Mercury exosphere

Leblanc, François; Doressoundiram, A.

doi:10.1016/j.icarus.2010.09.004

Cited by 14 publications

(4 citation statements)

References 43 publications

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“…They also observed the dawn enhancement of K first noted by Sprague [1992], again indicating a strong mobilization of K by thermal processes. Leblanc and Doressoundiram [2011] assembled all available Mercury exospheric measurements of K and compared them with models that include temperature-driven diffusion and evaporation, photo-and electron desorption, and ion sputtering. Also included in the simulations were the effects of radiation pressure on atoms and the thermal effects of Mercury's eccentric orbit.…”

Section: Implications For the Exospherementioning

confidence: 99%

Variations in the abundances of potassium and thorium on the surface of Mercury: Results from the MESSENGER Gamma‐Ray Spectrometer

et al. 2012

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A technique for converting gamma‐ray count rates measured by the Gamma‐Ray Spectrometer on the MESSENGER spacecraft to spatially resolved maps of the gamma‐ray emission from the surface of Mercury is utilized to map the surface distributions of the elements Si, O, and K over the planet's northern hemisphere. Conversion of the K gamma‐ray count rates to elemental abundances on the surface reveals variations from 300 to 2400 ppm. A comparison of these abundances with models for the maximum surface temperature suggests the possibility that a temperature‐related process is controlling the K abundances on the surface as well as providing K to the exosphere. The abundances of K and Th have been determined for several geologically distinct regions, including Mercury's northern smooth plains and the plains interior to the Caloris basin. The lack of a significant variation in the measured Th abundances suggests that there may be considerable variability in the K/Th abundance ratio over the mapped regions.

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Section: Implications For the Exospherementioning

confidence: 99%

Variations in the abundances of potassium and thorium on the surface of Mercury: Results from the MESSENGER Gamma‐Ray Spectrometer

et al. 2012

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“…Such differences are not necessarily in conflict since Na ejection rates from Mercuryʼs surface are episodic in nature, due to both space weather (Orsini et al 2018) and stochastic meteoroid bombardment (Cassidy et al 2021), and it is unknown whether the K ejection varies proportionally. Leblanc & Doressoundiram (2011) modeled the potassium exosphere and concluded that differences in transport, loss, and desorption efficiencies can explain the spatial variation in Na/K. When these differences are considered, they asserted that Mercuryʼs high Na/K ratio may in fact be consistent with initial solar or meteoric abundance.…”

Section: Introductionmentioning

confidence: 99%

The Spatial Distribution and Temperature of Mercury's Potassium Exosphere

Lierle¹,

Schmidt²,

Baumgardner³

et al. 2022

Planet. Sci. J.

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Aside from the well-studied sodium doublet, the potassium D lines are the only optical emissions in Mercury's exosphere that are amply bright to contrast with the dayside disk. Measurements of the K exosphere are limited compared to Na, but the K regolith abundance is better constrained, so new insights may help to understand surface–exosphere coupling. We use imaging spectroscopy to map the K brightness over Mercury's evening hemisphere, which shows an enhancement at low to midlatitudes, well equatorward of the Na peak. Both Na and K are brighter in the south, but the ratio between northern and southern hemisphere K emission appears less symmetric than that of Na. The disk-averaged Na/K column density ratio is between 70 and 130. During the same night, the dayside emission was mapped, we used a high-resolution spectrograph to attempt to resolve the Na and K line widths on the nightside. Forward-modeling the alkaline line profiles with hyperfine structure gives Na D1 and D2 line widths of 1114 ± 50 K and 1211 ± 45 K, respectively. D2 may appear hotter solely because its higher opacity adds preferentially to the profile wings. The K line width is surprisingly cold and cannot be easily distinguished from the instrumental line width, even at R = 137,500. Line widths roughly constrain K gas between the surface temperature and 1000 K, making it the coldest metallic constituent of Mercury's exosphere. Although Na and K are chemical analogs and often assumed to have similar properties, the results herein illustrate quite different characteristics between these elements in Mercury's exosphere.

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“…The exosphere of Mercury has also been examined in detail and contains ions and neutrals that originate from the solar wind interacting with the space environment and the planet’s surface. Evidence for excited alkali (Na), alkaline earth (Ca and Mg) atoms, H + , He + , He 2+ , Na + , and Ca + ions, and O, Al, K, and Fe atoms, was presented by Killen et al, , Vervack et al, Bida et al, Leblanc et al, and Raines et al Specifically, observations by the Mercury atmospheric and surface composition spectrometer (MACS) revealed the presence of neutral Mg in the antisunward region as well as differing spatial distributions of Mg, Ca, and Na atoms in both the tail and night side near the planet exosphere. Recent observations from the fast imaging plasma spectrometer (FIPS), taken <400 km from the surface, have shown a plasma cusp with energetic heavy ions (i.e., Na + and O + groups).…”

Section: Space-weathering Of Solar System Bodiesmentioning

confidence: 97%