface thermal and physical structure of the outer ice I shells of the Galilean satellites. At radar frequencies, the dielectric permittivity of single- and polycrystalline water ice I is anisotropic. Crystal orientation fabric (COF), which is indicative of strain history,...
Article
Full-text available
We combine new measurements of the temperature-dependent, broadband dielectric properties of terrestrial ice cores with 3-D thermomechanical modeling of the Europan ice shell, in order to improve constraints on the radar attenuation through the shell.
Article
We present a scenario that both builds the equatorial ridge and despins Iapetus through an impact-generated disk and satellite.
Article
The volume of melt produced in hypervelocity planetary impacts and the size and shape of the melted region are key to understanding the impact histories of solid planetary bodies and the geological effects of impacts on their surfaces and interiors. Prior work of Pierazzo et al. (Pierazzo, E., Vickery, A.M., Melosh, H.J. [1997]. Icarus 127, 408–423...
Presentation
Full-text available
PowerPoint Presentation from invited talk at the TNO 2010 meeting in Philadelphia, PA.
Article
Recent high-resolution Cassini images of the south polar terrain of Enceladus reveal regions of short-wavelength deformation, inferred to be compressional folds between the Baghdad and Damascus tiger stripes (Spencer, J.R., Barr, A.C., Esposito, L.W., Helfenstein, P., Ingersoll, A.P., Jaumann, R., McKay, C.P., Nimmo, F., Waite, J.H. [2009a]. Encela...
Poster
The interior state of Titan is important to understanding the formation and evolution of the saturnian system (Barr and Canup, 2008; Barr et al., 2010). Predictions regarding ice/rock separation in Titan during its early evolution can also guide future interpretations of its moment of inertia (MOI). Recent theories of satellite formation suggest Ti...
Article
Conditions similar to those that lead to a partially differentiated Callisto can produce a similar state for Titan. If satellite formation occurred at Saturn at the same time or later as Jupiter, and had a similar duration, a partially differentiated post-accretion state for Titan is plausible (Barr et al., 2010). If Titan accretes from meter-to-ki...
Article
We compare results from SPH and CTH simulations of Moon-forming impacts, in particular to determine the effect of resolution and simulation method on the fraction of orbiting protolunar disk material that originates from the impactor vs. the proto-Earth's mantle.
Poster
We show that Titan can accrete undifferentiated in a gas starved disk, even with modest amounts of ammonia mixed in with its ice, and that Titan can remain partially differentiated after an outer solar system late heavy bombardment.
Article
We show that the Ganymede/Callisto dichotomy arises as a natural result of dynamical sculpting of the outer solar system. Hypervelocity impacts occurring during an outer solar system late heavy bombardment trigger runaway differentiation in Ganymede, but not Callisto.
Article
Jupiter's large moons Ganymede and Callisto are similar in size and composition. However, Ganymede has a tectonically evolved surface and a large rock/metal core, whereas Callisto's surface shows no sign of resurfacing and the separation of ice and rock in its interior seems incomplete. These differences have been difficult to explain. Here we pres...
Article
The tidal stress at the surface of a satellite is derived from the gravitational potential of the satellite's parent planet, assuming that the satellite is fully differentiated into a silicate core, a global subsurface ocean, and a decoupled, viscoelastic lithospheric shell. We consider two types of time variability for the tidal force acting on th...
Article
A recent theory for the origin of late heavy bombardment impactors suggests an outer solar system source. Limits on the size of rocky core in Jupiter's moon Callisto are used to constrain the contribution of outer solar system impactors to the LHB.
Chapter
Full-text available
Enceladus is one of the most remarkable satellites in the solar system, as revealed by Cassini's detection of active plumes erupting from warm fractures near its south pole. This discovery makes Enceladus the only icy satellite known to exhibit ongoing internally driven geological activity. The activity is presumably powered by tidal heating mainta...
Article
Despite their similar sizes and compositions, Ganymede and Callisto have followed different evolutionary pathways. Ganymede has experienced extensive geological activity and has a large rock core. Callisto's surface is ancient. Core formation in Callisto has apparently been incomplete; its interior has layers of mixed ice and rock (Anderson et al.,...
Article
Heat transport across Europa's ice shell controls the thermal evolution of its interior and provides a source of energy to drive resurfacing. Recent improvements in knowledge of ice rheology, the behavior of convection, and the interaction between convection and lithospheric deformation have led to more realistic and complex models of the geodynami...
Article
The Pluto-Charon binary dwarf planet system is probably the result of an impact of similar-sized Kuiper Belt objects. The pair evolved from an unknown initial state to the dynamical end state in which we find them now, synchronously locked to each other. In this presentation, we investigate the implications of the evolution to this end state for th...
Article
An icy satellite whose interior is composed of a homogeneous ice/rock mixture must avoid melting during its entire history, including during its formation when it was heated by deposition of accretional energy and short-lived radioisotopes. Estimates of the temperature rise associated with radiogenic and accretional heating, coupled with limits on...
Article
Enceladus' south polar region has a large heat flux that is spatially associated with cryovolcanic and tectonic activity. Tidal dissipation and vigorous convection in the underlying ice shell are possible sources of heat, however, prior predictions of the heat flux carried by stagnant lid convection are too low to explain the observed heat flux. Th...
Article
The history and dynamics of the martian polar deposits (MPD), the largest known water reservoirs on Mars, are of great interest, but estimates of ice grain size are required before detailed modeling can be performed. We clarify the microphysical processes that may control grain size in the MPD. If the MPD are ∼2% dust by mass, the maximum ice grain...
Article
Enceladus is geologically active, with plumes of water vapor and dust erupting from its south polar terrain (SPT) [1,2]. The plumes are spatially associated with a region of anomalous heat flow, activity undoubtedly driven by the tidal flexing of Enceladus, which is in an eccentric orbit. Tidal strains of the magnitude possible in an ice shell that...
Article
We model convection beneath Enceladus' south polar region including a heat source from strike-slip motion along the tiger stripes to investigate the effect of the interaction between ridges and convection on the surface heat flux.
Article
The onset of convection in the power-law creep regime on the silicate and icy planetary bodies requires a finite amplitude initial perturbation. This is a nonlinear problem and thus, both the amplitude and shape of the perturbation are important. We performed numerical simulations of the onset of convection in a two-dimensional layer with a fixed t...
Article
Full-text available
The prolific activity and presence of a plume on Saturn's tiny moon Enceladus offers us a unique opportunity to sample the interior composition of an icy satellite, and to look for interesting chemistry and possible signs of life. Based on studies of the potential habitability of Jupiter's moon Europa, icy satellite oceans can be habitable if they...