The spatial distribution of molecular Hydrogen in the lunar atmosphere—New results

Thampi, Smitha V.; Sridharan, R.; Das, Tirtha Pratim; Ahmed, S.M.; Kamalakar, J. A.; Bhardwaj, Anil

doi:10.1016/j.pss.2014.12.018

Cited by 15 publications

(21 citation statements)

References 17 publications

(24 reference statements)

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“…At lunar temperatures hydrogen most readily desorbs in a molecular form, e.g., H 2 , because hydrogen is very reactive in atomic form (Starukhina, 2006). We assumed that implanted hydrogen predominantly desorbs as H 2 , which is consistent with exospheric observations by LACE (Hodges, 1973), LAMP (Cook et al., 2013; Stern et al., 2013), and CHACE (Thampi et al., 2015). Once in the exosphere, representative H 2 particles are tracked in the Moon's gravitational field assuming full thermal accommodation to the local surface temperature and no adsorption.…”

Section: Methodssupporting

confidence: 69%

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On the Effect of Magnetospheric Shielding on the Lunar Hydrogen Cycle

2021

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Section: Methodssupporting

confidence: 69%

“…Near-surface exosphere density vs. latitude. The dashed red curve shows CHACE H 2 data digitized from Thampi et al (2015) extrapolated to the surface from in situ measurements of the exosphere while the Moon was in the magnetotail. The corresponding model data shown by the solid black curve with squares is consistent with the CHACE observation.…”

Section: Resultsmentioning

confidence: 99%

On the Effect of Magnetospheric Shielding on the Lunar Hydrogen Cycle

2021

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“…Cook et al () analyzing LAMP spectra noted a dusk to dawn asymmetry of 1,700 ± 400 and 2,100 ± 300 cm −3 , respectively. Partial pressures measured by the Chandraayan‐I Chandra's Altitudinal Composition Explorer (CHACE) mass analyzer were used to infer near‐surface densities of 500–800 cm −3 (Thampi et al, ). In that study, the estimate of the neutral densities depended on the assumption of the surface temperature.…”

Section: Introductionmentioning

confidence: 99%

Solar Wind Implantation Into the Lunar Regolith: Monte Carlo Simulations of H Retention in a Surface With Defects and the H₂ Exosphere

et al. 2019

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The solar wind implants protons into the top 20–30 nm of lunar regolith grains, and the implanted hydrogen will diffuse out of the regolith but also interact with oxygen in the regolith oxides. We apply a statistical approach to estimate the diffusion of hydrogen in the regolith hindered by forming temporary bonds with regolith oxygen atoms. A Monte Carlo simulation was used to track the temporal evolution of bound OH surface content and the H2 exosphere. The model results are consistent with the interpretation of the Chandrayaan‐1 M3 observations of infrared absorption spectra by surface hydroxyls as discussed in Li and Milliken (2017, https://doi.org/10.1126/sciadv.1701471). The model reproduced the latitudinal concentration of OH by using a Gaussian energy distribution of f(U0 = 0.5 eV, UW = 0.078–0.1 eV) to characterize the activation energy barrier to the diffusion of hydrogen in space weathered regolith. In addition, the model results of the exospheric content of H2 are consistent with observations by the Lyman Alpha Mapping Project on the Lunar Reconnaissance Orbiter. Therefore, we provide support for hydroxyl formation by chemically trapped solar wind protons.

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“…Still, it should be noted that the abundance level of some of the molecular species (namely H 2 O, and CO 2 ), used in present calculations (ChACE measurements), is high compared to their other measurements at the equatorial planes [Stern, 1999;Cook et al, 2013]. The Moon has a surface-bound exosphere with a total neutral density of the order of 10 6 cm −3 , and a mean free path of about 3 × 10 3 km [Thampi et al, 2015]. In addition, we will show that without including photochemistry of the molecular ions (particularly, CO 2 and H 2 O), presence of plasma density at the Moon of magnitude as estimated using RO measurements cannot be explained.…”

Section: Photochemical Modelmentioning

confidence: 74%

On the origin of the ionosphere at the Moon using results from Chandrayaan‐1 S band radio occultation experiment and a photochemical model

Choudhary

Ambili

Choudhury

et al. 2016

Geophysical Research Letters

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The origin of the Moon's ionosphere has been explored using Chandrayaan‐1 radio occultation (RO) measurements and a photochemical model. The electron density near the Moon's surface, obtained on 31 July 2009 (∼300 cm−3), is compared with results from a model which includes production and recombination of 16 ions, solar wind proton charge exchange, and the electron impact ionization. The model calculations suggest that in the absence of transport, inert ions, namely Ar+, Ne+, and He+, dominate lunar ionosphere (density ∼5 × 104 cm−3). Interaction with solar wind, however, leads to their complete removal (∼2–3 cm−3). Assuming the Moon's exosphere to have CO2, H2O, O, OH, H2, CH4, and CO molecules in addition to the inert gases, the model calculations suggest that the lunar ionosphere is dominated by molecular ions, namely H2O+, CO 2+, and H3O+, with near‐surface density ∼250 cm−3. We surmise that lunar ionosphere can be molecular in nature.

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The spatial distribution of molecular Hydrogen in the lunar atmosphere—New results

Cited by 15 publications

References 17 publications

On the Effect of Magnetospheric Shielding on the Lunar Hydrogen Cycle

On the Effect of Magnetospheric Shielding on the Lunar Hydrogen Cycle

Solar Wind Implantation Into the Lunar Regolith: Monte Carlo Simulations of H Retention in a Surface With Defects and the H₂ Exosphere

On the origin of the ionosphere at the Moon using results from Chandrayaan‐1 S band radio occultation experiment and a photochemical model

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The spatial distribution of molecular Hydrogen in the lunar atmosphere—New results

Cited by 15 publications

References 17 publications

On the Effect of Magnetospheric Shielding on the Lunar Hydrogen Cycle

On the Effect of Magnetospheric Shielding on the Lunar Hydrogen Cycle

Solar Wind Implantation Into the Lunar Regolith: Monte Carlo Simulations of H Retention in a Surface With Defects and the H2 Exosphere

On the origin of the ionosphere at the Moon using results from Chandrayaan‐1 S band radio occultation experiment and a photochemical model

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Product

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Solar Wind Implantation Into the Lunar Regolith: Monte Carlo Simulations of H Retention in a Surface With Defects and the H₂ Exosphere