Probing the use of spectroscopy to determine the meteoritic analogues of meteors

Abstract

Context. Determining the source regions of meteorites is one of the major goals of current research in planetary science. Whereas asteroid observations are currently unable to pinpoint the source regions of most meteorite classes, observations of meteors with camera networks and the subsequent recovery of the meteorite may help make progress on this question. The main caveat of such an approach, however, is that the recovery rate of meteorite falls is low (<20 %), implying that the meteoritic analogues of at least 80% of the observed falls remain unknown. Aims. Spectroscopic observations of incoming bolides may have the potential to mitigate this problem by classifying the incoming meteoritic material. Methods. To probe the use of spectroscopy to determine the meteoritic analogues of incoming bolides, we collected emission spectra in the visible range (320-880 nm) of five meteorite types (H, L, LL, CM, and eucrite) acquired in atmospheric entry-like conditions in a plasma wind tunnel at the Institute of Space Systems at the University of Stuttgart (Germany). A detailed spectral analysis including a systematic line identification and mass ratio determinations (Mg/Fe, Na/Fe) was subsequently performed on all spectra.Results. It appears that spectroscopy, via a simple line identification, allows us to distinguish the main meteorite classes (chondrites, achondrites and irons) but it does not have the potential to distinguish for example an H chondrite from a CM chondrite. Conclusions. The source location within the main belt of the different meteorite classes (H, L, LL, CM, CI, etc.) should continue to be investigated via fireball observation networks. Spectroscopy of incoming bolides only marginally helps precisely classify the incoming material (iron meteorites only). To reach a statistically significant sample of recovered meteorites along with accurate orbits (>100) within a reasonable time frame (10-20 years), the optimal solution may be the spatial extension of existing fireball observation networks.

Luminosity calculation of meteor entry based on detailed flow simulations in the continuum regime

“…Nonetheless, spraying of the molten layer seams to be the most plausible explanation for the appearance of refractory elements in the spectra, as was also the conclusion of Borovička (1993). The rationale proposed here can also be supported by the experimental spectra of Drouard et al (2018), which does not consider the spraying of the molten thickness. From the high-resolution spectra, these latter authors observed an overestimation of Na with respect to Fe and Mg and a weak intensity of refractory Ca.…”

Spectral and orbital survey of medium-sized meteoroids

“…We present the first wide survey of spectral and physical properties of mm-to dm-sized meteoroids. While the specific material types (e.g., types of chondrites) cannot be distinguished from the low-resolution emission spectra (Borovička et al 2015;Drouard et al 2018), the combination of spectral, orbital, and atmospheric meteor data allows us to reveal the rough composition, structure, and source of meteoroids.…”

“…There have been successful models of meteor radiation providing relevant results of relative abundances of the main elements. These models have been mostly applied to individual bright fireball spectra captured in high resolution (Borovička 1993;Trigo-Rodriguez et al 2003;Ferus et al 2018;Drouard et al 2018). In order to survey larger samples of meteor spectra, a simplified method of spectral classification (Borovička et al 2005) has been introduced, which is also applicable to more effective low-resolution video observations.…”

Asteroid-Meteoroid Complexes

“…Borovička, 2001;Borovička et al, 2005;Koten et al, 2006). Laboratory spectroscopic experiment proves that intensity ratios are not informative of the abundance and cannot be used to determine the meteorite analogue (Drouard et al, 2018). Line ratios can be used, at best, to study the trend of elemental content in meteors which happen to possess similar physical conditions (including similar entry velocities, similar strengths and similar excitation temperatures).…”