TY - JOUR
T1 - Exposure of spectrally distinct material by impact craters on Mercury
T2 - Implications for global stratigraphy
AU - Ernst, Carolyn M.
AU - Murchie, Scott L.
AU - Barnouin, Olivier S.
AU - Robinson, Mark
AU - Denevi, Brett W.
AU - Blewett, David T.
AU - Head, James W.
AU - Izenberg, Noam R.
AU - Solomon, Sean C.
AU - Roberts, James H.
N1 - Funding Information:
The MESSENGER project is supported by the NASA Discovery Program under contracts NASW-00002 to the Carnegie Institution of Washington and NAS5-97271 to the Johns Hopkins University Applied Physics Laboratory. Support from the NASA MESSENGER Participating Scientist Program is also greatly appreciated (#NNX08AN29G, principal investigator D.T.B.). The authors thank two anonymous reviewers for their detailed and constructive comments, which have improved the quality of this manuscript.
PY - 2010/9
Y1 - 2010/9
N2 - MESSENGER's Mercury Dual Imaging System (MDIS) obtained multispectral images for more than 80% of the surface of Mercury during its first two flybys. Those images have confirmed that the surface of Mercury exhibits subtle color variations, some of which can be attributed to compositional differences. In many areas, impact craters are associated with material that is spectrally distinct from the surrounding surface. These deposits can be located on the crater floor, rim, wall, or central peak or in the ejecta deposit, and represent material that originally resided at depth and was subsequently excavated during the cratering process. The resulting craters make it possible to investigate the stratigraphy of Mercury's upper crust. Studies of laboratory, terrestrial, and lunar craters provide a means to bound the depth of origin of spectrally distinct ejecta and central peak structures. Excavated red material (RM), with comparatively steep (red) spectral slope, and low-reflectance material (LRM) stand out prominently from the surrounding terrain in enhanced-color images because they are spectral end-members in Mercury's compositional continuum. Newly imaged examples of RM were found to be spectrally similar to the relatively red, high-reflectance plains (HRP), suggesting that they may represent deposits of HRP-like material that were subsequently covered by a thin layer (∼1. km thick) of intermediate plains. In one area, craters with diameters ranging from 30. km to 130. km have excavated and incorporated RM into their rims, suggesting that the underlying RM layer may be several kilometers thick. LRM deposits are useful as stratigraphic markers, due to their unique spectral properties. Some RM and LRM were excavated by pre-Tolstojan basins, indicating a relatively old age (>4.0. Ga) for the original emplacement of these deposits. Detailed examination of several small areas on Mercury reveals the complex nature of the local stratigraphy, including the possible presence of buried volcanic plains, and supports sequential buildup of most of the upper ∼5. km of crust by volcanic flows with compositions spanning the range of material now visible on the surface, distributed heterogeneously across the planet. This emerging picture strongly suggests that the crust of Mercury is characterized by a much more substantial component of early volcanism than represented by the phase of mare emplacement on Earth's Moon.
AB - MESSENGER's Mercury Dual Imaging System (MDIS) obtained multispectral images for more than 80% of the surface of Mercury during its first two flybys. Those images have confirmed that the surface of Mercury exhibits subtle color variations, some of which can be attributed to compositional differences. In many areas, impact craters are associated with material that is spectrally distinct from the surrounding surface. These deposits can be located on the crater floor, rim, wall, or central peak or in the ejecta deposit, and represent material that originally resided at depth and was subsequently excavated during the cratering process. The resulting craters make it possible to investigate the stratigraphy of Mercury's upper crust. Studies of laboratory, terrestrial, and lunar craters provide a means to bound the depth of origin of spectrally distinct ejecta and central peak structures. Excavated red material (RM), with comparatively steep (red) spectral slope, and low-reflectance material (LRM) stand out prominently from the surrounding terrain in enhanced-color images because they are spectral end-members in Mercury's compositional continuum. Newly imaged examples of RM were found to be spectrally similar to the relatively red, high-reflectance plains (HRP), suggesting that they may represent deposits of HRP-like material that were subsequently covered by a thin layer (∼1. km thick) of intermediate plains. In one area, craters with diameters ranging from 30. km to 130. km have excavated and incorporated RM into their rims, suggesting that the underlying RM layer may be several kilometers thick. LRM deposits are useful as stratigraphic markers, due to their unique spectral properties. Some RM and LRM were excavated by pre-Tolstojan basins, indicating a relatively old age (>4.0. Ga) for the original emplacement of these deposits. Detailed examination of several small areas on Mercury reveals the complex nature of the local stratigraphy, including the possible presence of buried volcanic plains, and supports sequential buildup of most of the upper ∼5. km of crust by volcanic flows with compositions spanning the range of material now visible on the surface, distributed heterogeneously across the planet. This emerging picture strongly suggests that the crust of Mercury is characterized by a much more substantial component of early volcanism than represented by the phase of mare emplacement on Earth's Moon.
KW - Cratering
KW - Geological processes
KW - Mercury
KW - Mercury, surface
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U2 - 10.1016/j.icarus.2010.05.022
DO - 10.1016/j.icarus.2010.05.022
M3 - Article
AN - SCOPUS:77955769202
SN - 0019-1035
VL - 209
SP - 210
EP - 223
JO - Icarus
JF - Icarus
IS - 1
ER -