China’s Chang’e 3(CE-3)and Chang’e 4(CE-3)missions made historic progress by sending rovers equipped with scientific instruments to the new sites on the nearside and farside of the moon,respectively.The same lunar ...China’s Chang’e 3(CE-3)and Chang’e 4(CE-3)missions made historic progress by sending rovers equipped with scientific instruments to the new sites on the nearside and farside of the moon,respectively.The same lunar penetrating radar(LPR)that uses pulses of electromagnetic energy to reveal the underground structure and properties of the lunar soil"regolith"covering most of the lunar surface was carried by the rovers.It provided for the first time the opportunity for in situ LPR measurements of the subsurface substrate in two geologically different places on the moon.At present,the Yutu rover of CE-3 mission traveled along a path of total length of about 114 m while the Yutu 2 rover of CE-4 has traversed over 1000 m and keeps going.This paper summarizes the fruitful results so far obtained by LPRs,including the physical properties and layered structure of the lunar regolith and shallow crust beneath the two landing sites.The regolith layer thickness at the CE-3 site is thinner than that at the CE-4 site due to its relatively young age.The penetration depth below CE-4 site is about 2.85 times(in terms of the forward and return path delay)deeper than CE-3 as indicated by their different loss tangent values(0.0039±0.0002 vs.0.013),which is probably due to the differences in abundance of ilmenite and rocks in the regolith.Other physical parameters including dielectric permittivity vs.depth profile,bulk density and electrical conductivity have been estimated using various methods.Thanks to the low signal loss,CE-4 LPR is able to present clear cross section views of two buried craters and the paleo-surface(ancient surface)of the landing site.The multiple stratums observed by the low frequency channel of LPRs indicate several episodes of lava eruptions occurred in the late stage of the formation of the nearside Imbrium Basin and the farside Von Kármán crater despite the asymmetric volcanisms distributed on two sides.The discoveries revealed by LPRs advance our knowledges on the formation process and properties of lunar regolith,thickness of ejecta deposits caused by lunar impact events,the evolution of the nearside and farside volcanisms,etc.They also demonstrate the feasibility of applying ground penetrating radar for non-terrestrial explorations such as China’s first Martian mission,Tianwen 1 mission.展开更多
文摘China’s Chang’e 3(CE-3)and Chang’e 4(CE-3)missions made historic progress by sending rovers equipped with scientific instruments to the new sites on the nearside and farside of the moon,respectively.The same lunar penetrating radar(LPR)that uses pulses of electromagnetic energy to reveal the underground structure and properties of the lunar soil"regolith"covering most of the lunar surface was carried by the rovers.It provided for the first time the opportunity for in situ LPR measurements of the subsurface substrate in two geologically different places on the moon.At present,the Yutu rover of CE-3 mission traveled along a path of total length of about 114 m while the Yutu 2 rover of CE-4 has traversed over 1000 m and keeps going.This paper summarizes the fruitful results so far obtained by LPRs,including the physical properties and layered structure of the lunar regolith and shallow crust beneath the two landing sites.The regolith layer thickness at the CE-3 site is thinner than that at the CE-4 site due to its relatively young age.The penetration depth below CE-4 site is about 2.85 times(in terms of the forward and return path delay)deeper than CE-3 as indicated by their different loss tangent values(0.0039±0.0002 vs.0.013),which is probably due to the differences in abundance of ilmenite and rocks in the regolith.Other physical parameters including dielectric permittivity vs.depth profile,bulk density and electrical conductivity have been estimated using various methods.Thanks to the low signal loss,CE-4 LPR is able to present clear cross section views of two buried craters and the paleo-surface(ancient surface)of the landing site.The multiple stratums observed by the low frequency channel of LPRs indicate several episodes of lava eruptions occurred in the late stage of the formation of the nearside Imbrium Basin and the farside Von Kármán crater despite the asymmetric volcanisms distributed on two sides.The discoveries revealed by LPRs advance our knowledges on the formation process and properties of lunar regolith,thickness of ejecta deposits caused by lunar impact events,the evolution of the nearside and farside volcanisms,etc.They also demonstrate the feasibility of applying ground penetrating radar for non-terrestrial explorations such as China’s first Martian mission,Tianwen 1 mission.
