Estimates of primary ejecta and local material for the Orientale basin: Implications for the formation and ballistic sedimentation of multi-ring basins

Xie, Minggang; Zhu, M. H.

doi:10.1016/j.epsl.2016.02.012

Cited by 33 publications

(79 citation statements)

References 30 publications

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“…Assuming the incident angle of ejecta was 75°, Oberbeck et al () established an empirical model that can estimate the excavation efficiency ( μ ) of crater ejecta for given thickness of ejecta and the distance from crater center based on the analysis of Copernicus secondary craters (i.e., μ = 4.5 × 10 −5 r 0.87 , all in meters). However, recent works (e.g., Petro & Pieters, ; Xie & Zhu, ) suggested that the authors may have overestimated the excavation efficiency. Here we adopt half of excavation efficiency of Oberbeck et al () (i.e., μ = 2.25 × 10 −5 r 0.87 ) according to the result of Petro and Pieters ().…”

Section: Discussionmentioning

confidence: 99%

“…Journal of Geophysical Research: Planets (i.e., μ = 4.5 × 10 À5 r 0.87 , all in meters). However, recent works (e.g., Petro & Pieters, 2006;Xie & Zhu, 2016) suggested that the authors may have overestimated the excavation efficiency. Here we adopt half of excavation efficiency of Oberbeck et al (1975) (i.e., μ = 2.25 × 10 À5 r 0.87 ) according to the result of Petro and Pieters (2006).…”

Section: /2018je005577mentioning

confidence: 99%

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Geological Characteristics of Von Kármán Crater, Northwestern South Pole‐Aitken Basin: Chang'E‐4 Landing Site Region

et al. 2018

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Von Kármán crater (diameter = ~186 km), lying in the northwestern South Pole‐Aitken (SPA) basin, was formed in the pre‐Nectarian. The Von Kármán crater floor was subsequently flooded with one or several generations of mare basalts during the Imbrian period. Numerous subsequent impact craters in the surrounding region delivered ejecta to the floor, together forming a rich sample of the SPA basin and farside geologic history. We studied in details the targeted landing region (45.0–46.0°S, 176.4–178.8°E) of the 2018 Chinese lunar mission Chang'E‐4, within the Von Kármán crater. The topography of the landing region is generally flat at a baseline of ~60 m. Secondary craters and ejecta materials have covered most of the mare unit and can be traced back to at least four source craters (Finsen, Von Kármán L, Von Kármán L', and Antoniadi) based on preferential spatial orientations and crosscutting relationships. Extensive sinuous ridges and troughs are identified spatially related to Ba Jie crater (diameter = ~4 km). Reflectance spectral variations due to difference in both composition and physical properties are observed among the ejecta from various‐sized craters on the mare unit. The composition trends were used together with crater scaling relationships and estimates of regolith thickness to reconstruct the subsurface stratigraphy. The results reveal a complex geological history of the landing region and set the framework for the in situ measurements of the CE‐4 mission, which will provide unique insights into the compositions of farside mare basalt, SPA compositional zone including SPA compositional anomaly and Mg‐pyroxene annulus, regolith evolution, and the lunar space environment.

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Section: Discussionmentioning

confidence: 99%

Section: /2018je005577mentioning

confidence: 99%

Geological Characteristics of Von Kármán Crater, Northwestern South Pole‐Aitken Basin: Chang'E‐4 Landing Site Region

et al. 2018

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“…First, we discuss an ejecta blanket as a source of regolith. Earlier works showed the scaling law of the external crater profile as a function of distance from the crater rim (Fassett et al, ; McGetchin et al, ; Pike, ; Xie & Zhu, ). We define the thickness profile of the ejecta blanket of a simple crater as (e.g., Pike, ; Sharpton, )

h_{out} \sim σ r_{c} {(\frac{r}{r_{c}})}^{- κ}, r > r_{c},

where r c is the final crater radius, r is the distance from the crater center, and σ and κ are empirical parameters.…”

Section: Modeling Of Regolith Units As a Source Of Regolithmentioning

confidence: 98%

The Role of Breccia Lenses in Regolith Generation From the Formation of Small, Simple Craters: Application to the Apollo 15 Landing Site

et al. 2018

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Impact cratering is likely a primary agent of regolith generation on airless bodies. Regolith production via impact cratering has long been a key topic of study since the Apollo era. The evolution of regolith due to impact cratering, however, is not well understood. A better formulation is needed to help quantify the formation mechanism and timescale of regolith evolution. Here we propose an analytically derived stochastic model that describes the evolution of regolith generated by small, simple craters. We account for ejecta blanketing as well as regolith infilling of the transient crater cavity. Our results show that the regolith infilling plays a key role in producing regolith. Our model demonstrates that because of the stochastic nature of impact cratering, the regolith thickness varies laterally, which is consistent with earlier work. We apply this analytical model to the regolith evolution at the Apollo 15 site. The regolith thickness is computed considering the observed crater size‐frequency distribution of small, simple lunar craters (< 381 m in radius for ejecta blanketing and <100 m in radius for the regolith infilling). Allowing for some amount of regolith coming from the outside of the area, our result is consistent with an empirical result from the Apollo 15 seismic experiment. Finally, we find that the timescale of regolith growth is longer than that of crater equilibrium, implying that even if crater equilibrium is observed on a cratered surface, it is likely that the regolith thickness is still evolving due to additional impact craters.

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“…The fifth ring about 1,300 km in diameter was postulated by some early researchers (Hartmann & Kuiper, 1962;Hartmann & Wood, 1971), but it was poorly defined even if it exists (Moore et al, 1974). There have been controversies about whether the Outer Rook ring (Fassett et al, 2011;Head, 1974;Spudis et al, 1984) or the Inner Rook ring (Xie & Zhu, 2016) is more representative of the position of the transient cavity. The latest study based on high-resolution gravity data from Gravity Recovery and Interior Laboratory (GRAIL) and hydrocode simulation has concluded that the transient crater was~390 km in diameter but was not maintained because of the subsequent gravitation collapse (Johnson et al, 2016).…”

Section: Background Of Investigation Areamentioning

confidence: 99%

Lunar Orientale Impact Basin Secondary Craters: Spatial Distribution, Size‐Frequency Distribution, and Estimation of Fragment Size

et al. 2018

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Secondary impact craters, features created by projectiles ejected from a primary impact, contain important information about the primary cratering event and the nature and distribution of its ejecta. The Orientale impact basin (D ~ 930 km) is the youngest and the least degraded large impact basin on the Moon and has the most recognizable secondary impact craters. We identified and mapped 2,728 secondary craters in the investigated area of ~1.66 × 107 km2, covering an area from the rim of Orientale to six radii. Secondary crater diameters range from ~2 to 27 km, and the median diameter decreases as distance increases. Secondary craters are concentrated predominantly in the northwest and southwest. The ejecta deposit pattern inferred from secondary crater distribution suggests that the Orientale basin was formed by an oblique impact in which the downrange direction was 240°–265° in azimuth, and the incidence angle was steeper than 20°. The cumulative size‐frequency distribution of mapped secondary craters steepens as diameter increases and is very well approximated with a Weibull distribution with an exponent 1.32. A widely used crater scaling relationship predicts that the fragments that produced the secondary craters were predominantly in ~0.5–2‐km diameter range over the investigated area; the diameter of the largest fragment, however, decreases with increasing distance from Orientale. On the basis of the diameter of the largest secondary crater of Orientale, and other craters and basins, the largest secondary crater of the South Pole‐Aitken basin is estimated to be ~40 km in diameter. We explore the implications of these findings for the evolution of the megaregolith and future sample return missions.

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Estimates of primary ejecta and local material for the Orientale basin: Implications for the formation and ballistic sedimentation of multi-ring basins

Cited by 33 publications

References 30 publications

Geological Characteristics of Von Kármán Crater, Northwestern South Pole‐Aitken Basin: Chang'E‐4 Landing Site Region

Geological Characteristics of Von Kármán Crater, Northwestern South Pole‐Aitken Basin: Chang'E‐4 Landing Site Region

The Role of Breccia Lenses in Regolith Generation From the Formation of Small, Simple Craters: Application to the Apollo 15 Landing Site

Lunar Orientale Impact Basin Secondary Craters: Spatial Distribution, Size‐Frequency Distribution, and Estimation of Fragment Size

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