Small asteroids intersecting Earth's orbit can deliver extraterrestrial rocks to the Earth, called meteorites. This process is accompanied by a luminous phenomena in the atmosphere, called bolides or fireballs. Observations of bolides provide pre-atmospheric orbits of meteorites, physical and chemical properties of small asteroids, and the flux (i.e. frequency of impacts) of bodies at the Earth in the centimeter to decameter size range. In this chapter we explain the processes occurring during the penetration of cosmic bodies through the atmosphere and review the methods of bolide observations. We compile available data on the fireballs associated with 22 instrumentally observed meteorite falls. Among them are the heterogeneous falls Almahata Sitta (2008 TC$_3$) and Benešov, which revolutionized our view on the structure and composition of small asteroids, the Př\'ıbram-Neuschwanstein orbital pair, carbonaceous chondrite meteorites with orbits on the asteroid-comet boundary, and the Chelyabinsk fall, which produced a damaging blast wave. While most meteoroids disrupt into fragments during atmospheric flight, the Carancas meteoroid remained nearly intact and caused a crater-forming explosion on the ground.
Recent dynamical models of Solar System evolution and isotope studies of rock-forming elements in meteorites have suggested that volatile-rich asteroids formed in the outer Solar System beyond Jupiter's orbit, despite being currently located in the main asteroid belt. The ambient temperature under which asteroids formed is a crucial diagnostic to pinpoint the original location of asteroids and is potentially determined by the abundance of volatiles they contain. In particular, abundances and 13C/12C ratios of carbonates in meteorites record the abundances of carbon-bearing volatile species in …
C-complex asteroids, rich in carbonaceous materials, are potential sources of Earth's volatile inventories. They are spectrally dark resembling primitive carbonaceous meteorites, and thus, C-complex asteroids are thought to be potential parent bodies of carbonaceous meteorites. However, the substantial number of C-complex asteroids exhibits surface spectra with weaker hydroxyl absorption than water-rich carbonaceous meteorites. Rather, they best correspond to meteorites showing evidence for dehydration, commonly attributed to impact heating. Here, we report an old radiometric age of 4564.7 mil…
Investigations of the main asteroid belt and efforts to constrain that population's physical characteristics involve the daunting task of studying hundreds of thousands of small bodies. Taxonomic systems are routinely employed to study the large scale nature of the asteroid belt because they utilize common observational parameters, but asteroid taxonomies only define broadly observable properties and are not compositionally diagnostic (Tholen, 1984; Carvano et al., 2010, Hasselmann et al., 2012). This work builds upon the results of Hardersen et al. (2014, 2015), which has the goal of constrai…
Given the compositional diversity of asteroids, and their distribution in space, it is impossible to consider returning samples from each one to establish their origin. However, the velocity and molecular composition of primary minerals, hydrated silicates, and organic materials can be determined by in situ dust detector instruments. Such instruments could sample the cloud of micrometer-scale particles shed by asteroids to provide direct links to known meteorite groups without returning the samples to terrestrial laboratories. We extend models of the measured lunar dust cloud from LADEE to sho…
Hungaria Asteroid Family as the Source of Aubrite Meteorites
匈牙利小行星位于主小行星带内部，半长轴在1.8至2天文单位之间，离心率低，倾角为16至35度。匈牙利区的小型小行星主要由与（434）匈牙利有关的碰撞族组成。匈牙利族的主要光谱型是E型或X型（Warner et al，2009），主要是由于匈牙利族及其遗传家族的E型组成。人们普遍认为E型小行星与Aubrite陨石有关，也被称为顽火辉石无球粒陨石（Gaffey et al，1992）。在这里，我们探讨的假设，aubrites起源于匈牙利家庭。为了测试这种连接，我们比较模型宇宙射线暴露年龄模型流星体的轨道积分与aubrites。我们发现，长CRE年龄的Aubrites（最长的石质陨石群）反映了从匈牙利到地球的流星体的传递路线是不同的，从主带小行星。我们发现，匈牙利的流星体主要是通过Yarkovsky漂移穿过火星轨道到达地球的，没有轨道共振的帮助。我们的结论是，CRE年龄的Aubrites是完全一致的匈牙利家庭在1.7 AU的内部边界的一个占主导地位的来源。从这里，流星体通过火星穿越区域到达地球，由于碰撞（与匈牙利和内部主带物体），相对较快的交付时间是有利的。我们发现，在灶神星之后，（434）匈牙利是一个无球粒陨石群的小行星源的最佳候选者。
We identify spectral similarities between asteroids and meteorites. We identify spectral matches between 500 asteroid spectra and over 1,000 samples of RELAB meteorite spectra over 0.45-2.5 microns. We reproduce many major and previously known meteorite-asteroid connections and find possible new, more rare or less-established connections. Well-established connections include: ordinary chondrites (OC) with S-complex asteroids; pristine CM carbonaceous chondrites with Ch-type asteroids and heated CMs with C-type asteroids; HED meteorites with V-types; enstatite chondrites with Xc-type asteroids;…
Although spectral surveys and spacecraft missions provide information on small bodies, many important analyses can only be performed in terrestrial laboratories. For now, the total number of parent bodies represented in our meteorites collection is estimated to about 150 parent bodies, of which 50 parent bodies represented by the poorly studied ungrouped chondrites. Linking ungrouped meteorites to their parent bodies is thus crucial to significantly increase our knowledge of asteroids. To this end, the petrography of 25 ungrouped chondrites and rare meteorite groups was studied, allowing group…
Ordinary chondrites (H, L, and LL chondrites) are the most common type of meteorites comprising 80 per cent of the meteorites that fall on Earth. The source region of these meteorites in the main asteroid belt has been a basis of considerable debate in the small bodies community. L chondrites have been proposed to come from the Gefion asteroid family, based on dynamical models. We present results from our observational campaign to verify a link between the Gefion asteroid family and L chondrite meteorites. Near-infrared spectra of Gefion family asteroids (1839) Ragazza, (2373) Immo, (2386) Nik…
The unique CV-type meteorite Khatyrka is the only natural sample in which "quasicrystals" and associated crystalline Cu,Al-alloys, including khatyrkite and cupalite, have been found. They are suspected to have formed in the early Solar System. To better understand the origin of these exotic phases, and the relationship of Khatyrka to other CV chondrites, we have measured He and Ne in six individual, ~40-μm-sized olivine grains from Khatyrka. We find a cosmic-ray exposure age of about 2-4 Ma (if the meteoroid was <3 m in diameter, more if it was larger). The U,Th-He ages of the olivine grains s…
Context. Andesitic meteorites are among the oldest achondrites known to date. They record volcanic events and crust formation episodes in primordial planetesimals that took place about 4.565 Myr ago. However, no analogue for these meteorites has been found in the asteroid population to date. Aims. We searched for spectroscopic analogues of the andesitic meteorite Erg Chech 002 in the asteroid population using the Gaia DR3 spectral dataset. Methods. In order to identify which asteroids have the most similar spectrum to Erg Chech 002, we first determined the spectral parameters of Gaia DR3 aster…
On The Effect of Giant Planets on the Scattering of Parent Bodies of Iron Meteorite from the Terrestrial Planet Region into the Asteroid Belt: A Concept Study
Low-albedo, hydrated objects dominate the list of the largest asteroids. These objects have varied spectral shapes in the 3-$μ$m region, where diagnostic absorptions due to volatile species are found. Dawn's visit to Ceres has extended the view shaped by ground-based observing, and shown that world to be a complex one, potentially still experiencing geological activity. We present 33 observations from 2.2-4.0 $μ$m of eight large (greater than 200 km diameter) asteroids from the C spectral complex, with spectra inconsistent with the hydrated minerals we see in meteorites. We characterize their …
The observed near-Earth asteroid population contains very few objects with small perihelion distances, say, q<=0.2 au. NEAs that currently have orbits with larger q might be hiding a past evolution during which they have approached closer to the Sun. We present a probabilistic assessment of the minimum q that an asteroid has reached during its orbital history. At the same time, we offer an estimate of the dwell time, that is, the time q has been in a specific range. We have re-analyzed orbital integrations of test asteroids from the moment they enter the near-Earth region until they either col…
Understanding the compaction and differentiation of the planetesimals and protoplanets from the Asteroid Belt and the terrestrial planet region of the Solar System requires a reliable modeling of their internal thermal evolution. An important ingredient for this is a detailed knowledge of the heat conductivity of the chondritic mixture of minerals and metal in planetesimals. The temperature dependence of the heat conductivity is evaluated here from the properties of its mixture components by a theoretical model. This allows to predict the temperature dependent heat conductivity for the full ra…
In this work the potential mineral identification of meteorites is analysed for the mid-infrared range, to evaluate observational possibilities for future missions targeting small body surfaces. Three carbonaceous and three ordinary chondrite meteorites are examined by a diffuse reflection (DRIFT) instrument, and the presence of principal minerals is confirmed by a powder diffraction method as well. The possibilities and constraints of mineral identifications in the mid-infrared are simulated by artificially degrading the spectral resolution. Our research shows that for the definite identifica…
Here we report a comparison between reflectance spectroscopy of meteorites under asteroidal environment (high vacuum and temperature) and Main Belt and Near Earth Asteroids spectra. Focusing on the OH absorption feature around 3μm, we show that the asteroidal environment induces a reduction of depth and width of the band, as well as a shift of the reflectance minimum. We then decompose the OH feature into several components with a new model using Exponentially Modified Gaussians. Unlike previous studies, we confirme the link between these components, the aqueous alteration history and the amou…
We measured 3-micron reflectance spectra of 21 meteorites that represent all carbonaceous chondrite types available in terrestrial meteorite collections. The measurements were conducted at the Laboratory for Spectroscopy under Planetary Environmental Conditions (LabSPEC) at the Johns Hopkins University Applied Physics Laboratory (JHU APL) under vacuum and thermally-desiccated conditions (asteroid-like conditions). This is the most comprehensive 3-micron dataset of carbonaceous chondrites ever acquired in environments similar to the ones experienced by asteroids. The 3-micron reflectance spectr…
In studies of the oldest solar system bodies - comets and asteroids - it is their fragments - meteoroids - that provide the most accessible planetary material for detailed laboratory analysis in the form of dust particles or meteorites. Some asteroids and comets were visited by spacecrafts and returned interplanetary samples to Earth, while missions Hayabusa 2 and OSIRIX-REx visiting asteroids Ryugu and Bennu are ongoing. However, the lack of representative samples of comets and asteroids opens the space to gain more knowledge from direct observations of meteoroids. At collision with the Earth…
New Insights into Erg Chech 002 Analogues in the Main Belt from Near-Infrared Spectroscopy
Istituto di Astrofisica e Planetologia Spaziali, Istituto Nazionale di Astrofisica（空间天体物理学与行星学研究所，意大利国家天体物理研究所）；School of Physics and Astronomy, University of Leicester（莱斯特大学物理与天文学院）；Université Côte d’Azur, CNRS–Lagrange, Observatoire de la Côte d’Azur（蔚蓝海岸大学，法国国家科学研究中心-拉格朗日实验室，蔚蓝海岸天文台）；INAF – Osservatorio Astronomico di Roma.（意大利国家天体物理研究所罗马天文台）
The internal structure and strength of small asteroids and large meteoroids is poorly known. Observation of bright fireballs in the Earth's atmosphere can prospect meteoroid structure by studying meteoroid fragmentation during the flight. Earlier evaluations showed that meteoroid strength is significantly lower than that of the recovered meteorites. We present detailed study of atmospheric fragmentation of seven meteorite falls, all ordinary chondrites, and 14 other fireballs, where meteorite fall was predicted but the meteorites, probably also ordinary chondrites, were not recovered. All obse…
Carbonaceous chondrite meteorites are some of the oldest Solar System planetary materials available for study. The CI group has bulk abundances of elements similar to those of the solar photosphere. Of particular interest in carbonaceous chondrite compositions are labile elements, which vaporize and mobilize efficiently during post-accretionary parent-body heating events. Thus, they can record low-temperature alteration events throughout asteroid evolution. However, the precise nature of labile-element mobilization in planetary materials is unknown. Here we characterize the thermally induced m…
Over the past decade there has been a large increase in the number of automated camera networks that monitor the sky for fireballs. One of the goals of these networks is to provide the necessary information for linking meteorites to their pre-impact, heliocentric orbits and ultimately to their source regions in the solar system. We re-compute heliocentric orbits for the 25 meteorite falls published to date from original data sources. Using these orbits, we constrain their most likely escape routes from the main asteroid belt and the cometary region by utilizing a state-of-the-art orbit model o…
The evolution of the meteorite flux to the Earth can be studied by determining the terrestrial ages of meteorite collected in hot deserts. We have measured the terrestrial ages of 54 stony meteorites from the El Médano area, in the Atacama Desert, using the cosmogenic nuclide chlorine 36. With an average age of 710 ka, this collection is the oldest collection of non fossil meteorites at the Earth's surface. This allows both determining the average meteorite flux intensity over the last 2 Myr (222 meteorites larger than 10 g per km2 per Myr) and discussing its possible compositional variability…
The Mo and Ru isotopic compositions of meteorites and the bulk silicate Earth (BSE) hold important clues about the provenance of Earth's building material. Prior studies have argued that non-carbonaceous (NC) and carbonaceous (CC) meteorite groups together define a Mo-Ru 'cosmic' correlation, and that the BSE plots on the extension of this correlation. These observations were taken as evidence that the final 10-15% of Earth's accreted material derived from a homogeneous inner disk reservoir with an enstatite chondrite-like isotopic composition. Here, using new Mo and Ru isotopic data for previ…
The Earth contains between one and ten oceans of water, including water within the mantle, where one ocean is the mass of water on the Earth's surface today. With $n$-body simulations we consider how much water could have been delivered from the asteroid belt to the Earth after its formation. Asteroids are delivered from unstable regions near resonances with the giant planets. We compare the relative impact efficiencies from the $ν_6$ resonance, the 2:1 mean motion resonance with Jupiter and the outer asteroid belt. The $ν_6$ resonance provides the largest supply of asteroids to the Earth, wit…
The existence of Earth's Trojan asteroids is not well constrained and represents a major gap in our inventory of small bodies in near-Earth space. Their discovery would be of high scientific and human interest.
Enstatite chondrites and aubrites are meteorites that show the closest similarities to the Earth in many isotope systems that undergo mass-independent and mass-dependent isotope fractionations. Due to the analytical challenges to obtain high-precision K isotopic compositions in the past, potential differences in K isotopic compositions between enstatite meteorites and the Earth remained uncertain. We report the first high-precision K isotopic compositions of eight enstatite chondrites and four aubrites and find that there is a significant variation of K isotopic compositions among enstatite me…
