Author/Authors :
Burger، نويسنده , , Matthew H. and Killen، نويسنده , , Rosemary M. and McClintock، نويسنده , , William E. and Merkel، نويسنده , , Aimee W. and Vervack Jr.، نويسنده , , Ronald J. and Cassidy، نويسنده , , Timothy A. and Sarantos، نويسنده , , Menelaos، نويسنده ,
Abstract :
The Mercury Atmospheric and Surface Composition Spectrometer on the MESSENGER spacecraft has observed calcium emission in Mercury’s exosphere on a near-daily basis since March 2011. During MESSENGER’s primary and first extended missions (March 2011 – March 2013) the dayside calcium exosphere was measured over eight Mercury years. We have simulated these data with a Monte Carlo model of exospheric source processes to show that (a) there is a persistent source of energetic calcium located in the dawn equatorial region, (b) there is a seasonal dependence in the calcium source rate, and (c) there are no obvious year-to-year variations in the near-surface dayside calcium exosphere.
Keywords :
mercury , Atmospheres , Spectroscopy , Structure , Atmosphere , mercury
