Meteor hurricane at Mars on 2014 October 19 from comet C/2013 A1

International audienceComet C/2013 A1 will make a very close approach with the planet Mars on 2014 October 19. For this event, we compute the density of cometary dust particles around the Mars Express spacecraft, in order to assess the real risk for space probes. We also estimate the zenithal hourly rate (ZHR) and discuss observational opportunities for the resulting Martian meteor shower. We find, for a surface of 2.7 m 2 , that the Mars Express spacecraft will experience approximately 10 impacts from particles larger than 100 µm in size. The fluence per square metre is found to be 3.5 during the encounter. The equivalent ZHR is computed to be ZHR 4.75 × 10 9 h −1 , making this event the strongest meteor storm ever predicted. We call this event a 'meteor hurricane', which we define to be a meteor shower with ZHR exceeding 10 6 h −1

Characterisation of chaos in meteoroid streams. Application to the Geminids

Dynamically linking a meteor shower with its parent body can be challenging. This is in part due to the limits of the tools available today (such as D-criteria) but is also due to the complex dynamics of meteoroid streams. We choose a method to study chaos in meteoroid streams and apply it to the Geminid meteoroid stream. We decided to draw chaos maps. Amongst the chaos indicators we studied, we show that the orthogonal fast Lyapunov indicator is particularly well suited to our problem. The maps are drawn for three bin sizes, ranging from $10^{-1}$ to $10^{-4}$ m. We show the influence of mean-motion resonances with the Earth and with Venus, which tend to trap the largest particles. The chaos maps present three distinct regimes in eccentricity, reflecting close encounters with the planets. We also study the effect of non-gravitational forces. We determine a first approximation of the particle size $r_{lim}$ needed to counterbalance the resonances with the diffusion due to the non-gravitational forces. We find that, for the Geminids, $r_{lim}$ lies in the range $[3;8]\times 10^{-4}$ m. However, $r_{lim}$ depends on the orbital phase space.Comment: 14 pages, 14 figures, Published in A&

Characterisation of chaos and mean-motion resonances in meteoroid streams -- Application to the Draconids and Leonids

Context. Dynamically linking a meteor shower with its parent body is challenging, and chaos in the dynamics of meteoroid streams may be one of the reasons. For a robust identification of parent bodies, it is therefore necessary to quantify the amount of chaos involved in the evolution of meteoroid streams. Aims. The characterisation of chaos in meteoroid streams thanks to chaos maps is still a new field of study. We aim to study two very different meteoroid streams, the Draconids and the Leonids, in order to obtain a general view of this topic. Methods. We use the method developed in a previous paper dedicated to Geminids, drawing chaos maps with the orthogonal fast Lyapunov indicator. We choose four particle size ranges to investigate the effect of non-gravitational forces. As the dynamics is structured by mean-motion resonances with planets, we compute the locations and widths of the resonances at play. We use semi-analytical formulas valid for any eccentricity and inclination and an arbitrary number of planets. Results. We pinpoint which mean-motion resonances with Jupiter play a major role in the dynamics of each meteoroid stream. We show how those resonances tend to trap mostly large particles, preventing them from meeting with Jupiter. We also study particles managing to escape those resonances, thanks to the gravitational perturbation of Saturn for example. Finally, we explain why non-gravitational forces do not disturb the dynamics much, contrary to what is observed for the Geminids.Comment: Submited to A&

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

``Meteor streams'' do not exist.

International audienceThe difference between a meteoroid stream and a meteor shower is well understood today: meteoroid stream evolving in the interplanetary space cause meteor showers when they enter an atmosphere. For this reason, the expression ``meteor stream'' is a non-sense: meteors are organised as showers and do not exist outside an atmosphere. Although the usage of ``meteor stream'' in the literature decreases since the early 2000s, the effort to correctly use meteor-related vocabulary in order to clarify the different phenomena is to be continued

Retour sur la campagne d'observation des Géminides

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A (revised) confidence index for the forecasting of meteor showers

International audienceA confidence index for the forecasting of meteor showers is presented. The goal is to provide users with information regarding the way the forecasting is performed, so several degrees of confidence is achieved. This paper presents the meaning of the index coding system

A (revised) confidence index for the forecasting of the meteor showers

International audienceThe prediction of meteor shower is known to provide several quality results depending on how it is performed. As a consequence it is hard to have an idea of how much one can trust a given prediction. In this paper I will present a revised confidence index, aiming to provide users with information regarding the way the prediction was performed. An effort to quantify the influence of close encounters with the parent body of a meteor shower is part of this confidence index. In fine, a single code will be provided for each prediction of meteor showers at any planet with a focus on Earth, Mars and Venus