Variability of D and H in the Martian upper atmosphere observed with the MAVEN IUVS echelle channel. Issue 2 (15th February 2017)

• Record Type: Journal Article
• Authors: Clarke, J. T.; Mayyasi, M.; Bhattacharyya, D.; Schneider, N. M.; McClintock, W. E.; Deighan, J. I.; Stewart, A. I. F.; Chaufray, J.‐Y.; Chaffin, M. S.; Jain, S. K.; Stiepen, A.; Crismani, M.; Holsclaw, G. M.; Montmessin, F.; Jakosky, B. M.
• Is Part Of: Journal of geophysical research. Volume 122:Issue 2(2017)
• Page Start: 2336
• Page End: 2344
• Publication Date: 2017-02-15
• Subjects: mars -- atmosphere -- escape; Magnetospheric physics -- Periodicals; Space environment -- Periodicals; Cosmic physics -- Periodicals; Planets -- Atmospheres -- Periodicals; Heliosphere (Astrophysics) -- Periodicals; Geophysics -- Periodicals; 523.01
• DOI: 10.1002/2016JA023479
• Languages: English
• ISSNs: 2169-9380

Abstract

Abstract: The MAVEN IUVS instrument contains an echelle spectrograph channel designed to measure D and H Ly α emissions from the upper atmosphere of Mars. This channel has successfully recorded both emissions, which are produced by resonant scattering of solar emission, over the course of most of a martian year. The fundamental purpose of these measurements is to understand the physical principles underlying the escape of H and D from the upper atmosphere into space, and thereby to relate present‐day measurements of an enhanced HDO/H2 O ratio in the bulk atmosphere to the water escape history of Mars. Variations in these emissions independent of the solar flux reflect changes in the density and/or temperature of the species in the upper atmosphere. The MAVEN measurements show that the densities of both H and D vary by an order of magnitude over a martian year, and not always in synch with each other. This discovery has relevance to the processes by which H and D escape into space. One needs to understand the controlling factors to be able to extrapolate back in time to determine the water escape history from Mars at times when the atmosphere was thicker, when the solar flux and solar wind were stronger, etc. Further measurements will be able to identify the specific controlling factors for the large changes in H and D, which likely result in large changes in the escape fluxes of both species. Key Points: First observations with the MAVEN IUVS echelle channel are presented H and D Ly α emissions from Mars are highly variable, both absolutely and with respect to each other Observations are consistent with large seasonal changes with implications for history of water escape