The influence of surface roughness on volatile transport on the Moon

Prem, Parvathy; Goldstein, David; Varghese, Philip L.; Trafton, Laurence M.

doi:10.1016/j.icarus.2017.07.010

Cited by 24 publications

(33 citation statements)

References 27 publications

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“…It should be noted that even two lunar days after the simulated landing, ~10–30% of the exhaust water vapor released is found to persist in the lunar environment. The results shown in Figure 4 are consistent with previous work (Prem et al, 2018), which indicates that it takes one or two lunar days after an episodic release before the lunar exosphere reaches a quasi‐steady state (characterized by exponentially decaying loss and deposition rates) and that a “stickier” surface tends to prolong exospheric longevity.…”

Section: Resultssupporting

confidence: 90%

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The Evolution of a Spacecraft‐Generated Lunar Exosphere

et al. 2020

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Understanding how spacecraft alter planetary environments can offer important insights into key physical processes, as well as being critical to planning mission operations and observations. In this context, it is important to recognize that almost any powered lunar landing will be an active volatile release experiment, due to the release of exhaust gases during descent. This presents both an opportunity to study the interaction of volatiles with the lunar surface and a need to predict how nonindigenous gases are dispersed, and how long they persist in the lunar environment. This work investigates these questions through numerical simulations of the transport of water vapor during a nominal lunar landing and for two lunar days afterward. Simulation results indicate that the water vapor component of spacecraft exhaust is globally redistributed, with a significant amount reaching permanently shadowed regions (cold traps) near the closest pole, where temperatures are sufficiently low that volatiles may remain stable over geological timescales. Exospheric evolution and surface deposition patterns are highly sensitive to desorption activation energy, providing a means to constrain this critical parameter through landed or orbital measurements during future missions. Contamination of cold traps by exhaust gases is likely to scale with exhaust mass and proximity of the landing site to the poles. Exhaust propagation is perhaps the most widespread and long‐lived impact of spacecraft operations on a nominally airless solar system body and should be a key consideration in mission planning and in interpreting measurements made by landed lunar missions, particularly at near‐polar regions.

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Section: Resultssupporting

confidence: 90%

“…Longer‐term simulations (Prem et al, 2018) further indicate that ~67% of cold trapping after an episodic release occurs within the first two lunar days. Applying this scaling factor, we infer that ~20% of the total exhaust mass may ultimately be cold trapped.…”

Section: Resultsmentioning

confidence: 99%

The Evolution of a Spacecraft‐Generated Lunar Exosphere

et al. 2020

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“…In summer, as these molecules are mobilized, they are more likely to reach a permanent cold trap due to their vicinity to PSRs. Modeling by Prem et al () shows that surface roughness can have this effect by providing cold surfaces at high latitudes that can act as temporary reservoirs for molecules near the poles. A semiannual oscillation in argon observed by the Lunar Atmosphere and Dust Environment Explorer spacecraft has been linked to sequestration in transitory seasonal cold traps (Hodges & Mahaffy, ; Kegerreis et al, ).…”

Section: Discussionmentioning

confidence: 99%

Seasonal Polar Temperatures on the Moon

et al. 2019

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The Diviner Lunar Radiometer Experiment on the Lunar Reconnaissance Orbiter has been acquiring visible and infrared radiance measurements of the Moon for nearly 10 years. These data have been compiled into polar stereographic maps of temperatures poleward of 80° latitude at fixed local times and fixed subsolar longitudes to provide an overview of diurnal temperatures of the polar regions. The data have been divided into winter and summer seasons, defined by the times of year when the subsolar latitude is above or below the equator, to characterize the variations in seasonal temperatures that result from the 1.54° angle between the Moon's spin pole and the ecliptic plane. Since the illumination in the polar regions is perpetually at grazing angles, topography plays a dominate role in surface temperatures. Consequently, the surface and near‐surface thermal environment can vary in complex ways with time of day and season, which produces areas that are seasonally shadowed for prolonged periods and that are much more extensive than the permanently shadowed regions (PSRs). We find that surfaces below 110 K capable of cold trapping water over 1 Gyr increases by factors of 2.8 and 4.3 in the winter for the south and north polar regions, respectively, with seasonal residence times of adsorbed water molecules occurring at higher temperatures and thus larger areas.

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“…Prem et al () built upon the Stewart et al () study to investigate the effects of a transient atmosphere on the migration of water from a large impact to the lunar cold traps and found that a transient atmosphere would indeed enhance the migration survival of water by shielding molecules from photodestruction. Prem et al () found that the inclusion of surface roughness in their models also leads to a small (4–7%) but detectable enhancement in cold trap capture for lunar models. For this work, we use a constant migration efficiency value of 10%, which is consistent with the range determined from the simulations of Butler (), the only study of water migration that has been conducted for Mercury.…”

Section: Delivery Of Water Ice To Mercury By the Hokusai Impactmentioning

confidence: 99%

Examining the Potential Contribution of the Hokusai Impact to Water Ice on Mercury

2018

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The polar cold traps of Mercury host an estimated 1016–1018 g of water ice. The relative purity of the water‐ice deposits could indicate they were emplaced over a short time interval, and sharp albedo boundaries suggest that the water ice could have been emplaced relatively recently. Together, these lines of evidence are consistent with potential delivery by a single, large, young impact event. Hokusai is the most prominent large young impact crater on Mercury—if the bulk of Mercury's water‐ice inventory was indeed delivered by a single recent impact event, Hokusai is the best candidate source crater. This study constrains the impact conditions that created Hokusai from morphological and color observations of the crater and its ejecta. Results show that the Hokusai impact was recent and oblique. These parameters, coupled with retention and migration factors largely derived from existing lunar studies, are used to estimate the possible contribution of the Hokusai impact to water ice on Mercury. Assuming water‐rich asteroidal or cometary impactors, the Hokusai impact event could account for the inventory of water ice on Mercury for impact velocities less than ~30 km/s, a velocity that is achieved by 24–32% of impacts into Mercury, depending on the size distribution model employed. The single impact delivery scenario therefore remains viable for Mercury. Robust modeling of a single large impact event on Mercury would supply critical insight into the feasibility of this scenario.

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The influence of surface roughness on volatile transport on the Moon

Cited by 24 publications

References 27 publications

The Evolution of a Spacecraft‐Generated Lunar Exosphere

The Evolution of a Spacecraft‐Generated Lunar Exosphere

Seasonal Polar Temperatures on the Moon

Examining the Potential Contribution of the Hokusai Impact to Water Ice on Mercury

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