Imaging Mercury's polar deposits during MESSENGER's low‐altitude campaign

Chabot, N. L.; Ernst, C. M.; Paige, D. A.; Nair, Hari; Denevi, B. W.; Blewett, D. T.; Murchie, S. L.; Deutsch, A. N.; Head, J. W.; Solomon, Sean C.

doi:10.1002/2016gl070403

Cited by 35 publications

(44 citation statements)

References 31 publications

(51 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The interior of Mercury's north polar PSRs were directly viewed using MDIS imagery in a manner similar to the PSR images of the Moon. In contrast to the Moon, Mercury's PSRs show striking and distinctive features [ Chabot et al ., , ]. Dark deposits identified by MLA were also easily identified as dark in the MDIS images (Figure ).…”

Section: Timeline Of Psr Explorationmentioning

confidence: 89%

A tale of two poles: Toward understanding the presence, distribution, and origin of volatiles at the polar regions of the Moon and Mercury

Lawrence

2017

JGR Planets

View full text Add to dashboard Cite

The Moon and Mercury both have permanently shaded regions (PSRs) at their poles, which are locations that do not see the Sun for geologically long periods of time. The PSRs of the Moon and Mercury have very cold temperatures (<120 K) and as a consequence act as traps for volatile materials. Volatile enhancements have been detected and characterized at both planetary bodies, but the volatile concentrations at Mercury's poles are significantly larger than at the Moon's poles. This paper documents the study of PSR volatiles at the Moon and Mercury that has taken place over the past 60 years. Starting with speculative ideas in the 1950s and 1960s, the field of PSR volatiles has emerged into a thriving subfield of planetary science that has significant implications for scientific studies of the solar system, as well as future human exploration of the solar system. While much has been learned about PSRs and PSR volatiles, many foundational aspects of PSRs are still not understood. One of the most important unanswered questions is why the PSR volatile concentrations at the Moon and Mercury are so different. After describing the initial predictions and measurements of PSR volatiles, this paper documents a variety of PSR measurements, summarizes the current understanding of PSR volatiles, and then suggests what new measurements and studies are needed to answer many of the remaining open questions about PSR volatiles.

show abstract

Section: Timeline Of Psr Explorationmentioning

confidence: 89%

A tale of two poles: Toward understanding the presence, distribution, and origin of volatiles at the polar regions of the Moon and Mercury

Lawrence

2017

JGR Planets

View full text Add to dashboard Cite

show abstract

“…Earth‐based radar (e.g., Butler et al, ; Harmon et al, ; Harmon & Slade, ; Slade et al, ) and MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) observations (Chabot et al, , , , ; Deutsch et al, ; Lawrence et al, ; Neumann et al, ; Paige et al, ) have provided compelling evidence that Mercury's polar deposits are dominantly composed of water ice. Estimates of Mercury's water‐ice inventory range from ~10 16 to 10 18 g (Deutsch et al, ; Eke et al, ; Lawrence et al, ; Moses et al, ; Susorney et al, ).…”

Section: Introductionmentioning

confidence: 99%

“…The substantial differences between the water‐ice inventories observed in the polar regions of Mercury and the Moon could be explained by the lack of a recent, large, water‐delivering impact at the Moon. Additional MESSENGER measurements suggest the presence of low‐reflectance, organic‐rich lag deposits overlying some of the polar deposits (Chabot et al, , ; Neumann et al, ; Paige et al, ), thereby leading to the suggestion that both water ice and volatile organics were delivered to Mercury at the same time. Models of burial rate also suggest recent emplacement within the last few million years, lest such deposits be more deeply buried from regolith gardening (Crider & Killen, ).…”

Section: Introductionmentioning

confidence: 99%

“…Models of burial rate also suggest recent emplacement within the last few million years, lest such deposits be more deeply buried from regolith gardening (Crider & Killen, ). Moreover, Mercury Dual Imaging System (MDIS, Hawkins et al, ) images of polar deposits in Mercury's north polar region have revealed sharp albedo boundaries, which indicate that the volatiles must either be actively restored or were recently delivered to Mercury (Chabot et al, , ). Lunar‐ and Mercury‐based models have shown that significant volumes of water are retained after large impacts (Bruck Syal & Schultz, ; Moses et al, ; Ong et al, ; Stewart et al, ) and demonstrate that volatiles delivered by a single comet impact anywhere on the surface could ultimately migrate to cold traps (permanently shadowed regions) at both poles (Stewart et al, ).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

2018

Self Cite

View full text Add to dashboard Cite

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.

show abstract

“…PSRs within craters were imaged by the Mercury Dual Imaging System and were found to contain similar features with distinctive reflectance properties and sharp boundaries (Chabot et al, ). If these features are ice deposits, they could only outlast erosion if they were relatively young or continuously renewed at a rate that dominates the gardening rate (Chabot et al, ).…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2018

View full text Add to dashboard Cite

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

show abstract

Imaging Mercury's polar deposits during MESSENGER's low‐altitude campaign

Cited by 35 publications

References 31 publications

A tale of two poles: Toward understanding the presence, distribution, and origin of volatiles at the polar regions of the Moon and Mercury

A tale of two poles: Toward understanding the presence, distribution, and origin of volatiles at the polar regions of the Moon and Mercury

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

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

Contact Info

Product

Resources

About