scholarly journals Co-accretion + Giant Impact Origin of the Uranus System: Post-impact Evolution

2022 ◽  
Vol 924 (1) ◽  
pp. 6
Author(s):  
Julien Salmon ◽  
Robin M. Canup

Abstract We investigate aspects of the co-accretion + giant impact scenario proposed by Morbidelli et al. (2012) for the origin of the Uranian satellites. In this model, a regular satellite system formed during gas accretion is impulsively destabilized by a Uranus-tipping impact, producing debris that ultimately re-orients to the planet’s new equatorial plane and re-accumulates into Uranus’ current large moons. We first investigate the nodal randomization of a disk of debris resulting from disruptive collisions between the hypothesized prior satellites. Consistent with Morbidelli et al., we find that an impact-generated interior c-disk with mass ≥10−2 Uranus masses is needed to cause sufficient nodal randomization to appropriately realign the outer debris disk. We then simulate the reaccumulation of the outer debris disk into satellites and find that disks with larger initial radii are needed to produce an outer debris disk that extends to Oberon’s distance, and that Uranus’ obliquity prior to the giant impact must have been substantial, ≥40°, if its original co-accreted satellite system was broadly similar in radial scale to those at Jupiter and Saturn today. Finally, we explore the subsequent evolution of a massive, water-dominated inner c-disk as it condenses, collisionally spreads, and spawns new moons beyond the Roche limit. We find that intense tidal dissipation in Uranus (i.e., ( Q / k 2 ) U ≤ 10 2 ) is needed to prevent large icy moons spawned from the inner disk from expanding beyond the synchronous orbit, where they would be long lived and inconsistent with the lack of massive inner moons at Uranus today. We conclude that while a co-accretion + giant impact is viable it requires rather specific conditions.

2019 ◽  
Vol 885 (2) ◽  
pp. 132 ◽  
Author(s):  
Yuya Ishizawa ◽  
Takanori Sasaki ◽  
Natsuki Hosono

2021 ◽  
Author(s):  
Amirhossein Bagheri ◽  
Amir Khan ◽  
Michael Efroimsky ◽  
Mikhail Kruglyakov ◽  
Domenico Giardini

<p>The origin of the Martian moons, Phobos and Deimos, remains elusive. While the morphology and their cratered surfaces suggest an asteroidal origin, capture has been questioned because of potential dynamical difficulties in achieving the current near-circular, near-equatorial orbits. To circumvent this, in situ formation models have been proposed as alternatives. Yet, explaining the present location of the moons on opposite sides of the synchronous radius, their small sizes and apparent compositional differences with Mars has proved challenging. Here, we combine geophysical and tidal-evolution modelling of a Mars–satellite system to propose that Phobos and Deimos originated from disintegration of a common progenitor that was possibly formed in situ. We show that tidal dissipation within a Mars–satellite system, enhanced by the physical libration of the satellite, circularizes the post-disrupted eccentric orbits in <2.7 Gyr and makes Phobos descend to its present orbit from its point of origin close to or above the synchronous orbit. Our estimate for Phobos’s maximal tidal lifetime is considerably less than the age of Mars, indicating that it is unlikely to have originated alongside Mars. Deimos initially moved inwards, but never transcended the co-rotation radius because of insufficient eccentricity and therefore insufficient tidal dissipation. Whereas Deimos is very slowly receding from Mars, Phobos will continue to spiral towards and either impact with Mars or become tidally disrupted on reaching the Roche limit in <span class="stix">≲</span>39 Myr.</p>


Science ◽  
2005 ◽  
Vol 307 (5709) ◽  
pp. 546-550 ◽  
Author(s):  
R. M. Canup
Keyword(s):  

Sensors ◽  
2018 ◽  
Vol 18 (12) ◽  
pp. 4475 ◽  
Author(s):  
Zhipeng Wang ◽  
Wei Shao ◽  
Rui Li ◽  
Dan Song ◽  
Tinglin Li

Signal-In-Space User Range Errors (SIS UREs) are assumed to be overbounded by a normal distribution with a standard deviation represented by the User Range Accuracy (URA). The BeiDou Navigation Satellite System (BDS) broadcast URA is not compatible with the historical SIS URE performance that affects the Advanced Receiver Autonomous Integrity Monitoring (ARAIM) False Alert Probability (Pfa) and availability evaluation. This study compares the BDS broadcast and precise ephemeris from 1 March 2013 to 1 March 2017 to obtain SIS UREs. Through analyzing the statistical characteristics of the SIS UREs, we obtain the standard deviation σURE for the accuracy and continuity and σURA used for the integrity of the SIS UREs. The results show that the broadcast σURA of 2 m cannot completely overbound SIS UREs for all BDS satellites, but the σURA of 2.4 m can. Then, we use the σURA of 2.4 m to evaluate the ARAIM Pfa and availability. The results show that the Pfa may increase to 2 × 10−5 and exceed its limit by an order of magnitude. We also consider the differences between the SIS UREs of Geostationary Earth Orbit (GEO), Inclined Geo-Synchronous Orbit (IGSO), and Medium Earth Orbit (MEO). The results indicate that all Pfa values calculated by the computed σURE are less than the Pfa in the Integrity Support Message (ISM) for the worst-performing GEO satellite. The approximately 55% Pfa calculated by the computed σURE is less than the Pfa in ISM for the worst-performing IGSO satellite. Most Pfa values calculated by the computed σURE is less than the Pfa in the ISM for the worst-performing MEO satellite. For BDS satellites, the Pfa is mainly affected by σURE. When the σURA of 2.4 m is used to evaluate the availability, the computed availability is lower than the availability calculated by the broadcast σURA/σURE and the greatest degradation can reach 25%.


Nature ◽  
2016 ◽  
Vol 538 (7626) ◽  
pp. 487-490 ◽  
Author(s):  
Kun Wang ◽  
Stein B. Jacobsen

2020 ◽  
Vol 19 (4) ◽  
pp. 719-745
Author(s):  
Valery Volkov ◽  
Kulvits Kulvits ◽  
Aleksey Kovalenko ◽  
Vladimir Salukhov

The paper deals with issues related to optimizing the ballistic structure of a satellite system for remote sensing of the Earth. Approaches to the ballistic design of the satellite system, previously developed by specialists from various scientific schools, were focused on maintaining the structural stability of the system by deploying groupings with the same geometry and with the same inclinations, which ensured the same age-old departures of elements from all the orbits. At the same time, there is a whole range of tasks that require the formation of a satellite system in different orbits. To achieve the required level of stability of a new cluster of orbital structures we provide an approach, including: heuristic formation of many target different height orbits; identifying some basic near-circular orbit; selection of possible variants of iterative quasi-synchronous orbits; coordination of the composition of the vector of characteristics of traffic conditions and final calculation of an acceptable option that provides the specified accuracy of the route closure cycle. Testing of the proposed approach is carried out on the example of determining the parameters of orbits that ensures equality of effective days in a given range of heights. The method of selecting the degree of consideration of various physical factors of the space environment, which ensures the achievement of identical deviations of the forecast trajectory from the reference one, is presented. The characteristics of the mathematical model of quasi-synchronous orbit motion used in forecasting are calculated from the condition of stability at a given time interval. To get the appropriate estimates, we use corrections to the orbit parameters given from the Greenwich coordinate system. A detailed algorithm is described that provides the possibility of unambiguously determining the characteristics of a stable structure, in the implementation of which the transition from the solution of a normal system of equations to the solution of two triangular systems is performed. The analysis of the subject area has shown that the proposed approach is new, and the solved scientific problem belongs to the class of inverse problems of space cybernetics.


Nature ◽  
2006 ◽  
Vol 439 (7079) ◽  
pp. 946-948 ◽  
Author(s):  
S. A. Stern ◽  
H. A. Weaver ◽  
A. J. Steffl ◽  
M. J. Mutchler ◽  
W. J. Merline ◽  
...  

2007 ◽  
Vol 3 (S249) ◽  
pp. 301-303
Author(s):  
S.-L. Li ◽  
C. Agnor ◽  
D. N. C. Lin

AbstractTransit observations indicate a large dispersion in the internal structure among the known gas giants. This is a big challenge to the conventional sequential planetary formation scenario because the diversity is inconsistent with the expectation of some well defined critical condition for the onset of gas accretion in this scenario. We suggest that giant impacts may lead to the merger of planets or the accretion of planetary embryos and cause the diversity of the core mass. By using an SPH scheme, we show that direct parabolic collisions generally lead to the total coalescence of impinging gas giants whereas, during glancing collisions, the efficiency of core retention is much larger than that of the envelope. We also examine the adjustment of the gaseous envelope with a 1D Lagrangian hydrodynamic scheme. In the proximity of their host stars, the expansion of the planets' envelopes, shortly after sufficiently catastrophic impacts, can lead to a substantial loss of gas through Roche-lobe overflow. We are going to examine the possibility that the accretion of several Earth-mass objects can significantly enlarge the planets' photosphere and elevate the tidal dissipation rate over the time scale of 100 Myr.


Author(s):  
Kaveh Pahlevan

Ever since the Apollo programme, isotopic abundances have been used as tracers to study lunar formation, in particular to study the sources of the lunar material. In the past decade, increasingly precise isotopic data have been reported that give strong indications that the Moon and the Earth's mantle have a common heritage. To reconcile these observations with the origin of the Moon via the collision of two distinct planetary bodies, it has been proposed (i) that the Earth–Moon system underwent convective mixing into a single isotopic reservoir during the approximately 10 3 year molten disc epoch after the giant impact but before lunar accretion, or (ii) that a high angular momentum impact injected a silicate disc into orbit sourced directly from the mantle of the proto-Earth and the impacting planet in the right proportions to match the isotopic observations. Recently, it has also become recognized that liquid–vapour fractionation in the energetic aftermath of the giant impact is capable of generating measurable mass-dependent isotopic offsets between the silicate Earth and Moon, rendering isotopic measurements sensitive not only to the sources of the lunar material, but also to the processes accompanying lunar origin. Here, we review the isotopic evidence that the silicate–Earth–Moon system represents a single planetary reservoir. We then discuss the development of new isotopic tracers sensitive to processes in the melt–vapour lunar disc and how theoretical calculations of their behaviour and sample observations can constrain scenarios of post-impact evolution in the earliest history of the Earth–Moon system.


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