Radar Mapping of Mercury: Full-Disk Images and Polar Anomalies

Harmon, J. K.; Slade, M. A.

doi:10.1126/science.258.5082.640

Cited by 188 publications

(123 citation statements)

References 15 publications

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“…Radar mapping of Mercury suggested the presence of polar ice in 1991 Harmon and Slade 1992). Thermal models show that in permanently shadowed regions of high-latitude craters, water ice covered by a regolith layer can be stable to evaporation over billions of years (Paige et al 1992;Vasavada et al 1999).…”

Section: Water In the Planetsmentioning

confidence: 99%

The Main Belt Comets and ice in the Solar System

Snodgrass

Agarwal

Combi

et al. 2017

Astron Astrophys Rev

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We review the evidence for buried ice in the asteroid belt; specifically the questions around the so-called Main Belt Comets (MBCs). We summarise the evidence for water throughout the Solar System, and describe the various methods for detecting it, including remote sensing from ultraviolet to radio wavelengths. We review progress in the first decade of study of MBCs, including observations, modelling of ice survival, and discussion on their origins. We then look at which methods will likely be most effective for further progress, including the key challenge of direct detection of (escaping) water in these bodies.

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Section: Water In the Planetsmentioning

confidence: 99%

The Main Belt Comets and ice in the Solar System

Snodgrass

Agarwal

Combi

et al. 2017

Astron Astrophys Rev

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“…Radar backscatter from the lunar surface is modeled as a mixture of these specular and diffuse components. Diffuse scattering from rocky areas associated with fresh craters is assumed to have CPR of about 1.0; and ice is assumed to have CPR of 2.0, as observed in the polar features of Mercury and Mars and the surfaces of the icy Galilean satellites of Jupiter [Muhleman et al, 1991;Harmon and Slade, 1992;Butler et al, 1993;Ostro, 2002]. The differences in appearance between the lunar and mercurian polar craters suggest that more ice is present on Mercury than on the Moon, probably a result of the higher cometary flux near Mercury compared with the Moon [e.g., Hartmann et al, 1981] and the fact that the higher surface gravity on Mercury (~0.3 g) means that body will retain more water on its surface.…”

Section: Modeling the Radar Backscatter Of Rough And Icy Cratersmentioning

confidence: 99%

Evidence for water ice on the Moon: Results for anomalous polar craters from the LRO Mini‐RF imaging radar

et al. 2013

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[1] The Mini-RF radar instrument on the Lunar Reconnaissance Orbiter spacecraft mapped both lunar poles in two different RF wavelengths (complete mapping at 12.6 cm S-band and partial mapping at 4.2 cm X-band) in two look directions, removing much of the ambiguity of previous Earth-and spacecraft-based radar mapping of the Moon's polar regions. The poles are typical highland terrain, showing expected values of radar cross section (albedo) and circular polarization ratio (CPR). Most fresh craters display high values of CPR in and outside the crater rim; the pattern of these CPR distributions is consistent with high levels of wavelength-scale surface roughness associated with the presence of block fields, impact melt flows, and fallback breccia. A different class of polar crater exhibits high CPR only in their interiors, interiors that are both permanently dark and very cold (less than 100 K). Application of scattering models developed previously suggests that these anomalously high-CPR deposits exhibit behavior consistent with the presence of water ice. If this interpretation is correct, then both poles may contain several hundred million tons of water in the form of relatively "clean" ice, all within the upper couple of meters of the lunar surface. The existence of significant water ice deposits enables both long-term human habitation of the Moon and the creation of a permanent cislunar space transportation system based upon the harvest and use of lunar propellant.

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“…More importantly, radar led to the discovery of an anomalous class of materials inside permanently shadowed crater interiors in both polar regions. These materials exhibit high radar reflectivity and a circular polarity inversion consistent with a volume scatterer Harmon and Slade 1992). Water ice remains the leading candidate material to explain the shadowed deposits, but many unanswered issues remain and final resolution must await orbital observations (Harmon et al 2001).…”

Section: Introductionmentioning

confidence: 99%

The Mercury Dual Imaging System on the MESSENGER Spacecraft

et al. 2007

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The Mercury Dual Imaging System (MDIS) on the MESSENGER spacecraft will provide critical measurements tracing Mercury's origin and evolution. MDIS consists of a monochrome narrow-angle camera (NAC) and a multispectral wide-angle camera (WAC). The NAC is a 1.5°field-of-view (FOV) off-axis reflector, coaligned with the WAC, a fourelement refractor with a 10.5°FOV and 12-color filter wheel. The focal plane electronics of each camera are identical and use a 1,024 × 1,024 Atmel (Thomson) TH7888A chargecoupled device detector. Only one camera operates at a time, allowing them to share a common set of control electronics. The NAC and the WAC are mounted on a pivoting platform that provides a 90°field-of-regard, extending 40°sunward and 50°anti-sunward from the spacecraft +Z-axis-the boresight direction of most of MESSENGER's instruments. Onboard data compression provides capabilities for pixel binning, remapping of 12-bit data into 8 bits, and lossless or lossy compression. MDIS will acquire four main data sets at Mercury during three flybys and the two-Mercury-solar-day nominal mission: a monochrome global image mosaic at near-zero emission angles and moderate incidence angles, a stereocomplement map at off-nadir geometry and near-identical lighting, multicolor images at low incidence angles, and targeted high-resolution images of key surface features. These data will be used to construct a global image base map, a digital terrain model, global maps of color properties, and mosaics of high-resolution image strips. Analysis of these data will provide information on Mercury's impact history, tectonic processes, the composition and emplacement history of volcanic materials, and the thickness distribution and compositional variations of crustal materials. This paper summarizes MDIS's science objectives and technical design, including the common payload design of the MDIS data processing units, as well as detailed results from ground and early flight calibrations and plans for Mercury image products to be generated from MDIS data.

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Radar Mapping of Mercury: Full-Disk Images and Polar Anomalies

Cited by 188 publications

References 15 publications

The Main Belt Comets and ice in the Solar System

The Main Belt Comets and ice in the Solar System

Evidence for water ice on the Moon: Results for anomalous polar craters from the LRO Mini‐RF imaging radar

The Mercury Dual Imaging System on the MESSENGER Spacecraft

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