Spectral and orbital survey of medium-sized meteoroids

Abstract

Aims. 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. Methods. 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 spectral classification based on relative intensity ratios of Na, Mg, and Fe and corresponding monochromatic light curves. Heliocentric orbits, trajectory parameters, and material strengths inferred from empirical K B and P E parameters were determined for 146 meteoroids.Results. 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. The preservation of volatiles in larger meteoroids is directly observed. 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 α-Capricornids of the inactive comet 169P/NEAT and δ-Aquarids of the sungrazing 96P/Machholz. We also find a spectral similarity between κ-Cygnids and Taurids, which could imply a similar composition of the parent objects of the two streams.A&A proofs: manuscript no. AA_2019_36093_p Fig. 1: Slovak part of the global AMOS network. Observations of the AMOS-Spec and AMOS stations by the Astronomical and Geophysical Observatory in Modra (AGO), Arborétum Tesárske Mlyňany (ARBO), Kysucké Nové Mesto (KNM), and Važec (VAZ) were used in this work. Red, green, and blue labels designate operating standard AMOS cameras, spectral stations, and planned stations.low-resolution meteor spectra , the rough composition (chondritic, achondritic, metallic) can be identified. We attempt to verify this hypothesis and try to look for additional information about the meteoroid nature and structure that can be revealed from determined orbital and atmospheric parameters.One of the most surprising results of the study by Borovička et al. (2005) was the large number of the detected pure-iron meteoroids, suggesting that iron meteoroids prevail among mmsized meteoroids on asteroidal orbits. These results are...

Characterization of the June epsilon Ophiuchids meteoroid stream and the comet 300P/Catalina

“…The determined mean Na/Mg and Fe/Mg intensity ratios in JEO meteors are presented in Table 2. Sodium depletion in meteor spectra has previously been linked with processes of space weathering: thermal desorption during close perihelion approaches (q ≤ 0.2 au) and cosmic ray irradiation for meteors on Halley-type orbits (Borovička et al 2005;Kasuga et al 2006;Matlovič et al 2019). With the relatively short-period, Jupiter-family type orbit of the stream (Table 1) and q ≈ 0.89 au, these processes do not explain the obtained Na/Mg ratios.…”

“…Each analyzed spectrum was manually scanned in individual frames, calibrated, and fitted according to the procedure de-scribed in Matlovič et al (2019). After the reduction of the continuum radiation and atmospheric emission lines and bands, which are generally very faint in spectra of slow meteors, all present meteor emission lines were identified and measured.…”

“…All four meteors exhibit similar spectral features with corresponding Na/Mg/Fe intensity ratios in the 500 -600 nm region. This part of the spectrum lays in the region of high spectral sensitivity of the AMOS-Spec-HR (Matlovič et al 2019) and is typically used to characterize the spectral type of a meteoroid (Borovička et al 2005). The 500 -600 nm region was fitted by all contributing emission lines taken from published line lists (Borovička 1994a) and the NIST database (Kramida et al 2018).…”

Possibility of transporting material from Ceres to NEO region via 8:3 MMR with Jupiter

“…The delivery of meteoroids from Ceres might be of interest to meteor spectroscopists. Several works have now reported the detection of Na-rich meteoroids from asteroidal orbits (Borovička et al 2005;Vojáček et al 2015;Matlovič et al 2019). Though the increased Na content in some of these may be caused by an incomplete correction for the low excitation of Na I (Matlovič et al 2020), it is possible that some of these bodies reflect a real Na-rich asteroidal composition.…”

Iron Rain: measuring the occurrence rate and origin of small iron meteoroids at Earth

“…Augmenting these data from mm-sizes, Matlovič et al (2019) presented a combined spectral-physical-orbital survey of 202 meteors having peak brightness from -1 to -14, corresponding to cm to dm sizes. Only one pure iron spectra was found in their sample, corresponding to an abundance of 0.5%.…”