DOCSLIB.ORG

Tritonʼs Evolution with a Primordial Neptunian Satellite System

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Tritonʼs Evolution with a Primordial Neptunian Satellite System The Astronomical Journal, 154:208 (8pp), 2017 November https://doi.org/10.3847/1538-3881/aa9184 © 2017. The American Astronomical Society. All rights reserved. Tritonʼs Evolution with a Primordial Neptunian Satellite System Raluca Rufu1 and Robin M. Canup2,3 1 Department of Earth and Planetary Sciences, Weizmann Institute of Science, Rehovot 76100, Israel; [email protected] 2 Southwest Research Institute, Boulder, CO 80302, USA Received 2017 August 1; revised 2017 October 3; accepted 2017 October 3; published 2017 November 6 Abstract The Neptunian satellite system is unusual. The major satellites of Jupiter, Saturn, and Uranus are all in prograde, low-inclination orbits. Neptune on the other hand, has the fewest satellites, and most of the system’s mass is within one irregular satellite, Triton. Triton was most likely captured by Neptune and destroyed the primordial regular satellite system. We investigate the interactions between a newly captured Triton and a prior Neptunian satellite system. We find that a prior satellite system with a mass ratio similar to the Uranian system or smaller has a substantial likelihood of reproducing the current Neptunian system, while a more massive system has a low probability of leading to the current configuration. Moreover, Triton’s interaction with a prior satellite system may offer a mechanism to decrease its high initial semimajor axis fast enough to preserve small irregular satellites (Nereid-like) that might otherwise be lost during a prolonged Triton circularization via tides alone. Key words: planets and satellites: dynamical evolution and stability – methods: numerical 1. Introduction 105 years. Yet, it is unclear whether Triton can induce mutual collisions among such satellites before it experiences a disruptive Models of giant planet gas accretion and satellite formation collision. Due to its retrograde orbit, collisions between Triton suggest that gas giants may typically have prograde regular and a prograde moon would generally have higher relative satellite systems formed within circumplanetary gas disks velocities than those between two prograde moons. A disruptive produced during their gas accretion, consistent with the general ( collision onto Triton is inconsistent with its current inclined orbit properties of the satellite systems of Jupiter and Saturn e.g., (Jacobson 2009), as Triton would tend to re-accrete in the local Stevenson et al. 1986;Lubowetal.1999;Canup&Ward2002; Laplace plane. Mosqueira & Estrada 2003;Sasakietal.2010;Ogihara& The objective of this study is to explore how interactions ) ’ Ida 2012 . The origin of Uranus satellites remains unclear, as they (scattering or collisions) between Triton and putative prior ’ may have similarly formed as a result of Uranus limited gas satellites would have modified Tritonʼsorbitandmass.We accretion (e.g., Pollack et al. 1991; Mosqueira & Estrada 2003; evaluate whether the collisions among the primordial satellites Canup & Ward 2006), or as a result of a giant impact (e.g., are disruptive enough to create a debris disk that would Slattery et al. 1992), or a combination of both (Morbidelli accelerate Triton’s circularization, or whether Triton would et al. 2012). experience a disrupting impact first. We seek to find the mass Neptune has substantially fewer and mostly smaller satellites of the primordial satellite system that would yield the current than the other gas planets. The one massive satellite, Triton, is architecture of the Neptunian system. If the prior satellite highly inclined, therefore it was likely captured from a system is required to have a substantially different mass ratio separated KBO binary (Agnor & Hamilton 2006). If Neptune compared to Jupiter, Saturn, and Uranus, this would weaken had a primordial (pre-Triton) satellite system with a mass ratio the hypothesis that all the satellites in these systems accreted -4 of mMsat Nep ~ 10 as suggested by Canup & Ward (2006), in a similar way. Alternatively, more stochastic events (e.g., then Tritonʼs mass approaches the minimum value required for giant impacts) may have a greater influence on satellite a retrograde object to have destroyed the satellite system. Thus, formation for icy giants. the existence of Triton places an upper limit on the total mass of such a primordial system. The high initial eccentricity of Tritonʼs orbit may decay 2. Methods 9 ( by tidal dissipation in less than 10 years Goldreich et al. We perform N-body integrations using SyMBA code ) 1989; Nogueira et al. 2011 . However, the perturbations from (Duncan et al. 1998, based on previous work of Wisdom & an eccentric Triton destabilize small irregular satellites Holman 1991) of a newly captured Triton together with a 5 (Nereid-like) on a timescale of 10 years (Nogueira et al. hypothetical prograde satellite system for 107 years including 2011). Moreover, Ćuk & Gladman (2005) argue that Kozai effects of Neptuneʼs oblateness. The SyMBA code can cycles increase Triton’s mean pericenter, increasing the effectively resolve close encounters among orbiting bodies, circularization timescale beyond the age of the solar system. and perfect merger is assumed when an impact is detected. That study proposes that perturbations on pre-existing prograde We consider a primordial prograde satellite system com- satellites induced by Triton lead to mutual disruptive collisions posed of four satellites with similar mass ratios compared to between the pre-existing satellites. The resulting debris disk Neptune as Ariel, Umbriel, Titania, and Oberon to Uranus interacts with Triton and drains angular momentum from its (Laskar & Jacobson 1987). The total mass ratio of the satellite -4 orbit, reducing the circularization timescale to less than system is 1.04´ 10 (hereafter MUSats), in agreement with the common mass ratio for gaseous planets predicted by Canup & 3 Planetary Science Directorate. Ward (2006). Tritonʼs initial orbits are chosen from previous 1 The Astronomical Journal, 154:208 (8pp), 2017 November Rufu & Canup Table 1 Dynamical Survival Results: aT, Triton’s Initial Semimajor axis in Neptune Radii, qT, Triton’s Initial Pericenter in Neptune Radii, incT, Triton’s Initial Inclination # # Triton’s Survival # Triton’s Fall onto Planet # Triton’s Escape Set aRT []Nep qRT [ Nep] incT [] deg 0.3MUSats MUSats 3MUSats 0.3MUSats MUSats 3MUSats 0.3MUSats MUSats 3MUSats 1a 300 8.1 105 9 8 2 0 1 6 1 1 2 2a 300 8.1 157 10 7 3 0 3 7 0 0 0 3 300 8.1 157 10 0 1 0 10 6 0 0 3 4 1004 8.0 157 9 0 0 0 8 7 1 2 3 5 1004 8.0 105 6 4 0 1 2 4 3 4 6 6 128 8.0 157 10 2 0 0 8 10 0 0 0 7 128 8.0 105 10 5 2 0 5 7 0 0 1 8 512 8.0 157 9 1 1 0 7 5 1 2 4 9 512 8.0 105 8 4 1 0 2 5 2 4 4 10 2000 8.0 157 1 1 0 0 2 1 9 7 9 11 2000 8.0 105 2 2 1 0 2 1 8 6 8 12 300 6.8 105 10 3 2 0 2 5 0 5 3 13 512 8.0 175 10 0 0 0 9 9 0 1 1 14 300 6.8 175 10 0 0 0 10 8 0 0 2 15a 512 8.0 157 10 7 0 0 2 9 0 1 1 16a 512 8.0 105 10 7 1 0 0 3 0 3 6 17 512 12.5 157 10 4 2 0 5 5 0 1 3 18 512 17.5 157 10 6 1 0 2 4 0 2 5 19 1004 29 157 10 9 1 0 0 5 0 1 4 20 1004 37.9 157 10 9 5 0 0 0 0 1 5 Note. a Semimajor axis are similar to Ariel, Umbriel, Titania, and Oberon. studies of typical captured orbits (Nogueira et al. 2011; see Higher impact angles require higher energies to disrupt a Table 1 for full list of initial conditions). We choose to test body, as the velocity is not tangential to the normal plane. A three retrograde initial inclinations (105°, 157°, 175°). Tidal modified impact kinetic energy is required to incorporate the evolution over the simulated time is small and thus neglected geometric effects, (Nogueira et al. 2011). For each set of initial conditions, 10 ⎛ ⎞ simulations were performed with randomly varying longitude aMM12+ K* = ⎜ ⎟K* ()2 a ⎝ ⎠ of ascending nodes, argument of periapsis, and mean anomaly MM12+ of all the simulated bodies. In 16 sets of initial conditions, the assumed primordial satellites have the same ratio between the where α is the volume fraction of the smaller body (M ) semimajor axis and planet’s Hill sphere as Uranus’s satellites. 2 that intersects the second body (M1; Movshovitz et al. In four sets of initial conditions, the exact semimajor axes ) of Uranus’s satellites are assumed. Using the same initial 2016; Leinhardt & Stewart 2012 . The disrupting relation orbital parameters, we perform additional simulations with two transforms to different satellite system total mass ratios, 0.35´ 10-4 and -4 3.13´ 10 , corresponding to 0.3 MUSats and 3 MUSats, respec- KcUa* = ()3 tively. Overall, our statistics include 200 simulations for each satellite mass ratio. where c is the geometrical factor derived from the collision outcomes with three tested angles. The collisions were tested 2.1. Disruption Analysis on a limited number of impacting angles (direction of velocity We use disruption scaling laws, derived by Movshovitz et al. relative to the line connecting the centers at contact, 0°,30°, (2016) for non-hit-and-run impacts between two gravity- and 45°); therefore, we assume that the relation of c on the dominated bodies, to estimate whether the impacts recorded impact angle (θ) is given by the following step function: by the N-body code are disruptive.
Load more

Recommended publications
  • 7 Planetary Rings Matthew S
    7 Planetary Rings Matthew S. Tiscareno Center for Radiophysics and Space Research, Cornell University, Ithaca, NY, USA 1Introduction..................................................... 311 1.1 Orbital Elements ..................................................... 312 1.2 Roche Limits, Roche Lobes, and Roche Critical Densities .................... 313 1.3 Optical Depth ....................................................... 316 2 Rings by Planetary System .......................................... 317 2.1 The Rings of Jupiter ................................................... 317 2.2 The Rings of Saturn ................................................... 319 2.3 The Rings of Uranus .................................................. 320 2.4 The Rings of Neptune ................................................. 323 2.5 Unconfirmed Ring Systems ............................................. 324 2.5.1 Mars ............................................................... 324 2.5.2 Pluto ............................................................... 325 2.5.3 Rhea and Other Moons ................................................ 325 2.5.4 Exoplanets ........................................................... 327 3RingsbyType.................................................... 328 3.1 Dense Broad Disks ................................................... 328 3.1.1 Spiral Waves ......................................................... 329 3.1.2 Gap Edges and Moonlet Wakes .......................................... 333 3.1.3 Radial Structure .....................................................
    [Show full text]
  • PDF (03Ragozzine Exo-Interiors.Pdf)
    20 Chapter 2 Probing the Interiors of Very Hot Jupiters Using Transit Light Curves This chapter will be published in its entirety under the same title by authors D. Ragozzine and A. S. Wolf in the Astrophysical Journal, 2009. Reproduced by permission of the American Astro- nomical Society. 21 Abstract Accurately understanding the interior structure of extra-solar planets is critical for inferring their formation and evolution. The internal density distribution of a planet has a direct effect on the star-planet orbit through the gravitational quadrupole field created by the rotational and tidal bulges. These quadrupoles induce apsidal precession that is proportional to the planetary Love number (k2p, twice the apsidal motion constant), a bulk physical characteristic of the planet that depends on the internal density distribution, including the presence or absence of a massive solid core. We find that the quadrupole of the planetary tidal bulge is the dominant source of apsidal precession for very hot Jupiters (a . 0:025 AU), exceeding the effects of general relativity and the stellar quadrupole by more than an order of magnitude. For the shortest-period planets, the planetary interior induces precession of a few degrees per year. By investigating the full photometric signal of apsidal precession, we find that changes in transit shapes are much more important than transit timing variations. With its long baseline of ultra-precise photometry, the space-based Kepler mission can realistically detect apsidal precession with the accuracy necessary to infer the presence or absence of a massive core in very hot Jupiters with orbital eccentricities as low as e ' 0:003.
    [Show full text]
  • Orbital Lifetime Predictions
    Orbital LIFETIME PREDICTIONS An ASSESSMENT OF model-based BALLISTIC COEFfiCIENT ESTIMATIONS AND ADJUSTMENT FOR TEMPORAL DRAG co- EFfiCIENT VARIATIONS M.R. HaneVEER MSc Thesis Aerospace Engineering Orbital lifetime predictions An assessment of model-based ballistic coecient estimations and adjustment for temporal drag coecient variations by M.R. Haneveer to obtain the degree of Master of Science at the Delft University of Technology, to be defended publicly on Thursday June 1, 2017 at 14:00 PM. Student number: 4077334 Project duration: September 1, 2016 – June 1, 2017 Thesis committee: Dr. ir. E. N. Doornbos, TU Delft, supervisor Dr. ir. E. J. O. Schrama, TU Delft ir. K. J. Cowan MBA TU Delft An electronic version of this thesis is available at http://repository.tudelft.nl/. Summary Objects in Low Earth Orbit (LEO) experience low levels of drag due to the interaction with the outer layers of Earth’s atmosphere. The atmospheric drag reduces the velocity of the object, resulting in a gradual decrease in altitude. With each decayed kilometer the object enters denser portions of the atmosphere accelerating the orbit decay until eventually the object cannot sustain a stable orbit anymore and either crashes onto Earth’s surface or burns up in its atmosphere. The capability of predicting the time an object stays in orbit, whether that object is space junk or a satellite, allows for an estimate of its orbital lifetime - an estimate satellite op- erators work with to schedule science missions and commercial services, as well as use to prove compliance with international agreements stating no passively controlled object is to orbit in LEO longer than 25 years.
    [Show full text]
  • 1 Trajectory Design for the Transiting Exoplanet
    TRAJECTORY DESIGN FOR THE TRANSITING EXOPLANET SURVEY SATELLITE Donald J. Dichmann(1), Joel J.K. Parker(2), Trevor W. Williams(3), Chad R. Mendelsohn(4) (1,2,3,4)Code 595.0, NASA Goddard Space Flight Center, 8800 Greenbelt Road, Greenbelt MD 20771. 301-286-6621. [email protected] Abstract: The Transiting Exoplanet Survey Satellite (TESS) is a National Aeronautics and Space Administration (NASA) mission, scheduled to be launched in 2017. TESS will travel in a highly eccentric orbit around Earth, with initial perigee radius near 17 Earth radii (Re) and apogee radius near 59 Re. The orbit period is near 2:1 resonance with the Moon, with apogee nearly 90 degrees out-of-phase with the Moon, in a configuration that has been shown to be operationally stable. TESS will execute phasing loops followed by a lunar flyby, with a final maneuver to achieve 2:1 resonance with the Moon. The goals of a resonant orbit with long-term stability, short eclipses and limited oscillations of perigee present significant challenges to the trajectory design. To rapidly assess launch opportunities, we adapted the Schematics Window Methodology (SWM76) launch window analysis tool to assess the TESS mission constraints. To understand the long-term dynamics of such a resonant orbit in the Earth-Moon system we employed Dynamical Systems Theory in the Circular Restricted 3-Body Problem (CR3BP). For precise trajectory analysis we use a high-fidelity model and multiple shooting in the General Mission Analysis Tool (GMAT) to optimize the maneuver delta-V and meet mission constraints. Finally we describe how the techniques we have developed can be applied to missions with similar requirements.
    [Show full text]
  • Compendium of Space Debris Mitigation Standards Adopted by States and International Organizations”
    COMPENDIUM SPACE DEBRIS MITIGATION STANDARDS ADOPTED BY STATES AND INTERNATIONAL ORGANIZATIONS 17 JUNE 2021 SPACE DEBRIS MITIGATION STANDARDS TABLE OF CONTENTS Introduction ............................................................................................................................................................... 4 Part 1. National Mechanisms Algeria ........................................................................................................................................................................ 5 Argentina .................................................................................................................................................................... 7 Australia (Updated on 17 January 2020) .................................................................................................................... 8 Austria (Updated on 21 March 2016) ...................................................................................................................... 10 Azerbaijan (Added on 6 February 2019) .................................................................................................................. 13 Belgium .................................................................................................................................................................... 14 Canada...................................................................................................................................................................... 16 Chile.........................................................................................................................................................................
    [Show full text]
  • Secular Chaos and Its Application to Mercury, Hot Jupiters, and The
    Secular chaos and its application to Mercury, hot SPECIAL FEATURE Jupiters, and the organization of planetary systems Yoram Lithwicka,b,1 and Yanqin Wuc aDepartment of Physics and Astronomy and bCenter for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University, Evanston, IL 60208; and cDepartment of Astronomy and Astrophysics, University of Toronto, Toronto, ON, Canada M5S 3H4 Edited by Adam S. Burrows, Princeton University, Princeton, NJ, and accepted by the Editorial Board October 31, 2013 (received for review May 2, 2013) In the inner solar system, the planets’ orbits evolve chaotically, by including the most important MMRs (11).] It is the cause, for driven primarily by secular chaos. Mercury has a particularly cha- example, of Earth’s eccentricity-driven Milankovitch cycle. How- otic orbit and is in danger of being lost within a few billion years. ever, on timescales ≳107 years, the evolution is chaotic (e.g., Fig. Just as secular chaos is reorganizing the solar system today, so it 1), in sharp contrast to the prediction of linear secular theory. has likely helped organize it in the past. We suggest that extra- That appears to be puzzling, given the small eccentricities and solar planetary systems are also organized to a large extent by inclinations in the solar system. secular chaos. A hot Jupiter could be the end state of a secularly However, despite its importance, there has been little theo- chaotic planetary system reminiscent of the solar system. How- retical understanding of how secular chaos works. Conversely, ever, in the case of the hot Jupiter, the innermost planet was chaos driven by MMRs is much better understood.
    [Show full text]
  • NASA Process for Limiting Orbital Debris
    NASA-HANDBOOK NASA HANDBOOK 8719.14 National Aeronautics and Space Administration Approved: 2008-07-30 Washington, DC 20546 Expiration Date: 2013-07-30 HANDBOOK FOR LIMITING ORBITAL DEBRIS Measurement System Identification: Metric APPROVED FOR PUBLIC RELEASE – DISTRIBUTION IS UNLIMITED NASA-Handbook 8719.14 This page intentionally left blank. Page 2 of 174 NASA-Handbook 8719.14 DOCUMENT HISTORY LOG Status Document Approval Date Description Revision Baseline 2008-07-30 Initial Release Page 3 of 174 NASA-Handbook 8719.14 This page intentionally left blank. Page 4 of 174 NASA-Handbook 8719.14 This page intentionally left blank. Page 6 of 174 NASA-Handbook 8719.14 TABLE OF CONTENTS 1 SCOPE...........................................................................................................................13 1.1 Purpose................................................................................................................................ 13 1.2 Applicability ....................................................................................................................... 13 2 APPLICABLE AND REFERENCE DOCUMENTS................................................14 3 ACRONYMS AND DEFINITIONS ...........................................................................15 3.1 Acronyms............................................................................................................................ 15 3.2 Definitions .........................................................................................................................
    [Show full text]
  • Orbiting Debris: a Space Environmental Problem (Part 4 Of
    Orbiting Debris: A Since Environmential Problem ● 3 Table 2--of Hazardous Interference by environment. Yet, orbital debris is part of a Orbital Debris larger problem of pollution in space that in- cludes radio-frequency interference and inter- 1. Loss or damage to space assets through collision; ference to scientific observations in all parts of 2. Accidental re-entry of space hardware; the spectrum. For example, emissions at ra- 3. Contamination by nuclear material of manned or unmanned spacecraft, both in space and on Earth; dio frequencies often interfere with radio as- 4. Interference with astronomical observations, both from the tronomy observations. For several years, ground and in space; gamma-ray astronomy data have been cor- 5. Interference with scientific and military experiments in space; rupted by Soviet intelligence satellites that 14 6. Potential military use. are powered by unshielded nuclear reactors. The indirect emissions from these satellites SOURCE: Space Debris, European Space Agency, and Office of Technology As- sessment. spread along the Earth’s magnetic field and are virtually impossible for other satellites to Earth. The largest have attracted worldwide escape. The Japanese Ginga satellite, attention. 10 Although the risk to individuals is launched in 1987 to study gamma-ray extremely small, the probability of striking bursters, has been triggered so often by the populated areas still finite.11 For example: 1) Soviet reactors that over 40 percent of its available observing time has been spent trans- the U.S.S.R. Kosmos 954, which contained a 15 nuclear power source,12 reentered the atmos- mitting unintelligible “data.” All of these phere over northwest Canada in 1978, scatter- problem areas will require attention and posi- ing debris over an area the size of Austria; 2) a tive steps to guarantee access to space by all Japanese ship was hit in 1969 by pieces of countries in the future.
    [Show full text]
  • Estabilidade De Veículos Espaciais Em Ressonância
    sid.inpe.br/mtc-m21c/2018/03.12.13.05-TDI ESTABILIDADE DE VEÍCULOS ESPACIAIS EM RESSONÂNCIA Rubens Antonio Condeles Júnior Tese de Doutorado do Curso de Pós-Graduação em Engenharia e Tecnologia Espaciais/Mecânica Espacial e Controle, orientada pelos Drs. Antonio Fernando Bertachini de Almeida Prado, e Tadashi Yokoyama, aprovada em 06 de abril de 2018. URL do documento original: <http://urlib.net/8JMKD3MGP3W34R/3QMPS3E> INPE São José dos Campos 2018 PUBLICADO POR: Instituto Nacional de Pesquisas Espaciais - INPE Gabinete do Diretor (GBDIR) Serviço de Informação e Documentação (SESID) Caixa Postal 515 - CEP 12.245-970 São José dos Campos - SP - Brasil Tel.:(012) 3208-6923/6921 E-mail: [email protected] COMISSÃO DO CONSELHO DE EDITORAÇÃO E PRESERVAÇÃO DA PRODUÇÃO INTELECTUAL DO INPE (DE/DIR-544): Presidente: Maria do Carmo de Andrade Nono - Conselho de Pós-Graduação (CPG) Membros: Dr. Plínio Carlos Alvalá - Centro de Ciência do Sistema Terrestre (COCST) Dr. André de Castro Milone - Coordenação-Geral de Ciências Espaciais e Atmosféricas (CGCEA) Dra. Carina de Barros Melo - Coordenação de Laboratórios Associados (COCTE) Dr. Evandro Marconi Rocco - Coordenação-Geral de Engenharia e Tecnologia Espacial (CGETE) Dr. Hermann Johann Heinrich Kux - Coordenação-Geral de Observação da Terra (CGOBT) Dr. Marley Cavalcante de Lima Moscati - Centro de Previsão de Tempo e Estudos Climáticos (CGCPT) Silvia Castro Marcelino - Serviço de Informação e Documentação (SESID) BIBLIOTECA DIGITAL: Dr. Gerald Jean Francis Banon Clayton Martins Pereira - Serviço de Informação
    [Show full text]
  • 1 Resonant Kuiper Belt Objects
    Resonant Kuiper Belt Objects - a Review Renu Malhotra Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ, USA Email: [email protected] Abstract Our understanding of the history of the solar system has undergone a revolution in recent years, owing to new theoretical insights into the origin of Pluto and the discovery of the Kuiper belt and its rich dynamical structure. The emerging picture of dramatic orbital migration of the planets driven by interaction with the primordial Kuiper belt is thought to have produced the final solar system architecture that we live in today. This paper gives a brief summary of this new view of our solar system's history, and reviews the astronomical evidence in the resonant populations of the Kuiper belt. Introduction Lying at the edge of the visible solar system, observational confirmation of the existence of the Kuiper belt came approximately a quarter-century ago with the discovery of the distant minor planet (15760) Albion (formerly 1992 QB1, Jewitt & Luu 1993). With the clarity of hindsight, we now recognize that Pluto was the first discovered member of the Kuiper belt. The current census of the Kuiper belt includes more than 2000 minor planets at heliocentric distances between ~30 au and ~50 au. Their orbital distribution reveals a rich dynamical structure shaped by the gravitational perturbations of the giant planets, particularly Neptune. Theoretical analysis of these structures has revealed a remarkable dynamic history of the solar system. The story is as follows (see Fernandez & Ip 1984, Malhotra 1993, Malhotra 1995, Fernandez & Ip 1996, and many subsequent works).
    [Show full text]
  • Black Rain: the Burial of the Galilean Satellites in Irregular Satellite Debris
    Black Rain: The Burial of the Galilean Satellites in Irregular Satellite Debris William F: Bottke Southwest Research Institute and NASA Lunar Science Institute 1050 Walnut St, Suite 300 Boulder, CO 80302 USA [email protected] David Vokrouhlick´y Institute of Astronomy, Charles University, Prague V Holeˇsoviˇck´ach 2 180 00 Prague 8, Czech Republic David Nesvorn´y Southwest Research Institute and NASA Lunar Science Institute 1050 Walnut St, Suite 300 Boulder, CO 80302 USA Jeff Moore NASA Ames Research Center Space Science Div., MS 245-3 Moffett Field, CA 94035 USA Prepared for Icarus June 20, 2012 { 2 { ABSTRACT Irregular satellites are dormant comet-like bodies that reside on distant pro- grade and retrograde orbits around the giant planets. They were possibly cap- tured during a violent reshuffling of the giant planets ∼ 4 Gy ago (Ga) as de- scribed by the so-called Nice model. As giant planet migration scattered tens of Earth masses of comet-like bodies throughout the Solar System, some found themselves near giant planets experiencing mutual encounters. In these cases, gravitational perturbations between the giant planets were often sufficient to capture the comet-like bodies onto irregular satellite-like orbits via three-body reactions. Modeling work suggests these events led to the capture of ∼ 0:001 lu- nar masses of comet-like objects on isotropic orbits around the giant planets. Roughly half of the population was readily lost by interactions with the Kozai resonance. The remaining half found themselves on orbits consistent with the known irregular satellites. From there, the bodies experienced substantial col- lisional evolution, enough to grind themselves down to their current low-mass states.
    [Show full text]
  • NEAR of the 21 Lunar Landings, 19—All of the U.S
    Copyrights Prof Marko Popovic 2021 NEAR Of the 21 lunar landings, 19—all of the U.S. and Russian landings—occurred between 1966 and 1976. Then humanity took a 37-year break from landing on the moon before China achieved its first lunar touchdown in 2013. Take a look at the first 21 successful lunar landings on this interactive map https://www.smithsonianmag.com/science-nature/interactive-map-shows-all-21-successful-moon-landings-180972687/ Moon 1 The near side of the Moon with the major maria (singular mare, vocalized mar-ray) and lunar craters identified. Maria means "seas" in Latin. The maria are basaltic lava plains: i.e., the frozen seas of lava from lava flows. The maria cover ∼ 16% (30%) of the lunar surface (near side). Light areas are Lunar Highlands exhibiting more impact craters than Maria. The far side is pocked by ancient craters, mountains and rugged terrain, largely devoid of the smooth maria we see on the near side. The Lunar Reconnaissance Orbiter Moon 2 is a NASA robotic spacecraft currently orbiting the Moon in an eccentric polar mapping orbit. LRO data is essential for planning NASA's future human and robotic missions to the Moon. Launch date: June 18, 2009 Orbital period: 2 hours Orbit height: 31 mi Speed on orbit: 0.9942 miles/s Cost: 504 million USD (2009) The Moon is covered with a gently rolling layer of powdery soil with scattered rocks called the regolith; it is made from debris blasted out of the Lunar craters by the meteor impacts that created them.
    [Show full text]