An Upper Limit on Neutral Calcium in Mercury's Atmosphere

✍ Scribed by A.L. Sprague; R.W.H. Kozlowski; D.M. Hunten; F.A. Grosse

• Publisher: Elsevier Science
• Year: 1993
• Tongue: English
• Weight: 224 KB
• Volume: 104
• Category: Article
• ISSN: 0019-1035
• DOI: 10.1006/icar.1993.1080

✦ Synopsis

High-resolution spectroscopic measurements of Mercury were made at (4227 \AA) to search for neutral calcium in the atmosphere. An upper limit to the intensity is (9.0 \mathrm{kR}); the corresponding (\mathrm{Ca}) column abundance is (<7.4 \times 10^{8}) atoms (\mathrm{cm}^{-2}) with a (\mathrm{Ca} / \mathrm{Na}) ratio of (<\mathbf{0 . 0 0 5}). The lifetime of (\mathrm{Ca}) against photoionization is about (60 %) that of (\mathrm{Na}), and their cosmic abundances are similar; thus, it is likely that release of (\mathbf{C a}) to the atmosphere is less efficient, the surface is relatively enriched in (\mathrm{Na}), or both. O 1993 Academic Press, Inc.