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1.
Micrometeorite bombardment and irradiation by solar wind and cosmic ions cause variations in the optical properties of the small Solar System bodies surface materials. These space weathering processes are reasonably well understood for the Moon and S-type asteroids. The research is based on laboratory experiments performed by several groups on meteorites and minor bodies surface analogues, whose results have been applied to the spectral modeling and interpretation of observations from large surveys and space missions. Recent results from young asteroidal families, and the relation between spectral slopes and dynamical properties, have stressed the role of the solar wind exposure timescale. Space weathering processes remain poorly investigated in the case of other types of asteroids, and they are still unclear in the case of outer Solar System bodies, due to a strong dependence of the weathering process on the original composition.  相似文献   

2.
Tabaré Gallardo 《Icarus》2006,184(1):29-38
The aim of this work is to present a systematic survey of the strength of the mean motion resonances (MMRs) in the Solar System. We know by applying simple formulas where the resonances with the planets are located but there is no indication of the strength that these resonances have. We propose a numerical method for the calculation of this strength and we present an atlas of the MMRs constructed with this method. We found there exist several resonances unexpectedly strong and we look and find in the small bodies population several bodies captured in these resonances. In particular in the inner Solar System we find one asteroid in the resonance 6:5 with Venus, five asteroids in resonance 1:2 with Venus, three asteroids in resonance 1:2 with Earth and six asteroids in resonance 2:5 with Earth. We find some new possible co-orbitals of Earth, Mars, Saturn, Uranus and Neptune. We also present a discussion about the behavior of the resonant disturbing function and where the stable equilibrium points can be found at low and high inclination resonant orbits.  相似文献   

3.
The PLANCK mission, originally devised for cosmological studies, offers the opportunity to observe Solar System objects at millimetric and submillimetric wavelengths. In this paper we concentrate on the asteroids of the Main Belt, a large class of minor bodies in the Solar System. At present, more that 40 000 of these asteroids have been discovered and their detection rate is rapidly increasing. We intend to estimate the number of asteroids that can be detected during the mission and to evaluate the strength of their signal. We have rescaled the instrument sensitivities, calculated by the LFI and HFI teams for sources fixed in the sky, introducing some degradation factors to properly account for moving objects. In this way a detection threshold is derived for asteroidal detection that is related to the diameter of the asteroid and its geocentric distance. We have developed a numerical code that models the detection of asteroids in the LFI and HFI channels during the mission. This code performs a detailed integration of the orbits of the asteroids in the timespan of the mission and identifies those bodies that fall in the beams of PLANCK and their signal strength. According to our simulations, a total of 397 objects will be observed by PLANCK and an asteroidal body will be detected in some beam in 30% of the total sky scan-circles. A significant fraction (in the range from 50 to 100 objects) of the 397 asteroids will be observed with a high S/N ratio. Flux measurements of a large sample of asteroids in the submillimeter and millimeter range are relevant since they allow to analyze the thermal emission and its relation to the surface and regolith properties. Furthermore, it will be possible to check on a wider base, the two standard thermal models, based on a nonrotating or rapidly rotating sphere. Our method can also be used to separate Solar System sources from cosmological sources in the survey. This work is based on PLANCK LFI activities.  相似文献   

4.
The triaxial figures are very common shape of most of planetary satellites as well as of smaell bodies as asteroids. There are 21 satellites in the Solar System triaxial figures of which were detected in situ evidently (Davies et al., 1995). However, the total number of triaxiaxial satellites in the Solar System should be in fact larger. In this paper the general theory of triaxiality due to tidal forces is discussed in regard to the very recent numerical data. Since they orbit synchronously, as a rule: their orbital periods are equal to the rotational periods, the tidal forces may be responsible for their triaxial figures. On the other hand the origin of triaxiality of asteroids due to another process and the of their figures cannot be axplained by the tidal effects.  相似文献   

5.
Aspects of the design of small spacecraft with electric propulsion power plants for investigating minor bodies in the Solar System are examined. The results of design and ballistic analysis of transfer into an orbit of terrestrial asteroids using electric propulsion thrusters are given. The possible concept design of the spacecraft is determined and the structure of a small spacecraft with an electric propulsion power plant is presented. Parameters of the electric propulsion power plant of a small spacecraft for a flight to the minor bodies of the Solar System are estimated.  相似文献   

6.
Among 11 673 of near-Earth objects (NEOs), 52 asteroids are identified, which, together with the Eccentrids meteor system, comprise a single population of small bodies of the Solar System with the smallest orbits of high eccentricity. Some features of this unique system of bodies are discussed in this paper. The distribution of perihelion longitudes is studied for the given group of asteroids and compared to that of the Aten asteroids, which are the most similar to the Eccentrids. The dependence is obtained of the character of perihelion longitude distribution on the eccentricities of the NEO orbits. Eight asteroid stream of the Eccentrids are found. The Eccentrids asteroids approaching the Earth’s orbit along its whole length in their aphelia can pose a certain hazard for the Earth.  相似文献   

7.
The use of ground-based and space baseline observations of Solar System bodies is considered. Baseline observations allow one to determine the distance to observed objects and (in some cases) the parameters of their orbital motion. Certain results of baseline observations of near-Earth asteroids and the results of model analysis of spacecraft observations are presented.  相似文献   

8.
A review is given of the mineralogical and chemical composition of iron meteorites and the problems associated with their origin. A detailed discussion is presented of the physical and mechanical properties of iron meteorites and their dependence on the structure, chemical composition, and temperature. Iron meteorites are shown to characterize, with no distortions, the physical and mechanical properties of their parent bodies (metallic asteroids). The population of M-type asteroids and the main characteristics of the identified metallic asteroids are examined. Compared with iron meteorites, metallic asteroids have a different shape and are not fragments of larger metallic parent bodies. The estimates for the current deviatoric stress in metallic asteroids show that, since their formation, asteroids have not been heated to over 600°C and certainly have not been subjected to partial or complete melting. An empirical dependence is found of the critical dimensions of small metallic objects (which allow for gravitational deformation) on the yield strength at temperatures below 300 K. It is shown that the physical and mechanical data are also a strong argument against the hypothesis of the origin of iron meteorites and metallic asteroids from the iron core of a differentiated parent body.  相似文献   

9.
Solar System Research - An important characteristic of the disruption of cosmic bodies (asteroids at their collision in outer space, meteoroids and asteroids entering the Earth’s atmosphere)...  相似文献   

10.
A simple method for numerical integration of the equations of motion of small bodies of the Solar System is proposed, which is especially efficient in studying the orbits with small perihelion distances. The evolution of orbits of 121 numbered asteroids with perihelion distances q < 1.2 AU is investigated over the time interval of years 2000–2100 with allowance made for the gravitational influence of nine planets and three largest asteroids. The circumstances of close encounters of asteroids with the Earth and other terrestrial planets are presented.  相似文献   

11.
We have observed well-sampled phase curves for nine Trojan asteroids in B-, V-, and I-bands. These were constructed from 778 magnitudes taken with the 1.3-m telescope on Cerro Tololo as operated by a service observer for the SMARTS consortium. Over our typical phase range of 0.2-10°, we find our phase curves to be adequately described by a linear model, for slopes of 0.04-0.09 mag/° with average uncertainty less than 0.02 mag/°. (The one exception, 51378 (2001 AT33), has a formally negative slope of −0.02 ± 0.01 mag/°.) These slopes are too steep for the opposition surge mechanism to be shadow-hiding (SH), so we conclude that the dominant surge mechanism must be coherent backscattering (CB). In a detailed comparison of surface properties (including surge slope, B-R color, and albedo), we find that the Trojans have surface properties similar to the P and C class asteroids prominent in the outer main belt, yet they have significantly different surge properties (at a confidence level of 99.90%). This provides an imperfect argument against the traditional idea that the Trojans were formed around Jupiter’s orbit. We also find no overlap in Trojan properties with either the main belt asteroids or with the small icy bodies in the outer Solar System. Importantly, we find that the Trojans are indistinguishable from other small bodies in the outer Solar System that have lost their surface ices (such as the gray Centaurs, gray Scattered Disk Objects, and dead comets). Thus, we find strong support for the idea that the Trojans originally formed as icy bodies in the outer Solar System, were captured into their current orbits during the migration of the gas giant planets, and subsequently lost all their surface ices.  相似文献   

12.
Physical-mechanical properties of cometary nuclei matter are described in detail. As compared to other Solar System bodies, cometary nuclei are characterized by low strength properties. The ultimate tensile strength of cometary matter and cometary nuclei on the whole is about 2 kPa. An analysis performed based on a rheological model of a self-gravitating triaxial solid body showed that cometary nuclei less than 50–60 km (this actually being all known comets) are characterized by a constant ultimate tensile strength which is determined only by the matter composition and structure. The effective ultimate tensile strength for bodies larger than 50–60 km is determined by the body mass and figure parameters and increases according to the quadratic law depending on the body dimensions and mass. Such an increase of the effective strength can explain the absence or deficit of cometary nuclei more than 60 km in size, since it can significantly affect the parameters of the parent body destruction and the formation of a secondary population. The dependence of the mechanism and character of destruction on the parameters of the figure for Kuiper objects more than 50–60 km is size can yield a deficit of the population of the bodies whose figure parameters are a/c > 1.75 with respect to the bodies with a/c < 1.75 figure parameters.  相似文献   

13.
Solar System Research - In this paper, we summarize the experimental data on the features of the mineral, chemical, and isotopic compositions of minor bodies of the Solar System—asteroids,...  相似文献   

14.
Although the theory of Roche 1847 for the tidal disruption limits of orbiting satellites assumes a fluid body, a length to diameter of exactly 2.07:1, and a particular body orientation, the theory is commonly applied to the satellites of the Solar System and to small asteroids and comets passing nearby a planet. Clearly these bodies are neither fluid nor generally are that elongated, so a more appropriate theory is needed. Here we present exact analytical results for the distortion and disruption limits of solid spinning ellipsoidal bodies subjected to tidal forces, using the Drucker-Prager strength model with zero cohesion. It is the appropriate model for dry granular materials such as sands and rocks, for rubble-pile asteroids and comets, and for larger satellites, asteroids and comets where the cohesion can be ignored. This study uses the same approach as the studies of spin limits for solid ellipsoidal bodies given in [Holsapple, K.A., 2001. Icarus 154, 432-448; Holsapple, K.A., 2004. Icarus 172, 272-303]. It is a static theory that predicts conditions for breakup and predicts the nature of the deformations at the limit state, but does not track the dynamics of the body as it comes apart. The strength is characterized by a single material parameter associated with an angle of friction, which can range from zero to 90°. The case with zero friction angle has no shear strength whatsoever, so it is then the model of a fluid or gas. The case of 90° represents a material that cannot fail in shear, but still has zero tensile strength. Typical dry soils have angles of friction of 30°-40°. Since the static fluid case is included in the theory as a special case, the classical results of Roche [Roche, E.A., 1847. Acad. Sci. Lett. Montpelier. Mem. Section Sci. 1, 243-262] and Jeans [Jeans, J.H., 1917. Mem. R. Astron. Soc. London 62, 1-48] are included and re-derived in their entirety; but the general solid case has much more variety and applicability. We consider both the spin-locked case, appropriate for most satellites of the Solar System; and the zero spin case, a possible case for a passing stray body. Detailed plots of many special cases are presented, in terms of shape, orientation and mass densities. A very typical result gives a closest approach d=1.5(ρ/ρP)1/3R in terms of the planet radius R, and the satellite and planet mass densities ρ and ρP. We also use the theory to distinguish between conditions allowing global shape changes leading to new equilibrium states, or those leading to complete disruption. We apply the theory to the potentially hazardous Asteroid 99942 Apophis due to pass very near the Earth in 2029, and conclude it is extremely unlikely to experience any tidal readjustments during its passage. The states of many of the satellites of the Solar System are compared to the theory, and we find that all are well within their tidal disruption limits for expected values of the internal friction.  相似文献   

15.
The outcome of collisions between small icy bodies, such as Kuiper belt objects, is poorly understood and yet a critical component of the evolution of the trans-neptunian region. The expected physical properties of outer Solar System materials (high porosity, mixed ice-rock composition, and low material strength) pose significant computational challenges. We present results from catastrophic small body collisions using a new hybrid hydrocode to N-body code computational technique. This method allows detailed modeling of shock propagation and material modification as well as gravitational reaccumulation. Here, we consider a wide range of material strengths to span the possible range of Kuiper belt objects. We find that the shear strength of the target is important in determining the collision outcome for 2 to 50-km radius bodies, which are traditionally thought to be in a pure gravity regime. The catastrophic disruption and dispersal criteria, , can vary by up to a factor of three between strong crystalline and weak aggregate materials. The material within the largest reaccumulated remnants experiences a wide range of shock pressures. The dispersal and reaccumulation process results in the material on the surfaces of the largest remnants having experienced a wider range of shock pressures compared to material in the interior. Hence, depending on the initial structure and composition, the surface materials on large, reaccumulated bodies in the outer Solar System may exhibit complex spectral and albedo variations. Finally, we present revised catastrophic disruption criteria for a range of impact velocities and material strengths for outer Solar System bodies.  相似文献   

16.
We consider the application of interferometry to measuring the sizes and shapes of small bodies in the Solar System that cannot be spatially resolved by today’s single-dish telescopes. Assuming ellipsoidal shapes, we provide a formalism to derive the shape parameters from visibility measurements along three different baseline orientations. Our results indicate that interferometers can measure the size of an object to better than 15% uncertainty if the limb-darkening is unknown. Assuming a Minnaert scattering model, one can theoretically derive the limb-darkening parameters from simultaneous measurements of visibilities at several different projected baseline lengths to improve the size and shape determination to an accuracy of a few percent. The best size measurement can be reached when one axis of the object’s projected disk is aligned with one baseline orientation, and the measurement of cross-sectional area is independent of baseline orientation. We construct a 3-D shape model for the dwarf planet Haumea and use it to synthesize interferometric data sets. Using the Haumea model, we demonstrate that when photometric light curve, visibility light curve, and visibility phase center displacement are combined, the rotational period and sense of rotation can all be derived, and the rotational pole can be estimated. Because of its elongated shape and the dark red spot, the rotation of Haumea causes its optical photocenter to move in a loop on the sky. Our simulations show that this loop has an extend of about 80 μas without the dark red spot, and about 200 μas with it. Such movements are easily detectable by space-based astrometric interferometer designed e.g. for planet detection. As an example, we consider the possible contributions to the study of small bodies in the Solar System by the Space Interferometry Mission. We show that such a mission could make substantial contributions in characterizing the fundamental physical properties of the brightest Kuiper Belt Objects and Centaurs as well as a large number of main belt asteroids. We compile a list of Kuiper Belt Objects and Centaurs that are potentially scientifically interesting and observable by such missions.  相似文献   

17.
Composed of rocks, dirt, ices and metals, the small bodies of the Solar System generally show features of strength; and that property undoubtedly played a major role in their collisional evolution. But the quantification of strength is difficult because there are many different measures of strength, and those measures depend significantly on a body's composition, previous history and size. Although it is at the foundations of our scaling theories for the disruption of small bodies, and an essential part of code calculations, we have only recently begun to understand and come to grips with that strength property and in appropriate ways to model it in our theories and calculations.This is a general overview of strength theories for geological-type materials as needed for impact analyses. Dominant features of strength models are discussed, and comparisons of various models in the literature against that feature template is given. A summary of the use of strength theories in impact calculations is presented.  相似文献   

18.
Narrowband spectrophotometric observations of outer-belt asteroids (semi-major axis greater than 3.2 AU) have been used to investigate the surface compositions of the D- and P-class asteroids in an effort to learn about their origins and formation conditions. Spectra of 19 outer-belt asteroids and 2 main-belt D-class asteroids were obtained using two charge-coupled device spectrographs. No mineralogical absorption features were evident. The spectra can be divided into four groups based upon four discrete slopes among the spectra. The slope increases (reddens) with increasing heliocentric distance. All of the outer-belt asteroids are locked into orbits controlled by Jupiter's gravitational attraction. The distinct slope changes suggest that these asteroids are the remnants of a gradation in composition of planetesimals in the outer Solar System, which were selectively retained in location when other material was ejected from the Solar System. The spectrophotometry of Iapetus and infrared photometry of quiescent comets of other researchers suggest that this compositional gradation could extend through the orbits of Uranus and Neptune. Two possible explanations for this compositional gradation based upon changes in organic polymer materials are discussed.  相似文献   

19.
The compositions of the numerous bodies in the Solar System are determined from remote sensing observations, most often spectroscopic, and in some cases direct sampling. Laboratory studies of materials and processes are an essential component of the analysis and interpretation of all compositional data. Planetary atmospheres are composed of gases and aerosols, while the surfaces of the terrestrial planets, asteroids, comets, and planetary satellites are composed of minerals, ices, and organic solids. The principal spectroscopic characteristics of each of these materials are reviewed here. The tables present a synopsis of our current knowledge of the compositions of the principal bodies in the Solar System. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

20.
The level of precision of modern numerical ephemeris of the Solar System necessitates taking into account the gravitational influence of the largest asteroids on the terrestrial planets. This can be done in a straightforward manner when assuming that the mass of the asteroid is well known. Nevertheless, this is rarely the case, even for the largest asteroids. In this paper, we use recent determinations of the masses of Ceres, Pallas, and Vesta to both qualitatively and quantitatively determine the action of these asteroids on the orbital parameters of the Earth and Mars. This is done by the numerical integration by comparing the orbital motions of the perturbed planet when adding or not the perturbing asteroid to the classical 9 bodies problem (the Sun + the eight planets). Some preliminary results are discussed. Published in Russian in Astronomicheskii Vestnik, 2009, Vol. 43, No. 1, pp. 83–86. The text was submitted by the autors in English.  相似文献   

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