DOCSLIB.ORG

Current Understandings and Future Perspectives for Research of Icy Moons

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Current Understandings and Future Perspectives for Research of Icy Moons Current understandings and future perspectives for research of icy moons Jun Kimura Osaka University Is there a life elsewhere in the universe? Pursuing this question is a fundamental part for human beings, and a clue to the answer of this question may be found on the icy moons around giant planets. After magnificent achievements of the Cassini, Galileo and Voyager spacecraft missions, the existence of a thick liquid water layer underneath solid ice crusts with various icy tectonic features has been inferred for several icy moons. Such liquid layers are now understood as subsurface oceans. To date, the evidence for oceans is not fully conclusive and mainly based on electro-magnetic induction signals, surface morphology and thermal modeling. In addition, hydrated salts on surface and water pluming including non-water volatiles and organics support to exist the subsurface ocean and the environment to emerge and sustain life there. In the following, I review our current knowledge for the icy moons in terms of interior, surface tectonics, chemical composition and habitability, and also present possible science research targets and exploration missions in future. On each giant planet system, only one or two explorations have been performed to date. No spacecraft explorations orbiting icy moons have not yet been achieved and there are still many big issues to be solved for direct investigation of extra-terrestrial life. ⽔星 惑星・準惑星・ (直径150km以上の) 衛星 ⾦星 地球系 ⽕星系 ⽊星系 ⼟星系 天王星系 海王星系 カイパーベルト Pluto Amalthea Janus 衛星研究の現状と将来展望 Eris Haumea Makemake Larissa 5268 km Galatea Ceres Despina Sycorax 惑星以外の37天体は 木村 淳 （大阪大学） correct relative sizes 惑星圏研究会＠東北大学 28th Feb., 2018 Himalia Science of icy moons Spacecraft Explorations History of Outer Solar System Juno Interior Atmo/Magnetosphere Galileo Cassini •Ocean: depth, thick, composition • (Tomoki‐san’s & Shimizu‐san’s talk) • Degree and timing of layering • When magnetosphere formed? • Type of “Rock” •Chemical reactions (Titan) Habitability Voyager 1 Voyager 2 Pioneer 10 Tectonics Composition Pioneer 11 • Origin of crustal stress • Identification of organics New Horizons • Ice rheology • Primordial? Delivered? • Subduction/material transfer • Oxidants/Reductants flux •Geologic age • Role of clathrates Moons & Interior • Bulk density! (Radius & mass) dwarf planets Pluto • Geodetic measurements 1.9 3.5 1.1 1.3 1.3 1.9 1.2 Eris • Global shape, Gravity field 1.6 2.0 1.5 1.0 1.6 2.5 Haumea • Tidal responses (deformation, libration, obliquity) 3.3 g/cc 3.0 1.5 1.4 • Moment of Inertia Makemake ? 1.2 2.6‐3.3? >1.4 1.7 • Electro‐Magnetic responses 1.9 • Inductive M‐field, Aurora 1.9 Ceres 1.6 2.2 • Radar/Radio wave Most of moons & dwarf planets 1.8 0.5 have a surface composed mostly • Plume dynamics of ice. • Seismological measurements 1.1 Entire ice abundance? Bulk density 1.6 Water = 1.0 g/cc Rock = 3.0‐3.5 5.5 How can we know about ice abundance (ice/rock ratio)? Interior • Bulk density! (Radius and mass) Bulk density (Rock wt frac.) vs. Radius • Geodetic measurements • Global shape, Gravity field • Tidal responses (deformation, libration, obliquity) ~1.0 large response = soft interior (e.g., ocean) I=0.4 ~3.0 ? I<0.4 Eris • Moment of Inertia 2.0 g/cc 2.0 g/cc Small MoI = high deg of mass concentration • I=0.346 Electro‐Magnetic responses 0.311 • Inductive magnetic field, Aurora 0.355 (e.g., salty ocean) Assuming: int. conductivity 表層200km厚 がH O Water = 1.0 g/cc 2 表層1500km • 0.341 厚が Rock = 3.5 Radar/Radio wave H2O • Plume dynamics 0.33‐34? 表層30km厚 • Seismological measurements がH O 2 Magnetic field Atmosphere/ionosphere HST G140L spectra Hall+ 1998 • Inductive field (Eu, Ga, Ca), depends on… • Thin, radiolytically/thermally‐formed • Eu (O , 0.1uPa), Ga (O , 1uPa), Ca (CO , 0.8uPa), • Primary field changing and subsurface ocean properties; depth, 2 2 2 Rh (O2,CO2), Di (CO2), Tt (CO2) thickness and conductivity (Galileo MAG couldn’t discern, but JUICE MAG will!) • Metallic core driven field (Ga) • Convection in the molten core : recently induced? Reflected sunlight model • When the core has been formed? • Accretional heat is insufficient (cold start). Johnson+ 2004 CMB温度 • If the core has a low eutectic point • Thin, volcanically‐formed Excess oxygen line emission is interpreted as airglow (e.g., FeS‐Fe O , 1250 K) from tenuous oxygen atms. 3 4 , only radiogenic heat • Io (SO2, 0.1u‐0.1mPa), En (H2O), Tr (N2, 1Pa) could form the core later (Kimura in prep.). 核内断熱温度勾配 • Thick, Earth‐like (Titan) CMB熱流量 • How to know the timing of core formation • 1.45 atm@surface, N2 (97%), CH4 (2.7%), H2 and of starting dynamo? [Kimura+, 2009] (0.1%), hydrocarbons, tholins, lack of noble gases. • Climate (CH ‐C H ‐circulation: cloud, rain and lake, season) • e.g., Irradiated alteration signature on surface? 4 2 6 (Tomoki‐san’s talk) Eu=Europa, Ga=Ganymede, Ca=Callisto En=Enceladus, Rh=Rhea, Di=Dione, Tt=Titania, Tr=Triton Surface Morphology/Tectonics Coloring agent and process • Linear deformation: • Spotted deformation: • Agents: non‐H2O compounds crack, ridge, fault, band, groove… chaos, macula, lenticula… Rocks, organics, salts(?), acids(?)… • Lithospheric stress • Localized heat from below NaCl: 10 keV electrons, Europa • Processes: Icy sublimation and irradiation 20.9h 465 Grad dose Europa Iapetus Kimura+ 2011 4 Gyr Hand and Carlson 2016 Moore+ 1999 • Impact crater: Europa central peak/pit, rampart, multi‐ring, palimpsest… 10 km Surface Morphology/Tectonics How drive surface tectonics Ocean thickness evolution of Europa • Linear deformation: crack, ridge, fault, band, groove… 1565 Schematic view of stress build‐up and tectonism Water layer • Lithospheric stress stress source & ice shell thickness/rheology Rocky mantle 1428 Europa • Global: tide, nonsynchronous rotation, Metallic 575 polar wander, volume change core Ocean duration highly • Local: convection, flexure, impact depends on the ice rheology Europa stress field under perijove (Harada & Kurita, 2006) 1015 (CI) Tidal and/or convective stress w/ shorter timescale Kimura+ 2007, Kimura in prep.170220‐6‐7‐9‐8 Kimura+ 2007 Surface tensile stress build‐up w/ time Ocean freezing generates volume change Nimmo & Gaidos, 2002 0.1 MPa Caveat: and surface tensile stress Insufficient for Tensile strength of water ice ice strength Lithosphere viscosity 1023 Pas Solid‐state conv. in the shell Shear heating? Kimura+ 2007 Icy Plate Tectonics? Icy Plate Tectonics? • Missing surface area to balance the observed extension • Missing surface area to balance the observed extension • Transporting surface materials (e.g., irradiated‐formed oxidants) in • Transporting surface materials (e.g., irradiated‐formed oxidants) in deep? deep? Tectonic reconstruction Shell dynamics highly depends on the ice shell thickness/rheology Kattenhorn and Prockter, 2014 Surface Morphology/Tectonics Surface Morphology/Tectonics • Spotted deformation: • Linear deformation: • Spotted deformation: chaos, macula, lenticula… crack, ridge, fault, band, groove… chaos, macula, lenticula… Structure and dynamics • Localized heat from below • Lithospheric stress • Localized heat from below of the ice shell Europa Europa Europa • Solid‐state ice convection • Shallow ocean • Melt pocket in the shell Depends on interior evolution & Ice shell thickness changing 40 km Thin conductive shell period? Thick convective shell period? • Impact crater: Europa central peak/pit, rampart, multi‐ring, palimpsest… Collins & Nimmo, 2009 Sotin+, 2002 10 km 10 km Surface Morphology/Tectonics Cratering rates and estimated age are highly ambiguous 10 Projectiles Halley‐type + Callisto Projectiles [km‐2 yr‐1] population based Long‐period comet • Impact Crater: central peak/pit, rampart, multi‐ring, population based on Triton’s CSFD Smith+ 1981 1 palimpsest… on Eu & Ga’s CSFD • Size‐depth rel.: larger craters penetrate deeper 0.1 Reflects heat flux, ice shell thickness and Depth (km) 0.01 0.1 1 10 100 rheology mainly when the crater was formed. Diameter (km) 10 Dones+ 2009 Ganymede and Callisto Ganymede 1 Saturnian moons 0.1 30 km Depth (km) Cratering rates could be changed >10 times 0.01 0.1 1 10 100 Dones+ 2009 because of unknown population of projectiles Europa Diameter (km) to form crater with D>10km 10 Europa 1 Quite different than rocky planets Estimated ages have a great uncertainty 10 km (e.g., Mimas’ age ~4.4 Gyr? or 0.75 Gyr?). 0.1 • Size‐freq. distribution: surface age estimation Depth (km) Need to know a population of ecliptic 0.01 Large ambiguity (~Gyr) : low res. image & unk. impact flux 0.1 1 10 100 comets (e.g., by impact flash of Giant Planets?). Diameter (km) Schenk, 2002 CSFD=Cater Size‐Frequency Distribution Chemical composition Water + plume(s) Enceladus • Constraints: Bulk density, IR/UV reflectance, plume analysis • ~100 indv. jets in some cases turn on/off • no systematic relation to orbital phase • Major: H O and Rock (CI‐chondritic? should be confirmed by future Trojan expl.) 2 • ~1 km/s (vapor), ~10s m/s (grain), ~ 100 kg/s • Minor: no‐H2O ices, Salts, Acids, Organics SP • Comet‐like compositions CO , SO , CH , H SO C H , Europa by Keck Tele. IR 2 2 4 MgSO4, 2 4 x y • Gas: H O, CO , CH , NH , organics NH , N , CO Na SO H CO, 2 2 4 3 3 2 2 4 2 4 • Solid: H O, NaCl, carbonates, silica CH3CHO, SO Porco+ 2006 2 Ganymede CO2 abs. 2 (4.26 um) map by Galileo CH3OH, H Dark old Enceladus 3.44 um HCN cratered abs. by Cassini Europa terrain • 3~4 jets in some cases turn on/off O ice 2 • Bright ~ 1 km/s, ~ 500 kg/s/plume Organics younger Pure H • terrain (C‐H stretch) Not all observations could detect. • Likely
Load more

Recommended publications
  • “Savage and Deformed”: Stigma As Drama in the Tempest Jeffrey R
    “Savage and Deformed”: Stigma as Drama in The Tempest Jeffrey R. Wilson The dramatis personae of The Tempest casts Caliban as “asavageand deformed slave.”1 Since the mid-twentieth century, critics have scrutinized Caliban’s status as a “slave,” developing a riveting post-colonial reading of the play, but I want to address the pairing of “savage and deformed.”2 If not Shakespeare’s own mixture of moral and corporeal abominations, “savage and deformed” is the first editorial comment on Caliban, the “and” here Stigmatized as such, Caliban’s body never comes to us .”ס“ working as an uninterpreted. It is always already laden with meaning. But what, if we try to strip away meaning from fact, does Caliban actually look like? The ambiguous and therefore amorphous nature of Caliban’s deformity has been a perennial problem in both dramaturgical and critical studies of The Tempest at least since George Steevens’s edition of the play (1793), acutely since Alden and Virginia Vaughan’s Shakespeare’s Caliban: A Cultural His- tory (1993), and enduringly in recent readings by Paul Franssen, Julia Lup- ton, and Mark Burnett.3 Of all the “deformed” images that actors, artists, and critics have assigned to Caliban, four stand out as the most popular: the devil, the monster, the humanoid, and the racial other. First, thanks to Prospero’s yarn of a “demi-devil” (5.1.272) or a “born devil” (4.1.188) that was “got by the devil himself” (1.2.319), early critics like John Dryden and Joseph War- ton envisioned a demonic Caliban.4 In a second set of images, the reverbera- tions of “monster” in The Tempest have led writers and artists to envision Caliban as one of three prodigies: an earth creature, a fish-like thing, or an animal-headed man.
    [Show full text]
  • Self-Organizing Systems in Planetary Physics: Harmonic Resonances Of
    Self-Organizing Systems in Planetary Physics : Harmonic Resonances of Planet and Moon Orbits Markus J. Aschwanden1 1) Lockheed Martin, Solar and Astrophysics Laboratory, Org. A021S, Bldg. 252, 3251 Hanover St., Palo Alto, CA 94304, USA; e-mail: [email protected] ABSTRACT The geometric arrangement of planet and moon orbits into a regularly spaced pattern of distances is the result of a self-organizing system. The positive feedback mechanism that operates a self-organizing system is accomplished by harmonic orbit resonances, leading to long-term stable planet and moon orbits in solar or stellar systems. The distance pattern of planets was originally described by the empirical Titius-Bode law, and by a generalized version with a constant geometric progression factor (corresponding to logarithmic spacing). We find that the orbital periods Ti and planet distances Ri from the Sun are not consistent with logarithmic spacing, 2/3 2/3 but rather follow the quantized scaling (Ri+1/Ri) = (Ti+1/Ti) = (Hi+1/Hi) , where the harmonic ratios are given by five dominant resonances, namely (Hi+1 : Hi)=(3:2), (5 : 3), (2 : 1), (5 : 2), (3 : 1). We find that the orbital period ratios tend to follow the quantized harmonic ratios in increasing order. We apply this harmonic orbit resonance model to the planets and moons in our solar system, and to the exo-planets of 55 Cnc and HD 10180 planetary systems. The model allows us a prediction of missing planets in each planetary system, based on the quasi- regular self-organizing pattern of harmonic orbit resonance zones. We predict 7 (and 4) missing exo-planets around the star 55 Cnc (and HD 10180).
    [Show full text]
  • Architecture for Going to the Outer Solar System
    ARGOSY ARGOSY: ARchitecture for Going to the Outer solar SYstem Ralph L. McNutt Jr. ll solar system objects are, in principle, targets for human in situ exploration. ARGOSY (ARchitecture for Going to the Outer solar SYstem) addresses anew the problem of human exploration to the outer planets. The ARGOSY architecture approach is scalable in size and power so that increasingly distant destinations—the systems of Jupiter, Saturn, Uranus, and Neptune—can be reached with the same crew size and time require- ments. To enable such missions, achievable technologies with appropriate margins must be used to construct a viable technical approach at the systems level. ARGOSY thus takes the step past Mars in addressing the most difficult part of the Vision for Space AExploration: To extend human presence across the solar system. INTRODUCTION The Vision for Space Exploration “The reasonable man adapts himself to the world: the unreason- 2. Extend human presence across the solar system, start- able one persists in trying to adapt the world to himself. Therefore ing with a return to the Moon by the year 2020, in 1 all progress depends on the unreasonable man.” preparation for human exploration of Mars and other G. B. Shaw destinations 3. Develop the innovative technologies, knowledge, On 14 January 2004, President Bush proposed a new and infrastructures to explore and support decisions four-point Vision for Space Exploration for NASA.2 about destinations for human exploration 1. Implement a sustained and affordable human and 4. Promote international and commercial participation robotic program to explore the solar system and in exploration to further U.S.
    [Show full text]
  • Uranian and Saturnian Satellites in Comparison
    Compara've Planetology between the Uranian and Saturnian Satellite Systems - Focus on Ariel Oberon Umbriel Titania Ariel Miranda Puck Julie Cas'llo-Rogez1 and Elizabeth Turtle2 1 – JPL, California Ins'tute of Technology 2 – APL, John HopKins University 1 Objecves Revisit observa'ons of Voyager in the Uranian system in the light of Cassini-Huygens’ results – Constrain planetary subnebula, satellites, and rings system origin – Evaluate satellites’ poten'al for endogenic and geological ac'vity Uranian Satellite System • Large popula'on • System architecture almost similar to Saturn’s – “small” < 200 Km embedded in rings – “medium-sized” > 200 Km diameter – No “large” satellite – Irregular satellites • Rela'vely high albedo • CO2 ice, possibly ammonia hydrates Daphnis in Keeler gap Accre'on in Rings? Charnoz et al. (2011) Charnoz et al., Icarus, in press) Porco et al. (2007) ) 3 Ariel Titania Oberon Density(kg/m Umbriel Configuraon determined by 'dal interac'on with Saturn Configura'on determined by 'dal interac'on within the rings Distance to Planet (Rp) Configuraon determined by Titania Oberon Ariel 'dal interac'on with Saturn Umbriel Configura'on determined by 'dal interac'on within the rings Distance to Planet (Rp) Evidence for Ac'vity? “Blue” ring found in both systems Product of Enceladus’ outgassing ac'vity Associated with Mab in Uranus’ system, but source if TBD Evidence for past episode of ac'vity in Uranus’ satellite? Saturn’s and Uranus’ rings systems – both planets are scaled to the same size (Hammel 2006) Ariel • Comparatively low
    [Show full text]
  • Perfect Little Planet Educator's Guide
    Educator’s Guide Perfect Little Planet Educator’s Guide Table of Contents Vocabulary List 3 Activities for the Imagination 4 Word Search 5 Two Astronomy Games 7 A Toilet Paper Solar System Scale Model 11 The Scale of the Solar System 13 Solar System Models in Dough 15 Solar System Fact Sheet 17 2 “Perfect Little Planet” Vocabulary List Solar System Planet Asteroid Moon Comet Dwarf Planet Gas Giant "Rocky Midgets" (Terrestrial Planets) Sun Star Impact Orbit Planetary Rings Atmosphere Volcano Great Red Spot Olympus Mons Mariner Valley Acid Solar Prominence Solar Flare Ocean Earthquake Continent Plants and Animals Humans 3 Activities for the Imagination The objectives of these activities are: to learn about Earth and other planets, use language and art skills, en- courage use of libraries, and help develop creativity. The scientific accuracy of the creations may not be as im- portant as the learning, reasoning, and imagination used to construct each invention. Invent a Planet: Students may create (draw, paint, montage, build from household or classroom items, what- ever!) a planet. Does it have air? What color is its sky? Does it have ground? What is its ground made of? What is it like on this world? Invent an Alien: Students may create (draw, paint, montage, build from household items, etc.) an alien. To be fair to the alien, they should be sure to provide a way for the alien to get food (what is that food?), a way to breathe (if it needs to), ways to sense the environment, and perhaps a way to move around its planet.
    [Show full text]
  • Photometric and Spectroscopic Observations of Sycorax, Satellite of Uranus?
    A&A 376, 310–315 (2001) Astronomy DOI: 10.1051/0004-6361:20010934 & c ESO 2001 Astrophysics Photometric and spectroscopic observations of Sycorax, satellite of Uranus? J. Romon1,C.deBergh1,M.A.Barucci1, A. Doressoundiram1, J.-G. Cuby2,A.LeBras1,3,S.Dout´e4, and B. Schmitt4 1 Observatoire de Paris, Meudon, France 2 ESO, Chile 3 IAS, Orsay, France 4 Lab. de Plan´etologie de Grenoble, St Martin d’H`eres, France Received 9 May 2001 / Accepted 26 June 2001 Abstract. Sycorax is the brightest of the five irregular Uranian satellites recently discovered. These satellites are supposed to be captured bodies. We present visible and near-infrared photometry, as well as near-infrared spectroscopy of Sycorax. The overall shape of the spectrum is quite puzzling: it has a red slope in the visible (such as Centaurs and Transneptunian objects), whereas the reflectivity strongly decreases beyond 1 µmandis rather flat over the near-infrared range. We were not able to reproduce the spectral behaviour of Sycorax using simple materials. A rotational effect is suggested to explain the shape of the spectrum. BVRIJ magnitudes have been measured over a period of 1 hour, with five V measurements which do not show any strong variation. So only a strong change in the magnitude between the V measurements and the J measurement (30 min later) could explain the shape of the spectrum, but further investigation is required to conclude. Key words. planets and satellites: general – planets and satellites: individual: Sycorax 1. Introduction Table 1. Physical and orbital properties of Sycorax (RU = Uranian radius).
    [Show full text]
  • Vindicating Sycorax's Anti-Colonial Voice. an Overview of Some
    VINDICATING SYCORAX’S ANTI-COLONIAL VOICE. AN OVERVIEW OF SOME POSTCOLONIAL RE-WRITINGS FROM THE TEMPEST TO INDIGO XIANA VÁZQUEZ BOUZÓ Universidade de Vigo The aim of this essay is to place the Shakespearean character Sycorax as a symbol of anti- colonial and anti-patriarchal resistance. Throughout the analysis of this figure in The Tempest and its re-writings, I suggest a change from the theories that turned Caliban into an antiim- perial symbol towards a consideration of Sycorax for this role. I analyse the possibilities that this character opens in terms of re-writing, as well as the relation of the figure of the witch with her community. I also compare the ideas that Caliban personifies (including sexual violence), with those represented by Sycorax (the struggle against imperial and patriarchal forces). I ultimately defend that Sycorax fits better the position as a resistance symbol, since the strug- gles against masculine dominance must be addressed at the same level as those against imperi- alist oppressions. KEY WORDS : The Tempest , Sycorax, Indigo , anti-colonialism, anti-patriarchy. Reivindicación de la voz anti-colonial de Sycorax. Estudio de algunas reescrituras postcolo- niales desde The Tempest hasta Indigo El objetivo de este ensayo es proponer al personaje shakespeariano Sycorax como símbolo de resistencia anticolonial y antipatriarcal. A través del análisis de esta figura en The Tempest y sus reescrituras, sugiero un cambio desde las teorías que convirtieron a Caliban en un símbolo antiimperialista hacia una nueva consideración de Sycorax para este papel. Analizo las posibili- dades que este personaje abre en términos de reescritura, así como la relación entre la figura de la bruja y su comunidad.
    [Show full text]
  • Red Material on the Large Moons of Uranus: Dust from the Irregular Satellites?
    Red material on the large moons of Uranus: Dust from the irregular satellites? Richard J. Cartwright1, Joshua P. Emery2, Noemi Pinilla-Alonso3, Michael P. Lucas2, Andy S. Rivkin4, and David E. Trilling5. 1Carl Sagan Center, SETI Institute; 2University of Tennessee; 3University of Central Florida; 4John Hopkins University Applied Physics Laboratory; 5Northern Arizona University. Abstract The large and tidally-locked “classical” moons of Uranus display longitudinal and planetocentric trends in their surface compositions. Spectrally red material has been detected primarily on the leading hemispheres of the outer moons, Titania and Oberon. Furthermore, detected H2O ice bands are stronger on the leading hemispheres of the classical satellites, and the leading/trailing asymmetry in H2O ice band strengths decreases with distance from Uranus. We hypothesize that the observed distribution of red material and trends in H2O ice band strengths results from infalling dust from Uranus’ irregular satellites. These dust particles migrate inward on slowly decaying orbits, eventually reaching the classical satellite zone, where they collide primarily with the outer moons. The latitudinal distribution of dust swept up by these moons should be fairly even across their southern and northern hemispheres. However, red material has only been detected over the southern hemispheres of these moons, during the Voyager 2 flyby of the Uranian system (subsolar latitude ~81ºS). Consequently, to test whether irregular satellite dust impacts drive the observed enhancement in reddening, we have gathered new ground-based data of the now observable northern hemispheres of these moons (sub-observer latitudes ~17 – 35ºN). Our results and analyses indicate that longitudinal and planetocentric trends in reddening and H2O ice band strengths are broadly consistent across both southern and northern latitudes of these moons, thereby supporting our hypothesis.
    [Show full text]
  • Sycorax Character Profiles
    SYCORAX WANING: CHARACTER PROFILES By Russell Norris 2011 SYCORAX Background: Sycorax is a potent old witch of indeterminate age. She is banished to a remote island 18 years before The Tempest takes place and is dead long before Shakespeare’s tale begins there. To avoid execution in Algiers, Sycorax lets the sea-god Setebos impregnate her with an unholy child. She gives birth to her son Caliban, a half-human monster, alone on the island – where she lives out the closing years of her life. Sycorax is a powerful witch who draws her power from the moon via her god Setebos. While she can channel these dark lunar energies, she can’t necessarily control them. There is evidence that Shakespeare based Sycorax on the sorceress Medea from Greek mythology and I aim to colour Sycorax’s backstory with elements from Medea’s life. Among other heinous crimes, Medea murdered her own brother and children. In ancient Greece, murder of one’s own family was the most awful crime of all and three special demons were reserved to punish it: The Furies. Sycorax, for the murder of her brother and children in her youth, has been hunted by The Furies for most of her life. She has grown old moving from country to country and now, on this desolate island in the middle of the sea, The Furies are finally about to catch up with her. The “Medea” backstory: It’s worth going over the Medea legend just to fill in a few details: readers will not necessarily need to be familiar with this legend, but hopefully Sycorax Waning will inspire them to go away and find out more.
    [Show full text]
  • Irregular Satellites of the Giant Planets 411
    Nicholson et al.: Irregular Satellites of the Giant Planets 411 Irregular Satellites of the Giant Planets Philip D. Nicholson Cornell University Matija Cuk University of British Columbia Scott S. Sheppard Carnegie Institution of Washington David Nesvorný Southwest Research Institute Torrence V. Johnson Jet Propulsion Laboratory The irregular satellites of the outer planets, whose population now numbers over 100, are likely to have been captured from heliocentric orbit during the early period of solar system history. They may thus constitute an intact sample of the planetesimals that accreted to form the cores of the jovian planets. Ranging in diameter from ~2 km to over 300 km, these bodies overlap the lower end of the presently known population of transneptunian objects (TNOs). Their size distributions, however, appear to be significantly shallower than that of TNOs of comparable size, suggesting either collisional evolution or a size-dependent capture probability. Several tight orbital groupings at Jupiter, supported by similarities in color, attest to a common origin followed by collisional disruption, akin to that of asteroid families. But with the limited data available to date, this does not appear to be the case at Uranus or Neptune, while the situa- tion at Saturn is unclear. Very limited spectral evidence suggests an origin of the jovian irregu- lars in the outer asteroid belt, but Saturn’s Phoebe and Neptune’s Nereid have surfaces domi- nated by water ice, suggesting an outer solar system origin. The short-term dynamics of many of the irregular satellites are dominated by large-amplitude coupled oscillations in eccentricity and inclination and offer several novel features, including secular resonances.
    [Show full text]
  • Solar System Tables
    Solar System Physical Data Physical Properties of Solar System Members S o l a Equatorial Mass1 Density2 Gravity3 Albedo4 r S Diameter Earth=1 H O=1 Earth=1 y 2 s t e SUN 865,278 miles 1,392,530 km 332,946 1.41 27.9 n/a m MERCURY 3,032 miles 4,879 km 0.055 5.43 0.38 11% VENUS 7,521 miles 12,104 km 0.815 5.25 0.90 65% EARTH 7,926 miles 12,756 km 1 5.52 1.00 37% MARS 4,228 miles 6,805 km 0.107 3.95 0.38 15% JUPITER 88,844 miles 142,980 km 317.8 1.33 2.53 52% SATURN 74,900 miles5 120,540 km5 95.2 0.69 1.06 47% URANUS 31,764 miles 51,120 km 14.5 1.29 0.90 51% NEPTUNE 30,777 miles 49,530 km 17.2 1.64 1.14 41% PLUTO 1,433 miles 2,306 km 0.0025 2.03 0.08 30% 1Earth’s mass is 1.32 x 1025 pounds (5.97 x 1024 kg). 2Density per unit volume as compared to water. For comparsion, the density of alumium is 2.7 and iron is 7.7. 3Gravity at equator. 4Albedo is the amount of sunlight reflected by the Planet. 5Saturn without rings. Visible rings are approximately 170,000 miles (273,600 km) in diameter. Rotational Period Escape Oblateness2 Inclination (Planet’s Day) Velocity1 to Orbit3 SUN 25 to 35 days4 384 miles/s 617.5 km/s 0 7.2 5 ∞ MERCURY 58.7 days 2.6 miles/s 4.2 km/s 0 0.0 ∞ VENUS 243.0 days 6.5 miles/s 10.4 km/s 0 177.4 ∞ EARTH 1 day 6.96 miles/s 11.2 km/s 0.34% 23.4 ∞ MARS 24.62 hours 3.1 miles/s 5.0 km/s 0.74% 25.2 ∞ JUPITER 9.84 hours 37 miles/s 59.5 km/s 6.5% 3.1 ∞ SATURN 10.23 hours 22.1 miles/s 35.5 km/s 9.8% 25.3 ∞ URANUS 17.9 hours 13.2 miles/s 21.3 km/s 2.3% 97.9 ∞ NEPTUNE 19.2 hours 14.6 miles/s 23.5 km/s 1.7% 28.3 ∞ PLUTO 6.4 days 0.8 miles/s 1.3 km/s unknown 123 ∞ 1At equator.
    [Show full text]
  • SYSTEM SCIENCE and ORIGINS
    SYSTEM SCIENCE and ORIGINS Julie Casllo‐Rogez JPL/Caltech KISS WORKSHOP – SMALL BODIES INSTRUMENTS SHORT COURSE © 2012 California Institute of Technology. Government sponsorship acknowledged. Outline Introducon System science: How Cassini‐Huygens changed our understanding of satellite system formaon No system science: The Origin of Phobos/Deimos remains a mystery The way forward System Science • System exploraon encompasses rings, dust fields, satellites, planet, magnetosphere, atmospheres • Observed relaonship is a funcon of origin (common or not) and field interacon • Study of giant planet systems is key source of inFormaon to understand our Solar system, exoplanet systems – Satellites fed from Solar nebula materials Outline Introducon System science: How Cassini‐Huygens changed our understanding of satellite system formaon No system science: The Origin of Phobos/Deimos remains a mystery The way forward SATURN’S SYSTEM Why does it maer? The Saturnian system has been extensively 60 satellites explored by the Cassini Huygens mission – Largest ring system can help understand other systems 5+ different types of Home of two astrobiological targets satellites Artist’s concept CLUE # 1 - Giant Objects Embedded in A ring 100-m size objects discovered in images by their “propeller” like disturbances in passing ring material. These objects lie in 3 distinct belts inside Encke gap. Discovery of “giant” objects outside Encke gap, with sizes 0.5-1km! Some appear to be drifting radially. Tiscareno et al., DPS 2008 20 km 013-008-G Scale: SOI-041-A Wright Earhart 20 km Lindbergh Blériot Pan in Encke gap Daphnis in Keeler gap CLUE #2 – Surface Age < < < Planetocentric Impactors Odysseus on Tethys Herschel on Mimas CLUE #3 – SHAPES! The Soluon? Heterogeneous Accreon in a Ring Charnoz et al.
    [Show full text]