First observation of a meteor in the Martian atmosphere |
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First observation of a meteor in the Martian atmosphere
In passing close to the Sun, comets lose a large number of small particules, which spread out, but continue to travel along the orbit of the comet. When a planet like the Earth encounters this orbit, the particules disintegrate in the atmosphere, producing luminous phenomena, called meteors. This phenomenon has just been, for the first time, identified on Mars, by a team of researchers, with among them an astronomer from Paris Observatory.
First meteor observed in the Martian atmosphere, on 7th March 2004
(Credit : NASA/JPL/Cornell)
On the 7th of March 2004, the Spirit Rover observed a light streak in the Martian atmosphere. It was identified as a meteor produced by debris ejected from comet Wiseman-Skiff (1). This meteor certainly belongs to a regular shower of "shooting stars", cause by the close encounter between Mars and the orbit of this comet. This kind of shower is similar to Perseids or Leonids visible on Earth around 11th August and 17th November.
When a comet passes close to the Sun, many cm-size particules are ejected. They spread out in the vicinity of the cometary orbit. Every year at the same epoch, the Earth passes close to the "dusty" orbit of a comet and intercepts some particles (called meteoroids) which disintegrate and produce meteors. All the meteors belonging to the same shower seem to come from the same point in the Sky called the "radiant". This point allows to name a meteor shower: the Leonids generated by comet Tempel-Tuttle come from the Lion; the Perseids ejected by comet Swift-Tuttle from Perseus). The streak was captured by Spirit at a time when a meteor shower generated by comet Wiseman Skiff was already predicted by Selsis et al. (2004) (2). The "coincidence" becomes unlikely since the streak is aligned with the theoretical radiant associated to Wiseman-Skiff. Finally the nature of the meteor and its original comet were confirmed by the light curve of the meteor, the entry velocity and the configuration of the observation (angular distance between the streak, the radiant, the elevation, the orientation compared to the horizon).
Light curve of the first Martian meteor.
(Crédit : Selsis et al., 2005, Nature, NASA/JPL/Cornell)
It is the first identified Martian meteor. Its detection suggests the existence of a regular meteor shower, occuring each Martian year, and coming from the Cepheus constellation. On Earth, regular showers such as Leonids produce meteor outbursts, or even metor storms like the 1998 or 2002 Leonids. It happens when the Earth collides with a giant cloud of dust (meteoroids) ejected by the parent comet during its return close to the Sun (actually after centuries the particles are spread out along the cometary orbit in such a way that they entirely fill it, and thus cause a regular shower). The regular Martian shower associated to Wiseman Skiff is totally unknown, but a numerical simulation of the orbital evolution of particles ejected during the last returns of comet Wiseman-Skiff close to the Sun suggest an outburst of the Martian Cepheids for 20th December 2007.
French team:
Franck Selsis, Centre de Recherche Astronomique de Lyon, Ecole Normale Supérieure de Lyon
Jérémie Vaubaillon, Institut de Mécanique Céleste et de Calcul des Ephémérides, Observatoire de Paris
American team:
Mark T. Lemmon, Texas A&M University, Department of Atmospheric Science
James F. Bell III, Cornell University, Department of Astronomy
References
(1) F. Selsis, M. Lemmon, J. Vaubaillon, J. Bell ; Nature, 2005
(2) F. Selsis, J. Brillet, M. Rapaport ; Astronomy & Astrophysics, 2004
Contact
Jérémie Vaubaillon (Observatoire de Paris, IMCCE) vaubaill@imcce.fr
