Spectral and orbital survey of medium-sized meteoroids

We investigate the spectra, material properties, and orbital distribution of millimeter- to decimeter-sized meteoroids. Our study aims to distinguish the characteristics of populations of differently sized meteoroids and reveal the heterogeneity of identified meteoroid streams. We verify the surprisingly large ratio of pure iron meteoroids on asteroidal orbits detected among mm-sized bodies. Emission spectra and multi-station meteor trajectories were collected within the AMOS network observations. The sample is based on 202 meteors of -1 to -14 magnitude, corresponding to meteoroids of mm to dm sizes. Meteoroid composition is studied by relative intensity ratios of Na, Mg, and Fe. Heliocentric orbits, trajectory parameters, and material strengths inferred from empirical $K_B$ and $P_E$ parameters were determined for 146 meteoroids. An overall increase of Na content compared to the population of mm-sized meteoroids was detected, reflecting weaker effects of space weathering processes on larger meteoroids. We report a very low ratio of pure iron meteoroids and the discovery of a new spectral group of Fe-rich meteors. The majority of meteoroids on asteroidal orbits were found to be chondritic. Thermal processes causing Na depletion and physical processes resulting in Na-rich spectra are described and linked to characteristically increased material strengths. Numerous major and minor shower meteors were identified in our sample, revealing various degrees of heterogeneity within Halley-type, ecliptical, and sungrazing meteoroid streams. Our results imply a scattered composition of the fragments of comet 2P/Encke and 109P/Swift-Tuttle. The largest disparities were detected within the $\alpha$-Capricornids and $\delta$-Aquarids. We also find a spectral similarity between $\kappa$-Cygnids and Taurids, which could imply a similar composition of the parent objects of the two streams

Analysis of CN emission as a marker of organic compounds in meteoroids using laboratory simulated meteors

Fragments of small solar system bodies entering Earth's atmosphere have possibly been important contributors of organic compounds to the early Earth. The cyano radical (CN) emission from meteors is considered as potentially one of the most suitable markers of organic compounds in meteoroids, however, its detection in meteor spectra has been thus far unsuccessful. With the aim to improve our abilities to identify CN emission in meteor observations and use its spectral features to characterize the composition of incoming asteroidal meteoroids, we present a detailed analysis of CN emission from high-resolution spectra of 22 laboratory simulated meteors including ordinary, carbonaceous, and enstatite chondrites, as well as a large diversity of achondrites (i.e., ureilite, aubrite, lunar, martian, howardite, eucrite, and diogenite), mesosiderite, and iron meteorites. We describe the variations of CN emission from different classes of asteroidal meteor analogues, its correlation and time evolution relative to other major meteoroid components. We demonstrate that CN can be used as a diagnostic spectral feature of carbonaceous and carbon-rich meteoroids, while most ordinary chondrites show no signs of CN. Our results point out strong correlation between CN and H emission and suggest both volatile features are suitable to trace contents of organic matter and water molecules present within meteoroids. For the application in lower resolution meteor observations, we demonstrate that CN can be best recognized in the early stages of ablation and for carbon-rich materials by measuring relative intensity ratio of CN band peak to the nearby Fe I-4 lines

Aperçu du projet MetSpec - météores artificiels en test au sol

International audienceWe provide an overview of the MetSpec project, which aims to connect meteorite ablation laboratory experiments with meteor spectral observations in the atmosphere aiming at the development of a methodology to identify incoming planetary material distribution into the Earth’s atmosphere. We have selected 28 meteorites of different types to represent known planetary material compositions coming from asteroids, Vesta, Mars and the Moon. Some samples have been tested twice which resulted in overall 31 experiments. Three distinct test campaigns were realized in 2020, 2021 and 2022 with the High Enthalpy Flow Diagnostics Group in the Plasma Wind Tunnel PWK1 where they have developed a unique testing scenario. During the last and most elaborated campaign, 16 cameras observed the artificial meteors in the laboratory. Besides videos and online live streaming, instruments included several spectrometers, and optical and imaging instruments covering UV, visible and IR spectral range. This special collection in Icarus collects the resulting output from the different instruments and results. This overview article provides an introduction and summarizes the main findings of the experimental campaigns.Nous présentons une vue d'ensemble du projet MetSpec, qui vise à relier les expériences d'ablation de météorites en laboratoire aux observations spectrales de météorites dans l'atmosphère, dans le but de développer une méthodologie permettant d'identifier la distribution des matériaux planétaires entrants dans l'atmosphère terrestre. Nous avons sélectionné 28 météorites de différents types pour représenter les compositions connues de matériaux planétaires provenant d'astéroïdes, de Vesta, de Mars et de la Lune. Certains échantillons ont été testés deux fois, ce qui a donné lieu à 31 expériences au total. Trois campagnes d'essais distinctes ont été réalisées en 2020, 2021 et 2022 avec le High Enthalpy Flow Diagnostics Group dans la soufflerie à plasma PWK1, où ils ont développé un scénario d'essai unique. Au cours de la dernière campagne, la plus élaborée, 16 caméras ont observé les météores artificiels dans le laboratoire. Outre les vidéos et la diffusion en direct, les instruments comprenaient plusieurs spectromètres et des instruments optiques et d'imagerie couvrant les gammes spectrales de l'UV, du visible et de l'IR. Cette collection spéciale d'Icarus rassemble les résultats obtenus par les différents instruments. Cet article présente une introduction et résume les principaux résultats des campagnes expérimentales