Detection of Mercury's Potassium Tail

Abstract : Ground-based observations of Mercury's exosphere bridge the gap between the MESSENGER and BepiColombo missions and provide a broad counterpart to their in situ measurements. Here we report the first detection of Mercury's potassium tail in both emission lines of the D doublet. The sodium to potassium abundance ratio at 5 planetary radii down-tail is approximately 95, near the mid-point of a wide range of values that have been quoted over the planet's disk. This is several times the Na/K present in atmospheres of the Galilean satellites and more than an order of magnitude above Mercury's usual analogue, the Moon. The observations confirm that Mercury's anomalously high Na/K ratios cannot be explained by differences in neutral loss rates. The width and structure of the Na and K tails is comparable and both exhibit a persistent enhancement in their northern lobe. We interpret this as a signature of Mercury's offset magnetosphere; the exosphere's source rates are locally enhanced at the southern surface, and sloshing from radiation pressure and gravity guides this population into the northern region of the tail.
Type de document :
Communication dans un congrès
49th Annual Division for Planetary Sciences Meeting, Oct 2017, Provo, United States
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Contributeur : Catherine Cardon <>
Soumis le : jeudi 14 décembre 2017 - 18:14:28
Dernière modification le : mercredi 21 mars 2018 - 18:58:12




Carl Schmidt, François Leblanc, Luke Moore, Thomas A. Bida. Detection of Mercury's Potassium Tail. 49th Annual Division for Planetary Sciences Meeting, Oct 2017, Provo, United States. 〈insu-01664385〉



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