How surface composition and meteoroid impacts mediate sodium and potassium in the lunar exosphere

Colaprete, A.; Sarantos, M.; Wooden, D. H.; Stubbs, T. J.; Cook, Amanda; Shirley, M.

doi:10.1126/science.aad2380

Cited by 67 publications

(71 citation statements)

References 31 publications

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“…From this data, Colaprete et al (2016) reported a factor of 2 variation in atmospheric intensity over a lunation, with a notable enhancement during the Geminids meteor shower. LADEE collected data during local noon from November 2013 through March 2014 and was restricted to ±20 • lunar latitude.…”

Section: Introductionmentioning

confidence: 81%

“…The mass spectrometer deployed by Apollo 17, the Lunar Atmosphere Composition Experiment (LACE), found argon and helium at night (Hoffman et al, 1973). The location of the craters used for limb referencing (orange boxes) and the potassium density peak location (shaded blue) according to Colaprete et al (2016) are marked on the right map. Argon decreased to LACE's sensitivity limit of 2 × 10 2 cm −3 at about −135 • solar zenith angle (SZA).…”

Section: Introductionmentioning

confidence: 99%

“…The location of the craters used for limb referencing (orange boxes) and the potassium density peak location (shaded blue) according to Colaprete et al (2016) are marked on the right map. Fluctuations in the potassium emission parameters are dependent on lunar phase, solar activity, micrometeoroid bombardment, surface abundances, and lunar latitude (Colaprete et al, 2016;Killen & Ip, 1999). been made by spacecraft in lunar orbit (e.g., molecular hydrogen, Stern et al, 2013;neon, Benna et al, 2015;helium, Stern et al, 2012;and methane, Hodges, 2016).…”

Section: Introductionmentioning

confidence: 99%

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High‐Resolution Potassium Observations of the Lunar Exosphere

Rosborough

Oliversen

Mierkiewicz

et al. 2019

Geophysical Research Letters

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We observed lunar exospheric potassium D1 (7,698.9646 Å) emissions using a high‐spectral resolution Fabry‐Perot spectrometer in 2014. We present the first potassium line profile measurements, which are representative of the potassium velocity distribution. Inferred temperatures are greater during the waxing gibbous phase, 1920±630 K and lower at waning gibbous phase, 980±200 K. Exosphere models suggest that the measured line widths are a combination of photon‐stimulated desorption and impact vaporization sources. The relative potassium emission intensity decreases by ∼2.5 between lunar phases 80° and 30° and is brightest off the northwest limb near the Aristarchus crater, which is a potassium‐rich surface region. Additionally, the emissions off the northern limb are brighter than the southern limb. The intensity decrease and the greater line width during the waxing gibbous versus the waning gibbous phase suggests a dawn‐dusk asymmetry.

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Section: Introductionmentioning

confidence: 81%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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High‐Resolution Potassium Observations of the Lunar Exosphere

Rosborough

Oliversen

Mierkiewicz

et al. 2019

Geophysical Research Letters

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“…Global images of the lunar atmosphere can also be used to study the behavior of the lunar exosphere as the Moon moves in and out of the terrestrial magnetotail, modulating solar wind sputtering and enabling identification of the distant terrestrial magnetopause and possibly bow shock. Imaging can also reveal the global effects of meteoroid bombardment (e.g., Colaprete et al 2016).…”

Section: The Moonmentioning

confidence: 99%

Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

et al. 2018

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Both heliophysics and planetary physics seek to understand the complex nature of the solar wind's interaction with solar system obstacles like Earth's magnetosphere, the ionospheres of Venus and Mars, and comets. Studies with this objective are frequently conducted with the help of single or multipoint in situ electromagnetic field and particle observations, guided by the predictions of both local and global numerical simulations, and placed in con- text by observations from far and extreme ultraviolet (FUV, EUV), hard X-ray, and energetic neutral atom imagers (ENA). Each proposed interaction mechanism (e.g., steady or transient magnetic reconnection, local or global magnetic reconnection, ion pick-up, or the KelvinHelmholtz instability) generates diagnostic plasma density structures. The significance of each mechanism to the overall interaction (as measured in terms of atmospheric/ionospheric loss at comets, Venus, and Mars or global magnetospheric/ionospheric convection at Earth) remains to be determined but can be evaluated on the basis of how often the density signatures that it generates are observed as a function of solar wind conditions. This paper reviews efforts to image the diagnostic plasma density structures in the soft (low energy, 0.1-2.0 keV) X-rays produced when high charge state solar wind ions exchange electrons with the exospheric neutrals surrounding solar system obstacles. The introduction notes that theory, local, and global simulations predict the characteristics of plasma boundaries such the bow shock and magnetopause (including location, density gradient, and motion) and regions such as the magnetosheath (including density and width) as a function of location, solar wind conditions, and the particular mechanism operating. In situ measurements confirm the existence of time-and spatial-dependent plasma density structures like the bow shock, magnetosheath, and magnetopause/ionopause at Venus, Mars, comets, and the Earth. However, in situ measurements rarely suffice to determine the global extent of these density structures or their global variation as a function of solar wind conditions, except in the form of empirical studies based on observations from many different times and solar wind conditions. Remote sensing observations provide global information about auroral ovals (FUV and hard X-ray), the terrestrial plasmasphere (EUV), and the terrestrial ring current (ENA). ENA instruments with low energy thresholds (∼ 1 keV) have recently been used to obtain important information concerning the magnetosheaths of Venus, Mars, and the Earth. Recent technological developments make these magnetosheaths valuable potential targets for high-cadence wide-field-of-view soft X-ray imagers.Section 2 describes proposed dayside interaction mechanisms, including reconnection, the Kelvin-Helmholtz instability, and other processes in greater detail with an emphasis on the plasma density structures that they generate. It focuses upon the questions that remain as yet unanswered, such as the significanc...

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“…source rate for sodium and potassium for east longitudes of -60° to 0° [Colaprete et al, 2015[Colaprete et al, , 2016, which would straddle the dusk terminator at this time. Therefore, a compositional variation in neutral density appears plausible, though such a variation might lead to a distribution even more skewed to the dusk side than what we observe.…”

Section: Inferred Ion Production Rates and Exospheric Source Structurementioning

confidence: 99%

Structure and composition of the distant lunar exosphere: Constraints from ARTEMIS observations of ion acceleration in time‐varying fields

et al. 2016

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By analyzing the trajectories of ionized constituents of the lunar exosphere in time‐varying electromagnetic fields, we can place constraints on the composition, structure, and dynamics of the lunar exosphere. Heavy ions travel slower than light ions in the same fields, so by observing the lag between field rotations and the response of ions from the lunar exosphere, we can place constraints on the composition of the ions. Acceleration, Reconnection, Turbulence, and Electrodynamics of Moon's Interaction with the Sun (ARTEMIS) provides an ideal platform to utilize such an analysis, since its two‐probe vantage allows precise timing of the propagation of field discontinuities in the solar wind, and its sensitive plasma instruments can detect the ion response. We demonstrate the utility of this technique by using fully time‐dependent charged particle tracing to analyze several minutes of ion observations taken by the two ARTEMIS probes ~3000–5000 km above the dusk terminator on 25 January 2014. The observations from this time period allow us to reach several interesting conclusions. The ion production at altitudes of a few hundred kilometers above the sunlit surface of the Moon has an unexpectedly significant contribution from species with masses of 40 amu or greater. The inferred distribution of the neutral source population has a large scale height, suggesting that micrometeorite impact vaporization and/or sputtering play an important role in the production of neutrals from the surface. Our observations also suggest an asymmetry in ion production, consistent with either a compositional variation in neutral vapor production or a local reduction in solar wind sputtering in magnetic regions of the surface.

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How surface composition and meteoroid impacts mediate sodium and potassium in the lunar exosphere

Cited by 67 publications

References 31 publications

High‐Resolution Potassium Observations of the Lunar Exosphere

High‐Resolution Potassium Observations of the Lunar Exosphere

Imaging Plasma Density Structures in the Soft X-Rays Generated by Solar Wind Charge Exchange with Neutrals

Structure and composition of the distant lunar exosphere: Constraints from ARTEMIS observations of ion acceleration in time‐varying fields

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