Alternate oscillations of Martian hydrogen and oxygen upper atmospheres during a major dust storm

Abstract

Dust storms on Mars play a role in transporting water from its lower to upper atmosphere, seasonally enhancing hydrogen escape. However, it remains unclear how water is diurnally transported during a dust storm and how its elements, hydrogen and oxygen, are subsequently influenced in the upper atmosphere. Here, we use multi-spacecraft and space telescope observations obtained during a major dust storm in Mars Year 33 to show that hydrogen abundance in the upper atmosphere gradually increases because of water supply above an altitude of 60 km, while oxygen abundance temporarily decreases via water ice absorption, catalytic loss, or downward transportation. Additionally, atmospheric waves modulate dust and water transportations, causing alternate oscillations of hydrogen and oxygen abundances in the upper atmosphere. If dust- and wave-driven couplings of the Martian lower and upper atmospheres are common in dust storms, with increasing escape of hydrogen, oxygen will less efficiently escape from the upper atmosphere, leading to a more oxidized atmosphere. These findings provide insights regarding Mars’ water loss history and its redox state, which are crucial for understanding the Martian habitable environment.

On the Periodic Variation of the Ion Density in the Martian Dayside Ionosphere During the Regional Dust Storm in September 2016

“…The periodogram results (Figures 3 and 4 together with Tables 1 and 2) show that there are likely three distinct peak periodicities including the short (∼1 day), moderate (6–9 days), and long (>9 days up to several weeks) scales with their sufficient confidence levels higher than 90%. The moderate (6–9 days) peak periodicities identified in the Martian ionosphere are approximately comparable to those identified in the neutral H and O atmosphere during the same regional dust storm in September 2016 (Masunaga et al., 2022).…”

“…In this study, we regard the periodicities higher than 90% confidence levels as the sufficiently significant peak periodicities. These peak periodicities between 6 and 9 days are likely comparable to those revealed in the neutral H and O atmosphere with a period of ∼6.6 and ∼6.8 days based on the remote observations by the Hisaki space telescope (Masunaga et al, 2022).…”

“…In this study, we particularly focused on periodic ion density variations during the regional dust storm event on 4 September 2016 in which the 6–7‐day periodic atmospheric waves and periodic variations of neutral H and O abundances coexist as reported by Masunaga et al. (2022). Note that this regional dust storm occurred in the solar longitude (Ls) of ∼216° in Mars Year (MY) 33, which corresponds to the southern spring dust storm period.…”

“…One of the remarkable findings associated with dust storm effects on the Martian upper atmosphere is that water vapor, usually confined to lower altitudes (≲10-30 km) (e.g., Clancy & Nair, 1996;Lefèvre & Krasnopolsky, 2017, and references therein), is rapidly transported to higher altitudes (>60 km) due to the rapid atmospheric heating, and subsequent water dissociation causes an enhancement in hydrogen escape in the upper atmosphere (Chaffin et al, 2021;Heavens et al, 2018). Furthermore, Masunaga et al (2022) recently reported that the hydrogen and oxygen airglow in the upper atmosphere of Mars periodically (and alternately) varied with a period of ∼6.6 and ∼6.8 days during the regional dust storm in September 2016 based on the remote observations by the Hisaki space telescope (Yoshikawa et al, 2014;Yoshioka et al, 2013). Masunaga et al (2022) also found that the periodic H and O variations in the upper atmosphere are likely associated with periodic variations of the air temperature likely caused by baroclinic waves near the surface.…”

Enhanced Hydrogen Escape on Mars during the 2018 Global Dust Storm: Impact of Horizontal Wind Field

“…Of particular interest is the influence of the Martian dust storms on water escape, which has been extensively investigated over the past five years (e.g., Heavens et al 2018;Stone et al 2020;Chaffin et al 2021;Masunaga et al 2022). Dust storms are an important meteorological phenomenon on Mars that often occurs during perihelion when Mars is closest to the Sun, namely the Martian southern summer.…”