Photochemical escape of atomic C and N on Mars: clues from a multi-instrument MAVEN dataset

Cui, Jun; Wu, Xiaoshu; Jiang, Fayu; Wei, Yong

doi:10.1051/0004-6361/201833749

Cited by 31 publications

(39 citation statements)

References 51 publications

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“…At the face value, this is counterintuitive as the idealized Chapman theory predicts a sharp decline in ion/electron density near the terminator (e.g., Fox & Yeager, ), but be cautious that the altitude range considered here is well above the main ionospheric peak where the SZA variation in ion/electron density is substantially reduced (Fox & Yeager, ). A similar feature of the photolysis rate is responsible for the lack of SZA variation in atomic C and N escape on Mars, as recently reported in Cui et al (). To summarize, none of the characteristics reported in section can be explained by the scenario of solar EUV/X‐ray ionization.…”

Section: Implications On Plasma Sourcessupporting

confidence: 80%

Structural Variability of the Nightside Martian Ionosphere Near the Terminator: Implications on Plasma Sources

Cao

Cui

et al. 2019

JGR Planets

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With the aid of the Neutral Gas and Ion Mass Spectrometer measurements made onboard the Mars Atmosphere and Volatile Evolution, we examine the morphology of the nightside Martian ionosphere near the terminator at 150–250 km in terms of the extension into darkness for a selected set of ion species: O 2+, NO+, HNO+, N 2+/CO+, CO 2+, and HCO+. Our analysis reveals several interesting characteristics, including the presence of dawn‐dusk and north‐south asymmetries and the variability among different species. A full interpretation of the Neutral Gas and Ion Mass Spectrometer observations relies on the combination of impact ionization by precipitating electrons and day‐to‐night plasma transport, as two important sources of plasma in the nightside Martian ionosphere near the terminator. The former partially contributes to the north‐south asymmetry, whereas the latter favorably explains not only the dawn‐dusk asymmetry but also NO+ and HCO+ as two exceptions which are more extended into darkness as compared to the other species on the dusk side. A comparison between the two plasma sources further indicates that the effect of day‐to‐night transport tends to be suppressed over the southern hemisphere. The above results highlight the impacts of crustal magnetic fields on the structural variability of the nightside Martian ionosphere near the terminator, manifest as the shielding of precipitating electrons and the suppression of day‐to‐night transport, both by the presence of strong magnetic anomalies clustering over the southern hemisphere of the planet.

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Section: Implications On Plasma Sourcessupporting

confidence: 80%

Structural Variability of the Nightside Martian Ionosphere Near the Terminator: Implications on Plasma Sources

Cao

Cui

et al. 2019

JGR Planets

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“…Fox () predicted a sharp decline in density toward high altitudes for N( 4 S) and N( 2 D) whereas the profiles derived here remain fairly constant with altitude in panel b. This discrepancy should be due to the fact that our chemical equilibrium calculations do not include transport, which is, at least partly, driven by atomic N escape on Mars (Cui, Wu, et al, ).…”

Section: No Abundance Under Chemical Equilibriummentioning

confidence: 63%

Nitric Oxide Abundance in the Martian Thermosphere and Its Diurnal Variation

Cui

Ren

et al. 2020

Geophysical Research Letters

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As an important species of the Martian thermosphere, NO is chemically and radiatively active. However, its abundance is poorly constrained due to difficulties in both remote sensing and in situ measurements. In this study, we use the Neutral Gas and Ion Mass Spectrometer measurements made onboard the Mars Atmosphere and Volatile Evolution to derive the N( 4 S), N( 2 D), and NO abundances in the Martian thermosphere based on time-dependent odd N chemistry. At a reference altitude of 160 km, our calculations suggest that the NO abundance is maximized in the afternoon whereas the N( 4 S) and N( 2 D) abundances maximized in the morning, both driven by the variation of the ambient N 2 mixing ratio. The difference in chemical loss time scale implies a strong diurnal variation for NO and N( 2 D) but a weak variation for N( 4 S).Plain Language Summary NO is usually regarded as a good tracer of energy input into the upper atmospheres of terrestrial planets. On Mars, NO is mainly produced via the reaction of atomic N in the excited state with ambient CO 2 and lost via the reaction with atomic N in the ground state. Existing investigations of NO abundance in the Martian upper atmosphere are extremely limited due to difficulties in both remote sensing and in situ measurements. In this study, we propose a useful approach to determine the NO abundance on both the dayside and nightside of Mars by combining our knowledge of the odd N chemistry with available neutral and ion density measurements of relevant chemical reactants. On the dayside, we find the NO abundance to be maximized late in the afternoon, which is driven by the variation of N 2 mixing ratio in the background atmosphere. Our analysis also allows the diurnal variation of NO to be explored for the first time, revealing a strong day-night difference by 3 orders of magnitude. This is caused by the fast depletion of NO on the nightside where its production source drops to a minimum level in the absence of solar radiation.

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“…Mars has thus become a unique testing ground to understand the atmospheric loss processes of terrestrial planets. In the past several decades, two classes of loss processes driven by solar wind and radiation have been proposed (Jakosky et al, 2018; Shizgal & Arkos, 1996): thermal processes including evaporative escape (Jeans, 1925) and hydrodynamic escape (Pepin, 1991); nonthermal processes including photochemical escape (Cui et al, 2019; Johnson et al, 2008; McElroy, 1972), ion sputtering (Luhmann et al, 1992), and ion heating or acceleration (Brain et al, 2015; Lundin et al, 2004; Wei et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Rapid Landau Heating of Martian Topside Ionospheric Electrons by Large‐Amplitude Magnetosonic Waves

Liu

Gao

et al. 2020

Geophysical Research Letters

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Atmospheric escape is a fundamental process in the long-term habitability evolution of terrestrial planets. Recent observations on Mars have found the concurrence of the severe ionospheric erosion and the large-amplitude, quasi-perpendicular magnetosonic waves. However, whether and then how these magnetosonic waves had contributed to the ionospheric erosion remains unclear. Here we propose a new candidate mechanism, electron Landau heating by magnetosonic waves, for the Martian ionospheric erosion. In contrast to the cyclotron resonance with oxygen atomic and molecular ions above the escape energies, the magnetosonic waves Landau-resonate with the thermal electrons at energy channels of the order of 0.01-0.1 eV. Through the Landau resonance over tens of minutes, the large-amplitude (12 nT) magnetosonic waves can heat the topside ionospheric electrons to ∼2 times the normal temperature. The topside ionospheric electron heating could result in the enhancement of the ambipolar electric potential and eventually facilitate the escape of ionospheric plasma. Plain Language Summary An atmosphere of sufficient density is a fundamental condition for a habitable terrestrial planet. Mars as a terrestrial planet in the habitable zone of our solar system lost much of its atmosphere over billions of years and has thus become a unique testing ground to understand the planetary atmospheric loss processes. Recent observations on Mars have shown that the severe erosion of the ionosphere, an ionized part of the upper atmosphere, was accompanied by the large-amplitude, quasi-perpendicular magnetosonic waves. However, whether and then how these magnetosonic waves had contributed to the ionospheric erosion remains unclear. On the basis of space observations and numerical calculations, we propose a new physical mechanism, electron Landau heating by magnetosonic waves, for the Martian ionospheric erosion. The large-amplitude magnetosonic waves can heat the topside ionospheric electrons to ∼2 times the normal temperature over tens of minutes, enhance the ambipolar electric potential, and eventually facilitate the escape of ionospheric plasma. The electron Landau heating process may also contribute to the ionospheric erosion of other terrestrial planets within and beyond our solar system.

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Photochemical escape of atomic C and N on Mars: clues from a multi-instrument MAVEN dataset

Cited by 31 publications

References 51 publications

Structural Variability of the Nightside Martian Ionosphere Near the Terminator: Implications on Plasma Sources

Structural Variability of the Nightside Martian Ionosphere Near the Terminator: Implications on Plasma Sources

Nitric Oxide Abundance in the Martian Thermosphere and Its Diurnal Variation

Rapid Landau Heating of Martian Topside Ionospheric Electrons by Large‐Amplitude Magnetosonic Waves

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