The Chang’E-4 mission has been exploring the lunar farside.Two scientific targets of the rover onboard are(1)resolving the possible mineralogy related to the South Pole-Aitken basin and(2)understanding the subsurface...The Chang’E-4 mission has been exploring the lunar farside.Two scientific targets of the rover onboard are(1)resolving the possible mineralogy related to the South Pole-Aitken basin and(2)understanding the subsurface processes at the lunar farside.Publications to date that are based on the reflectance spectra and radar data obtained by the rover have shown a persistent inconsistency about the local stratigraphy.To explain both the abnormal surface topography at the landing site and the unexpected radargram observed by the rover,the Alder crater has been frequently reported to be older than the mare basalts at that landing site.However,this argument is not supported by earlier geological mapping nor recent crater statistics.Resolving this controversy is critical for a full understanding of the geological history of the landing area and for correct interpretations of the scientific data returned.Employing detailed crater statistics,rigorous statistical analyses,and an updated crater chronology function,this study is determined to resolve the relative ages of the Alder crater,Finsen crater,and the mare basalts on the floor of Von Kármán.Our results reveal that while background secondaries and local resurfacing have widely occurred in the study area,affecting age determinations,the statistics are significant enough to conclude that the Alder crater is the oldest among the three targets.This independent constraint is consistent with both the crosscutting relationships of different terrains in this area and global stratigraphic mapping.Our results exclude Alder as a possible contributor of the post-mare deposits at the landing site,appealing for a more systematic stratigraphy study to resolve the provenances of these deposits.展开更多
The Chinese Chang’e-3 mission landed close to the eastern rim of the ~450 m diameter Ziwei crater. Regional stratigraphy of the landing site and impact excavation model suggest that the bulk continuous ejecta deposit...The Chinese Chang’e-3 mission landed close to the eastern rim of the ~450 m diameter Ziwei crater. Regional stratigraphy of the landing site and impact excavation model suggest that the bulk continuous ejecta deposits of the Ziwei crater are composed by Erathothenian-aged mare basalts. Along the traverse of the Yutu rover, the western segment features a gentle topographic uplift(~0.5 m high over ~4 m), which is spatially connected with the structurally-uplifted crater rim. Assuming that this broad topographic uplift has physical properties discontinuous with materials below, we use data returned by the high-frequency lunar penetrating radar onboard the Yutu rover to estimate the possible range of relative permittivity for this topographic uplift. Only when the relative permittivity is ~9 is the observed radar reflection consistent with the observed topography, suggesting that the topographic uplift is composed of basaltic blocks that were excavated by the Ziwei crater. This result is consistent both with the impact excavation model that predicts deeper basaltic materials being deposited closer to the crater rim, and with observation of numerous half-buried boulders on the surface of this hill. We note that this study is the first to use topography and radargram data to estimate the relative permittivity of lunar surface uplifts, an approach that has had many successful applications on Mars. Similar approaches can apply other ground penetrating radar data for the Moon, such as will be available from the ongoing Chang’e-4 mission.展开更多
The prototype for investigations of formation mechanisms and related geological effects of large impact basins on planetary bodies has been the Orientale basin on the Moon.Its widespread secondaries,light plains,and n...The prototype for investigations of formation mechanisms and related geological effects of large impact basins on planetary bodies has been the Orientale basin on the Moon.Its widespread secondaries,light plains,and near-rim melt flows have been well mapped in previous studies.Flow features are also widely associated with secondaries on planetary bodies,but their physical properties are not well constrained.The nature of flow features associated with large impact basins are critically important to understand the emplacement process of basin ejecta,which is one of the most fundamental processes in shaping the shallow crusts of planetary bodies.Here we use multisource remote sensing data to constrain the physical properties of flow features formed by the secondaries of the Orientale basin.The results suggest that such flows are dominated by centimeter-scale fine debris fines;larger boulders are not abundant.The shattering of target materials during the excavation of the Orientale basin,landing impact of ejecta that formed the secondaries,and grain comminution within the flows have substantially reduced particle sizes,forming the fine flows.The discovery of global-wide fine debris flows formed by large impact basins has profound implications to the interpretation of both previously-returned samples and remote sensing data.展开更多
Glass is ubiquitous in lunar regolith,and volcanism and hypervelocity impacts are the major mechanisms of forming lunar glasses.Volcanic glasses on the Moon occur as quenched skin of basaltic rocks or as glass spherul...Glass is ubiquitous in lunar regolith,and volcanism and hypervelocity impacts are the major mechanisms of forming lunar glasses.Volcanic glasses on the Moon occur as quenched skin of basaltic rocks or as glass spherules in pyroclastic deposits.Lunar volcanic glass spherules are less than 1 mm in diameters,and most are less than 300μm[1].Impact glasses on the Moon are formed by cooling of impact melt and/or condensation of impact vapor,and impact glass spherules have rotational shapes,smooth surfaces,and largely clast-free interiors[2].Recognized impact glass spherules on the Moon are dominantly sub-millimeter in sizes,and few are up to~8 mm in diameter[3].Glass spherules record important information about the mantle composition and the history of lunar volcanism and impact cratering[4].Transparent and translucent glasses on the Moon are less than 1 mm in diameters,and larger ones are dark and opaque[5].Hitherto discovered macro-sized glass globules on the Moon(up to~4 cm in diameter)are opaque impact glass(Fig.1a,b)that usually contains hollows and lithic clasts[6].展开更多
基金the B-type Strategic Priority Program of the Chinese Academy of Sciences(Grant No.XDB41000000)the Science and Technology Development Fund of Macao(0042/2018/A2)+1 种基金the National Natural Science Foundation of China(No.41773063)the pre-research Project on Civil Aerospace Technologies(No.D020201 and D020202)that is funded by Chinese National Space Administration.
文摘The Chang’E-4 mission has been exploring the lunar farside.Two scientific targets of the rover onboard are(1)resolving the possible mineralogy related to the South Pole-Aitken basin and(2)understanding the subsurface processes at the lunar farside.Publications to date that are based on the reflectance spectra and radar data obtained by the rover have shown a persistent inconsistency about the local stratigraphy.To explain both the abnormal surface topography at the landing site and the unexpected radargram observed by the rover,the Alder crater has been frequently reported to be older than the mare basalts at that landing site.However,this argument is not supported by earlier geological mapping nor recent crater statistics.Resolving this controversy is critical for a full understanding of the geological history of the landing area and for correct interpretations of the scientific data returned.Employing detailed crater statistics,rigorous statistical analyses,and an updated crater chronology function,this study is determined to resolve the relative ages of the Alder crater,Finsen crater,and the mare basalts on the floor of Von Kármán.Our results reveal that while background secondaries and local resurfacing have widely occurred in the study area,affecting age determinations,the statistics are significant enough to conclude that the Alder crater is the oldest among the three targets.This independent constraint is consistent with both the crosscutting relationships of different terrains in this area and global stratigraphic mapping.Our results exclude Alder as a possible contributor of the post-mare deposits at the landing site,appealing for a more systematic stratigraphy study to resolve the provenances of these deposits.
基金supported by the National Natural Science Foundation of China (41773063, 41525015 and 41830214)the Science and Technology Development Fund of Macao (0042/2018/A2)the Opening Fund of the Key Laboratory of Lunar and Deep Space Exploration, CAS (no.ldse201702)
文摘The Chinese Chang’e-3 mission landed close to the eastern rim of the ~450 m diameter Ziwei crater. Regional stratigraphy of the landing site and impact excavation model suggest that the bulk continuous ejecta deposits of the Ziwei crater are composed by Erathothenian-aged mare basalts. Along the traverse of the Yutu rover, the western segment features a gentle topographic uplift(~0.5 m high over ~4 m), which is spatially connected with the structurally-uplifted crater rim. Assuming that this broad topographic uplift has physical properties discontinuous with materials below, we use data returned by the high-frequency lunar penetrating radar onboard the Yutu rover to estimate the possible range of relative permittivity for this topographic uplift. Only when the relative permittivity is ~9 is the observed radar reflection consistent with the observed topography, suggesting that the topographic uplift is composed of basaltic blocks that were excavated by the Ziwei crater. This result is consistent both with the impact excavation model that predicts deeper basaltic materials being deposited closer to the crater rim, and with observation of numerous half-buried boulders on the surface of this hill. We note that this study is the first to use topography and radargram data to estimate the relative permittivity of lunar surface uplifts, an approach that has had many successful applications on Mars. Similar approaches can apply other ground penetrating radar data for the Moon, such as will be available from the ongoing Chang’e-4 mission.
基金the B-type Strategic Priority Program of the Chinese Academy of Sciences,Grant No.XDB41000000the National Natural Science Foundation of China(41773063,41525015 and 41830214)+1 种基金the Science and Technology Development Fund of Macao(0042/2018/A2)the Pre-research Project on Civil Aerospace Technologies(No.D020101)of CNSA.
文摘The prototype for investigations of formation mechanisms and related geological effects of large impact basins on planetary bodies has been the Orientale basin on the Moon.Its widespread secondaries,light plains,and near-rim melt flows have been well mapped in previous studies.Flow features are also widely associated with secondaries on planetary bodies,but their physical properties are not well constrained.The nature of flow features associated with large impact basins are critically important to understand the emplacement process of basin ejecta,which is one of the most fundamental processes in shaping the shallow crusts of planetary bodies.Here we use multisource remote sensing data to constrain the physical properties of flow features formed by the secondaries of the Orientale basin.The results suggest that such flows are dominated by centimeter-scale fine debris fines;larger boulders are not abundant.The shattering of target materials during the excavation of the Orientale basin,landing impact of ejecta that formed the secondaries,and grain comminution within the flows have substantially reduced particle sizes,forming the fine flows.The discovery of global-wide fine debris flows formed by large impact basins has profound implications to the interpretation of both previously-returned samples and remote sensing data.
基金supported by the Strategic Priority Program of the Chinese Academy of Sciences(XDB41000000)the Pre-research Project on Civil Aerospace Technologies(D020101,D020202)of China National Space Administration+2 种基金the National Natural Science Foundation of China(41773063)the Key Research Program of Frontier Sciences,Chinese Academy of Sciences(QYZDY-SSWDQC028)the Fundamental Research Funds for the Central Universities。
文摘Glass is ubiquitous in lunar regolith,and volcanism and hypervelocity impacts are the major mechanisms of forming lunar glasses.Volcanic glasses on the Moon occur as quenched skin of basaltic rocks or as glass spherules in pyroclastic deposits.Lunar volcanic glass spherules are less than 1 mm in diameters,and most are less than 300μm[1].Impact glasses on the Moon are formed by cooling of impact melt and/or condensation of impact vapor,and impact glass spherules have rotational shapes,smooth surfaces,and largely clast-free interiors[2].Recognized impact glass spherules on the Moon are dominantly sub-millimeter in sizes,and few are up to~8 mm in diameter[3].Glass spherules record important information about the mantle composition and the history of lunar volcanism and impact cratering[4].Transparent and translucent glasses on the Moon are less than 1 mm in diameters,and larger ones are dark and opaque[5].Hitherto discovered macro-sized glass globules on the Moon(up to~4 cm in diameter)are opaque impact glass(Fig.1a,b)that usually contains hollows and lithic clasts[6].
