THE ASTEROID BELT AS A RELIC FROM A CHAOTIC EARLY SOLAR SYSTEM

ABSTRACT In two recent papers published in MNRAS, Namouni and Morais claimed evidence for the interstellar origin of some small Solar system bodies, including: (i) objects in retrograde co-orbital motion with the giant planets and (ii) the highly inclined Centaurs. Here, we discuss the flaws of those papers that invalidate the authors’ conclusions. Numerical simulations backwards in time are not representative of the past evolution of real bodies. Instead, these simulations are only useful as a means to quantify the short dynamical lifetime of the considered bodies and the fast decay of their population. In light of this fast decay, if the observed bodies were the survivors of populations of objects captured from interstellar space in the early Solar system, these populations should have been implausibly large (e.g. about 10 times the current main asteroid belt population for the retrograde co-orbital of Jupiter). More likely, the observed objects are just transient members of a population that is maintained in quasi-steady state by a continuous flux of objects from some parent reservoir in the distant Solar system. We identify in the Halley-type comets and the Oort cloud the most likely sources of retrograde co-orbitals and highly inclined Centaurs.

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Natural transportation routes in the Solar System

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319009438 ◽

2019 ◽

Vol 15 (S350) ◽

pp. 471-473

Author(s):

Nataša Todorović

Keyword(s):

Solar System ◽

Large Fraction ◽

Outer Part ◽

Asteroid Belt ◽

Water Molecules ◽

Early Solar System ◽

Type Water ◽

Transportation Routes

AbstractThe aim of this work is to explain the possible mechanism in the early Solar System, by which water-rich asteroids may have been delivered to Earth. Carbonaceous (C-type) asteroids, with a large fraction of water molecules, dominate in the outer part of the asteroid belt and the possibility of their migration toward Earth is still not well explained. In this work, we observe very efficient dynamical routes along which C-type water-bearing asteroids are delivered to Earth.

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Arrival and magnetization of carbonaceous chondrites in the asteroid belt before 4562 million years ago

Communications Earth & Environment ◽

10.1038/s43247-020-00055-w ◽

2020 ◽

Vol 1 (1) ◽

Author(s):

Timothy O’Brien ◽

John A. Tarduno ◽

Atma Anand ◽

Aleksey V. Smirnov ◽

Eric G. Blackman ◽

...

Keyword(s):

Solar System ◽

Arrival Time ◽

Carbonaceous Chondrite ◽

Parent Body ◽

Asteroid Belt ◽

Carbonaceous Chondrites ◽

Early Solar System ◽

Outer Disk ◽

Main Asteroid Belt ◽

Insight Into

AbstractMeteorite magnetizations can provide rare insight into early Solar System evolution. Such data take on new importance with recognition of the isotopic dichotomy between non-carbonaceous and carbonaceous meteorites, representing distinct inner and outer disk reservoirs, and the likelihood that parent body asteroids were once separated by Jupiter and subsequently mixed. The arrival time of these parent bodies into the main asteroid belt, however, has heretofore been unknown. Herein, we show that weak CV (Vigarano type) and CM (Mighei type) carbonaceous chondrite remanent magnetizations indicate acquisition by the solar wind 4.2 to 4.8 million years after Ca-Al-rich inclusion (CAI) formation at heliocentric distances of ~2–4 AU. These data thus indicate that the CV and CM parent asteroids had arrived near, or within, the orbital range of the present-day asteroid belt from the outer disk isotopic reservoir within the first 5 million years of Solar System history.

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Exploring the Bimodal Solar System via Sample Return from the Main Asteroid Belt: The Case for Revisiting Ceres

Space Science Reviews ◽

10.1007/s11214-020-00671-0 ◽

2020 ◽

Vol 216 (4) ◽

Cited By ~ 1

Author(s):

Thomas H. Burbine ◽

Richard C. Greenwood

Keyword(s):

Solar System ◽

Asteroid Belt ◽

Early Solar System ◽

Main Belt ◽

Sample Return ◽

Dawn Mission ◽

Overwhelming Evidence ◽

Sample Return Mission ◽

The Rich ◽

Cost Implications

Abstract Sample return from a main-belt asteroid has not yet been attempted, but appears technologically feasible. While the cost implications are significant, the scientific case for such a mission appears overwhelming. As suggested by the “Grand Tack” model, the structure of the main belt was likely forged during the earliest stages of Solar System evolution in response to migration of the giant planets. Returning samples from the main belt has the potential to test such planet migration models and the related geochemical and isotopic concept of a bimodal Solar System. Isotopic studies demonstrate distinct compositional differences between samples believed to be derived from the outer Solar System (CC or carbonaceous chondrite group) and those that are thought to be derived from the inner Solar System (NC or non-carbonaceous group). These two groups are separated on relevant isotopic variation diagrams by a clear compositional gap. The interface between these two regions appears to be broadly coincident with the present location of the asteroid belt, which contains material derived from both groups. The Hayabusa mission to near-Earth asteroid (NEA) (25143) Itokawa has shown what can be learned from a sample-return mission to an asteroid, even with a very small amount of sample. One scenario for main-belt sample return involves a spacecraft launching a projectile that strikes an object and flying through the debris cloud, which would potentially allow multiple bodies to be sampled if a number of projectiles are used on different asteroids. Another scenario is the more traditional method of landing on an asteroid to obtain the sample. A significant range of main-belt asteroids are available as targets for a sample-return mission and such a mission would represent a first step in mineralogically and isotopically mapping the asteroid belt. We argue that a sample-return mission to the asteroid belt does not necessarily have to return material from both the NC and CC groups to viably test the bimodal Solar System paradigm, as material from the NC group is already abundantly available for study. Instead, there is overwhelming evidence that we have a very incomplete suite of CC-related samples. Based on our analysis, we advocate a dedicated sample-return mission to the dwarf planet (1) Ceres as the best means of further exploring inherent Solar System variation. Ceres is an ice-rich world that may be a displaced trans-Neptunian object. We almost certainly do not have any meteorites that closely resemble material that would be brought back from Ceres. The rich heritage of data acquired by the Dawn mission makes a sample-return mission from Ceres logistically feasible at a realistic cost. No other potential main-belt target is capable of providing as much insight into the early Solar System as Ceres. Such a mission should be given the highest priority by the international scientific community.

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Asteroid compositional «rings»: clues to the compositions of primordial planetesimals in the middle solar system

International Astronomical Union Colloquium ◽

10.1017/s0252921100101812 ◽

1984 ◽

Vol 75 ◽

pp. 703-712

Author(s):

E.F. Tedesco

Keyword(s):

Solar System ◽

Final Stage ◽

Heliocentric Distance ◽

Solar Nebula ◽

Satellite System ◽

Asteroid Belt ◽

Planetary Rings ◽

Early Solar System ◽

Physical Conditions

ABSTRACTIt has recently been established that the distribution of asteroid taxonomic types at distances between 2.1 and 5.3 astronomical units is highly structured. There are four major, overlapping but nevertheless compositionally distinct, “rings” of asteroids present within this range of heliocentric distance. These “rings”, within which ~ 80% of each of four major taxonomic types (S, C, P, and D) fall, are centered at 2.6 (0.7), 2.9 (0.8), 3.4 (0.7), and 4.6 (1.5) AU respectively, where the numbers within parentheses are the ring “widths” in AU. The overall physical resemblence between the asteroid “rings” and planetary rings is poor; physically the asteroid belt more closely resembles a debris strewn satellite system. This structure is consistent with these objects having been formed directly from the solar nebula at, or near, the heliocentric distances at which we find them today. Once the mineralogy of these taxonomic types is firmly established, and complications arising from post-accreationary metamorphism are dealt with, they may be used as probes of physical conditions in the early solar system. In particular, the identification of primordial planetesimals will allow us to obtain a first-hand look at the siblings of the planetesimals responsible for the final stage of planetary accretion.

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Panel discussion: does chemical evidence give diagnostic tests for the credibility of physical models of the origin of the Solar System?

Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences ◽

10.1098/rsta.1988.0076 ◽

1988 ◽

Vol 325 (1587) ◽

pp. 631-641

Keyword(s):

Solar System ◽

Panel Discussion ◽

Physical Models ◽

Asteroid Belt ◽

Early Solar System ◽

Irregular Satellites ◽

Resisting Medium ◽

Eccentric Orbits ◽

Wide Range ◽

Cometary Material

M. M. Woolfson. Under the conditions of the capture theory, planets were originally formed in highly eccentric orbits which were close to, but not exactly coplanar. A resisting medium rounded off these orbits but, because it produced a non-central gravitational force on the planets, it also caused their orbits to precess. Differential precession gave intersecting orbits from time to time and it is possible to compute characteristic times for major interactions between pairs of planets. It turns out that these are similar to the rounding-off times and it can be concluded that some major event in the early Solar System was more likely than not. In 1977 Dormand and I postulated a planetary collision in the asteroid-belt region. Such a model readily explains the known characteristics of asteroids and meteorites, especially as a wide range of thermal regimes was present during the collision event. Other Solar System features that could be explained in a very straightforward way included the terrestrial planets, irregular satellites, e.g. the Moon and Triton, and the origin of cometary material.

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Dynamical Evolution of the Early Solar System

Annual Review of Astronomy and Astrophysics ◽

10.1146/annurev-astro-081817-052028 ◽

2018 ◽

Vol 56 (1) ◽

pp. 137-174 ◽

Cited By ~ 53

Author(s):

David Nesvorný

Keyword(s):

Solar System ◽

Kuiper Belt ◽

Dynamical Evolution ◽

Giant Planets ◽

Asteroid Belt ◽

Dynamical Instability ◽

Orbital Energy ◽

Interstellar Space ◽

Early Solar System ◽

Planetary Migration

Several properties of the Solar System, including the wide radial spacing of the giant planets, can be explained if planets radially migrated by exchanging orbital energy and momentum with outer disk planetesimals. Neptune's planetesimal-driven migration, in particular, has a strong advocate in the dynamical structure of the Kuiper belt. A dynamical instability is thought to have occurred during the early stages with Jupiter having close encounters with a Neptune-class planet. As a result of the encounters, Jupiter acquired its current orbital eccentricity and jumped inward by a fraction of an astronomical unit, as required for the survival of the terrestrial planets and from asteroid belt constraints. Planetary encounters also contributed to capture of Jupiter Trojans and irregular satellites of the giant planets. Here we discuss the dynamical evolution of the early Solar System with an eye to determining how models of planetary migration/instability can be constrained from its present architecture. Specifically, we review arguments suggesting that the Solar System may have originally contained a third ice giant on a resonant orbit between Saturn and Uranus. This hypothesized planet was presumably ejected into interstellar space during the instability. The Kuiper belt kernel and other dynamical structures in the trans-Neptunian region may provide evidence for the ejected planet. We favor the early version of the instability where Neptune migrated into the outer planetesimal disk within a few tens of millions of years after the dispersal of the protosolar nebula. If so, the planetary migration/instability was not the cause of the Late Heavy Bombardment. Mercury's orbit may have been excited during the instability.

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Laboratory and in-situ analysis of comet dust

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100102122 ◽

1988 ◽

Vol 46 ◽

pp. 8-9

Author(s):

D.E. Brownlee ◽

A.L. Albee

Keyword(s):

Electron Microscopy ◽

Solar System ◽

Laboratory Study ◽

Isotopic Analysis ◽

Building Blocks ◽

Sem Analysis ◽

Early Solar System ◽

Cometary Material ◽

Comet Dust

Comets are primitive, kilometer-sized bodies that formed in the outer regions of the solar system. Composed of ice and dust, comets are generally believed to be relic building blocks of the outer solar system that have been preserved at cryogenic temperatures since the formation of the Sun and planets. The analysis of cometary material is particularly important because the properties of cometary material provide direct information on the processes and environments that formed and influenced solid matter both in the early solar system and in the interstellar environments that preceded it.The first direct analyses of proven comet dust were made during the Soviet and European spacecraft encounters with Comet Halley in 1986. These missions carried time-of-flight mass spectrometers that measured mass spectra of individual micron and smaller particles. The Halley measurements were semi-quantitative but they showed that comet dust is a complex fine-grained mixture of silicates and organic material. A full understanding of comet dust will require detailed morphological, mineralogical, elemental and isotopic analysis at the finest possible scale. Electron microscopy and related microbeam techniques will play key roles in the analysis. The present and future of electron microscopy of comet samples involves laboratory study of micrometeorites collected in the stratosphere, in-situ SEM analysis of particles collected at a comet and laboratory study of samples collected from a comet and returned to the Earth for detailed study.

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