New observations of molecular nitrogen in the Martian upper atmosphere by IUVS on MAVEN

Michael H. Stevens (1) , J. S. Evans (2) , Nick M. Schneider (3) , A. Ian F. Stewart (3) , Justin Deighan (3) , Sonal K. Jain (3) , Matteo Crismani (3) , Arnaud Stiepen (3) , Michael S. Chaffin (3) , William E. Mcclintock (3) , Greg M. Holsclaw (3) , Franck Lefèvre (4, 5) , Daniel Y. Lo (6) , John T. Clarke (7) , Franck Montmessin (5) , Stephen W. Bougher (8) , Bruce M. Jakosky (3)

1 NRL - Naval Research Laboratory
2 Computational Physics, Inc.
3 LASP - Laboratory for Atmospheric and Space Physics [Boulder]
4 PLANETO - LATMOS
5 PLANETO - LATMOS
6 LPL - Lunar and Planetary Laboratory [Tucson]
7 CSP - Center for Space Physics [Boston]
8 AOSS - Department of Atmospheric, Oceanic, and Space Sciences [Ann Arbor]

We identify molecular nitrogen (N2) emissions in the Martian upper atmosphere using the Imaging Ultraviolet Spectrograph (IUVS) on NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN) mission. We report the first observations of the N2 Lyman-Birge-Hopfield (LBH) bands at Mars and confirm the tentative identification of the N2 Vegard-Kaplan (VK) bands. We retrieve N2 density profiles from the VK limb emissions and compare calculated limb radiances between 90 and 210 km against both observations and predictions from a Mars general circulation model (GCM). Contrary to earlier analyses using other satellite data, we find that N2 abundances exceed GCM results by about a factor of 2 at 130 km but are in agreement at 150 km. The analysis and interpretation are enabled by a linear regression method used to extract components of UV spectra from IUVS limb observations.

Mots clés: MAVEN; thermosphere; Mars; ultraviolet; spectroscopy; airglow

Domaines: Physique Atmosphérique et Océanique [physics.ao-ph]

Michael H. Stevens, J. S. Evans, Nick M. Schneider, A. Ian F. Stewart, Justin Deighan, et al.. New observations of molecular nitrogen in the Martian upper atmosphere by IUVS on MAVEN. Geophysical Research Letters, 2015, 42 (21), pp.9050-9056. ⟨10.1002/2015GL065319⟩. ⟨insu-01238173⟩