P21A-2061
Retrieval of Mars' Upper Atmospheric Composition using Dayglow Observations by IUVS on MAVEN
Tuesday, 15 December 2015
Poster Hall (Moscone South)
Joseph Scott Evans1, Michael H Stevens2, Jerry D Lumpe Jr3, Nicholas McCord Schneider4, Ian F Stewart5, Justin Deighan5, Sonal Jain5, Michael Chaffin5, Matteo Michael James Crismani5, Arnaud Stiepen4, Bill McClintock5, Greg Holsclaw5, Franck Lefèvre6, Daniel Lo7, John T Clarke8, Francis Epavier5, Ed Thiemann5, Phillip C Chamberlin9, Stephen W Bougher10, Jared Micheal Bell11, Paul R Mahaffy9, Mehdi Benna9 and Bruce Martin Jakosky5, (1)Computational Physics Inc, Springfield, VA, United States, (2)US Naval Research Laboratory, Washington, DC, United States, (3)Computational Physics, Inc., Boulder, CO, United States, (4)University of Colorado at Boulder, Boulder, CO, United States, (5)Laboratory for Atmospheric and Space Physics, Boulder, CO, United States, (6)LATMOS Laboratoire Atmosphères, Milieux, Observations Spatiales, Paris Cedex 05, France, (7)University of Arizona, Tucson, AZ, United States, (8)Boston University, Boston, MA, United States, (9)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (10)University of Michigan Ann Arbor, Ann Arbor, MI, United States, (11)National Institute of Aerospace, Yorktown, VA, United States
Abstract:
We present direct retrievals of neutral and ion number densities in Mars’s upper atmosphere using FUV and MUV dayglow observations from 130 – 200 km. Atmospheric composition is inferred using the Atmospheric Ultraviolet Radiance Integrated Code [Strickland et al., 1999] adapted to the Martian atmosphere [Evans et al., 2015]. For our retrievals we use emission features observed by IUVS on MAVEN under daytime conditions over both northern and southern hemispheres from October 2014 to September 2015. We use retrieved CO2 densities to derive temperature variability between 150 – 220 km. We also investigate the sensitivity of neutral and ion density retrievals to variability in solar irradiance, solar longitude, and local time. We compare our retrievals to predictions from the Mars Global Ionosphere-Thermosphere Model [MGITM, Bougher et al., 2015], as well as in situ measurements by the Neutral Gas Ionizing Mass Spectrometer [NGIMS, Mahaffy et al., 2014], and quantify the differences throughout the altitude region of interest. The N2/CO2 ratio is used to show that N2 is in the diffusively separated region of the Martian atmosphere with a mean mixing ratio that is consistent with model predictions from MGITM, as well as in situ measurements by Viking 1 & 2 [Nier and McElroy, 1977] and NGIMS.
