Evidence of Non‐Thermal Hydrogen in the Exosphere of Mars Resulting in Enhanced Water Loss

Bhattacharyya, D.; Clarke, J. T.; Mayyasi, M.; Shematovich, V.; Bisikalo, D.; Chaufray, J. Y.; Thiemann, E.; Halekas, J.; Schmidt, C.; Bertaux, J. L.; Chaffin, M. S.; Schneider, N. M.

doi:10.1029/2023je007801

Cited by 5 publications

(2 citation statements)

References 59 publications

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“…The Martian H corona spans several planetary radii that extend beyond the orbital altitude of the MAVEN spacecraft Bhattacharyya et al, 2023;Chaufray et al, 2008;Nagy et al, 1990). Subsequently, the IUVS ECH disk-pointed observations include a significant amount of illuminated H atoms that are resonantly scattering Solar photons, even when the line-of-sight is pointed at the night-side of the planet.…”

Section: Methodsmentioning

confidence: 99%

An Empirical Predictive Model for Atmospheric H Lyman‐α Emission Brightness at Mars

Mayyasi,

Mayyasi

2024

Earth and Space Science

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Characterizing the abundance of atmospheric hydrogen (H) at Mars is critical for determining the current and, subsequently, the primordial water content on the planet. At present, the atmospheric abundance of Martian H is not directly measured but is simulated using proprietary models that are constrained with observations of H Lyman‐α emission brightness, as well as with observations of other atmospheric parameters, such as temperature and Solar UV irradiance. Publicly available brightness measurements require further processing to have scientific utility. To make the data needed to model H abundances and escape rates more accessible to the community, we use H Lyman‐α emissions made with the Mars Atmosphere and Volatile Evolution (MAVEN) mission. The near decade‐spanning data set is reduced to obtain disk‐pointed averages of the H brightness in the upper atmosphere of Mars and then analyzed for statistical trends across multiple variables. The H Lyman‐α emission brightness is found to be dependent on Solar illumination, Solar cycle, and season. The resulting data trends are used to derive empirical fits to build a predictive framework for future observations or an extrapolative tool for estimates of water content at previous epochs. Data that was intentionally not included in the empirical derivations are used to validate the predictions successfully to within 18% accuracy, on average. This first‐of‐its kind predictive model for H brightness is presented to the community and can be used with atmospheric models to further derive and interpret the abundances and escape rate of H atoms at Mars.

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Section: Methodsmentioning

confidence: 99%

An Empirical Predictive Model for Atmospheric H Lyman‐α Emission Brightness at Mars

Mayyasi,

Mayyasi

2024

Earth and Space Science

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“…This distribution is particularly essential when fitting brightness profiles at higher altitudes Bhattacharyya et al, 2015;Chaffin et al, 2014;Chaufray et al, 2008;Clarke et al, 2014). Recently, Bhattacharyya et al (2023) attempted to constrain the hot component of atomic hydrogen by making high altitude observations of Mars, and their model fitting suggests that the Martian water loss rate via non-thermal escape could be as high as 26% of the total thermal escape rate near perihelion and solar minimum conditions. They attributed this higher non-thermal escape rate to solar wind charge exchange at higher altitudes.…”

Section: Summary Conclusion and Future Prospectsmentioning

confidence: 99%

Variability of Atomic Hydrogen Brightness in the Martian Exosphere: Insights From the Emirates Ultraviolet Spectrometer on Board Emirates Mars Mission

Susarla,

Deighan,

Chaffin

et al. 2024

JGR Space Physics

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The Emirates Mars Ultraviolet Spectrometer (EMUS), aboard the Emirates Mars Mission (EMM), has been conducting observations of ultraviolet emissions within the Martian exosphere. Taking advantage of the distinctive orbit of the EMM around Mars, EMUS utilizes a dedicated strafe observation strategy to scan the illuminated Martian exosphere at tangential altitudes ranging from 130 to over 20,000 km. To distinguish between emissions of Martian origin and those from the interplanetary background, EMUS conducts specialized background observations by looking away from the planet. This approach has allowed us to investigate the radial and seasonal variations in Martian coronal emission features at H Lyman‐α, β and γ wavelengths. Our analysis supports the previous studies indicating that Martian exospheric hydrogen Lyman emission brightness attains its highest levels around the southern summer solstice and reaches its lowest levels when Mars is near aphelion. Additionally, a secondary peak emission at all altitudes is observed after perihelion during Martian Year (MY) 36, which can be attributed to a Class C dust storm. Our study establishes a strong correlation between solar flux and coronal brightness for these emissions, highlighting the impact of solar activity on the visibility of Martian corona. In addition, we have examined interannual variability and found that emission intensities in MY 37 surpassed those in MY 36, primarily due to increased solar activity. These observations help to understand potential seasonal patterns of exospheric hydrogen, which is driven by underlying mechanisms in the lower atmosphere and solar activity, eventually suggesting an impact on water loss in the Martian atmosphere.

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The present epoch may not be representative in determining the history of water on Mars

Jakosky

2024

Proc. Natl. Acad. Sci. U.S.A.

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Understanding the history of water on Mars is important for understanding both its geological and potential biological history. The abundance and physical state of water has evolved through time, from the surface having an early warmer and wetter environment to the present-day colder and drier one. Although multiple lines of evidence support this change, attempts to determine the abundance of water on the planet, the history of water at the surface, and the sequestration into both permanent and exchangeable sinks have yielded a wide range of results. I explore the uncertainties in the processes and interpretation, to understand our ability to quantitatively determine the water inventory and its changes through time. Results indicate that the present state of models and of the data constraining them preclude determining a unique history for water. This uncertainty does not affect the conclusion that significant amounts of water have been lost to space and to other sinks and that these losses are consistent with the changes in climate and surface environment.

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Evidence of Non‐Thermal Hydrogen in the Exosphere of Mars Resulting in Enhanced Water Loss

Cited by 5 publications

References 59 publications

An Empirical Predictive Model for Atmospheric H Lyman‐α Emission Brightness at Mars

An Empirical Predictive Model for Atmospheric H Lyman‐α Emission Brightness at Mars

Variability of Atomic Hydrogen Brightness in the Martian Exosphere: Insights From the Emirates Ultraviolet Spectrometer on Board Emirates Mars Mission

The present epoch may not be representative in determining the history of water on Mars

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