Hydrogen escape from Mars enhanced by deep convection in dust storms

Heavens, N. G.; Kleinböhl, A.; Chaffin, Michael; Halekas, J. S.; Kass, D. M.; Hayne, P. O.; McCleese, D. J.; Piqueux, S.; Shirley, James H.; Schofield, J. T.

doi:10.1038/s41550-017-0353-4

Cited by 150 publications

(201 citation statements)

References 36 publications

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“…However, the Martian thinner atmosphere increases the power of thermal tides, especially extratropical tides, during dust storm activity 18,50 . Our work suggests a potential mechanism that allows atmospheric water content to be rapidly transported from the polar source 42,51 to the low and middle latitudes by the nighttime tidal wind and then lifted by daytime deep convection 9 and further transported to the Northern Hemisphere by the intensified meridional circulation 52 . This may contribute to the rapid enhancement of water content at high altitudes and hydrogen escape during the southern-summer-season global dust storms, such as that observed in MY 28 9 .…”

Section: Discussionmentioning

confidence: 92%

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Dust tides and rapid meridional motions in the Martian atmosphere during major dust storms

Zhang

et al. 2020

Nat Commun

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The atmosphere of Mars is strongly affected by the spatial and temporal variability of airborne dust. However, global dust variability within a sol (Martian day) is still poorly understood. Although short-term dynamic processes are crucial, detailed comparisons of simulated diurnal variations are limited by relatively sparse observations. Here, we report the discovery of ubiquitous, strong diurnal tides of dust in the Southern Hemisphere of Mars. Driven by the westward-propagating migrating diurnal thermal tide, zonally distributed dust fronts slosh back and forth in a wide latitudinal range of up to 40°within one sol during major dust storms. Dust tides-tidal transport of dust in this way-rapidly transport heat and constituents meridionally, allowing moist air near the summer pole to be rapidly transported to lower latitudes during the night, where it then can be lifted by daytime deep convection and contribute to hydrogen escape from Mars during global dust storms.

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Section: Discussionmentioning

confidence: 92%

“…Observations have shown interannual, interseasonal, and diurnal variability in the dust distributions [4][5][6][7][8] . The rapid vertical transport of dust and water to high altitudes in the midto-high latitudes within just a few sols during global dust storms was recently discovered 9,10 . This short-term dynamic process on dusty Mars is intriguing.…”

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confidence: 99%

Dust tides and rapid meridional motions in the Martian atmosphere during major dust storms

Zhang

et al. 2020

Nat Commun

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“…The brightness of H Lyman‐α will increase when the number of H atoms along the LOS increases and/or the temperature of the H atoms increases thus broadening the spectral line. In the narrow timeframe (days) of the solar event observations, no mechanism is expected to enhance the flux of H atoms from lower altitudes, especially since Mars is close to aphelion with little dust storm activity (Chaffin et al, ; Heavens et al, ). The neutral temperature enhancement following flares has a much shorter timescale (hours) (Thiemann et al, ) and is therefore the most plausible driver of the observed brightness enhancement.…”

Section: Resultsmentioning

confidence: 99%

Significant Space Weather Impact on the Escape of Hydrogen From Mars

Mayyasi

Bhattacharyya

Clarke

et al. 2018

Geophysical Research Letters

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In September 2017, an active region of the Sun produced a series of strong flares and a coronal mass ejection that swept past Mars producing enhanced ionization and heating in the upper atmosphere. Emissions from atmospheric hydrogen Lyman‐α were also enhanced at Mars. Temperatures derived from neutral species scale heights were used in conjunction with the H Lyman‐α observations to simulate the effects of this space weather event on Martian hydrogen properties in the exosphere. It was found that hydrogen abundance in the upper atmosphere decreased by ~25% and that the H escape rate increased by a factor of 5, mainly through an increase in upper atmospheric temperature. This significant escape rate variation is comparable to seasonally observed trends but occurred at much shorter timescales. Such solar events would statistically impact extrapolation of Martian water loss over time.

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“…This layer is difficult to implement using a simple Conrath description and was not considered in our simulations. In reality it may be caused by nonlocal deep convective events when the GDS develops (Heavens et al, ; Spiga et al, ; Wang et al, ).…”

Section: Discussionmentioning

confidence: 99%

Explanation for the Increase in High‐Altitude Water on Mars Observed by NOMAD During the 2018 Global Dust Storm

Neary

Daerden

Aoki

et al. 2020

Geophysical Research Letters

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The Nadir and Occultation for MArs Discovery (NOMAD) instrument on board ExoMars Trace Gas Orbiter measured a large increase in water vapor at altitudes in the range of 40-100 km during the 2018 global dust storm on Mars. Using a three-dimensional general circulation model, we examine the mechanism responsible for the enhancement of water vapor in the upper atmosphere. Experiments with different prescribed vertical profiles of dust show that when more dust is present higher in the atmosphere, the temperature increases, and the amount of water ascending over the tropics is not limited by saturation until reaching heights of 70-100 km. The warmer temperatures allow more water to ascend to the mesosphere. Photochemical simulations show a strong increase in high-altitude atomic hydrogen following the high-altitude water vapor increase by a few days. Plain Language Summary The ExoMars Trace Gas Orbiter (TGO) is currently in orbit aroundMars measuring the composition of the atmosphere. TGO was able to make observations before, during, and after a large planet-encircling dust storm that occurred from June to August 2018. The TGO measurements provide the first opportunity to observe how water vapor is distributed with height in the atmosphere during a global-scale dust event. It was found that there was a large increase in water vapor very high (40-100 km) in the atmosphere during the dust storm. Using a three-dimensional numerical model of the Mars atmosphere, we found that when dust from the storm is transported up to levels above~40 km, it warms the atmosphere due to solar absorption, and this in turn prevents ice clouds from forming at heights of 40-60 km and allows more water vapor to ascend to greater heights in the atmosphere. This is of interest in terms of the planetary evolution, as water molecules at greater heights are more readily dissociated by sunlight and lost from the atmosphere. This is an important factor for understanding the changes that have occurred since the period when surface features on Mars indicate that liquid water was present.

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Hydrogen escape from Mars enhanced by deep convection in dust storms

Cited by 150 publications

References 36 publications

Dust tides and rapid meridional motions in the Martian atmosphere during major dust storms

Dust tides and rapid meridional motions in the Martian atmosphere during major dust storms

Significant Space Weather Impact on the Escape of Hydrogen From Mars

Explanation for the Increase in High‐Altitude Water on Mars Observed by NOMAD During the 2018 Global Dust Storm

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