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The relation between the surface composition anomaly and the distribution of the exosphere of Mercury
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  • Yudai Suzuki,
  • Kazuo Yoshioka,
  • Go Murakami,
  • Ichiro Yoshikawa
Yudai Suzuki
University of Tokyo

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Kazuo Yoshioka
The University of Tokyo
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Go Murakami
Japan Aerospace Exploration Agency
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Ichiro Yoshikawa
University of Tokyo
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In celestial bodies with collisionless atmospheres, such as Mercury, the spatial distribution of the exosphere is expected to reflect the surface composition. In this study, we discuss whether the distribution of Mg, Ca, and Na, the primary exospheric components on Mercury, have exosphere-surface correlation (ESC) by analyzing the observation data of the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) onboard the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. As a result, it was found that Mg has strong ESC, Ca has weak ESC and Na has little ESC. The Monte Carlo simulations of trajectory in the exosphere show that the weak ESC of Ca is due to the relatively large solar radiation acceleration. Na has ESC only in high-temperature regions around 0°E. This can be explained well by considering that the weakly physisorbed Na layer on the surface is depleted under high temperature and that the distribution of strongly chemisorbed Na atoms is reflected in the exosphere. Based on these results, the conditions for components with ESC in celestial bodies with thin atmospheres include low volatility and little solar radiation acceleration.