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
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 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].
