共查询到20条相似文献，搜索用时 46 毫秒
1.
J. Borg J.-P. Bibring Y. Langevin Ph. Salvetat B. Vassent 《Meteoritics & planetary science》1993,28(5):641-648
Abstract— The COMET program is a program for the collection of micron to submicron interplanetary dust particles in low Earth orbits. Since collection takes place as the Earth crosses a given meteor stream, the particles are mainly of cometary origin. The grain remnants, located at their impact positions on high purity metallic collectors, are analysed in the laboratory for chemical and isotopical identification. The COMET-1 experiment took place in 1985 October, during encounter with the Draconid meteor stream, related to the Giacobini-Zinner comet. The fluence of extraterrestrial grains that had impacted our detectors was ～10x higher than the value of the mean meteroid fluence at ～1AU, which suggests that most of the grains originated from the Giacobini-Zinner comet. One of the most important results of their chemical analysis was that ～90% of them are enriched in low Z elements (C and O have undoubedly been identified). They could contain a CHON phase similar to that observed in the close environment of Halley's nucleus. The first imagery of the grain remnants by field emission scanning electron microscopy suggests that they are very low density aggregates still present at the impacting positions which, in most cases, are very different from the impact craters observed for the same mean relative velocity for full grains of the same size. These results show that the COMET program has constituted an important step towards the analysis of cometary material and the understanding of the evolution of the early Solar System. 相似文献
2.
Three bright fireballs belonging to the August θ‐Aquillid (ATA) meteor shower were photographed by the Tajikistan fireball network in 2009. Two of them are classified as the meteorite‐dropping fireballs according to the determined parameters of the atmospheric trajectories, velocities, masses, and densities. Detection of the more dense bodies among cometary meteoroids points to a heterogeneous composition of the parent comet, and supports the suggestion that some meteorites might originate in the outer solar system, in the given case from the Jupiter‐family comet reservoir. A search for the stream's parent was undertaken among the near‐Earth asteroids (NEAs); as a result, the asteroid 2004MB6 was identified as a possible progenitor of the ATA meteoroid stream. Investigation of the orbital evolution of the 2004MB6 and the fireball‐producing meteoroid TN170809A showed that both objects have similar secular variations in the orbital elements during 7 kyr. The comet‐like orbit of the 2004MB6 and its association with the ATA shower suppose a cometary origin of the asteroid. 相似文献
3.
Aerogel collectors have been deployed in low-Earth orbit to collect orbital debris and micrometeorites. An array of silica aerogel collectors is currently en-route back to Earth following an encounter with the Comet Wild-2 on board the Stardust spacecraft. Stardust is returning, for laboratory analysis, cometary and interstellar dust grains which impacted into the aerogel collectors at hypervelocities. While the morphology of impact craters in aerogels has been studied empirically, a theoretical understanding of the physical mechanisms responsible for the formation of impact craters in these solids is lacking. Here we propose and test a model of compaction driven impact cratering in aerogels. Our model derives impact crater dimensions directly from energy and momentum deposition. 相似文献
4.
P. B. Babadzhanov 《Earth, Moon, and Planets》1996,72(1-3):305-310
Probably most meteor showers have a cometary origin. Investigation of Near-Earth asteroids' orbital evolution to determine whether they have related meteor showers is necessary to determine which asteroids evolved from comets. The results of calculations show that asteroid Orthos' orbit is an octuple Earth-crosser. Therefore, if Orthos has an old meteoroid stream it may produce eight meteor showers observable on the Earth. The existence of four Orthos' Northern meteor showers is confirmed by our search in the published catalogues of meteor radiants and orbits or in the archives of the IAU Meteor Data Center (Lund, Sweden). 相似文献
5.
P. B. Babadzhanov 《Earth, Moon, and Planets》1995,71(3):305-310
Probably most meteor showers have a cometary origin. Investigation of Near-Earth asteroids' orbital evolution to determine whether they have related meteor showers is necessary to determine which asteroids evolved from comets. The results of calculations show that asteroid Orthos' orbit is an octuple Earth-crosser. Therefore, if Orthos has an old meteoroid stream it may produce eight meteor showers observable on the Earth. The existence of four Orthos' Northern meteor showers is confirmed by our search in the published catalogues of meteor radiants and orbits or in the archives of the IAU Meteor Data Center (Lund, Sweden). 相似文献
6.
P. B. Babadzhanov 《Earth, Moon, and Planets》1995,68(1-3):165-170
Probably the majority of meteor showers has a cometary origin. Investigation of Near-Earth asteroids' orbital evolution to determine whether they have related meteor showers are necessary to determine which asteroids evolved from comets. The results of calculations show that asteroid Orthos' orbit is an octuple Earth-crosser. Therefore, if Orthos has an old meteoroid stream it may produce eight meteor showers observable on the Earth. The existence of four Orthos' Northern meteor showers is confirmed by our search in the published catalogues of meteor radiants and orbits or in the archives of the IAU Meteor Data Center (Lund, Sweden). 相似文献
7.
P. B. Babadzhanov I. P. Williams G. I. Kokhirova 《Monthly notices of the Royal Astronomical Society》2008,386(4):2271-2277
Using the Everhart radau19 numerical integration method, the orbital evolution of the near-Earth asteroid 2003EH1 is investigated. This asteroid belongs to the Amor group and is moving on a comet-like orbit. The integrations are performed over one cycle of variation of the perihelion argument ω. Over such a cycle, the orbit intersect that of the Earth at eight different values of ω. The orbital parameters are different at each of these intersections and so a meteoroid stream surrounding such an orbit can produce eight different meteor showers, one at each crossing. The geocentric radiants and velocities of the eight theoretical meteor showers associated with these crossing points are determined. Using published data, observed meteor showers are identified with each of the theoretically predicted showers. The character of the orbit and the existence of observed meteor showers associated with 2003EH1 confirm the supposition that this object is an extinct comet. 相似文献
8.
We examine the hypothesis about the formation of meteor streams near the Sun. Families of short-perihelion orbit comets, many of which pass just a few radii from the solar surface at perihelion and have high dust production efficiencies, are assumed to be candidates for the parent bodies of these meteor streams. Our statistical analysis of orbital and kinematic parameters for short-perihelion meteoric particles recorded at the Earth and comets from the Kreutz family and the Marsden, Kracht, and Meyer groups led us to certain conclusions regarding the proposed hypothesis. We found a correlation between the ecliptic longitude of perihelion for comet and meteor orbits and the perihelion distance. This correlation may be suggestive of either a genetic connection between the objects of these two classes or the result of an as yet unknown mechanism that equally acts on short-perihelion comet and meteor orbits. A reliable conclusion about this genetic connection can be reached for the meteors that belong to the Arietids stream and the Marsden comet group. 相似文献
9.
We are entering in a new era of space exploration signed by sample return missions. Since the Apollo and Luna Program, the study of extraterrestrial samples in laboratory is gathering an increased interest of the scientific community so that nowadays exploration program of the Solar System is characterized by swelling sample return missions. Beside lunar samples, the NASA Stardust mission was the first successful space mission that on 15 January 2006 brought to Earth solid extraterrestrial samples collected from comet 81P/Wild 2 coma. Grains were collected during cometary fly-by into aerogel and once on Earth have been extracted for laboratory analyses. In the coming two decades many space missions on going or under study will harvest samples from minor bodies. Measurements required for detailed analysis that cannot be performed from a robotic spacecraft, will be carried out on Earth laboratories with the highest analytical accuracy attainable so far. An intriguing objective for the next sample return missions is to understand the nature of organic compounds. Organic compounds found in Stardust grains even if processed to large extend during aerogel capturing are here reported. Major objectives of Marco Polo mission are reported. Various ground-based observational programs within the framework of general characterizations of families and classes, cometary–asteroid transition objects and NEOs with cometary albedo are discussed and linked to sample return mission. 相似文献
10.
PETER JENNISKENS 《Earth, Moon, and Planets》2004,95(1-4):723-732
The successful application of modern observing techniques for Leonid storm observations show that meteor (shower) detections will have a bright future if the field will pursue difficult but important questions. How to forecast a satellite threatening meteor storm? What happens to the organic matter in meteors and can this be an important source of prebiotic molecules? What range of variations in composition and morphology exists among cometary grains and what does this tell us about the origin of the solar system? What long-period comets approach Earth orbit and can meteoroid streams provide early warning for giant impacts? What are the sources of interstellar and interplanetary grains? Just to mention a few. To answer these questions will need new technologies and facilities, some of which are being developed for other use. This may include NASA’s Stratospheric Observatory For Infrared and sub-millimeter Astronomy (SOFIA). In addition, big-science space missions can drive the field if meteor detections are an integral part. Special events, such as meteor outbursts and the “artificial meteor” from the reentry of sample return capsules from interplanetary space, can mobilize observing and theoretical efforts. These and other future opportunities are briefly discussed. 相似文献
11.
The meteoroid streams associated to short-period comets 9P/Tempel 1 (the target of the Deep Impact mission). and 67P/Churyumov-Gerasimenko (the target of the Rosetta mission) are studied. Their structure is overwhelmingly under the
control of Jupiter and repeated relatively close encounters cause a reversal of the direction of the spatial distribution
of the stream relative to the comet* an initial stream trailing the comet as usually seen eventually collapses, becomes a
new stream leading the comet and even splits into several components. Although these two comets do not produce meteor showers
on Earth, this above feature shows that meteor storms can occur several years before the perihelion passage of a parent body. 相似文献
12.
Štefan Gajdoš 《Earth, Moon, and Planets》2008,102(1-4):117-123
A new meteroid stream—October Ursa Majorids—was announced by Japanese observers on Oct. 14–16, 2006 (Uehara et al. 2006).
Its weak manifestation was detected among coincidental major meteor showers (N/S Taurids, Orionids), as its meteors radiated
from a higher placed radiant on the northern sky. We have tried to find out previous displays of the stream throughout available
meteor orbits databases, and among ancient celestial phenomena records. Although we got no obvious identification, there are
some indications that it could be a meteor shower of cometary origin with weak/irregular activity, mostly overlayed by regular
coincidental meteor showers. With a procedure based on D-criterion (Southworth and Hawkins 1963) we found a few records in IAU MDC database of meteor photographic orbits which fulfill
common similarity limits, for October Ursae Majorids. However, their real association cannot be established, yet. With respect
to the mean orbit of this stream, we suggest for its parent body a long-period comet. 相似文献
13.
Jemma DAVIDSON Henner BUSEMANN Ian A. FRANCHI 《Meteoritics & planetary science》2012,47(11):1748-1771
Abstract– Interplanetary dust particles (IDPs) are the most primitive extraterrestrial material available for laboratory studies and may, being likely of cometary origin, sample or represent the unaltered starting material of the solar system. Here we compare IDPs from a “targeted” collection, acquired when the Earth passed through the dust stream of comet 26P/Grigg‐Skjellerup (GSC), with IDPs from nontargeted collections (i.e., of nonspecific origin). We examine both sets to further our understanding of abundances and character of their isotopically anomalous phases to constrain the nature of their parent bodies. We identified ten presolar silicates, two oxides, one SiC, and three isotopically anomalous C‐rich grains. One of seven non‐GSC IDPs contains a wealth of unaltered nebula material, including two presolar silicates, one oxide, and one SiC, as well as numerous δD and δ15N hotspots, demonstrating its very pristine character and suggesting a cometary origin. One of these presolar silicates is the most 17O‐rich discovered in an IDP and has been identified as a possible GEMS (glass with embedded metal and sulfides). Organic matter in an anhydrous GSC IDP is extremely disordered and, based on Raman spectral analyses, appears to be the most primitive IDP analyzed in this study, albeit only one presolar silicate was identified. No defining difference was seen between the GSC and non‐GSC IDPs studied here. However, the GSC collectors are expected to contain IDPs of nonspecific origin. One measure alone, such as presolar grain abundances, isotopic anomalies, or Raman spectroscopy cannot distinguish targeted cometary from unspecified IDPs, and therefore combined studies are required. Whilst targeted IDP populations as a whole may not show distinguishable parameters from unspecified populations (due to statistics, heterogeneity, sampling bias, mixing from other cometary sources), particular IDPs in a targeted collection may well indicate special properties and a fresh origin from a known source. 相似文献
14.
The structures of the meteor streams of cometary origin—Draconids, Ursids, Perseids, and Lyrids—and the streams presumably connected with asteroids—Taurids and α-Capricornids—are compared. The comparative analysis was performed by the mass distribution of meteoroids in the stream and the activity profile for the meteors with the maximum recorded stellar magnitude +3 m and brighter. Visual observations of 1987–2008 from the database of the International Meteor Organization (IMO) and earlier sources were considered. It has been shown that the structures of the meteor streams of cometary and, presumably, asteroidal origin differ somewhat by the activity profile and the mass distribution of meteoroids in the cross-section of a stream along the Earth’s orbit. 相似文献
15.
Apostolos A. Christou Jeremie Vaubaillon Paul Withers 《Earth, Moon, and Planets》2008,102(1-4):125-131
We have simulated the formation and evolution of comet 1P/Halley’s meteoroid stream by ejecting particles from the nucleus
5000 years ago and propagating them forward to the present. Our aim is to determine the existence and characteristics of associated
meteor showers at Mars and Venus and compare them with 1P/Halley’s two known showers at the Earth. We find that one shower
should be present at Venus and two at Mars. The number of meteors in those atmospheres would, in general, be less than that
at the Earth. The descending node branch of the Halley stream at Mars exhibits a clumpy structure. We identified at least
one of these clumps as particles trapped in the 7:1 mean motion resonance with Jupiter, potentially capable of producing meteor
ourbursts of ZHR∼1000 roughly once per century. 相似文献
16.
Tempel—Tuttle彗星与近年的狮子座流星雨 总被引：1，自引：0，他引：1
对狮子座流雨的历史进行了回顾和讨论，并利用“彗星－地球轨道分离（CEOS）及地球滞后彗星时间（TE－C）”统计图进行分析，发现几乎所有的狮子座流星都位于一个倾斜的方框内，而这倾斜方框械右边界的斜率大约为15m/s，方框的宽度大约为4yr，它表明，33年一度的狮子座流星雨一般不会有超过4年的爆发期，更细致的分析表明，最强的流星暴位于一弯曲的细窄条带，在慧星一次回归期，亮流星的比例将年衰减，这些事实，可以用运动，碎裂，扩散和尘埃彗尾模型进行解释，由15m/s速度得到的流星体尺度大小也与事实相容，并且，这表明与地球相遇的流星体粒子是以有限的速度偏离彗星时间（TE－C）就越长，由此倾斜方框的存在，可以对未来狮子座流星雨进行了预报，表明在1998－2000年期间将有较强的狮子座流星雨，中心在1999年，至于2000年以后，要在100多年以后才会有较强的流星暴，而狮子座流星雨的辉煌期可以说已经过去。 相似文献
17.
I. P. Williams 《Celestial Mechanics and Dynamical Astronomy》2001,81(1-2):103-113
Meteors are streaks of light seen in the upper atmosphere when particles from the inter-planetary dust complex collide with the Earth. Meteor showers originate from the impact of a coherent stream of such dust particles, generally assumed to have been recently ejected from a parent comet. The parent comets of these dust particles, or meteoroids, fortunately, for us tend not to collide with the Earth. Hence there has been orbital changes from one to the other so as to cause a relative movement of the nodes of the meteor orbits and that of the comet, implying changes in the energy and/or angular momentum. In this review, we will discuss these changes and their causes and through this place limits on the ejection process. Other forces also come into play in the longer term, for example perturbations from the planets, and the effects of radiation pressure and Poynting–Robertson drag. The effect of these will also be discussed with a view to understanding both the observed evolution in some meteor streams. Finally we will consider the final fate of meteor streams as contributors to the interplanetary dust complex. 相似文献
18.
P. Gronkowski 《Monthly notices of the Royal Astronomical Society》2009,397(2):883-889
The catastrophic thermodynamic destruction of large cometary heterogeneous grains lying on the surface of a comet nucleus is examined. The core–mantle grain-structure model is assumed. Grain fragmentation as an explanation of sudden changes in cometary brightness is proposed. The approach presented to the problem of cometary outbursts is a development of a previous author's paper. The proposed mechanism is based on the idea of thermodynamical destruction of heterogeneous cometary grains. Numerical simulations have been carried out for a wide range of values of physical characteristics of cometary material. The results obtained are consistent with observational data. The main conclusion of this paper is that thermodynamical fragmentation of large grains can explain variations in brightness and also outbursts of comets. 相似文献
19.
One minute counts obtained during the meteor outburst of α-Monocerotids on November 22, 1995, are analyzed in order to examine the possibility of filamentary structure in the stream profile. None is found. It is argued that far-comet type outbursts are due to the Earth's passage through the dust trail of a long period comet, thus offering a direct means of studying such comet dust trails. Hence, the meteor stream activity curve is the first accurate cross section of dust densities through a comet dust trail. 相似文献
20.
P. Gronkowski 《Astronomische Nachrichten》2002,323(1):49-56
Cometary outbursts, sudden increases in luminosity have not been clearly explained so far and their source is still a mystery. Various possible mechanisms as a source of cometary outbursts at large distances from the Sun have been considered. It has been stated that plausible mechanisms are the polymerization of HCN and the amorphous water ice transformation combined with electrostatic destruction of cometary grains in the head of the comet. The calculations have been carried out for a large range of cometary parameters and it has been shown that the proposed scenario of the outburst gives a jump in the comet brightness which is consistent with the real jump observed during the 29P/Schwassmann‐Wachmann 1 outbursts. 相似文献