Dayside Temperature Maps of the Upper Mesosphere and Lower Thermosphere of Mars Retrieved From MAVEN IUVS Observations of O I 297.2 nm Emission

Abstract

Past and present remote sensing observations and in situ measurements of the Martian atmosphere, augmented by robust multidimensional modeling efforts, have demonstrated that loss of atomic oxygen and hydrogen into space has irreversibly depleted Mars' atmospheric water reservoir (Chaffin et al., 2017;Stone et al., 2020). The drivers of thermal escape of hydrogen are primarily space weather, waves and tides, and lower atmosphere dynamics related to dust storms and deep convection. Understanding the loss of water at Mars therefore requires that we establish a direct causal link between Mars' water reservoir, lower atmosphere weather, and vertical transport mechanisms. Quantifying the coupling between the lower, middle, and upper atmospheres of Mars, especially during solar

MAVEN/IUVS Observations of OH Prompt Emission: Daytime Water Vapor in the Thermosphere of Mars

“…IUVS consists of two detectors, one that observes the far ultraviolet (FUV, 115–190 nm) and another that observes the middle ultraviolet (MUV, 180–340 nm) (McClintock et al., 2015). Until the work presented here, IUVS operational retrievals were limited to wavelengths shorter than 300 nm (e.g., Evans et al., 2015, 2023; Stevens et al., 2015) primarily due to the limited sensitivity of the MUV channel at longer wavelengths. However, revisions to the calibration at the longer wavelengths using IUVS stellar observations (see Figure S1 in Supporting Information ) have now allowed us to quantitatively analyze the MUV wavelengths out to 316 nm, which includes the OH A 2 Σ + ‐‐ X 2 Π (0,0) vibrational band near 308 nm and the OH(1,1) band near 314 nm, as we will show.…”

“…We also assemble the limb profiles of CO 2 densities and temperatures for the same scans from the recent work of Evans et al. (2023). Figure 12a shows the number of co‐averaged limb scans with LT during the above time period.…”

“…The spectral analysis for the OH problem uses the same general approach applied to the IUVS emissions that allow for the operational retrieval of carbon dioxide (CO 2 ; Evans et al, 2015Evans et al, , 2023, molecular nitrogen (Evans et al, 2015;Stevens et al, 2015), and atomic oxygen. The approach is to identify and model all of the blended components contributing to the limb spectrum and fit them simultaneously to the observed spectral shape at each tangent altitude.…”

“…We assemble all of the periapse limb profiles for water vapor and OH densities in MY35 observed between L s = 299 and 335° into five 2-hr local time (LT) bins sequentially from 7 ± 1 hr to 15 ± 1 hr. We also assemble the limb profiles of CO 2 densities and temperatures for the same scans from the recent work of Evans et al (2023).…”

“…colorado.edu/; Jain et al, 2023). Retrieved CO 2 densities and derived temperatures are publicly available in Evans et al (2022). Concurrent MAVEN/EUV (Level 2; Version 14 Revision 3) data are publicly available on the PDS (Eparvier, 2017).…”