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1.
Absorption bands near 0.43 and 0.60–0.80 m, with a relative intensity of approximately 5–10%, were discovered in the reflectance spectra of five M asteroids (21, 75, 161, 201, and 497) and two S asteroids (11 and 198). It is highly probable that these absorption bands are related to oxidized and/or hydrated silicates that incorporate OH structural groups. Absorbed water in the surface material of about 24% of the known M asteroids and three E asteroids has been identified by a group of astronomers at the University of Arizona (Rivkin et al., 1995; Rivkin, 1997; Rivkin et al., 2000) on the basis of the characteristic 3-m absorption band. In addition to this, four of the six E-type asteroids observed spectrally in the visible region quite recently were found to have an absorption band at 0.5 m (Burbine et al., 1998; Fornasier and Lazzarin, 2001), which could likewise be associated with the presence of hydrated silicates in their material. The above data contradict the generally accepted viewpoint on the nature of M, S, and E asteroids, which is based on their common observed characteristics as bodies that arose at high temperatures (in the 1000–2000°C range). This contradiction, however, can be eliminated if use is made of the cosmogonic model developed by V.S. Safronov and co- workers. According to this model, the initial evolution of the main-belt asteroids was directly influenced by the process of the growth of Jupiter and was later controlled by its gravitational field. 相似文献
2.
V. V. Busarev 《Solar System Research》2016,50(1):13-23
This paper presents and discusses selected reflectance spectra of 40 Main Belt asteroids. The spectra have been obtained by the author in the Crimean Laboratory of the Sternberg Astronomical Institute (2003–2009). The aim is to search for new spectral features that characterize the composition of the asteroids’ material. The results are compared with earlier findings to reveal substantial irregularities in the distribution of the chemical-mineralogical compositions of the surface material of a number of minor planets (10 Hygiea, 13 Egeria, 14 Irene, 21 Lutetia, 45 Eugenia, 51 Nemausa, 55 Pandora, 64 Angelina, 69 Hesperia, 80 Sappho, 83 Beatrix, 92 Undina, 129 Antigone, 135 Hertha, and 785 Zwetana), which are manifest at different rotation phases. The vast majority of the analyzed high-temperature asteroids demonstrate subtle spectral features of an atypical hydrated and/or carbonaceous chondrite material (in the form of impurities or separate units), which are likely associated with the peculiarities of the formation of these bodies and the subsequent dynamic and impact processes, which lead, inter alia, to the delivery of atypical materials. Studies of 4 Vesta aboard NASA’s Dawn spacecraft have found that asteroids of similar types can form their own phyllosilicate generations provided that their surface material contains buried icy or hydrated fragments of impacting bodies. The first evidence has been obtained of a spectral phase effect (SPE) at small phase angles (≤4°) for 10 Hygiea, 21 Lutetia, and, possibly, 4 Vesta. The SPE manifests itself in an increasing spectral coefficient of brightness in the visible range with decreasing wavelength. This effect is present in the reflectance spectrum of CM2 carbonaceous material at a phase angle of 10° and absent at larger angles (Cloutis et al., 2011a). The shape of Hygeia’s reflectance spectra at low phase angles appears to be controlled by the SPE during the most part of its rotation period, which may indicate a predominantly carbonaceous chondrite composition on a part of the asteroid’s surface. For Vesta, the SPE may manifest itself in the flat or slightly concave shape of the asteorid’s reflectance spectra at some of the rotation phases, which is likely caused by the increased number of dark spots on corresponding parts of its surface. 相似文献
3.
Europa and Callisto are two “extreme members” in a sequence of the Galilean ice satellites formed at different distances from Jupiter. The difference in their mean density probably reflects the material density gradient that appeared even in the subplanetary disk of Jupiter. At the same time, general peculiarities in the composition of the surfaces of Europa and Callisto apparently characterize the accumulated effect of all subsequent evolutionary processes, including current volcanic activity on the satellite Io and its ionized material transfer in Jovian magnetosphere, as well as chemical reactions taking place under low-temperature (within ~90–130 K) and irradiation conditions. In 2016–2017, we observed the leading and trailing hemispheres of Europa and Callisto in the spectral range of 1.0–2.5 μm at 2-m telescope of Caucasian Mountain Observatory (CMO) of Sternberg Astronomical Institute (SAI) of Moscow State University (MSU). We found that, on a global scale, Europa and Callisto exhibit similar spectral characteristics and, particularly, the maxima in the distributions of sulfuric acid hydrate in the trailing hemispheres of the both moons, which agrees with the data of previous measurements. This can be considered as evidence for general ion implantation on these and other moons in the radiation belts of Jupiter. Moreover, our spectral data suggest that water ice and hydrates (clathrates) of other compounds are dominant or abundant in the leading hemispheres of Europa and Callisto. Specifically, we detected a weak absorption band of CH4 clathrate centered at ~1.67 μm in the reflectance spectra of the leading (the band is more intense) and trailing (the band is less intense) hemispheres of Europa. Weak signs of the same absorption band are also in the reflectance spectra of Callisto measured at its different orientations. 相似文献
4.
Spectrophotometric observations of 145 Adeona, 704 Interamnia, 779 Nina, and 1474 Beira—asteroids of close primitive types—allowed us to detect similar mineralogical absorption bands in their reflectance spectra centered in the range 0.35 to 0.92 μm; the bands are at 0.38, 0.44, and 0.67–0.71 μm. On the same asteroids, the spectral signs of simultaneous sublimation activity were found for the first time. Namely, there are maxima at ～0.35–0.60 μm in the reflectance spectra of Adeona, Interamnia, and Nina and at ～0.55–075 μm in the spectra of Beira. We connect this activity with small heliocentric distances of the asteroids and, consequently, with a high insolation at their surfaces. Examination of the samples of probable analogues allowed us to identify Fe3+ and Fe2+ in the material of these asteroids through the mentioned absorption bands. For analogues, we took powdered samples of carbonaceous chondrites Orgueil (CI), Mighei (CM2), Murchison (CM2), and Boriskino (CM2), as well as hydrosilicates of the serpentine group. Laboratory spectral reflectance study of the samples of low-iron Mg serpentines (<2 wt % FeO) showed that the equivalent width of the absorption band centered at 0.44–0.46 μm strongly correlates with the content of Fe3+ in octahedral and tetrahedral coordinations. Our conclusion is that this absorption band can be used as a qualitative indicator of Fe3+ in the surface matter of asteroids and other solid celestial bodies. The comparison of the listed analog samples and the asteroids by parameters of the spectral features suggests that the silicate component of the asteroids' surface material is a mixture of hydrated and oxidized compounds, including oxides and hydroxides of bivalent and trivalent iron and carbonaceous-chondritic material. At the same time, the sublimation activity of Adeona, Interamnia, Nina, and Beira at high surface temperatures points to a substantial content of water ice in their material. This contradicts the previously existing notions on the C-type and similar asteroids as bodies containing water only in the bound state. Moreover, since the sublimation process simultaneously occurs in four primitive-type bodies at small heliocentric distances, we may suppose that this phenomenon is common for the main-belt asteroids. 相似文献
5.
V. V. Busarev 《Solar System Research》2011,45(1):43-52
The reflectance spectra of asteroids 10 Hygiea (C-type), 135 Hertha (M-type), and 196 Philomela (S-type) are obtained in a
range of 0.40–0.91 μm with different time intervals. In this paper, the technique of the spectral measurements of asteroids
is analyzed and the reflectance spectra of Hygiea, Hertha, and Philomela are interpreted. The main physical and chemical factors
and processes influencing the spectral characteristics of asteroids are considered. It is determined that the spectra of Hertha
and Hygiea contain variations exceeding the measurement errors several times at different relative rotation phases, whereas
spectral variations of Philomela caused by its rotation hardly exceed the error limits. Most probably, these variations are
caused by local manifestations of the impact metamorphism of the material of asteroids in serious impact events. Results show
that, to determine the prevailing spectral type and the corresponding mineralogy of each asteroid, one should estimate and
take into account the changes in its spectral characteristics for a time interval comparable to the rotation period. 相似文献
6.
V. V. Busarev 《Solar System Research》2010,44(6):507-519
Asteroid 21 Lutetia is one of the objects of the Rosetta mission carried out by the European Space Agency (ESA). The Rosetta spacecraft launched in 2004 is to approach Lutetia in July 2010, and then it will be directed to the comet Churyumov-Gerasimenko.
Asteroid 4 Vesta is planned to be investigated in 2011 from the Dawn spacecraft launched by the National Aeronautics and Space Administration (NASA) in 2007 (its second object is the largest
asteroid, 1 Ceres). The observed characteristics of Lutetia and Vesta are different and even contradictory. In spite of the
intense and versatile ground-based studies, the origin and evolution of these minor planets remain obscure or not completely
clear. The types of Lutetia and Vesta (M and V, respectively) determined from their spectra correspond to the high-temperature
mineralogy, which agrees with their albedo estimated from the Infrared Astronomical Satellite (IRAS) observations. However,
according to the opinion of some researchers, Lutetia is of the C type, and, therefore, its mineralogy is of the lowtemperature
type. In turn, hydrosilicate formations have been found in some places on the surface of Vesta. Our observations also testify
that at some relative phases of rotation (RP), the reflectance spectra of Lutetia and Vesta demonstrate features confirming
the presence of hydrosilicates in the surface material. However, this fact can be reconciled with the magmatic nature of Lutetia
and Vesta if the hydrated material was delivered to their surfaces by falling primitive bodies. Such small bodies are probably
present everywhere in the main asteroid belt and can be the relicts of silicate-icy planetesimals from Jupiter’s formation
zone or the fragments of primitive-type asteroids. When interpreting the reflectance spectra of Lutetia and Vesta, we discuss
the spectral classification by Tholen (1984) from the standpoint of its general importance for the estimation of the mineralogical
type of the asteroids and the study of their origin and evolution. 相似文献
7.
V. V. Prokof’eva-Mikhailovskaya V. V. Busarev N. N. Gor’kavyi A. N. Rublevskii 《Kinematics and Physics of Celestial Bodies》2011,27(6):291-298
A new spectral-frequency method (SFM) for the study of solid body surfaces is briefly described. This method allows estimation
of the sizes of various spots. Estimates for the sizes of spots on asteroid surfaces made by the SFM and other methods are
compared and discussed. The sizes of spots on the surface of asteroid 1620 Geographos determined by the SFM are well consistent
with those of the craters obtained from radar data. The sizes of hydrosilicate spots on the surface of asteroid 21 Lutetia
found by the SFM agree with those of the craters determined by the Rosetta spacecraft. The size of a blue spot on the surface
of asteroid 4 Vesta found by the SFM is consistent with the size of the well-known crater on the south pole of the asteroid.
It is inferred that the SFM is a promising method for the estimation of the sizes of spots on asteroid surfaces. 相似文献
8.
V. V. Busarev V. V. Prokof’eva-Mikhailovskaya A. N. Rublevskii N. N. Gor’kavyi 《Kinematics and Physics of Celestial Bodies》2012,28(1):1-8
We discuss possible mechanisms for the formation of albedo spots on asteroids. We infer that the most likely mechanisms are
impact cratering and related processes. This is confirmed by the reflectance spectra of the asteroids 10 Hygiea, 135 Hertha,
and 196 Philomela, the results of a spectral frequency analysis of the sizes of features on the surface of 4 Vesta and 21
Lutetia, and the estimates for the parameters of impact features. 相似文献
9.
We obtained ～1000 B, V, and R magnitude measurements for asteroid 21 Lutetia quasi-simultaneously with the digital TV system of a 0.5-m MTM-500 meniscus telescope from November 3 through November 11, 2004. We performed a frequency analysis of the B-V and V-R color indices and the V magnitudes based on data averaged over five measurements, which provided an accuracy of the mean color indices and magnitudes of ～0. m 005 and 0. m 08, respectively. Our analysis of the color indices showed the absence of the known period, 0.d3405 (8.h172), and the presence of several periods at a confidence level of 7–10 σ, including P 0 = 2.h93 (1/P = 8.17c/d) and its alias 2.h64 (1/P = 9.17c/d). Our analysis of the V-band data revealed the periods P 1 = 0.d70 and P 2 = 3.d20; both periods yielded double-peaked light curves with amplitudes of 0. m 12 and 0. m 10. The first period is probably the rotation period of the main component, while the second period may be equal to the orbital period of the satellite with one side facing the main body. Another model of the asteroid is also possible: P 0 = 2.h93 is the rotation period of the main body, P 1 = 0.d70 is the orbital period of the synchronous satellite, and P 2 = 3.d20 is the precession period. 相似文献
10.
V. V. Prokof’eva-Mikhailovskaya Yu. V. Batrakov V. V. Bochkov V. V. Busarev L. G. Karachkina 《Solar System Research》2007,41(4):307-313
We discuss the results of the analysis of three sets of observations of asteroid 21 Lutetia—spectrophotometry, simultaneous BVR photometry, and spectrometry—which show that the asteroid is not a monolithic body. The frequency analysis of the B-V and V-R color indices and the V values, which were obtained from simultaneous BVR measurements in 2004 and calculated from the spectrophotometric observations performed in 2000 (the synthetic values and the color indices), allowed us to demonstrate that the known rotation period of 8.h172 of the asteroid does not exist at all. At a rather high confidence level, six new periods were found: 2.h0, 2.h93, 16.h8, 1.d25, 3.d25, and 60d. During spectral observations with a 1.25-m telescope at the southern laboratory of the Sternberg Astronomical Institute in Nauchnyi (Crimea) in 2004, the spectra of two components spaced 2.8″ apart were registered. In the short-wavelength spectral range, quick variations of the reflectance of the components were observed. They show the changes in their spectral types from S to C. The analysis of the synthetic values of the color indices determined from the spectrophotometric observations in 2000 confirmed the presence of quick spectral variations. We conclude that asteroid 21 Lutetia is a complex satellite system. This statement is confirmed by the analysis of data published in different sources. 相似文献