Photochemical escape of atomic C, N, and O during the 2018 global dust storm on Mars

Abstract

Dust storm is an important meteorological phenomenon on Mars. By modifying the structure of the Martian atmosphere and ionosphere, it plays an indispensable role in the Martian photochemistry and atmospheric loss. This study is devoted to evaluating the effects of the 2018 global dust storm (GDS) on the photochemical escape of atomic C, N, and O on Mars based on multi-instrument measurements made by the Mars Atmosphere and Volatile EvolutioN spacecraft. The dataset is divided into the non-dusty and dusty stages, for which the hot atom production rates from a variety of channels are calculated. A one-dimensional Monte Carlo model is then constructed to obtain the escape probability profile for each channel. By combining the above results, we derive the photochemical escape rates, both prior to and during the GDS. Our calculations suggest that the GDS-induced C, N, and O escape is generally reduced by ∼30–$40\%$ relative to the quiet, pre-GDS state, in direct contrast to the well-known result of GDS-induced strong enhancement of atomic H escape. We further propose that the GDS-induced variation of photochemical escape essentially reflects the competition between two effects: the modification of hot atom production (enhancement for photodissociation or reduction for dissociative recombination) driven by the variation of the background atmosphere and the reduction of escape probability due to atmospheric expansion. During the GDS, the latter is usually more effective and responsible for the overall reduction of photochemical escape on Mars.

Mars Hot Oxygen Density and Effective Temperature Derived From the MAVEN IUVS Observations

“…Previous analyses of the in situ measurements from MAVEN NGIMS have shown that the global dust storm of 2018 led to a decrease of the (thermal) O density in the Martian thermosphere (Elrod et al., 2020; Farahat et al., 2021). Modeling studies indicated that the hot O density can also be suppressed and the escape rate can be reduced by ∼30%–40% during global dust storms (Huang et al., 2023; Lee et al., 2020). In our analysis, the IUVS observations acquired during the global dust storm of 2018 have been included (i.e., Cases 6 and 7 in Table 1).…”

EMM EMUS Observations of Hot Oxygen Corona at Mars: Radial Distribution and Temporal Variability

“…The effects of episodic events such as solar flares (Lee et al, 2018) and dust storms (Huang et al, 2022;Lee et al, 2020), as well as the influence of solar wind on oxygen corona (Ramstad et al, 2023;Shematovich, 2021) Figure 9. (a) Time series of normalized EUVM 130.4 nm solar irradiance (blue), moving average corresponding to three solar rotations (orange), and the residual signal after subtracting the moving average (green).…”

“…The effects of episodic events such as solar flares (Lee et al., 2018) and dust storms (Huang et al., 2022; Lee et al., 2020), as well as the influence of solar wind on oxygen corona (Ramstad et al., 2023; Shematovich, 2021) needs further investigation. The effect of Martian crustal magnetic fields on the oxygen corona, if any, is also in need of investigation, although we do not expect to see any crustal field effects at these very high altitudes, since the corona is expected to become more uniform as the spatial variations become more globally averaged.…”

Non‐Thermal Escape of Sulfur and Oxygen on Io Driven by Photochemistry

“…Therefore, a more sophisticated one-dimensional Monte Carlo approach is applied to obtain the escape probabilities of hot neutrals produced via various channels in Io's dayside upper atmosphere. The model is modified from our existing models of photochemical escape on Mars (Huang et al, 2023) and other solar system objects (Gu et al, 2020(Gu et al, , 2021, and capable of depicting the behavior of escaping neutrals over a vast transition region near the exobase.…”