Stability of ice on the Moon with rough topography

Rubanenko, Lior; Aharonson, O.

doi:10.1016/j.icarus.2017.05.028

Cited by 26 publications

(29 citation statements)

References 38 publications

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“…The 1‐D slope distribution of realistic airless topography sometimes deviates from this idealized model due to the presence of craters. However, the calculated shadow and temperature distributions and the resulting cold‐trap fractions of rough surface resemble those observed on the Moon (Bandfield et al, ; Smith, ; Rubanenko & Aharonson, ). To verify that this is also true for Mercury, we compared the modeled north pole cold‐trap fraction using real topography to that of a rough random surface with the same root‐mean‐square (RMS) slope σ s ∼7°.…”

Section: Evidence For Ice Inside Micro Cold Trapssupporting

confidence: 52%

“…A common way to model rough topography on airless bodies is to use random Gaussian surfaces (e.g., Bandfield et al, ; Davidsson & Rickman, ; Hagfors, ; Jamsa et al, ; Smith, ; Rubanenko & Aharonson, ). This artificial realization has a Gaussian slope distribution and a power law power spectrum.…”

Section: Evidence For Ice Inside Micro Cold Trapsmentioning

confidence: 99%

“…This choice of the surface size is a compromise between the model running time, which is squared in N , and the error in the calculated PSR area fraction, which is ∼3 % (compared to a surface with N = 1,000 × 1,000 pixels). A more detailed description of the model and the generation of rough random surfaces is provided in Rubanenko and Aharonson ().…”

Section: Evidence For Ice Inside Micro Cold Trapsmentioning

confidence: 99%

“…Higher σ s affects the cold‐trap area fraction by simultaneously increasing the PSR area fraction and the amount of reflected and thermally emitted radiation from nearby illuminated, warm slopes. Therefore, higher surface roughness does not necessarily translate into a higher cold‐trap area fraction (Rubanenko & Aharonson, ). On Mercury this effect is amplified compared to the Moon due to the higher temperature of illuminated slopes and the consequent higher reflected visible and emitted infrared flux.…”

Section: Evidence For Ice Inside Micro Cold Trapsmentioning

confidence: 99%

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Ice in Micro Cold Traps on Mercury: Implications for Age and Origin

et al. 2018

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Evidence in radar, reflectance, and visible imagery indicates that surface and subsurface water ice is present inside permanently shadowed regions in the north polar region of Mercury. The origin of this ice and the time at which it was delivered to the planet are both unknown. Finding the smallest, most easily eroded ice deposits on Mercury can help answer these questions. Here we present evidence for volatiles trapped in cold traps of scales ∼ 1-10 m. We consider two possible delivery methods for these deposits: a gradual, slow accumulation by micrometeorites or solar wind implantation and an episodic deposition, either primordial or by a recent comet impact. We conclude that the mechanism that best explains the presence of volatiles in these micro cold traps is a comet impact that most likely occurred in the last ∼ 100 Ma.Plain Language Summary Craters near the north pole of Mercury, one of the warmest planets in the solar system, cast persistent shadows that are so cold they can trap water ice for billions of years. Although many observations show that ice is present inside these polar cold traps, its age and the way it was delivered to the planet are not well known. Here we present evidence for the presence of ice deposits on scales of 1-10 m, the smallest discovered so far, near the north pole of Mercury. Due to the relative shallowness of these micro cold traps, an episodic deposition, such as a comet impact, is a more probable delivery mechanism than an ongoing slow accumulation by micrometeorites. Using previously estimated surface erosion rates, we find that the age of this ice is most likely lower than 100 million years.Lately, it was hypothesized that ice may persist in micro cold traps that form in PSRs cast by craters and random small-scale topographic features (Hayne & Aharonson, 2015). In this case, the term micro does not mean Key Points: • Using MLA data and a thermal illumination model, we find evidence for ice trapped in micro cold traps of scales < 10 m and thickness < 1 m • Surface micro cold traps occupy 1%-2% of the polar region, compared to ∼ 7% occupied by the larger cold traps • A recent comet impact is more likely to explain our findings than continuous delivery by, for example, solar wind implantation or micrometeorites

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Section: Evidence For Ice Inside Micro Cold Trapssupporting

confidence: 52%

Section: Evidence For Ice Inside Micro Cold Trapsmentioning

confidence: 99%

Section: Evidence For Ice Inside Micro Cold Trapsmentioning

confidence: 99%

Section: Evidence For Ice Inside Micro Cold Trapsmentioning

confidence: 99%

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Ice in Micro Cold Traps on Mercury: Implications for Age and Origin

et al. 2018

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“…Such low diffusivities are found in highly porous, regolith type materials (e.g. the diffusivity of the lunar regolith is 5 × 10 −9 ≤ κ ≤ 5 × 10 −8 m 2 s −1 according to parameters given by Rubanenko and Aharonson 2017) then we require only that κ < 0.3 × 10 −6 m 2 s −1 , much more compatible with solid rock.…”

Section: Mechanismsmentioning

confidence: 99%

Hubble Space Telescope Observations of 3200 Phaethon at Closest Approach

Jewitt

Mutchler

Agarwal

et al. 2018

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We present Hubble Space Telescope observations of the active asteroid (and Geminid stream parent) 3200 Phaethon when at its closest approach to Earth (separation 0.07 AU) in 2017 December. Images were recorded within ∼1 • of the orbital plane, providing extra sensitivity to low surface brightness caused by scattering from a large-particle trail. We placed an upper limit to the apparent surface brightness of such a trail at 27.2 magnitudes arcsecond −2 , corresponding to an in-plane optical depth ≤ 3 × 10 −9 . No co-moving sources brighter than absolute magnitude 26.3, corresponding to circular equivalent radius ∼12 m (albedo 0.12 assumed), were detected. Phaethon is too hot for near-surface ice to survive. We briefly consider the thermodynamic stability of deeply-buried ice, finding that its survival would require either a very small (regolith-like) thermal diffusivity (< 10 −8 m 2 s −1 ), or the unexpectedly recent injection of Phaethon (timescale 10 6 yr) into its present orbit, or both.

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Lunar explorations—Discovering water, minerals, and underground caves and tunnel complexes

Joseph¹

2023

Water Worlds in the Solar System

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Stability of ice on the Moon with rough topography

Cited by 26 publications

References 38 publications

Ice in Micro Cold Traps on Mercury: Implications for Age and Origin

Ice in Micro Cold Traps on Mercury: Implications for Age and Origin

Hubble Space Telescope Observations of 3200 Phaethon at Closest Approach

Lunar explorations—Discovering water, minerals, and underground caves and tunnel complexes

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