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Scott S Sheppard - One of the best experts on this subject based on the ideXlab platform.
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light curves of Dwarf plutonian Planets and other large kuiper belt objects their rotations phase functions and absolute magnitudes
The Astronomical Journal, 2007Co-Authors: Scott S SheppardAbstract:I report new time-resolved light curves and determine the rotations and phase functions of several large Kuiper Belt objects, which includes the Dwarf planet Eris (2003 UB313). Three of the new sample of 10 trans-Neptunian objects display obvious short-term periodic light curves. (120348) 2004 TY364 shows a light curve which if double-peaked has a period of 11:70 � 0:01 hr and a peak-to-peak amplitude of 0:22 � 0:02 mag. (84922) 2003 VS2 has a well-defined double-peaked light curve of 7:41 � 0:02 hr with a range of 0:21 � 0:02 mag. (126154) 2001 YH140shows variability of 0:21 � 0: 04magwithapossib le13 :25 � 0:2hr single-peaked period. The seven new Kuiper Belt objects in the sample which show no discernible variations within the uncertainties on short rotational timescales are (148780) 2001 UQ18, (55565) 2002 AW197, (119979) 2002 WC19, (120132) 2003 FY128, (136108) Eris 2003 UB313, (90482) Orcus 2004 DW, and (90568) 2004 GV9 .F our of the 10 newly sampled Kuiper Belt objects were observed over a significant range of phase angles to determine their phase functions and absolute magnitudes. The three medium- to large-sized Kuiper Belt objects 2004 TY364, Orcus, and 2004 GV9 show fairly steep linear phase curves (� 0.18 to 0.26 mag deg � 1 ) between phase angles of 0.1 � and 1.5 � .T his is consistent with previous measurements obtained for moderately sized Kuiper Belt objects. The extremely large Dwarf planet Eris (2003 UB313) shows a shallower phase curve (0:09 � 0:03 mag deg � 1 ) which is more similar to the other known Dwarf planet Pluto.It appears that the surface properties of the largest Dwarf Planets inthe Kuiper Belt may be different than the smaller Kuiper Belt objects. This may have to do with the larger objects’ ability to hold more volatile ices, as well as sustain atmospheres. Finally, it is found that the absolute magnitudes obtained using the phase slopes found for individual objects are a few tenths of magnitudes different than that given by the Minor Planet Center.
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light curves of Dwarf plutonian Planets and other large kuiper belt objects their rotations phase functions and absolute magnitudes
arXiv: Astrophysics, 2007Co-Authors: Scott S SheppardAbstract:(Abridged) I report new light curves and determine the rotations and phase functions of several large Kuiper Belt objects, including the Dwarf planet Eris (2003 UB313). (120348) 2004 TY364 shows a light curve which if double-peaked has a period of 11.70+-0.01 hours and peak-to-peak amplitude of 0.22+-0.02 magnitudes. (84922) 2003 VS2 has a well defined double-peaked light curve of 7.41+-0.02 hours with a 0.21+-0.02 magnitude range. (126154) 2001 YH140 shows variability of 0.21+-0.04 magnitudes with a possible 13.25+-0.2 hour single-peaked period. The seven new KBOs in the sample which show no discernible variations within the uncertainties on short rotational time scales are 2001 UQ18, (55565) 2002 AW197, (119979) 2002 WC19, (120132) 2003 FY128, (136108) Eris 2003 UB313, (90482) Orcus 2004 DW, and (90568) 2004 GV9. The three medium to large sized Kuiper Belt objects 2004 TY364, Orcus and 2004 GV9 show fairly steep linear phase curves (~0.18 to 0.26 mags per degree) between phase angles of 0.1 and 1.5 degrees. The extremely large Dwarf planet Eris (2003 UB313) shows a shallower phase curve (0.09+-0.03 mags per degree) which is more similar to the other known Dwarf planet Pluto. It appears the surface properties of the largest Dwarf Planets in the Kuiper Belt maybe different than the smaller Kuiper Belt objects. This may have to do with the larger objects ability to hold more volatile ices as well as sustain atmospheres. The absolute magnitudes obtained using the measured phase slopes are a few tenths of magnitudes different from those given by the MPC.
Paul J Tackley - One of the best experts on this subject based on the ideXlab platform.
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stagnant lid tectonics perspectives from silicate Planets Dwarf Planets large moons and large asteroids
Geoscience frontiers, 2018Co-Authors: Robert J Stern, Taras Gerya, Paul J TackleyAbstract:To better understand Earth's present tectonic style–plate tectonics–and how it may have evolved from single plate (stagnant lid) tectonics, it is instructive to consider how common it is among similar bodies in the Solar System. Plate tectonics is a style of convection for an active planetoid where lid fragment (plate) motions reflect sinking of dense lithosphere in subduction zones, causing upwelling of asthenosphere at divergent plate boundaries and accompanied by focused upwellings, or mantle plumes; any other tectonic style is usefully called “stagnant lid” or “fragmented lid”. In 2015 humanity completed a 50+ year effort to survey the 30 largest Planets, asteroids, satellites, and inner Kuiper Belt objects, which we informally call “planetoids” and use especially images of these bodies to infer their tectonic activity. The four largest planetoids are enveloped in gas and ice (Jupiter, Saturn, Uranus, and Neptune) and are not considered. The other 26 planetoids range in mass over 5 orders of magnitude and in diameter over 2 orders of magnitude, from massive Earth down to tiny Proteus; these bodies also range widely in density, from 1000 to 5500 kg/m3. A gap separates 8 silicate planetoids with density = 3000 kg/m3or greater from 20 icy planetoids (including the gaseous and icy giant Planets) with density = 2200 kg/m3 or less. We define the “Tectonic Activity Index” (TAI), scoring each body from 0 to 3 based on evidence for recent volcanism, deformation, and resurfacing (inferred from impact crater density). Nine planetoids with TAI = 2 or greater are interpreted to be tectonically and convectively active whereas 17 with TAI <2 are inferred to be tectonically dead. We further infer that active planetoids have lithospheres or icy shells overlying asthenosphere or water/weak ice. TAI of silicate (rocky) planetoids positively correlates with their inferred Rayleigh number. We conclude that some type of stagnant lid tectonics is the dominant mode of heat loss and that plate tectonics is unusual. To make progress understanding Earth's tectonic history and the tectonic style of active exoPlanets, we need to better understand the range and controls of active stagnant lid tectonics.
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stagnant lid convection in bottom heated thin 3 d spherical shells influence of curvature and implications for Dwarf Planets and icy moons
Journal of Geophysical Research, 2014Co-Authors: Chloe Yao, Frederic Deschamps, J P Lowman, Carmen Sanchezvalle, Paul J TackleyAbstract:Because the viscosity of ice is strongly temperature dependent, convection in the ice layers of icy moons and Dwarf Planets likely operates in the stagnant lid regime, in which a rigid lid forms at the top of the fluid and reduces the heat transfer. A detailed modeling of the thermal history and radial structure of icy moons and Dwarf Planets thus requires an accurate description of stagnant lid convection. We performed numerical experiments of stagnant lid convection in 3-D spherical geometries for various ice shell curvatures f (measured as the ratio between the inner and outer radii), effective Rayleigh number Ram, and viscosity contrast Δ�� . From our results, we derived scaling laws for the average temperature of the well-mixed interior, �� m, and the heat flux transported through the shell. The nondimensional temperature difference across the bottom thermal boundary layer is well described by (1 − �� m )= 1.23 �� f 1.5 ,
William B Mckinnon - One of the best experts on this subject based on the ideXlab platform.
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geologically diverse pluto and charon implications for the Dwarf Planets of the kuiper belt
Annual Review of Earth and Planetary Sciences, 2021Co-Authors: Jeffrey M Moore, William B MckinnonAbstract:Pluto and Charon are strikingly diverse in their range of geologies, surface compositions, and crater retention ages. This is despite the two having similar densities and presumed bulk compositions...
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the solar nebula origin of 486958 arrokoth a primordial contact binary in the kuiper belt
Science, 2020Co-Authors: William B Mckinnon, O M Umurhan, D C Richardson, J C Marohnic, James Tuttle Keane, W M Grundy, D P Hamilton, David NesvornýAbstract:INTRODUCTION The close flyby of the Kuiper Belt object (486958) Arrokoth (formerly 2014 MU69) by NASA’s New Horizons spacecraft revealed details of the body’s structure, geology, and composition. Arrokoth is a member of the cold classical component of the Kuiper Belt, a population of Dwarf Planets and smaller bodies thought to be only modestly dynamically or collisionally disturbed, unlike the asteroids of the inner Solar System, comets, or other groups of Kuiper Belt objects. Data from this flyby provides the opportunity to observe the results of primordial planetesimal accretion, largely unobscured by later geological or dynamical processes. RATIONALE Planetesimal formation is an unsolved problem in planetary science. Many mechanisms have been proposed in which small solid particles (dust and pebbles) agglomerate into planetesimals and ultimately into Planets. The flyby of Arrokoth provides data that constrain planetesimal formation theories and allow us to construct models of Arrokoth’s specific physical characteristics. The accretion processes that operated in the cold classical region of the Kuiper Belt during the formation of the Solar System are expected to have also occurred elsewhere in the protosolar nebula. Arrokoth is a contact binary about 35 km long composed of two unequally sized lobes. Each lobe is flattened or lenticular in shape, and the planes of flattening of both (determined from their principal axes) are closely aligned, to within 5°. The smaller lobe is slightly oblong, with its long axis pointing down the long axis of the binary as a whole (to within 5°). The surface and overall structure of Arrokoth do not display any obvious signs of catastrophic or subcatastrophic collision, and the join or neck between the two lobes is narrow. Each lobe is compositionally similar to within the precision of spectral measurements. RESULTS We show that stresses in the neck region today are compatible with the structural integrity of Arrokoth for densities (several 100 kg m−3) and material strengths (a few kilopascals) similar to those observed in comets, but at mass scales ~1000 times the mass of typical cometary nuclei. We performed numerical simulations of collisions between two bodies on the scale of the two lobes of Arrokoth, assuming those density and strength parameters. We found that impacts at or greater than their mutual escape speed (a few meters per second) would have been highly damaging. The close geometric alignment of the lobes is highly unlikely to the be the result of a chance collision alone but can be readily understood as the result of tidal evolution of a tight, co-orbiting binary. This requires a mechanism to extract angular momentum from the binary orbit, causing the orbit to shrink, and the two components to gently merge. Numerical models show that overdense concentrations of particles in the protosolar gas nebula can become gravitationally unstable and collapse to form planetesimals. The angular momentum in the simulated pebble clouds is high enough that formation of co-orbiting binaries is efficient and with binary characteristics that are a good match to binaries observed in the Kuiper Belt today. We examined a range of mechanisms to extract or transfer angular momentum from a co-orbiting binary and drive an ultimate merger, including mutual tides, tidal effects of the Sun (Kozai-Lidov oscillations), collisions with smaller Kuiper Belt objects, the ejection of third bodies, asymmetric radiation forces, and gas drag. We found that for bodies the size of Arrokoth, gas drag may be most effective in this merger process over the lifetime of the protosolar nebula. CONCLUSION We show that models of Arrokoth’s formation and evolution support accretion of the binary through the gravitational collapse of an overdense pebble cloud in the presence of protosolar nebular gas, either as a contact binary initially or as a co-orbiting binary that later inspiraled and gently merged. Similar accretional processes and binary planetesimal formation likely occurred throughout the early Solar System.
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convection in a volatile nitrogen ice rich layer drives pluto s geological vigour
Nature, 2016Co-Authors: William B Mckinnon, F Nimmo, Teresa Wong, P Schenk, O L White, J H Roberts, Jeffrey M Moore, J R Spencer, Alan D Howard, O M UmurhanAbstract:The volatile-ice-filled basin informally named Sputnik Planum is central to Pluto’s geological activity; this ice layer is organized into cells or polygons, and it is now shown that convective overturn in a several-kilometre-thick layer of solid nitrogen can explain both the presence of the cells and their great width. NASA's New Horizons spacecraft has revealed fascinating details of the surface of Pluto, including a vast ice-filled basin known as Sputnik Planum, which is central to Pluto's geological activity. Much of the surface of Sputnik Planum, consisting mostly of nitrogen ice, is divided into irregular polygons that are tens of kilometres in diameter and whose centres rise tens of metres above their sides. Two papers in this issue of Nature analyse New Horizons images of this polygonal terrain. Both conclude that it is continually being resurfaced by convection, but arrive at contrasting models for the process. Alexander Trowbridge et al. report a parameterized convection model in which the nitrogen ice is vigorously convecting, ten or more kilometres thick and about a million years old. William McKinnon et al. — from the New Horizons team — show that 'sluggish lid' convective overturn in a several-kilometre-thick layer of solid nitrogen can explain both the presence of the cells and their great width. The vast, deep, volatile-ice-filled basin informally named Sputnik Planum is central to Pluto’s vigorous geological activity1,2. Composed of molecular nitrogen, methane, and carbon monoxide ices3, but dominated by nitrogen ice, this layer is organized into cells or polygons, typically about 10 to 40 kilometres across, that resemble the surface manifestation of solid-state convection1,2. Here we report, on the basis of available rheological measurements4, that solid layers of nitrogen ice with a thickness in excess of about one kilometre should undergo convection for estimated present-day heat-flow conditions on Pluto. More importantly, we show numerically that convective overturn in a several-kilometre-thick layer of solid nitrogen can explain the great lateral width of the cells. The temperature dependence of nitrogen-ice viscosity implies that the ice layer convects in the so-called sluggish lid regime5, a unique convective mode not previously definitively observed in the Solar System. Average surface horizontal velocities of a few centimetres a year imply surface transport or renewal times of about 500,000 years, well under the ten-million-year upper-limit crater retention age for Sputnik Planum2. Similar convective surface renewal may also occur on other Dwarf Planets in the Kuiper belt, which may help to explain the high albedos shown by some of these bodies.
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evolution of icy satellites
Space Science Reviews, 2010Co-Authors: Gerald Schubert, William B Mckinnon, F Sohl, H Hussmann, V Lainey, D L Matson, Christophe Sotin, G Tobie, D Turrini, T Van HoolstAbstract:Evolutionary scenarios for the major satellites of Jupiter, Saturn, Neptune, and Pluto-Charon are discussed. In the Jovian system the challenge is to understand how the present Laplace resonance of Io, Europa, and Ganymede was established and to determine whether the heat being radiated by Io is in balance with the present tidal dissipation in the moon. In the Saturnian system, Enceladus and Titan are the centers of attention. Tidal heating is the likely source of activity at the south pole of Enceladus, although the details of how the heating occurs are not understood. An evolutionary scenario based on accretion and internal differentiation is presented for Titan, whose present substantial orbital eccentricity is not associated with any dynamical resonance. The source and maintenance of methane in Titan’s present atmosphere remain uncertain. Though most attention on the Saturnian moons focuses on Titan and Enceladus, the mid-size satellites Iapetus, Rhea, Tethys, and the irregular satellite Phoebe also draw our interest. An evolutionary scenario for Iapetus is presented in which spin down from an early rapidly rotating state is called upon to explain the satellite’s present oblate shape. The prominent equatorial ridge on Iapetus is unexplained by the spin down scenario. A buckling instability provides another possible explanation for the oblateness and equatorial ridge of Iapetus. Rhea is the only medium-size Saturnian satellite for which there are gravity data at present. The interpretation of these data are uncertain, however, since it is not known if Rhea is in hydrostatic equilibrium. Pluto and Charon are representative of the icy Dwarf Planets of the Kuiper belt. Did they differentiate as they evolved, and do either of them have a subsurface liquid water ocean? New Horizons might provide some answers when it arrives at these bodies.
Hilke E Schlichting - One of the best experts on this subject based on the ideXlab platform.
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a single sub kilometre kuiper belt object from a stellar occultation in archival data
Nature, 2009Co-Authors: MARTIN WENZ, Edmund P. Nelan, Mario Livio, A Galyam, Eran O. Ofek, Ramazan Sari, Hilke E Schlichting, Shay ZuckerAbstract:Kuiper belt objects occupy a region of the Solar System beyond the orbit of Neptune. Many — including the Dwarf Planets Pluto, Haumea and Makemake — are more than 100 km in diameter. At the opposite end of the scale, sub-kilometre-sized objects cannot be observed directly. But they should be detectable as occultations of background stars and one such detection is now reported. A survey of archival data reveals an occultation by a body with a radius of about 500 metres at a distance of 45 astronomical units (Neptune orbits at about 30 AU) from the Sun. The fact that just one event was found in the survey suggests a deficit of sub-kilometre bodies, compared to that expected from extrapolation of the population of '50-km' bodies: this may mean that the smaller Kuiper belt objects are gradually disappearing as they collide with one another. The Kuiper belt is a remnant of the primordial Solar System. Small, sub-kilometre-sized, Kuiper belt objects elude direct detection, but the signature of their occultations of background stars should be detectable. Analysis of archival data now reveals an occultation by a body with an approximately 500-metre radius at a distance of 45 astronomical units. The detection of only one event reveals a deficit of sub-kilometre-sized Kuiper belt objects and implies that these small bodies are undergoing collisional erosion. The Kuiper belt is a remnant of the primordial Solar System. Measurements of its size distribution constrain its accretion and collisional history, and the importance of material strength of Kuiper belt objects1,2,3,4. Small, sub-kilometre-sized, Kuiper belt objects elude direct detection, but the signature of their occultations of background stars should be detectable5,6,7,8,9. Observations at both optical10 and X-ray11 wavelengths claim to have detected such occultations, but their implied abundances are inconsistent with each other and far exceed theoretical expectations. Here we report an analysis of archival data that reveals an occultation by a body with an approximately 500-metre radius at a distance of 45 astronomical units. The probability of this event arising from random statistical fluctuations within our data set is about two per cent. Our survey yields a surface density of Kuiper belt objects with radii exceeding 250 metres of , ruling out inferred surface densities from previous claimed detections by more than 5σ. The detection of only one event reveals a deficit of sub-kilometre-sized Kuiper belt objects compared to a population extrapolated from objects with radii exceeding 50 kilometres. This implies that sub-kilometre-sized objects are undergoing collisional erosion, just like debris disks observed around other stars.
Shay Zucker - One of the best experts on this subject based on the ideXlab platform.
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a single sub kilometre kuiper belt object from a stellar occultation in archival data
Nature, 2009Co-Authors: MARTIN WENZ, Edmund P. Nelan, Mario Livio, A Galyam, Eran O. Ofek, Ramazan Sari, Hilke E Schlichting, Shay ZuckerAbstract:Kuiper belt objects occupy a region of the Solar System beyond the orbit of Neptune. Many — including the Dwarf Planets Pluto, Haumea and Makemake — are more than 100 km in diameter. At the opposite end of the scale, sub-kilometre-sized objects cannot be observed directly. But they should be detectable as occultations of background stars and one such detection is now reported. A survey of archival data reveals an occultation by a body with a radius of about 500 metres at a distance of 45 astronomical units (Neptune orbits at about 30 AU) from the Sun. The fact that just one event was found in the survey suggests a deficit of sub-kilometre bodies, compared to that expected from extrapolation of the population of '50-km' bodies: this may mean that the smaller Kuiper belt objects are gradually disappearing as they collide with one another. The Kuiper belt is a remnant of the primordial Solar System. Small, sub-kilometre-sized, Kuiper belt objects elude direct detection, but the signature of their occultations of background stars should be detectable. Analysis of archival data now reveals an occultation by a body with an approximately 500-metre radius at a distance of 45 astronomical units. The detection of only one event reveals a deficit of sub-kilometre-sized Kuiper belt objects and implies that these small bodies are undergoing collisional erosion. The Kuiper belt is a remnant of the primordial Solar System. Measurements of its size distribution constrain its accretion and collisional history, and the importance of material strength of Kuiper belt objects1,2,3,4. Small, sub-kilometre-sized, Kuiper belt objects elude direct detection, but the signature of their occultations of background stars should be detectable5,6,7,8,9. Observations at both optical10 and X-ray11 wavelengths claim to have detected such occultations, but their implied abundances are inconsistent with each other and far exceed theoretical expectations. Here we report an analysis of archival data that reveals an occultation by a body with an approximately 500-metre radius at a distance of 45 astronomical units. The probability of this event arising from random statistical fluctuations within our data set is about two per cent. Our survey yields a surface density of Kuiper belt objects with radii exceeding 250 metres of , ruling out inferred surface densities from previous claimed detections by more than 5σ. The detection of only one event reveals a deficit of sub-kilometre-sized Kuiper belt objects compared to a population extrapolated from objects with radii exceeding 50 kilometres. This implies that sub-kilometre-sized objects are undergoing collisional erosion, just like debris disks observed around other stars.
