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Seasonal Variations of Mercury's Magnesium Dayside Exosphere from MESSENGER ObservationsThe Ultraviolet and Visible Spectrometer channel of the Mercury Atmospheric and Surface Composition Spectrometer instrument aboard the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft made near-daily observations of solar-scattered resonant emission from magnesium in Mercury's exosphere during the mission's orbital phase (March 2011-April 2015, approx.17 Mercury years). In this paper, a subset of these data (March 2013-April 2015) is described and analyzed to illustrate Mg's spatial and temporal variations. Dayside altitude profiles of emission are used to make estimates of the Mg density and temperature. The main characteristics of the Mg exosphere are (a) a predominant enhancement of emission in the morning (6 am-10 am) near perihelion, (b) a bulk temperature of approx. 6000 K, consistent with impact vaporization as the predominant ejection process, (c) a near-surface density that varies from 5/cu cm to 50/cu cm and (d) a production rate that is strongest in the morning on the inbound leg of Mercury's orbit with rates ranging from 1×10(exp 5)/sq cm/s to 8×10(exp 5)/sq cm/s.
Document ID
20160013305
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
Authors
Merkel, Aimee W.
(Colorado Univ. Boulder, CO, United States)
Cassidy, Timothy A.
(Colorado Univ. Boulder, CO, United States)
Vervack, Ronald J., Jr.
(Johns Hopkins Univ. Laurel, MD, United States)
McClintock, William E.
(Colorado Univ. Boulder, CO, United States)
Sarantos, Menelaos
(Maryland Univ. Baltimore County Baltimore, MD, United States)
Burger, Matthew H.
(Space Telescope Science Inst. Baltimore, MD, United States)
Killen, Rosemary M.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Date Acquired
November 8, 2016
Publication Date
January 1, 2017
Publication Information
Publication: Icarus
Publisher: Elsevier Inc.
Volume: 281
e-ISSN: 1090-2643
Subject Category
Space Sciences (General)
Report/Patent Number
GSFC-E-DAA-TN36899
GSFC-E-DAA-TN37878
Funding Number(s)
CONTRACT_GRANT: NNG11PL02A
CONTRACT_GRANT: NAS5-97271
CONTRACT_GRANT: NAS5-03127
CONTRACT_GRANT: NASW-00002
Distribution Limits
Public
Copyright
Other
Keywords
Ultraviolet
Exosphere
Spectrometer

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